Mining Revue 2/2011 EN

SUMMARY

Camelia BARBU Some principles design of a local integrated sustainable renewable energetic system 2

Grigore BUIA, Csaba LORINŢ XXIst Century metals Li, Te, Se, Nb-Ta - National situation 6

Ioan DUMITRESCU, Camelia STĂNOI, Nicolae KANDO Study of nickel on steel cathode used for water electrolysis 10

Iosif DUMITRESCU, Vilhelm ITU, Adrian SUCIU, Rodica COSTANDOIU, Cătălin GĂMAN DLC-1, 2 and 3 cable connecting device cost reduction by design improvements 13

Cristian-Marcel FELEA State aid for coal mining industry 18

Dumitru FODOR, Ioan Călin VEDINAŞ Environmental impact of the metaliferrous ore mining and processing in Romania 22

Cristian Constantin MUZURAN Technical considerations on infrastructure rehabilitation of the Jiu’s Valley mining basin 30

Nicolae NIŢESCU, Aron POANTA, Anne-Marie NIŢESCU, Dan DOJCSAR, Bogdan SOCHIRCĂ Some considerations for precision and fits choice in building machines 36

Dragoş PĂSCULESCU, Andrei ROMĂNESCU Fault analysis in high voltage networks through modern numerical relays 45

Vasile ZAMFIR, Horia VÎRGOLICI, Olimpiu STOICUŢA Positional synthesis of four-bar mechanism 48

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SOME PRINCIPLES DESIGN OF A LOCAL INTEGRATED SUSTAINABLE RENEWABLE ENERGETIC SYSTEM

Camelia BARBU*

Abstract: In this paper the main renewable energy resources in order to design of an integrated renewable energetic system are first presented. Second, is presented the integrated energetic system concept. The integrated system has following characteristics: microclimate; envinroment integrated; sustainable; renewable; clean energy; software oriented; systemic structure. This principle is used for designing a proposed energetic system to produce renewable energy based on sun, water, wind and biomass in an environmental local microclimate context. Keywords: microclimate, renewable energy, solar, wind, water, biomass, modeling and simulation. Introduction The simple definition of sustainability can be that: the quality of a process to be maintained in the same state boundless time. The sustainable development is a collection of methods in order to accomplish a sustained development of

environment to protect the natural capital for long-term profits. Such energetic system keeps a dynamical equilibrium between electrical energy extracted and environment protection. In this balance are taken into account the following types of renewable energy resources: solar energy; solar radiation; wind energy; hydro energy; biomass. The possibilities to use hydro energy depend on the geographical and climate conditions. Several countries have a great potential in hydro electricity production. The Nordic countries have much potential comparing with others. The hydro-plants depend on the natural water cycle, in which the water evaporated due to solar radiation together with wind and clouds energy transportation falls back on Earth as precipitations. On the other hand wind energy is very popular in electricity generation, because of very high potential in many countries. In many cases the costs are comparable to conventional energy cost. In European western countries the wind is the main renewable energy resource.

Fig.1 Wind turbine and pico-hydro system

The photovoltaic effect means the direct change

of light in electricity by active use of solar energy. This is a completely new technology that was possible due to semiconductors technology improvements. Today, the solar energy is used today in many countries. ____________________________________ * Asist.eng. Ph.D – University of Petroşani

The biomass as an organic matter can be used directly (grass, grain, leaves, wood) or indirectly by fermentation (alcohol or the fuel oils). The use of biomass does not represent only a renewable energy source, but also an opportunity for rural places of a sustainable development.

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Revista Minelor - Mining Revue no. 2 / 2011

Fig.2 Biomass plant and solar panels

The achievement of an energetic system containing the main renewable energy sources integrated in the same location is an efficient and modern solution. So, in fig.3 is presented a renewable sustainable energetic system consisting of the main four energy sources power plants, like pico-hydro, wind turbine, solar cells and biomass.

It is not so easy difficult to combine more different power plants together because of the environment conditions of having sun, water, wind, biomass in the same area. But, it is possible to find some area where all the conditions or three of them can be created with a rational investment.

Fig.3 Energetic system: wind turbine, pico-hydro, photovoltaic panels and biomass

In order to apply the theory we consider a

natural environmental area, which has a surface, a relief with a valley and water, some forestry and land. This area can produce four kind of energy based on water, wind, solar and biomass.

The problem is if the investments are rational and efficient to be done. It is necessary to study the different renewable power plants in order to see which the best for the real conditions are. Also, it is necessary to modeling and simulation before draw the conclusions regarding the implementation.

It is necessary to draw an integration plan in order to implement a renewable energetic system. It is necessary to study the local microclimate for finding the methods for positive influences.

In fig.4 you can see typically area discussed above. This area is in Mountain and are a surface of about 20 km2, a valley with 35 degree slope, 40% of surface is covered by forestry and the albedo land.

The energetic productivity can be 0.025 W/m2 and this area can produce 500 kW. This is not so match, but is enough for the isolated houses.

This situation can be improved by a good management as in fig.4 and the energy production can be improved, by implementing a water turbine, some wind turbines, a biomass plant and some solar panels, so in one word a renewable integrated sustainable energetic system.

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Fig.4 Renewable sustainable integrated system - proposed situation

Modeling and simulation of an integrated renewable energetic system

The rain energetic process is a complex phenomenon and in a simplified view can be represented as having two closed loops, as we can see in fig.5. The first and main loop contains the following subprocesses: water and micro particles, land micro particles, evaporation, condensation, clouds microparticles and rain. The second loop contains the following subprocesses: land microparticles and clouds microparticles.

The inputs and outputs of each subprocess represent the relative transformation rates between water states: water, microparticles, steam, ice and rain droplets. In the block diagram above there are used the notations: qs – sun delivered energy; rp – rain particles forming rate; rmn – clouds microparticles forming rate; rm – water microparticles forming rates; rs – microparticles sedimentation rate; ran – clouds supply microparticles rate; rme – evaporation microparticles rate; rc – condensation rate; re – evaporation rate; zt – wind rate.

Fig.5 Simplified rain energetic process

An integrated sustainable renewable energetic system is an energetic system consisting of electromechanical equipments, unitary organized, in order to produce and distribute electric power using primary energetic resources obtained from a well delimited area. The principal elements of an energetic system are: interconnected electric power plants as micro-electric wind turbines, pico-hydro power plants, micro-solar electric power station together with distribution electric networking.

Based on these sources it is designed an integrated renewable sustainable energetic system.

The concept consists in designing an energetic system to produce clean energy like: solar, hydro, wind, biomass based environment and local microclimate.

For each subsystem (wind turbines, pico-hydro turbine and solar panels) was written a mathematical model and below is presented the model of an renewable integrated sustainable energetic system and simulation results (fig.6). As we can see, the electrical power depends on solar radiation, wind speed and water flow.

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Fig.6 Modeling and simulation of a renewable energetic integrated sustainable system

Conclusions

• The structure of an integrated sustainable renewable energetic system is presented in this paper. The element components of this system are: pico-hydro, wind turbine, solar cells and biomass plant.

• Before designing and implementation of a renewable system is necessary to develop a local climate study and an integration management plan.

• Another important step is the modeling and simulation of entire renewable system before start to implement.

• In most of the cases, the initial investments are recoverable and this solution can be very attractive for the future.

• Based on the principles presented above it is possible to establish a mathematical model to determine the optimum of the environment management in order to extract the maximum electrical energy.

References

1. Tabacaru-Barbu I.C., Pop E., Leba M. Study regarding integrated sustainable renewable energetic system design in local climate context European Symposium on Renewable Energy in European Universities of Architecture, Bucuresti, 2007

2. Pop E., Tabacaru Barbu I.C., Leba M. Modeling and simulation of integrated energetic parks in local climate context, microCAD International Scientific Conference, 22-23 March 2007, Applied Information Engineering, Miskolc, Hungary, pag. 213-218, ISBN 978-963-661-742-4, ISBN 978-963-661-754-7 3. Pop E., Leba M., Tabacaru-Barbu I.C., Buzdugan L. Optimal Renewable Energetic System Placement Based on Microclimate Energy and Environment III, Proceedings of the 3rd IASME/WSEAS International Conference on Energy & Environment (EE ’08), University of Cambridge, Cambridge, UK, February 20-22, ISBN 978 960 6766 43 5, ISSN 1790 5095, pp. 186-191, 2008 4. Tabacaru-Barbu I.C. Contributions Regarding the Modeling, Simulation And Implementation of Methods and Techniques of a Sustainable Integrated Renewable Energetic System Achievement Ph.D. Thesis, University of Petrosani, 2009

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XXIst CENTURY METALS Li, Te, Se, Nb-Ta NATIONAL SITUATION

Grigore BUIA*, Csaba LORINŢ**

Key words: lithium, tellurium, selenium, niobium, tantalum, national resource / reserve Introduction

As noted in the previous article "Li, Te, Se, Nb-Ta - XXI CENTURY METALS?", beginning of the third millennium placed under the sign of the new information era, is dependent on new mineral resources. Thus, metals such as Li, Te, Se, Nb-Ta, through their properties and uses of modern technology, generate a increasingly large demand on the market, is also a challenge for the mining industry. With this new approach, the authors aim to highlight the national potential with regard to these new resources.

Commonnesses, History, Breviary

Lithium Lithium was discovered in 1817 by Johan

August Arfvedson Stockholm, Sweden. The metal itself was isolated in 1821 by William T. Brande. The first lithium minerals discovered were spodumen and petalit and have been found on the Swedish island of Uto by the mineralogy Joze Bonifacio Andrada e Silva, during a tour made in Europe in 1790. [5].

In 1817, Arfvedson analyzed petalit and realized that it contained a previously unknown metal, calling it lithium because he came from a stone. He announced the discovery in 1818, identifying lithium as a new alkali metal and alkaline version lighterr than sodium. Will discover later that lepidolite and spodumen also contain lithium [5].

Lithium is found in reservoirs evaporative and pegmatic, small amounts of lithium are found in ocean water and some living organisms. The main use is in the manufacture of lithium batteries and Li-Ion batteries, considered the most durable, reliable and environmentally friendly. Lithium is also used as alloys in aerospace engineering and nuclear physics: the lithium atoms fission was the first nuclear reaction carried out by the mankind, and lithium deuterit is fuel for thermonuclear weapons [4].

____________________________________ * Prof.eng. Ph.D. – University of Petroşani ** Asist.eng. Ph.D – University of Petroşani

Tellurium Tellurium has been discovered in Romania in

1782 by Austrian scientist Franz-Joseph Müller von Reichenstein. Tellurium is relatively rare (Clarke 0.0018 ppm.) and is usually found in combination with other elements (gold, silver), forming telluride. Tellurium appears as isomorphic placeholder for lead, Tellurium as selenium, focuses exclusively in magmatic deposits belonging to hydrothermal phase.

Tellurium as selenium, is concentrating exclusively in magmatic deposits, belonging hydrothermal phase.

Just because of the rarity, pure, tellurium is very expensive. Estimated, the minimum exploitable gold-silver telluride is about 15 ppm. [6].

Tellurium is a silver semi-metal with hexagonal crystal structure. It is considered to be of relatively low toxicity, but it is recommended to avoid long exposure to tellurium, in particular to prevent inhalation exposure. Among the many uses of tellurium, can be mentioned: energy industry (thermoelectric devices), steel processing, coloring glass and plastics, metal alloys (due to its ductility), solar panels and semiconductor manufacturing, etc.. [4].

Selenium Selenium was discovered by Berzelius in

1817, and studied further by other researchers. Chemically speaking, selenium is very close to the sulfur, which it greatly resembles. Origin of the name derives from the Greek word Selene (moon). It forms its own minerals but not exploitable accumulations. Selenium is found predominantly in galena and chalcopyrite, where it appears as isomorphic substitute of sulfur.

Estimative, the minimum exploitable. is about 20 ppm [6].

Selenium increases its conductivity easily a thousand times when it is moved from darkness to strong sunlight, which is used to build it luxmeter. It is also used in the manufacture of photoelectric cells, cameras, copiers, and electric current recovery, etc..

Salts (ex. mercury selenite) were used in laboratories for medical analysis, for determination of total nitrogen in the blood / serum [4].

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Niobium Niobium or columbium is a rare metal, hard,

flexible, light gray color, shiny, highly resistant to corrosion. Niobium is used in the manufacture of stainless steel in electrical engineering, in radio electronics, etc.., niobium alloys, are currently enjoying particular attention due to a remarkable resistance to high temperatures. The best results are obtained by alloying niobium with hafnium, molybdenum, vanadium and zirconium. Thus, for the engine combustion chambers of the rocket C-103 alloy is used, containing 88.3% niobium, hafnium 10%, 1% 0.7% titanium and zirconium. In the case of the spacecraft with slow reentry into the atmosphere, control surfaces are made from alloy B-66 mark, with the following chemical composition: 89.5% niobium, molybdenum 5%, 5% vanadium and 0.5% tantalum.

Tantalum Tantalum is used for weights for scales and

vacuum tube filaments. Appears in the form of compounds and is solid at room temperature. Tantalum alloys are intended for aerospace construction. Tantalum alloys with hafnium, niobium, titanium, vanadium presents very good mechanical properties at high temperatures. As an example is tantalum-hafnium alloy, which contains 20% Hf, which owns the 1.2000C, tensile breaking strength of 42 daN/mm2. For the construction of cosmic rockets it is used T-222 alloy which contains: 87.5% tantalum 10% tungsten and 2.5% hafnium.

According to data presented in the first report made so far in the EU, published on 17 June 2010 concerning access to mineral raw materials, niobium and tantalum are also part of a list of 14 raw materials that are considered to be "critical" for the European industry, with antimony (antimony), beryllium, cobalt, fluorine, gallium, germanium, graphite, indium, manganese, platinum metals, rare earths, tungsten (tungsten). [3].

National situation

Telurium Telurium is present as a minor element in

galenea, chalcopyrite and pyrite associated with laramic and neogen deposits in particular in: Băiţa Bihor, Coranda, Ilba, Cavnic-Bolduţ etc., where it appears in average content of between 40-120 ppm. [6]

Tellurium also appears in neogene sulfosalt volcanoes from Băiuţ (As, Cd, Ga, Tl ± Se, Ge, Te, Co, Ni, Cr, Ti) [1], and Văratec (As, Cd, Bi, Te, Co, Ni, V, Ti, W) (Borcoş M., 1984) [10] from Gutai Mountains and Ţibleş (Cd, Mn, Ti, F, I) [9],

where it can be recovered along with other elements.

At Sacaramb, together with gold-silver telluride, was also revealed in sulfosalts (As, As, Bi, St, Te, Co, Ni). [2].

In mineral form in România this element was identified at Săcărâmb, Cordurea, Musariu Nou, Faţa Băii şi Vâlcoi, as it follows:

At Sacaramb in the Metaliferi Mountains, in Brad-Sacaramb neogene volcanoes,in sarmatian - Sacaramb Sarmatian series, with Au and Ag, together with Pb and Zn in hydrothermal deposits of Miocene age.

Host rock is composed from andesite and biotite quartz with hornblende, propilitic, adularitic, argilitic in venis deposit oriented to NE and NW and which form a network in the middle area of the central volcanic device. The chemical composition is: Au, Ag, Te ± Pb, Zn, Cu and secondary Cd, Ga, In, As, Sb, Bi, Se, Sn, Co, Ni, and the mineralogical composition is: pyrite mispichel, blend, galen, chalcopyrite + nagyagite (Pb5A(Te,Sb)4S5-8), krenerite (Au,Ag)Te2) sylvanite (Au,AgTe4), altaite, frohbergite (FeTe2), hessite (Ag2Te), petzite (Ag3AuTe2), tellurium, tetrahedron, boulangerite, jamesonite, antimonite, native arsenic distributed differentiated on groups of seams, the mentioned association being dominant in their lower parts. [8].

At Cordura in the Metaliferi Mountains, in the Brad-Sacaramb neogene volcanoes in neogene andesitic volcanic complex structure in cretaceous sedimentary formations, from a complex of Mesozoic alkaline rocks.

Host rock is composed from quarztifere andesitic with hornblende and biotite, sarmatian-panoniene, propilitizate, argilizate, sericitizate, adularizate, silicifiate. The deposit presents as veins with Au, Ag ± Pb, Zn, Cu, Te, Cd, Sb, Hg, Ti, Mn, As of hydrothermal origin. From the mineralogical point of view, the deposit contains pyrite, tetraedrite, bornite, bournonite, calcopyrite, galene, nagygite (Pb5A (Te,Sb)4S5-8), hessite, gold, marcasite, realgar, cinnabar (Berbeleac I., 1984) [10].

At Musariu Nou in the Metaliferi Mountains, in the neogene volcanoes in the Brad-Sacaramb area, in a subvolcanic body neogene andesitic. Host rock is composed from andesite - andesite-cuarţifere Badenian-Sarmatian, propilitizate, cloritizate, adularizate, sericitizate, argilizate, silicified, sandstone marl, etc. The deposit form is also veins with impregnations. From the elementary point of view are distinguished Au, Ag ± Pb, Zn, Cu, As, Cd, Mn, Ti, Se, Te, Tl, Sn, Ga, Co, Ni, V ± Bi, Sb, Mo, Cr, B minerals such as pyrite, mispichel, chalcopyrite, blend, tetraedrite, galena, frohbergite (FeTe2), weisite, sylvanite (Au,AgTe4),

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nagyagite (Pb5A (Te, Sb)4 S5-8), krenerite (Au, Ag)Te2), calaverite (AuTe2), montbrayte ((Au,Sb)2Te3), telur, petzite (Ag3AuTe2), hessite (Ag2Te), empressite (AgTe), altaite (PbTe) etc. in associations characteristic of gold-telluride (M. Borcea, 1984) [10].

At Faţa Băii in the Metaliferi Mountains, in Zlatna-Stănija volcanic area in the veins of hydrothermal origin with nagyagit (Pb5A (Te, Sb) 4 S5-8) and tellurium.

At Vâlcoi in the Metaliferi Mountains, Rosia Montana-volcanic area Bucium Baia de Aries, stationed in Cretaceous sedimentary formations are hydrothermal veins with Au, Ag ± Te, Pb, Zn, Cu (M. Borcea, 1984) [10].

Selenium Selenium in its elementary form was notified

as a minor component in the sulfosari* associated to the hydrothermal volcanism from Baia Mare area (Nistru, Cavnic, Heja and Băiuţ) and the South Apuseni (Pârâul lui Avram, Deva, Valea Morii-Barza), with levels ranging from 42-65 ppm average. [6]

In mineral form, this element was identified in Romania in Certej and Sacaramb selenide in as: eucairit (CuAgSe), Naumannite (Ag 2Se) and klockmannite (CuSe), hydrothermal veins in quartzite of gold-silver telluride associated to andesites belonging to the Neogene calc-alkaline magmatism from Metaliferi Mountains [7]

Lithium Lithium has been reported in Romania Getic

area in Sebeş-Lotru group form Sebes Mountains, in metamorphic pegmatite at Conţu Superior-Orata. Deposits of Proterozoic age environment with biotite paragneiss, kyanite, gneiss and schist anfibolice, have veins with spodumen pegmatit (LiAl [Si2O6]). Chemical analysis revealed the Li2O content (0.84%), K2O (2.02%), Na2O (4.17%), minerals such as oligoclas, microcline, pertite, albite, spodumen, quartz, muscovite, biotite, apatite, garnet, epidote, zeolites (Hârtopanu I., 1984) [10].

Niobium and tantalum have not been reported in Romania neither mineral or elemental form.

Areas of economic interest for the elements Li, Te, Se

1 – Gutâi-Ţibleş Mountains (by minor elements); 2 – Metaliferi Mountains (by minor elements); 3 – Metaliferi Mountains (by own minerals);

4 – Sebeşului Mountains

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Conclusions

The beginning of the third millennium, placed under the sign of the new information era, is dependent on new mineral resources. Thus, metals such as Li, Te, Se, Nb-Ta, through their properties and uses of modern technology, generate a demand increasingly large market, being also a challenge for the mining industry.

In the current world situation, Romania could be a leading provider of tellurium and selenium from minerals, concentrates and quartered in mining waste ponds and waste dumps of old mines associated with them.

Regarding lithium occurrence in Romania remains a potential source requiring detailed exploration works, while niobium and tantalum have not been reported in our country neither mineral or elemental form. References

1. Borcoş M., Gheorghiţă I. Revue roumain de geologie et geophysique, Geography, Geology, 20, 2, Bucureşti, 1976;

2. Ciobanu C., Cook N., Damian Gh., Damian F., Buia Gr. Telluride and sulphosalt associations at Sacaramb – “Gold-Silver-Tellurid Deposits of the Golden Quadrilateral, South Apuseni Mts., Romania, 31 st. aug. – 7 sept., 2004” – IAGOD Guidebook Series 12;

3. http://ec.europa.eu/commission_2010-2014/tajani/hot-topics/raw-materials/index_ro.htm

4. http://ro.wikipedia.org

5. Emsley J. Nature's building blocks: an A-Z guide to the elements, Oxford University Press, 2003, ISBN:0198503407, pag. 236/560;

6. Chesu M. Elemente minore in minereuri neferoase din Romania, Ed. Tehnica, 1983;

7. Popescu C. Gh., Neacşu A., Cioacă M., Filipescu D. The selenium and Se-minerals in the Săcărâmb ore deposits – Metaliferi Mountains, Romania;

8. Udubaşa G., a.o Arhiva IGG, 1981-1983;

9. Udubaşa G., a.o. Analele institutului de geologie şi geofizică, LXI, 1984;

10. V. Arsenescu, C. Biţoianu, I. Berbeleac, T. Berzea, M. Borcoş, S. Bordea, S.G. Boştinescu, I. Dinică, H. Hann, P. Hârtopanu, I. Hârtopanu, I. Intorsureanu, H. Krautner, D. Jipa, C. Lazăr, M. C. Micu, M. Mureşan, L. Nedelcu, S. Peltz, S. Radan, D. Russo-Săndulescu, M. Săndulescu, G. Udubaşa Harta substanţelor minerale utile (ediţia a II-a) Partea a doua, Sistematizare Gitologică

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STUDY OF NICKEL ON STEEL CATHODE USED FOR WATER ELECTROLYSIS

Ioan DUMITRESCU*, Camelia STĂNOI**, Nicolae KANDO***

Abstract: Present paper presents a study of Ni/steel cathode, used in alkaline water electrolysis. Continuous cathodic electrolysis of a nickel coated steel electrode in a saturated NaOH aqueous solution were carried out to assess the electrode’s durability. The electrode’s potential under the same operation conditions was exponentialy dependent of the current density. Key words: alkaline water electrolysis, cathode, hydrogen, potential, steel, nickel

Introduction

Hydrogen and oxygen evolution, by water electrolysis, is a process of great technological importance since it solves the problem of conversion of electrical energy, into hydrogen.

Research into water electrolysis has concentrated mainly on the development of catalysts lowering the voltages involved in the process.

The electrodes for most of all types of the electrochemical cells need to be stable, i.e., to be insoluble, for anodic and cathodic reactions; the anodic reactions are oxygen evolution and/or chlorine evolution, and the cathodic reaction is usually hydrogen evolution.

Therefore, steel substrate with nickel coating is the most popular configuration and is utilized as both of anode and cathode; Ni/steel electrodes are produced by nickel electroplating.

In this study, we focused on H2 and O2 evolution behaviors of the Ni/steel electrode prepared at different temperatures.

Ni/steel electrodes were prepared by electrodeposition: NiSO4•7H2O……….250-310 g/l NiCl2•6H2O………….50 –60 g/l H3BO3…………………40-45 g/l

The bath’s temperature was of 25 °C and current density of1A/dm2.

As a substrate steel was used. This is highly corrosion resistive at low temperatures. Polarization curves were measured in the wide potential range where H2 evolution occurred. ____________________________________ * Prof.eng. Ph.D – University of Petroşani ** Physicist Ph.D. – “I.G. Duca” school Petroşani *** Eng. – “I.G. Duca” school Petroşani

Constant current electrolysis

The catodic electrolysis of the electrode was carried out using a conventional three-electrode cell equipped with a platinum plate counter electrode and a calomel electrode as reference electrode. A 6 mol dm−3 NaOH solution was used in both the working and reference compartments, which were connected each other with a liquid junction. The potential of the electrode and the cell voltage between the working and counter electrodes were monitored during the electrolysis.

Commercially available electrochemical instrumentations such as a potentiostat/galvanostat and two digital multimeters were used for all experiments. Temperature was controlled within 293 K using a thermostat with circulating water. Results and discussion

The electrode showed a low decomposition potential (980 mV) for H2 evolution compared to the uncovered steel electrode, as shown in fig. 1.

Nickel on steel electrode is better than steel, on the electrocatalysis for H2 evolution. However, for H2 evolution the coating layer, nichel is a good catalyst for H2 evolution. Hydrogen evolution potential and cell voltage is presented in fig. 1

Equation for curve that fits the experimental data is : Model: Exponential Equation: j =A+ B*exp(R0*V) (1) A= -22.0865 ± 15.43039 B= 0.16226 ± 0.08045 R0 = 0.00522 ± 0.00035

The above equation (1) shows that current density j(mA/cmp), depends exponentially of electrode’s potential(V). The constant A in equation(1) is not part of Butler -Volmer equation, and it might be the missing part in theory, that shows that “j” is a function of electrode’s material (Z), and of concentration of the electrolyte.

The potential and the current density values are listed in the table below (tab.1). As can be seen the potential decreases as the electrolyte’s temperature rises.

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Table 1 Potentials and current densities for Ni/steel hydrogen electrode

960 980 1000 1020 1040 1060 1080 1100 1120 1140 1160 1180 1200 1220 1240 1260 1280 1300 1320 1340-1 0

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

1 1 0

1 2 0 B

U (m V )

j(mA

/cm

p)

C a to d d e o te l n ich e la t

Fig. 1 Current potential curve for Ni on steel

Figure 1 shows the potential of an Ni on steel

electrode vs. current density at 293 K. The cathodic curve, corresponding to

hydrogen evolution from basic aqueous solutions, show a decrease of 100 mV for the overvoltage, compared with steel electrode.

The current density of Ni/steel electrode, for hydrogen evolution, in a 6 mol dm-3 NaOH solution, increases as cathodic potential increase.

Therefore, the Ni/steel electrode is expected to posess a high durability in the alkaline solution.

For a cathode made of steel, that is currently used in commercial electrolyzers, the equation j(V) is: Model: Exponential Equation: j = A + B exp(R0*V) (2) A = -104.31084 ± 12.77676 B = 20.48325 ± 5.29357

The potential values for steel are listed in the table below (tab.2). As one can see, these values are higher than those for steel with electrodeposited nickel, at the same current densities.

Table 2 Potentials and current densities for steel electrode

J(mA/cm2) 10 20 30 40 50 60 70 80 90 100 150 200

Votel(mV) 1010 1061 1104 1149 1182 1224 1258 1290 1320 1368 1540 1660

Conclusion

It has been shown that the overpotential for water electrolysis decreased with 100 mV.

A Ni/steel coated electrode shows little variation in hydrogen evolution potential, during

constant current electrolysis, in a NaOH solution. The consumption rate of the coating is relatively small.

However, the electrode has a high durability for hydrogen evolution in the concentrated alkaline solution. A Ni/steel system is expected to apply for

J(mA/cm2) 10 20 30 40 50 60 70 80 90 100 150 200

V20°C(mV) 1015 1045 1083 1120 1156 1184 1209 1240 1270 1296 1440 1540

Vsteel(mV) 1010 1062 1104 1149 1182 1224 1258 1290 1320 1368 1540 1660

Vsteel– VNi/steel -5 17 21 29 26 40 49 50 50 72 100 120

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both of hydrogen evolution cathodes, and for oxiygen electrodes, used in alkaline water electrolysis, for hydrogen gas production.

Compared to steel electrodes, steel with electrodeposited nickel, decreases the potential for

the same current density. The average of potential reduction, is between 8.6 % and 26.38 %, as the current density increases. The amount of hydrogen is higher, as “j” increases.

Table 3

j ( mA/cmp) 10 20 30 40 50 60 70 80 90 100 150

V(mV) 8.6% 7.9% 9.3% 10.3.% 11.75% 13.48% 14.94% 15.89% 16.97% 19.15% 24.02%

That means that Ni/steel, used as hydrogen

electrode, lowers the electric energy costs and increases both of electrolyzer’s efficiency and the hydrogen production. References 1. Otogawa R., Morimitsu M., Matsunaga M. Electrochim. Acta, 44, 1509 (1998).

2. Stănoi C. Energetica electrolizei apei Ed. Universitas, Petroşani, 2007 3. Kunihiro T., Morimitsu M., Matsunaga M. J. Appl. Electrochem, 30, 359 (2000) 4. H. Journal of New Materials for Electrochemical Systems 7, 323-327 (2004) 5. Journal of New Materials for Electrochemical Systems 7, 323-327 (2004)

12


DLC-1, 2 AND 3 CABLE CONNECTING DEVICE COST REDUCTION BY DESIGN IMPROVEMENTS

Iosif DUMITRESCU*, Vilhelm ITU*, Adrian SUCIU**,

Rodica COSTANDOIU***, Cătălin GĂMAN****

Abstract: DLC-1, 2 and 3 cable connecting devices are used in the winding installations, to safely fix the winding cable to the extraction vessel (cage), with a safety coefficient higher than 8. The paper shows new device design solutions, leading to simplification and standardization of solutions from technological point of view, without decreasing the safety coefficient, improving technical performances and their costs. Key words: cable connecting device, design improvement Cable connecting device design and operation

Cable connecting devices are known to be very important from extraction point of view. They are subject to significant static and dynamic loads during the extraction process. Moreover, additional strains can come up in the form of transversal, longitudinal or torsion oscillations, due to incorrect mounting or excessive wear of the shaft guiding devices.

Connecting devices are classified function of design and function of the extraction cable used.

From the point of view of cable retaining manner, connecting devices fall into tightening devices and self-tightening devices.

Self-tightening devices can be carried out in several design variants, but for this paper we chose the ones with the cable wedged on one side. (Fig. 1)

DLC-1, DLC-2 and DLC-3 metal self-tightening cable connecting devices, of round section and one side wedging, are used to safely fix of winding installation cables of extraction vessels, with minimum 10 safety coefficient.

Design and operational characteristics of DLC-1, DLC-2 and DLC-3 devices shown in Fig. 2 are given in Table 1.

When ordering, it is required for the beneficiary to give the d cable diameter, the D bolt diameter and the Gt width of the extraction vessel rod.

____________________________________ * Assoc.prof.eng. Ph.D – University of Petroşani ** Eng. Ph.D S.C. CNH S.A. Petroşani *** Eng. Ph.D University of Petroşani **** Eng. S.C. Electroutil Aliser S.R.L. Aninoasa

Fig. 1 Cable connecting device with one side

self-tightening , the previous solution ]

DLC-1, DLC-2 and DLC-3 type cable connecting devices are one side wedged core design variant. The extraction cable is wrapped around the, 9, feather shaped metal core.

The core can slide inside into a metal structure made up of left-right shields, 4-5 reference points and right-left jaws, 3 and 6 reference points, which are made rigid one against the other by means of special 7 screws and 8 adjustment pegs. Adjustment peg are intended to provide execution and precise positioning of elements in the mechanical resistance structure in view of ensuring the wedging angle.

Right jaw, 9 reference point, is inwardly provided with a groove similar to the one on the core, which together provide the cable’s wedging surface. The two cable fixing surfaces are lined with an anti-friction alloy based on lead and tin, providing cable protection against crushing.

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Fig. 2 Cable connecting device, with one side self

tightening, the new solution

The higher the suspended load, the more significant the friction force between the cable and the two surfaces. In the lower side, the shields are provided with holes for the main bolt, 13, reference point, which provides the connection with the extraction vessel. The principal bolt is mounted in the gland of 15, the main bolt gland, which allows the use of various bolt diameters, without processing the boreholes in the shields, the bolt’s

mounting diameter being obtained only by processing its inside.

Moreover, the gland has also the role to protect boreholes in the shields against becoming oval i the area where there might be direct contact with the main bolt.

The main bolt is fixed on the one hand with the help of a stopping plate, 12, which also hinders the bolt to be twisted, and on the opposite side by means of 14, an inclined wedge.

The boreholes centers in the shields, that is the centre of the main connecting bolt matches the cable axis, which is accomplished by adopting the right thickness of the 19 guiding rules, function of the cable diameter in the (d...d’), cable group, the rule’s thickness variation is 2 mm.

In order to provide the cable’s fixing capacity, in the device, as an additional possibility, the free end of the cable was fixed in a pair of 1, clamps, leaning on the upper part of the shields.

By guiding the cable on the lined centre, and fixing it between an elastic element 16, and a fixed guidance 17, the fatigue of the cable in the area of entering in the device is reduced, the number of broken wires of the cable in the respective area being less.

De-wedging of the core, which is releasing the cable from the device case, is made by detaching the clamps 1 from the cable and the nuts from the 18, dowel pin, and pushing the core downwards. The travel distance is limited by the right and left lugs, 10 and 20.

The 11, label is used to identify the cable connecting device.

Table 1 Characteristics of DLC-1, DLC-2 and DLC-3 cable connecting devices

Value Nr. crt. Characteristic Unit DLC-1 DLC-2 DLC-3 1 Maximum static load ton (kN) 10,2 (102) 17,5 (175) 27 (270)

2 Cable diameter, d mm 25; 26…30 31…35

36…40; 41…45

46…50; 51…55

3 Cable wrapping radius , R mm 173 220 270 4 Cable fixing modality - One-side self-tightening 5 Bolt diameter, D mm 70; 80 80; 90 90; 100; 110 6 Space btw. shields, S mm 55 60 70

height, h mm 120 160 200 width, l mm 190 250 300 7 Shield dimension

(in bolt area) thickness, s mm 20 28 35 height, H mm 1141 1445 1775 width, L mm 520 670 820 8 Clearance gauge dimensions thickness, G mm 202 233 262

9 Weight without cable pulling device and cable grips kg 181 376 649

10 Space btw. cable axis and B, pulling device screw axis mm 110 141 166

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The cable pulling device, Fig. 3, is only used to connect the cable in the unit, to pull the cable end through the unit. This should not be ordered for each device, given that they are interchangeable and can only be used in the mounting of the device. To mount the winding cable to the connecting devices, for each typo-dimension, cable pulling devices are required.

The main component parts of the cable pulling devices are shown in Fig. 3.

Fig. 3 Cable end pulling device

The cable pulling device is made up of a threaded axis, provided with a square thread Pt 36x6, on which the nut 22 moves. By a parallel wedge, 26, the threaded axis slides in support 25, which in its turn is fixed to the cable connecting device, to the right jaw, 3 by means of M16 fixing screw, 27 reference point.

The extraction cable, which will be pulled, is fixed in the 23, fixed collar and 24, clamp.

The fixing groove of the cable is function of its diameter, per diameter groups.

By manual actuation of the 22, nut, the relative movement of the entire mechanism is ensured, that is pulling the free end of the cable of the winding installation.

Checking the idle operation, in both senses, of the free cable end pulling mechanism, is done by manual actuation of the lever of a fixed wrench over the coupling nut, with less than 50 N actuation force.

The cable connecting devices should provide interchangeability of component elements, to avoid cable wear and slipping of the cable. To this end, the surfaces of the fixed jaws and metal core, touching the metal cable, are covered with a 3,5 – 4 mm thick Y-Sn10/STAS 202-86 antifriction alloy layer. Similarly, the main bolt and its glands in the shields should not show plastic deformation in the contact area, as a result of operation.

The main elements (right shield, left shield, main bolt, metal core, fixed jaws) should be sized in such a way as to have a higher safety coefficient than 10 at maximum load.

The scaling of the cable connecting device, in view of warning against cable crushing, is done by carving 1,2 and 3 marks (Fig. 1, from B) on the core on the lower edge of the lug, on both sides, in the following way:

- for division 1, a minimum diameter gauge of the cable range for which the device was made(25; 26; 31 mm for DLC-1, 36; 41 mm for DLC-2 and 46; 51 mm for DLC-3), is inserted in the groove made between the core and the right jaw, and the core is tightened until the gauge is blocked. Division 1 shows the correct operation of the device;

- for division 2, a 3 mm thick plate is inserted between the core sides and the right jaw and the core is tightened until blocking. Division 2 shows the limit for the use of the devices;

- for division 3, a contact is made between the core and the right jaw, tightening the core by means of the dowel pin’s nut. Division 3 shows the complete crushing of the cable and the device’s self-blocking.. Design and technology improvement of devices

The shields are basic elements of the cable connecting devices, playing both a part in the structure, being a support for the assembling of the other reference points, and in the resistance, transmitting the cable traction force from the cable to the bolt.

Fig. 4 shows the two design solutions, the original one, Fig. 4a, and the improved one, Fig. 4b.

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Fig. 4 Shield design variants

In the initial variant, the inside shield surface was milled, to gain the two support thresholds for the jaws, the shields’ assembling holes having H7 tolerance, using screws for centring.

For the new variant, for which the execution documentation was drawn up, these disadvantages were eliminated, thus having:

- more than six times reduction of energy, tools and manoeuvre consumption, for 2148,17 cm3 initial value of the volume to be cut, and 357,47 cm3 or the improved variant, for DLC-1;

- a 42% increase of cross section of the shield plate from 190x14 mm to 190x20 mm, DLC -1;

- centring holes on the screw body, both on jaws and on shields were removed, being replaced by pass-through holes, and centring is done by means of two pins; this led to the use of standardized screws and pins, that is reduction of shield and jaw processing manoeuvre and cost;

- the contact area between the inclined jaw and the shield increased by 5% to reduce contact pressure;

- the connection radius between the plate and the body of the shield increased, from 100 to 150 mm, to reduce the tension concentrator, for DLC-1.

The shield weight increases by 9,2 kg, and the pulling device of the cable end by 11,4 kg, respectively, but this disadvantage is partially eliminated by its demountable structure. The device weight increase is actually less than 5%.

The groove of the metal core and jaws, used to tighten the cable, is covered by a 3-4 mm layer from Y-Sn10/STAS 202-86 anti-friction material, applied by casting. This layer of material has the role to protect the cable wire from crushing.

To prevent the applied layer from exfoliation, in the initial variant, Fig. 5a, 8 mm diameter and 15 mm deep holes were made, with 30º inclination, all along the length of the groove controlled.

This is a difficult, high manoeuvre technology, and their degree of filling with molten material cannot be controlled.

Fig. 5 Metal core design variants

In the improved variant of the cable connecting device, these disadvantages were eliminated, by penetration holes for the cable in the groove, Fig. 5b.

This is easily done before the milling of the cable groove, and allows the filling degree with molten metal to be controlled.

Figure 6a shows the design of the inclined wedge grip, which did not have protection layer against cable crash. The additional blocking of the cable end is made with a screw and two clamps, one fixed, the other mobile; this solution may lead to a cable shear strain in the respective area.

Fig. 6 Wedge grip design variants

Similarly, additional blocking of the cable end can be done only after cable end pulling device is demounted.

The metal core tightening lever arm between the wedge grips was reduced and transferred to the vertical wedge grip, to improve the device’s working manner.

Fig. 6b shows the new solution for the inclined wedge grip, simpler and easier to be developed, and Fig. 6c show the new solution for the vertical wedge grip.

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An essential improvement brought about to the cable connecting devices to the vessels of the winding installation, is the separate structure of the cable end pulling device, Fig. 7, in view of tightening the cable in the unit. In the previous cable connecting devices, this device was included in the device structure.

Fig. 7 Device to pull the cable end

In the previous cable connecting devices, this device was included in the design of the device on the inclined wedge grip (Fig. 6).

In the new ones, it is a separate design, and the same cable end pulling device can be used for all DLC devices, only by changing the cable fastening jaws. Conclusions

When a new documentation is drawn up, for the execution of the DLC-1, 2 and 3 cable connecting devices, the following improvements were established:

- cutting down the shields’ processing surface; - using standardized screws and two centring

pins to position the jaw against the shields, removing the holes and special screws with centring bodies;

- using a device for independent pulling of the cable end, apart from the device structure;

- anti-friction alloy protection lining, all along the metal core groove, and simplification of it fixing solution on the cable groove;

- support arm for core wedging was taken from the inclined jaw and was attached to the vertical jaw, thus the design solution was simplified, the arm length and the load momentum of the jaw were reduced;

- glands were mounted in the bolt holes, resulting in rapid adaptation of the device to the extraction vessel rod, and in the increase of the duration of use of the device by replacing the oval shaped hole gland by the bolt;

- improvement of the bolt fixing solution against the shields, by double fixing, at both ends;

All these improvement resulted in manoeuvre and manufacturing cost reduction and improvement of technical characteristics of the cable connecting devices. References

1. Dumitrescu I., Jula D., Kovacs I., Cozma B. Numerical analysis of cable connecting devices for one side wedged winding engine vessels, KOD 2008, Proceedings, The Fifth International Symposium about forming and design in mechanical engineering, ISBN 978-86-7892-104-9, pag. 195-198.

2. Dumitrescu I., Jula D., Itu V., ş.a. Execuţie desene pentru piesele de schimb vase de extracţie (DLC, tije, arcuri, DEC şi DLCLE), Contract 193/2008ASL cu C.N.H. Petroşani.

3. Magyari A. Instalaţii mecanice miniere, Editura Tehnică, Bucureşti, 1990.

4. Muscă G. Proiectarea asistată folosind Solid Edge, Editura Junimea, Iaşi, 2006.

5. * * * Solid Edge Software v.19, Academic license ADA Computers Bucureşti.

17


STATE AID FOR COAL MINING INDUSTRY

Cristian Marcel FELEA* Abstract After December 31, 2010, EC Regulation 1407/23 in July 2002, which regulated the forms of state aid for European coal industry has expired. The European Commission has examined through specific institutional mechanisms, either the opportunity to extend the provisions of the regulation, or approach a new paradigm, by shifting from the sector rule to of application to the general rule of the state aid. It was chosen, with the majority of Member States under the Treaty of European Union Training (TFEU) for the second approach. Problem definition at the debate moment

The negotiations at institutional level between representatives of member states, were based on the following topics proposed by the Commission officials: (i) the possibility to close the coal mines in several Member States, (ii) the social impact of mine closure, (iii) the impact of mine closure has on the environment and (iv) the impact on security of energy supply.

Regarding to the first theme discussion, the European Commission data showed that in Germany, Romania and Spain, the production costs for coal mining are very high compared with the prices (current or expected) market. A bit improved, but with a negative estimation for the future, is the industry situation in Hungary and Slovakia. For these reasons, access by the general state aid could be a valid option.

The most sensitive topic of discussion was that of the social impact, especially because in an important country such as Germany between employers and Government on the one hand, and unions, on the other hand, there is a social pact which includes commitments to preserve jobs until the year 2018. Available evidence from the Commission in 2010 indicated that, without state aid, 42,000 jobs (in countries such as Germany, Romania, Spain and possibly Hungary) may be threatened directly and another 55,000 indirectly. If the impact of these numbers, at the Union level is not significant, instead to the mining areas it is dramatic. And, more importantly, creating of large flows of redundant workers in these regional markets would be impossible reabsorbed in other ____________________________________ * Eng. Ph.D. – University of Petroşani

sectors. Environmental impact of mine closure is not

considered significant. This assumes, however, the closed areas rehabilitation, which brings a financing problem that must be taken into account in the economy of solving problems.

Regarding coal energy supply security, the analysis started from the restricted contribution of subsidized coal to global energy sources of the Union. In 2010, the subsidized coal production to been the source of 5.1% of EU electricity production. Moreover, if taken into account only the type of state aid for covering loss of production (for Romania), the figure is reduced to 1.4% for the whole Union, with the remark that for some of those countries the figure is obviously higher. But coal can be imported from a variety of exporting countries, and in recent years coal supply on the market rose on average with 7% annually. In these circumstances it was considered that an additional aid for the security of supply problems would be worthless. Specifically, the Commission considers that it can be more effective building up stocks of imported coal, rather than the production of subsidies.

The Commission has redefined in debates the strategic objective as being related to promoting for the future, of transition to an energy policy based on renewable and sustainable use in terms of the environmental protection for indigenous energy sources.

At the same time, the evaluation of the possible scenarios for the best policy approach to the granting of state aid after 2010 for the coal mining industry was based on minimizing the potential negative impact of the mines closure, as a result of the elimination of subsidies, especially in terms of social and environmental issues, at the same time reducing as much as possible the effect of distortion of competition within the Union's internal market. Scenarios considered

The first option was that of accessing state aid in accordance with norms generally valid in the EU. This scenario, as zero option was not seriously considered, according to the policy objectives outlined above. This scenario would have assumed that it will no longer be adopted a new legal instrument specifically, after the expiry of Regulation 1407/2002.

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The second scenario was based on Article 107, par. (3), lit. (c) TFEU, under which Member States would have to grant aid for the close of the activity, limited to: aid to cover payments for employees who are redundant or early retirement, retraining costs for the labor and counseling of those left without jobs. The costs may also be supported to complete the contracts that are in progress (up to 6 months) and for the greening of the perimeters where the closure took place. These types of aid could be granted up until the end of 2013.

In of the third scenario, based on Article 107, par. (3), lit. (e) TFEU this time, it is considered that Member States may grant aid for mines operation in a decreasing scale, in order to cover losses related to current production, as long as it is accompanied by clearance activities in a well defined closure plan; stating that the aid would only cover the existing mines in operation on request. The scheme would have supposed a gradual elimination of aid operation for a period of not more than 10 years, with a degressivity of 10% per year.

Scenario four is also based on Article 107, par. (3), lit. (e) TFEU, which would allow Member States to grant aid to social costs (social benefits for employees and former employees) and environmental issues related to the closure of coal mines and the rehabilitation of former mining.

The fifth option is a combination of options 3 and 4. Thus, it could enable Member States to provide support both to closure (as in option 3) as well as aid to cover exceptional costs, as in scenario 4.

The sixth scenario was considered to extend for another 10 years of Regulation no. 1407/2002. For this scenario all Member States were strongly interested.

From the comparative analysis of scenarios outlined above, during the debate the following issues were highlighted: a) The second option was that which the European

Commission has proposed and supported as basic option. This option would provide the opportunity to move to closure of mines and even to extend the closing deadline to complete the contracts the mine had already completed and should be honored. In this alternative can be organized more correctly also the social aspects of closure by providing direct support to affected workers, and environmental debt financing during the closure would be provided.

b) The third option would not save the permanent workplaces, but may allow a gradual reduction of labor. The aid to reduce the production of a

mine uncompetitive production, linking it to minimize the tendency to direct redundancies, as might occur with the means to assist through labor redeployment to other activities. The gradual closure also facilitates the gradual implementation measures to protect the environment and landscape area.

c) The fourth option allows Member States to guarantee the social debt financing, the environmental ones, in the context of the gradual closure of coal mines. Such a support may allow the mining company not to reallocate resources from other potentially competitive mines to mines that would be closed.

d) Option five takes into account that in the case of the gradual closure of a mine, is likely to be needed aid and debt taken on together with other types of aid, mainly those of operating.

e) It is being remarked in the six scenario case that even after another ten years of extension, at the new expiration date of the regulation is very likely that the same mining companies to be still uncompetitive. So it would not be solved, but the existing problem would be postponed until the end of 2010.

Based on this analysis, the 2 and 5 options were considered those who should be taken into account and developed. The qualitative difference between the two, is the importance given by policymakers, a priority is resolving social issues or the economic ones. It has opted for the priority of the social issues. Requirements of the decision 2010/787/E.U.

In the preamble of the decision are stated the principles that formed the basis for this legal text, namely: a) Coal aid is compatible with the proper

functioning of the European internal market in the context of categorical closure of uncompetitive mines, in strict accordance with the decision;

b) The aid covers the costs of coal for production of electricity, power and heat cogeneration, the production of coke, if this use takes place in the Union.

According to Article 3 of Decision - Aid for closing a mining company qualifies to receive aid to cover losses from actual production and is compatible with the common market if: - exploitation in case is part of a closure plan

whose deadline does not extend beyond October 31, 2018;

- production units concerned must permanently be closed under the closure plan;

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- notified aid must not exceed the difference between production costs and incomes planned for a planned coal year. Aid effectively paid shall be subject to to annual adjustments based on actual costs and incomes, no later than the end of coal production following the year for which aid was granted;

- the amount of aid per tone coal equivalent shall not result in a price of the Union coal at point of use lower that for coal of similar quality from third countries;

- units of production must be developed activity until December 31, 2009;

- the total amount of aid granted by a Member State should have a downward trend: 25% by the end of 2013, and 40% by the end of 2014, 60% by the end of 2016 and no more than 75% end of 2017, compared to 2011;

- Member State should develop an action plan aimed at reducing the environmental impact of coal production from production units which are granted state aid.

- according to Article 4 of Decision - State aid in order to cover exceptional costs - is granted to companies who are or have been in existence related to the production of coal to enable them to cover costs arising or resulting from the closure of coal, but not related to current production.

- this aid can be used to cover: (i) costs only supported by companies which are in process of closing or have closed production units, including units receiving assistance for the closure and (ii) costs supported by several companies.

- the first category of costs are, among others, part:

- the cost of social insurance payments resulting from early retirement of workers;

- other exceptional expenses for workers who lose their job;

- the cost to companies for retraining of workers; - free delivery of a quantity of coal workers who

lose their jobs and the workers who benefit from this right before closing, or cash equivalent grant;

- further work to ensure safety underground, following the closure of production units;

- damage caused by mining, on condition that they have been caused by production units subject to closure;

- all duly justified costs related to rehabilitation of former mining;

- residual costs to cover former miners' health insurance;

-costs related to revocation or modification of current contracts for a maximum value of six months of production;

- costs for re-cultivation areas. From the second category of costs are

contribution increases for covering social security costs, from reducing the number of contributors and expenditures for various utilities. Essential aspects in assessing the new legal framework

Limited contribution of subsidized coal in global energy sources no longer justifies the maintenance the State aid to ensure energy supply in the European Union. Union policies to encourage renewable energy sources and secure economy, sustainable, low carbon emissions, would not justify support for competitive coal mines, indefinitely.

However, EU Member States should be able to attenuate the social and regional consequences of the mine closure, in the absence of state aid - granted in accordance with Regulation 1407/2002, become uncompetitive.

In order for the new legal framework for state aid for the coal industry not to affect the Union's internal market competition, it must be given digressive and strictly limited to units planned for irrevocably closure.

Companies should also be eligible for support to cover the costs, in accordance with normal practice, does not directly affect the production costs. This aid is intended to cover exceptional costs arising from the closure of production.

To help prevent this kind of aid bring unjustified benefits for to businesses that close only a part the exploitation, they should have separate accounts for each component of the production units.

In the case of Romania, the new framework of economic policy measures affecting the Coal industry stationed in the Jiu Valley. By mid 2011, the Ministry of Economy, Trade and Business will have to notify the European Commission the form of state aid that has been chosen.

As resulting from the foregoing, those production units that are part of a closure plan until the end of 2018 will benefit of the aid. At least officially, intentions are to include such a plan for closing three of the seven coal mines in the National Hard Coal Company SA, following that the other four exploitations to continue their business without the benefit of an additional revenue through allocations from the state budget.

It results from this that the implications of new frame for a state aid of substance induce adjustments since: - mines that are closing will need to identify a

market without competing with other

20


exploitations which continue their work without state aid;

- mines will be continuing their work to streamline their activity very high so that they should be able, predictable and sustainable, to cover the costs of their earnings;

- will appear differences related to human resources, the management of human and material resources between the two categories of mines during their function, until the closure of those who are part of a closure plan. Also, intensive use of production factors will be

different, so the management of the next two categories of coal producers by the same economic entity is not recommended

References 1. http://eur-lex.europa.eu/LexUriServ/LexUriServ. do?uri=OJ:L:2010:336:0024:0029:RO:PDF

2. Felea C.M. Notificarea ajutorului de stat în industria cărbunelui Revista Minelor, nr. 2 (212)/2009

21


ENVIRONMENTAL IMPACT OF THE METALIFERROUS ORE MINING AND PROCESSING IN ROMANIA

Dumitru FODOR*, Ioan Călin VEDINAŞ**

Abstract A sustained metal ore mining and beneficiation activity was developed in the past in Romania and it strongly impacted the environment as a whole and it occupied and damaged large surface areas of land as a result of the waste dump, tailings management facilities locations as well as of the erection of the industrial plants reuqired for the production process. The paper deals with the impact with the time of the mining industry on the territory as there have been built more than 350 waste dumps and 60 tailings management facilities. There are shown the observations and measurements performed on site throughout the years and the works completed to enhance the stability and safety of such big waste and tailings deposits. The final part of the paper deals with the concerns involved by the construction of a national complex system for environment monitoring mainly aiming at the tailings management facilities and waste dumps of the mining zones. ____________________________________ * Prof.eng. Ph.D – University of Petroşani ** Eng. Ph.D – University of Petroşani

Overview

There are many and various useful mineral deposits hosted by Romanian territory, such as: mineral fuels, ferrous, non-ferrous and rare metal ores, precious metal ores, non-metal substances, etc.

The mining and processing of the solid raw materials on Romanian territory have been developed since old times. The Romanian mining industry had been continuously developping until the last decade of the XXth century when it faced deep changes and adjustments to the transition to the market economy.

The most important metal ore deposits of Romania are located within the mountaineering areas of the North and West parts of the country, going from Bucovina to Maramures and Apuseni Mountains up to Moldova Nouă.

Until the year 1990 there were more than 40 mining exploitations and almost 30 processing plants operating in these regions and there were mined out more than 50 million tons per year of gold-silver, copper, base metal and iron-manganese ores (figure no.1).

Fig. 1 Map of ferrous and non-ferrous deposits of Romania

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The conditions of the ore deposits of Romania are generally difficult and very difficult because of the complicated tectonics, small and medium reserves, thin layers and veins, low grades, deep mines, difficult hydro-geological conditions etc. Considering all these factors, only small scale exploitations were developed, but they had a strong and easily visible impact on the environment.

Classic methods and technologies were used for the opening, preparation and exploitation works within the activity of the ore deposit beneficiation in Romania.

In order to eliminate the subventions from the State budget and to render profitable the mining operations, even since the last decade of the XXth century, the Romanian Government decided to accelerate the closure process of some mines where the geological reserves were depleted and the geological and mining conditions were difficult incurring high and very high mining costs. A significant number of mines have been closed or under preservation so far as well as the activity areas of Bucovina, Maramureş, Munţii Apuseni and Banat where the geoloigical conditions were difficult, the reserves were limited and they incurred high operating costs. The review, preservation and closure processes of the Romanian mines is ongoing and only the profitable mines still remain in operation. Mining industry and environment

The mining industry has a significant impact on the environment during all the technological stages of the mining and processing processes. Regardless the method applied for an ore deposit

beneficiation, numerous physical and chemical operations are required and there result on one hand, the useful minerals and on the other hand, the waste material mined out with the useful mineral.

The useful minerals themselves of the crude ores existing in Romania, represent almost always low percentages of the total ore bulk mined out of the deposit and consequently, the solid waste tonnages resulted at the ore mining and processing are high and very high, and in addition to it there results waste material at the opening and preparation work, particularly at the open pit stripping works.

Besides the solid wastem the mining industry is generating also liquid and gaseous residues which amounts are many times more significant than the solid ones.

Regardless their aggregation status these residues imapct all the environmental factors: soil, air, water, flora and fauna.

Air and water pollution of the mining zones

Throughout the entire period, when the mining activity was developed in a sustained manner with high production rates, the concerns for the air and water protection were permanent in the sense that the pollution and air and water impact had been investigated and there were implemented suitable measures to keep them within admissible value range according to the existing legislation both at national and European levels.

During the exploitation works and after their closure, the acid characteristic as well as the high mineralization rate and very high contents of Cu, Zn, Fe of the mine waters was noticed (figure no.2).

Fig. 2 Acid drainage resulted at the old underground mines

Also, the huge amounts of used waters

resulted at the processing plants were contaminated by metal ions, simple and complex cyanides, phenoles, xanthates, simple reagents, oils, etc. and had a strong toxic impact on the natural receivers and neighbouring areas.

It is to be underlined here that throughout the years, several technical accidents, ecological disasters occurred at the mines of Apuseni Mountains and Maramuresului Mountains and they caused the contamination of the river waters of the areas and of large surface areas with mining residues containing heavy metals and different

23


toxic matters with devastating impact on the flora and fauna of the region. There are to be mentionned the accidents which took place some years ago at the processing plant and tailings management facilities of Baia de Arieş, Gura-Barza, Certej, Baia Mare and Baia Borşa.

The most well – known accident which took place during the last years, was the one of S.C. Aurul S.A. Baia Mare, when on the 30th January 2000, there occurred a 25m burst of the starter dam from AURUL tailings facility and for about 10 hours, approximately 100,000 m3 of water containing suspensions and cyandes was flowing out. As a result, there were contaminated with cyanide the river water courses of the zone, a large surface area of farming land and the phreatic cloth downstream the accident site.

This accident had serious consequences on the flora and fauna pf the rivers from the area and serious trans-boundary implications.

Land occupation and degradation

The mining industry projects occupy large surface areas which get damaged by the exploitation, waste dumping and useful mineral stockpiling as well as by the location of

constructions and installations required for the production development. At the same time, the mining industry is cuasing relief modification and relocation of industrial projects and human settlements. Under many circumstances, the land is damaged because of the subsidence events and sliding of dumps and tailings management facilities resulting in accidents with a serious and very serious impact.

Immediately after the year 2000, there were inventored all the surfaces of Romania occupied by the mining industry for different purposes. On this occasion, a special attention was paid to the existing waste dumps and tailings management facilities and to their technical condition.

It was concluded that the metal ore mining and beneficiation operations in Romania occupied several thosuands hectars of lands. Approximately half of the surface area is used for the production process development while the other half is affected by the residual produc stockpiling , waste dumps and tailings management facilities.

The metal mining units administrated more than 350 waste dumps where a volume of 150 millions m3 were stockpiled covering a total surface area of 700 ha (table no.1).

Table 1 List of waste dumps of the metal mining of Romania

No Name of entity Subsidiary/Mining

exploitation

Number of mining

exploitation

No of waste

dumps

Volume stockpiled (Mil m3)

Occupied surface

area (ha)

Technical condition

and stability

1. C.N.C.A.F,,MINVEST” S.A. DEVA 21 179 106,74 417,25 Good ÷ Low

1.1 Devamin Subsidiary 9 78 14,55 143,69 1.2 Avram Iancu Subsidiary 4 32 57,01 146,20 1.3 Bălan Subsidiary 1 15 1,66 25,63 1.4 Moldova Nouă Subsidiary 1 7 32,05 84,07 1.5 Other mining units 6 47 1,45 17,66

Good ÷ Low

2. C.N.,,REMIN” BAIA MARE 19 197 48,10 263,80 Good ÷ Low 2.1 Baia Mare Subsidiary 8 60 2,94 39,69 Good 2.2 Baia Borşa Subsidiary 4 35 1,31 25,37 Low 2.3 Rodna Subsidiary 3 23 0,50 13,73 Low 2.4 Bucovina Subsidiary 4 79 43,35 185,01 Low TOTAL MINING COMPANIES 40 376 154,84 681,05 Good ÷ Low

The biggest existing waste dumps of

Romania resulted at the metal ore mining are at Roşia Poieni, Moldova Nouă, Roşia Montană, Teliuc Ghelar, Brad and Leşul Ursului, (figure no.3).

All these waste dumps are very high with high slope angles requiring continuous monitoring and naintenance because erosion events occurred at man of these dumps and they are impacted by the superficial and depth sliding events. As a result,

these dumps and many others are under permanent surveillance and observation particularly because there are roads, industrial objectives and even dwellings within their impact zone and all these could be affected by the slide events.

Several waste dumps of the mining zones constituted sources of construction materials or even they were exploited to recover the useful components.

24


Fig. 3 General view of Cuibarului and Geamăna waste dump

of E.M. Roşia Poieni - ,,Avram Iancu“ Subsidiary Further to the field analysis there resulted that

more than 100 waste dumps require high capital investments for the levelling, stabilization and recultivation works so that they could be re-used for the economic purpose of the region where they are located.

So far, under the guidance of the Ministry of National Economy and of the National Agency of

Mineral Resources there have been performed levelling, slope reshaping works as well as the construction of intermediate berms at the major waste dumps to reduce the overall slope angles and for their stabilization by coevring them with topsoil layer and grass seeding or berm and sloep afforestation (figure nr.4).

Fig. 4 Waste dump slope arrangement:

a) before rehabilitation works; b) after rehabilitation works As a result of the metal ore processing in the

plants there were built 64 tailings management facilities occupying a surface area of about 1,350 ha and stockpiling about 360 mil.m3 of waste, table no.2.

The tailings management facilities are usually located on the river meadows of the exploitation zones, they are 20-30 m high and even higher and

occupy a tens of hectars each of them. These engineering constructions occur as relief shapes in contrast with the meadow relief.

The annual volumes of flotation tailings deposited in the tailings management facilities during the last years were most times over 5 millions tons, and the volume of water discharged in the emissary amounts to about 60 millions m3.

25


Table 2 Situation of TMF's of the metal ore mining exploitations of Romania No Name of the entity

Subsidiary / Mining exploitation Number of

mining exploitations

Total number of

TMF's

Occupied surface area

(ha)

Stockpiling capacity

(Mil. t) 1. C.N.C.A.F. ,,MINVEST” S.A. DEVA 21 37 855,34 228,70

1.1 Devamin Subsidiary 9 18 351,27 64,801.2 Avram Iancu Subsidiary 4 11 272,02 59,061.3 Bălan Subsidiary 1 5 111,05 34,511.4 Moldova Nouă Subsidiary 1 3 121,00 70,331.5 Other mining units 6 - - -2. C.N. ,,REMIN” S.A. BAIA MARE 19 27 495,99 128,25

2.1 Baia Mare Subsidiary 8 11 338,30 77,022.2 Baia Borşa Subsidiary 4 6 63,57 18,282.3 Rodna Subsidiary 3 2 19,30 6,212.4 Bucovina Subsidiary 4 8 74,82 26,74TOTAL MINING COMPANIES 40 64 1.351,33 356,95

The tailings management facilities of Moldova – Noua, Bălan, Deva, Roşia-Poieni, Roşia-Montană, Certej, Baia-Mare, Cavnic, Baia-Sprie, Baia-Borşa and Tarniţa are the largest of the system and there are stockpiled huge amounts of tailings and consequently it requires a particular monitoring and permanent maintenance works.

Preoccupations for improving the environment monitoring of the mining zones

After the accident of Baia Mare from 2000, of Romania, they proceeded with the field investigation of each tailings management facility verifying their technical condition revealing all the adverse geo – mining events such as: subsidence, overflowing, erosion, suffosions, seepage, and superficial and depth sliding events (figure no.5).

Fig. 5 Events recorded at the tailings management facilties: a) – seepage; b) – erosion; c) – ravines;

d) – sliding limited in space; e) – overall sliding; f) – ravines, brakage and sliding events

In order to perform the stability studies there were made geotechnical investigations of the material of the foundation ground , the rise dam and tailings facility beach. Tot his aim, there were

collected samples from different alignments for which the physical and mechanic properties were determined. Also, the there was determined the perviousness of the material deposited in the

26


tailings facility and the capacity of eliminating the water from it.

Fore each tailings management facility there were made stability calculations based on different profiles which showed negative events. The methods based on curve and plane sliding surfaces were used. The results of the stability review confirmed the stability was high enough for each and every tailings facility.

Further the field observations under the coordination of the Ministry of Economy, through the General Directorate of Mineral Resources and the National Agency for Mineral Resources , there was proceeded with the closure and safety measures of the tailings management facilities which showed negative geo-mining events and of those involving high risks.

The most frequent works performed included: construction of guard channels to catch the torrents and block the run – offs from the valley sides, flowing out in the valleys from the base of the tailings management facilities, thes eworks were necessary to enhance the stability of the heavy precipitations which could cause the dam burst, the tailings flowing and the serious damage of the downstream zones; reshaping of the main dams with overall slopes of 1:3 to ensure the tailings facility stability; main dam rises designing safety berms ; reshaping of the slopes impacted by the seepage and material engagement; placing vegetal soil on top and then grass seeding or afforestation of the TMF reshaped slopes and beaches (figure no.6).

Fig. 6 The dam and crest of wave of Herepeia TMF E.M. Deva ,,Devamin”Subsidiary:

a) before the work completion; b) after the finalisation of the environmental rehabilitation works Further on, it proceeded with the permanent

monitoring of the tailings management facilities by controlling the hydrostatic water level of the tailings facility bodies using the piezometers and by controlling the deformations using the topographic landmarks which reveal continuously the sectors where the deformations are active or under stabilization. Also, in case of high risk tailings facility therew ere mounted and operated meteorological mini-stations.

In Romania, the preservation and closure process of the mines and non-profitable open pits

started in 1998 and it was developed in compliance with the Mining Law. The strategy of the mining industry regarding the closure and ecologization of the mining objectives provides that the process finalisation date is the year 2010 and to this aim, a budget estimate of about 80 millions Euro/year has been scheduled.

In Romania, the dynamics of the programmed / achieved investments funds for the closure and ecologization work completion during the last three years, is ina ccordance with the graphic of figure no.7.

Fig. 7 Dynamics of the programmed and achieved investments for the execution of closure and ecologization

works of the mining exploitations of Romania The works for the tailings management and

waste dump safety were performed by Romanian companies , within the due time and at the set up

costs in strict compliance with the international procedures and mainly funded by the Romanian Goevrnment, which for some works, concluded

27


partnership agreements with the World Bank Group (BIRD) and the European Bank of Reconstruction and Development (BERD).

At present, in Romania, there is implemented the National Computer Assisted Monitoring System (SNIM), which aims at the improvment of the monitoring strategy of the tailings facility and waste dump stability as well as of all the environmen t components from the old and current

mining zones of the country. In a first stage, this ,,SNIM” system will monitor only the tailings facilities and waste dumps where there is a potential high risk of stability loss , from the C.N. ,,Remin” Baia-Mare and C.N.C.A.F. ,,Minvest” Deva mining companies and later on, it will be gradually extended to all the mining objectives of these companies and to the existing mining companies of Romania (figure no.8).

Fig. 8 Zoning of mining objectives by water basins

So far, there have been undertaken the

following steps regarding the overall design developed for this aim:

Identification of the mining objectives and their classification depending on their risk rate which could cause mining accidents with severe impacts on the environment and even ecological disasters.

The zoning of the potentially rick mining objectives of the Siret and Tisa river basins.

There have been established four central laboratories for analyzing the environmental components, namely in Siret Water Basin at Vatra Dornei (Suceava county); and in Mures Water Basin at Abrud (Alba county), Baia-Mare (Maramures county) and Deva municipal (Hunedoara county).

Putting into operation the Computer Assisted Monitoring Systme of Siret river basin at S.C. ,,MINBUCOVINA” S.A. - Mestecăniş station (Suceava county), which is carrying out the environment monitoring for the tailings facilities of

the Northern zone of the country. There already have been monitored the tailings management facilities of Târnicioara, Dumitrelu, Pârâul Cailor, Valea Straja, Poarta Veche and Dealu Negru, and then there will be integrated within this system other tailings facilities and waste dumps of the zone, too. For each tailings facility the following parameters are delivered to the Mestecanis station: amount of infiltrated water; level of the underground water level; movement of the dam crest of wave; water pressure in the pores; quantity and quality of the dam leakages; seismic activity, meteorological conditions (rain, temperature, wind speed and direction, humidity); etc. The connection to the National Computer Assisted Monitoring System, of the zonal monitoring system of S.C. ,,MINBUCOVINA” S.A.- Mestecăniş station (Suceava county),will be carried out immediately when the SNIM becomes operational.

28


Until the end of the year 2011 there will be also implemented the Computer Assisted Monitoring System which covers the Tisa river basin including three data collection centres in Baia-Mare, Abrud ( Cuprumin head-office) and Deva municipal.

Each centre will include the followings: A fix laboratory where there will be

processed the samples collected on field, there will be evaluated tje analysis results and there will be introduced in the monitoring – warning system.

A mobile laboratory performing the air, water and soil, sampling of each tailings management facility and waste dump. The samples will be preserved and transported for complex analysis to the fix laboratory. The mobile laboratory will be able to perform analyses on site and also will collect the data from the apparata and devices mounted on field and which are not under GSM coverage (Global System for Mobile communications).

A central information geographic system (G.I.S.) which will collect , record store and deliver the data in the SNIM (National Computer Assisted Monitoring System), to the central national unit of the National Agency for Mineral Resources and from there, to all the government institutions , in order to draw their attention and warn them in order to get a rapid response in case of emergency

In a future stage, SNIM will extend to all the country regions so that to cover and monitor all the mining objectives of Romania. At this stage, all the mines which could possibly cause accidents with severe consequences for the environment will be compulsorily under monitoring at national level.

The results of the monitoring performed by SNIM referring to different mining objectives will be accessed through internet by any person or interested institution of the country or from abroad and thus this information will become public.

References

1. Fodor D., Lazăr M. Urmările pe termen lung ale industriei miniere din România şi gestionarea acestora” – Revista Minelor nr.11, pag.7-13 / 2004

2. Fodor D., Lazăr M., Rotunjanu I. ,,Probleme de stabilitate a haldelor de steril şi a iazurilor de decantare” – Revista Minelor nr.5, pag.23-28 / 2004

3. Găbudeanu B. ,,Iazuri de decantare din industria minieră puse în siguranţă pentru prima dată în România prin Agenţia Naţională pentru Resurse Minerale – Unitatea de Management a Proiectului” – Revista Minelor nr.1, pag.2-6 / 2009

4. Fodor D., Baican G. ,,Impactul industriei miniere asupra mediului” – Editura Infomin Deva, pag.200-238 / 2001.

5. Pătruţi Al., Sardan D. ,,Reducerea riscului de producere a accidentelor miniere în bazinul Tisei.” – prezentare simpozion Sibiu, iunie 2009.

6. Ferenczi C. ,,Echipamente pentru reţeaua de monitorizare a

depozitelor de deşeuri, provenite din industria extractivă” – prezentare simpozion Sibiu, iunie 2009.

29


TECHNICAL CONSIDERATIONS ON INFRASTRUCTURE

REHABILITATION OF THE JIU’S VALLEY MINING BASIN

Cristian Constantin MUZURAN*

Abstract Existing technological infrastructure in the Jiu’s Valley mining basin has a high degree of physical wear and maintain its operation requires significant rehabilitation works to change the design component and an upgrade to increase performance or imposing as its abandonment recovery depending on the circumstances and their economic value when the decision to close the mine. Introduction

Recovery of mining infrastructure in the Jiu Valley mining basin is a long process and not many times with many risks and difficulties in its deployment. Its implementation requires a long-lasting material and logistical effort and well organized from the decision makers for the final result should be measurable and effective. This recovery operation is carried out in phases mining infrastructure and coordinated since the mine closure process is a tortuous process with many large financial and technical-productive recovery is in many cases as a central objective of not strike cost the mining company on the acquisition of additional equipment / mining equipment, and reuse them to be in maximum security conditions. Working methodology used in the work of the technical-productive recovery mining

In order to operationalize the decision to recover the existing mining infrastructure is necessary to achieve its prior analysis, followed by the establishment of order and priority of making recovery capability at that time and theto establish the logical framework on how to recovery followed finally by the possibilities of its recovery, that is recovered for reuse infrastructure.

Putting this methodology will be under a recovery plan based on an approved rehabilitation program drawn up by each unit adapted to the geo-mining and mining-technical infrastructure that the existing productive. To complete this process specialist teams are necessary in this type of operation, according to the technical design of closure, so the implementation schedules for such operations. ____________________________________ *Eng. Ph.D stud. University of Petroşani

Equipment will be recovered as follows: · lifts (scraper conveyor, conveyor belt, winches, rails, monorail equipment, gearboxes, electric motors); · combine (combining forward and / or slaughter); · support elements (hydraulic columns, beams GSA, SG-23 plates); · elements ventilation (fans, ventilation pipes, air ducts flanged bushings) · drainage facilities (water pumps, high pressure pumps) and accessories (pipes and hoses, hydraulic fluid); · power plants and transport supply (transformers, caskets, electric cables); · telecommunications installations and control systems (phones, cable telegrizumetric captured methane).

Recovery program is based on a comprehensive recovery plan and it has often heavy, being made with specialized personnel well established in terms of livestock, and the qualifications needed for recovery operations with the schedule of operation of the mine.

Recovery plan includes the following technical-productive activities: · Location on topographic plans of the mine (area, area) of equipment / machinery existing at date of analysis

The landscape plans will set the limit mining perimeter, that will identify areas , which will close. In the mining stopes there, preparatory work, suites, galleries, inclined planes, vertical wells (blind or days) and special mining (rooms, pump house, niche, materials storage). • Identifying and inventorying infrastructure by drawing up a list.

The list will contain all technical details of the physical condition of equipment potentially recoverable from zone / area proposed to be closed. Information obtained in this process will be used to select equipment / machinery possible to recover.

Components of each device is assigned an identification number to be able to make a detailed description, which will include: localization, technical and physical state estimation and age of equipment, being accompanied by such photographs to be identified and determined. ·Establishing score

Corresponding to each equipment / machinery in the existing / proposed area to be closed,

30


depending on its features and shares, determine a score, which is a complex process and requires an analysis based on criteria they have set the number of 11, defined that are assigned importance weights from 4% to 14% in order for recovery (Table no.1).

In turn the criteria are identified by five characteristics that are given notice of reliability expressed qualitatively and quantitatively. Score is calculated with the equation:

11i i

1S P N= ⋅∑ (1)

where: - Pi the weight of criterion i; - Ni Note Feature creditworthiness given criterion i.

The following shows you the decision to recover its own proposal, which differs from the currently known and applied, as indicated in manual mine clearance, by:

- Changes and additions to the criteria; - Redistribution of the weights; - Detailer characteristics; - Qualitative and quantitative characteristics

of reliability by providing notes; - Decision on the recovery of equipment,

tools based on a scoring scale. · Decision and selection of equipment or components that can be recovered.

In this stage there are cases that require a mandatory rehabilitation, required by law, environment, safety. In these circumstances the decision to recover without the need for evaluating equipment. In other cases it is necessary to select equipment based on scores established for recovery equipment. I propose the following classification of the solutions on how to restore the economic and technical infrastructure at a mine subject to the closing process.

If: S = [1 ÷ 2] - total surrender (100%) (2) S = (2 ÷ 3] - partial abandonment (50%) (3) S = (3 ÷ 4] - partial recovery (50%) (4) S = (4 ÷ 5] - total recovery (100%) (5)

Decision recovered infrastructure

Taking into account that the decision is taken on the recovery of the equipment is taken into account only the economic aspects with reference to the recovery of equipment, this process requires a global approach using a range of criteria including analysis and other technical issues such as type related to the usefulness, reuse or replacement of infrastructure in other subunits recovered for its intended initial mining

Finality recovery plan will involve the recovery or reuse of technical-productive recovered. Recovery arrangements for equipment that can be recovered will be given to the following possibility: · Capitalization through sale; · Redistribution in mining subunits; · Dropout underground taking full or partial cost recovery as a landmark.

The estimated cost of recovery equipment compared to the amount resulting from the capitalization is one of the indicators that determine the presentation of proposals to restore or forsake them.

The final decision for the recovery of technical-productive if the mine closes below is systematized in figures no.1 and 2.

Depending on the recovery of costs (Cr), proceeds from the sale (Vv) and acquisition costs (Ca) may be taken the following decisions on the recovery of technical-productive to be recovered from the underground:

a. Sale of infrastructure recovered if: Vv> Cr> Ca (6)

Recovery can be made either through sale to other economic units (other than those belonging to CNH SA Petrosani), or as scrap metal.

b. Reuse of infrastructure recovered if: Vv <Cr <Ca (7)

Given that not all equipment can be reused, but only partly because of the technical condition and wear large, the total cost of recovery is less than the purchase price.

For certain equipment where recovery is required (for electrical equipment such as motors, fans, electric winches or cables) they will reuse.

c. Abandonment of infrastructure recovered if: Cr> Vv> Ca (8)

31


Table 1 Analysis model of the status of equipment / machinery

Note creditworthiness, Ni

Nr. UNIT.

Criterion

The weight criterion,

Pi

Characteristic criterion

Qualitative Quantitave

SCORE

S=∑ ⋅11

1ii NP

Very Inaccessible very unfavorable 1 Inaccessible unfavorable 2 Difficult good 3 Accessible favorable 4

1.

ACCESSIBILITY

P1=10%=0,10

Easily accessible very favorable 5

Unusable very unfavorable 1 Very old unfavorable 2 old good 3 Usable favorable 4

2.

TECHNICAL AND PHYSICAL CONDITION

P2=12%=0,12

New very favorable 5

Destroyed very unfavorable 1 Partially degraded unfavorable 2 Replaced main components good 3 Replaced secondary components

favorable 4

3.

MAINTENANCE HISTORY

P3=4%=0,04

There were no interventions Very favorable 5

5-10 km very unfavorable 1 3-5 km unfavorable 2 1-3 km good 3 0,5-1 km favorable 4

4.

DISTANCE TO SURFACE TRANSPORT

P4=6%=0,06

0-0,5 km very favorable 5

Non/transportable very unfavorable 1 Special transport unfavorable 2 Mechanical transport good 3 Monorai transport favorable 4

5.

DIFFICULTIES TRANSPORTATION

P5=6%=0,06

Manual transport very favorable 5

Degraded 100% very unfavorable 1

Degraded 75% unfavorable 2 Degraded 50% good 3 Degraded25 % favorable 4

6.

DEGREE OF DEGRADATION

P6=7%=0,07

New foarte favorabil 5

Risk of subsidence very unfavorable 1

Danger of explosion unfavorable 2 Fire Danger good 3 Flood Risk favorable 4

7.

SAFETY ZONE

P7=9%=0,09

Area harmless very favorable 5

Amortized 100%/quashed very unfavorable 1

Amortized75% unfavorable 2 Amortized 50% good 3 Amortized 25% favorable 4

8.

RESIDUAL VALUE

P8=14%=0,14

New very favorable 5

unsalable very unfavorable 1

marketable 25 % unfavorable 2 marketable 50 % good 3 marketable 75% favorable 4

9.

DEGREE OF MERCHANTABILITY

P9=14%=0,14

Total marketable very favorable 5

There can be reused very unfavorable 1

Reuse 25% unfavorable 2 Reuse 50 % good 3 Reuse 75% favorable 4

10.

DEGREE OF REUSABLE

P10=14%=0,14

Total Reuse very favorable 5

Total Constraints very unfavorable 1

Significant Constraints unfavorable 2 Point Constraints good 3 Significant constraints favorable 4

11.

LEGISLATIVE AND ENVIRONMENTAL CONSTRAINTS

P11=4%=0,04

Without constraints very favorable 5

32


Fig. 1 Decision analysis on the recovery of machinery / equipment

REAL VALUE IN TIME RECOVERY

Vr

Add transport costs (Ct) and those with labor (Cm) from place

to place storage recovery

FINAL COST RECOVERY Cr =Ct+Cm+Vr

DECISION / OR SELECTION OF ABANDONMENT RECOVERY

DISTRIBUTION Subunits -CNH SA Petrosani Cr <Ca

SALE Dismemberment

Undressing Valuing the scrap metal

or Used Parts

Cr <Vv

ABORT underground Cr> Vv

INPUT VALUE

Vi

33


Fig.2 Systematization decision on the recovery of underground infrastructure

JUDGEMENT ON THE ISSUE OF GOVERNMENT MINING UNIT CLOSURE.

The logistics and management of mining recovery in the establishment of mining infrastructure

Selection of mining infrastructure will

recover

COMMENCEMENT OF ACTION FOR RECOVERY OF UNDERGROUND INFRASTRUCTURE COMPLETION OF PLAN OF REHABILITATION AND TECHNICAL AND ORGANIZATIONAL

MEASURES

Temporary underground storage and reuse in other areas depending on their physical

Recovery of total or partial evacuation of the area gradually dezansamblării storing them to change, adapt, reuse and transfer to other sub-units for sale as mining or waste metal

Abandoning their total or partial underground

COMPILE DATABASE INFRASTRUCTURE FOR UNDERGROUND RECOVERY

Statement of assets recovered from the scheduled areas and conservation buffer strips Monthly Report / Annual

COMPARATIVE STUDY RECOVERY OF

UNDERGROUND INFRASTRUCTURE

MONITORING OF UNDERGROUND INFRASTRUCTURE RECOVERY DECISIONS

Statement of assets recovered from areas scheduled for damming and conservation of underground and surface storage.Final report on a monthly / annual

Statement of assets recovered from areas scheduled to remain in underground storage impoundments and the common escape routes Monthly Report / Annual

Statement of assets recovered from areas scheduled for damming and conservation re-transferred to other sectors andMonthly Report / Annual

Mining unit or being proposed for closure / liquidation

Mandatory Recovery Hazardous Materials

34


Technical and organizational measures for disposal, transport and storage of equipment / machines that will be recovered

All areas will be subject to mine action recovery, is important in order to be doing it. It will be phased in gradually, following a certain priority in the proceedings.

Measures will be taken in the recovery action are: · Setting order of priority and vital for consumers to be retained in office; · Decommissioning of technical equipment; · Decommissioning of power stations and electricity distribution points; · Decommissioning of electric power stations correlated with the program closing; · Dismantling of force 6 kV; · Disposal facility 0.4 kV; · Order of removal and installation of electromechanical equipment and materials will be recovered for use; · Removal, plant and equipment recovered; · Removing technological equipment used in closing the connections to the area; · Works for dismantling the constructs electromechanical; · Works necessary for the recovery of materials, equipment, facilities, vehicles and other assets that can be recovered; · Recovering technology and transportation equipment; · Loading-unloading and transport electromechanical equipment and installation; · Storing and evaluating the technical condition of equipment recovered.

Conclusions

Recovery of underground infrastructure is done through monthly reports, quarterly and annually by subunits-CNH SA Petrosani subordinate to it in the existing recovery capability.

Given that recovery action is a complex program that involves many costs, especially with living labor to support the mining sub paper proposes a relatively simple and clear methodology for deciding on the correct and efficient recovery technical-productive mines under liquidation process.

Motion made will be considered useful to those interested and involved in this process. References 1. Băican, G. Mining Industry Strategy, a component of sustainable development no.6/2003 Mining Revue

2. Georgescu, M. ş.a. Analysis of the mining industry in Romania and its impact on the environment, Petroşani, 2007

3. Mironovici, R., Turdean, N. Considerations for Mine Closure Handbook, No. 10-11/2001 Mining Revue

4. Muzuran, C.C. Solutions regarding the recovery of the technical and productive infrastructure of the mines under liquidation in the Jiu’s Valley Mining Basin PhD thesis, University of Petrosani, 2010

5. Muzuran, C.C. Criteria for recovery machinery / equipment in underground mining units undergoing closure or liquidation. Scientific papers of the international symposium Academic SIMPRO 2010 Mining Engineering Section, Petrosani, 2010.

6. *** Mine Closure Handbook, nr.10-11/2001 Mining Revue, September 2001

35


SOME CONSIDERATIONS FOR PRECISION AND FITS CHOICE IN BUILDING MACHINES

Nicolae NIŢESCU*, Aron POANTĂ*, Anne-Marie NIŢESCU**,

Dan DOJCSAR**, Bogdan SOCHIRCĂ* In the paper are presented some aspects in regard to the precision choice, the fit’s group and optimal way of fit, used in building machines. The optimal designing of clearance, interference and transition fits in base of basic shaft using the „key” relation and the made table with numerical examples represents the base of establishing algorithms and programs for computing design. Keywords: utilization key, monograms, abacus, adjustment. Introduction

With a great importance in the technical, functional and economic point of view, the grade of tolerance of the piece manufacturing and the fits are established and chosen corresponding to the achievement possibilities, to the assembling and processing economical, to the functional parameters which are imposed by the operation and running conditions and to other factors.

The types of the initial data which are well known by the designers in the designing background, when needs to prescribe a fit are: a) only the qualitative neither the quantitative fit aspect are known; b) the quantitative fit aspect are known too and, in this case, is imposed the extreme edge of the assemblage characteristics (Jmax and Jmin ; Smax and Smin).

In the case of point a) situation, these steps are made: - the fit system is chosen from the two possibilities: the fit (assembly) system with basic hole and the fit system with basic shaft. Anyway is recommended the fit system with basic hole. The fit system with basic shaft is chosen only for then assemblies which technological or functional conditions impose this system; - is established the fit type (the fit character): clearance fit, transition fit (passing by or uncertain) or inference fit; ____________________________________ * Prof.eng. Ph.D – University of Petroşani ** Lect.eng. Ph.D – University of Petroşani *** Asist.eng. Ph.D – University of Petroşani

- the basic fit is chosen in function of this domain literature recommendations (books, papers, standards, instructions etc.), standard’s settlements, designer experience, but even of the respective ensemble characteristics (the temperature domain, the volume and the types of the strains the speed, assemblage length, the number of the supports etc.). In the choice process of the grade of tolerance levels for the shaft and the fit is taken into consideration the principle “rougher possible, but with as small tolerance as necessary to running”[2]; - computing the deviations.

In the case of point b) situation when appears the problem of establishing of the optimal fit type, the grade of tolerance and the proper fit selections are not so simple.

The grade of tolerance levels (ISO standards), in the case of fits, are chosen in function of the following factors [1]:

− assemblage quality- which lay in the assembled parts property to be, n dimensions, closest to the nominal value mentioned in the diagram;

− the functional determinant level of the assemblage which is bigger than the assemblage tolerance characteristic is smaller vice versa. The grade of tolerance level selection

The designer, in the grade of tolerance level selection process, follows these steps: I. On the base of functional conditions, is imposed a variation of the assemblage characteristic (clearance or interference), proper to a certain assemblage, between two approximate limits, like an example: J = (0,009...0,052) mm, where the clearance tolerance is:

mJJT minmaxj μ=−=−= 43952 (1) From the general expression of the tolerance:

iCxITxT ⋅== (2) is computed the number of the tolerance steps Cxaj, for the clearance fit which is considerate, even for the nominal dimension, at 35 mm i.e. in the domain (30...40] mm with mmm 35=φ :

2853285069143

0010450 3

≅==

=φ+φ

==

,,

,,

Ti

TCx

mm

jjaj (3)

36


for each twin parts of the fit : 14228

2==ajCx

.

From the table of the tolerance units number, in function of the IT characteristics (table1), results, for the analyzed fit example, class 6 (which has(C6=10) and class (C7=16)).

Since it was established the precision classes

7, respectively 6: 67Nφ (on the base of the fact

that the shaft can be manufactured more refined at the some cost), results: C6 + C7 = 10 + 16 ≅ 28.

These characteristics will satisfy the tolerance parts values which will ensure the clearance imposed by the functional conditions.

Table 1

II. The second criterion is detailed presented in [1], [3], [4], [5], [6], [7]. The fit type selection for the clearance group

In table 2 [1], [5] is presented the condition which appears at the clearance fits in one of them “moments of life”, beginning with assembling, continuing with working and ending with disassembling of the twin parts.

In the following paragraphs is about the selection of the fit type.

On the ground of the running, from table 2, the fits can have these behaviors: A) Statically (F*), groups II, III and IV, when the fit type “is selected” in this way that the assemblage needs dynamics only at installation. For maximal grade of tolerance maintaining will be selected the fit H/h. Can be selected even the transition fits H/js or H/j which are clearance fits actually. For no importance assemblages, to have easiness in assembling can be selected the fit from the beginning of the alphabet (H/g; H/e ...). B) The fit has a dynamical working (M). In this case, the designer can meet two variants: B.l. He has the technical and functional parameters like the data input of the problem; B.2. There are imposed the admissible extreme characteristics of the assemblage (Jmax and Jmin).

In the case B1, t is computed the average clearance (Jmed), i.e. functional optimum clearance, and after this is composed and used the table 3, on the ground of the basic hole, and from [1], (in [5]

is presented the table composing and using on the ground f the basic shaft) can be computed:

1. the fit type; 2. the grade of tolerance level for each piece in

part; 3. the admissible deviations from nominal

dimension of the two twin parts; 4. the assemblage characteristics; 5. the fit correction at the manufacturing; 6. the fit correction by functional thermic

analysis; 7. the fit correction at the rugosity; 8. the changing from fit with unitary hole

system (H/) to fit with unitary shaft system (/h), if is necessary;

9. the deviations showing on the diagram. B.1.1. The average clearance: if the assemblage is in cylindrical shape:

60

nv ⋅φ⋅π= (m/s)

where n is the rotation speed in rotations/minute (if Φ is in meters). In this way can be computed with [3] the average clearance like:

460

80 n,J med⋅φ⋅π

⋅φ=ψ⋅φ= (μm) (4)

In the diagram (1) is presented table3 which,

in border I, contains the standard tolerance IT01, IT0; IT1 … IT16 with grade of tolerance 01, 0, 1, 2 … 16 (recommended at special (finesses) mechanics to be from 1 to 10, and for the grade of tolerance in the machines building from 5 to 12 in generally). In the border II are presented the fundamental deviations of the shafts, for the 11 types of clearance fits: 8 fits named with a single letter (from a to h) and the other 3 fits named with two letters (cd, ef and fg).

The values es≤0 from the border II will be, in absolute value, equal to the minimum clearance of the respective fit: es = Jmin.

In the bottom side of the table 3 from diagram 1 is presented he places of the tolerance fields in function of the fit type and the meaning of the values which are written in borders I and II.

If : ITxTT dD == than can be computed the used “key of the abacus” from table 3 and [1]:

(5)

37


In [5] is established the “key of the abacus” composed for the clearance fits computing purpose on the ground of the unitary shaft.

In other words, the computed average clearance is equal to the minimum clearance (value from the border II of the table 3 in the absolute value : ⎜es ⎜, which on the column corresponds to a

letter, and this letter will be the symbol of the designed fit type), plus a tolerance field ITx, which is founded in border I of the table 3 and this field is in correspondence to a number on the column. This symbol number represents the grade of tolerance (the grade of tolerance level) of the designed fit.

Table 2 The clearance fits groups

The behavior of the twin pairs pieces Class Assembling Running Disassembling

Examples

I-st M M M bearings, guides, mobile joints

II-nd M F* M toothed wheels mounted by wedges on the shafts, mobile casing on the tools-machine guides, fixed spanner

III-rd M (1)F* (2)M* M (1) see class II examples; (2) balladeer toothed wheels

IV-th M F* F* assemblages soldered on the pieces circumference

Table 3

Fig.1. The places of the tolerance fields in function of the fits type (clearance case)

The “Key” condition is: ⎜es ⎜≈ ITx or es >

ITx , and the best is that the two values to be closest.

Example : a sliding bearing with Φ = 8mm in diameter running with n = 10.000 rot/min, in class B1.

B.1.1 and B.1.2. The designing of the fit type and the grade of tolerance levels:

m,,,

n,J med

μ=⋅⋅π

⋅⋅=

=πφ

⋅φ=ψ⋅φ=

15960

100000080808

6080

4

4

We chose Jmed = 9μm. It is established the “Key” formula [5].

Taking into consideration the assemblage in the

unitary hole fit system, the designed fit will be:

448

gH

φ . In [10] are presented the stages from B.1.3.

to B.1.9.

38


B.2. In the clearance fit designing process are imposed the extreme (admissible) fit characteristics: Jmax and Jmin. In this case the designer task is more simple using table 3 again.

Taking into consideration the formula: Taj = Jmax - Jmin = ITxD + ITxd ; but accepting the simplification: ITxD = ITxd = ITx , results: Jmax = Jmin + 2 ITx , and if it is known the values Jmax and Jmin than we can calculate ITx like :

2minmax JJ

ITx−

= .

In table 3 is selected from the border I the nearest value to the computed ITx , value which represents on the column the grade of tolerance group. Again, from table 3 - border II, it is selected the imposed ⎜es ⎜= Jmin.

Example : for Ф35 : Jmax = 52μm; Jmin =

9μm; ITx = 2

952 − = 21,5μm (value approximated

to 25, and, in table 3 – border I, we will find the grade of tolerance 7) . Jmin = 9μm means that

minJes = (from border II) for the shaft : „g”. It means that the fit is: 6/735 gHφ .

The inference fit designing

The inference fits are chosen in the case of twin pairs parts which will achieve a inference (holding) state on the ground of the assemblage characteristic S (the inference which is achieved between the hole and the shaft).

In certain cases, where it is better to have inferences with small values, and the functional conditions involves a superior inference (holding) level to the level ensured by fit, for that achievement, at the inference fits too, there are equipped with afferent mechanical parts. In this way, the inference fits are classified in: - inference fits with holding by control ; - inference fits with holding by control with inference level compensation.

The inference fits can be assembled in these variants: - “cool” pressed inference fits ; - “warm” assembled inference fits (milled - in the heating hole case).

For the cool pressed inference fits, the rugosity on the pieces surface will be smoothed, the effective inferences after assemblage will be decreased, and because these don’t give an exactly information about the inference level, and because these depends on the assemblage diameter too (φ=d), in [1] is defined the relative effective average inference like:

2minmax

med

medmedEmedER

SSS

;cSS

S

+=

φ−

=φ

= (6)

where, more than the well known symbols, the symbol “c” is a variable which depends on several factors: the rugosity value and shape, the inference value, the holes width, the hole overlay length over the shaft, the elasticity absolute values of the twin pieces stuff etc.

In function of the relative effective inference (minimum, average etc.), in [1] the inference fits are classified in four groups:

1. very hard inference fits, with SminER = 1μm/mm (1‰);

2. hard inference fits, with SmedER = 1μm/mm (1‰);

3. medium inference fits, with SmedER = 0,5μm/mm (0,5‰);

4. light inference fits, with SmedER = 0,25μm/mm (0,25‰).

At the inference fits designing, he designer can meet two situations:

A. The assemblage technical and functional information are given;

B. The inference extreme characteristics are imposed (Smax and Smin ).

A. The inference fits from the first case are designed by computing the minimum inference, following these stages:

A1. the fit type designing; A2. the grade of tolerance levels designing; A3. the deviations computing; A4. the assemblage characteristic computing; A5. the computing of the manufacturing fit

control; A6. the computing of the rugosity fit control

(except for the warm assembled inference fit); A7. the fit control check-up by thermic analysis; A8. the designed fit change from a grade of

tolerance type to other (in case from H/ to /h or vice versa);

A9. the fit check-up at the maximum inference and σc (the flow limit of the stuff);

A10. the deviations showing on the diagram.

In table 4 there are presented the standard tolerances (border I) for the grade of tolerance levels 01, 0, 1, 2 … 16 and the fundamental inference deviations of the shafts (border II).

From fig.2 (attacked to the table 4) is established the “Key” used for abacus [1]. In [6] is established the “Key” used for abacus designed for the control system with unitary shaft base.

39


The linking formula (if ITxD= ITxd = ITx) is:

(7)

In other words, the calculated minimun

interference is equal to the lower deviation (see value in the 2nd frame of table 4) which corresponds

vertically to a letter, this will the be symbol of the projected fit, minus a tolerance zone ITx, which can be found in the 1st frame of table for and to whom a digit corresponds vertically. This will be the symbol digit which represents the precision class (precision) of the projected fit. Example: Given the following data desing the fit type from the interference group, for assembling a cogwheel on a tubular shaft (fig 3): d = Ф = 10mm; d1 = 5mm; d2 = 20mm; ℓ = 10mm; P = 180daN; μ = 0,08; υ = 0,3; EA = 2,1 · 104daN/mm2 = EB;

Table 4

Fig.2 Tolerance zones depending on the type of the fit (for intereference fit)

1670801010

180 ,,d

Pp =⋅⋅⋅μ

=μπ

= daN/mm2,

or in the case were the torque is known (T), for example T =

900daNmm,from 52

102

⋅=== PPdPT daN/mm),

which replaced in the formulae of pressure:

1670801010

9002222 ,

,dTp =

⋅⋅⋅π⋅

=μπ

= daN/m2

366613025012501

30

1051

1051

1

1

2

2

21

21

,,,,

,

dddd

k A

=−−+

=

=−

⎟⎠⎞

⎜⎝⎛−

⎟⎠⎞

⎜⎝⎛+

=υ−

⎟⎠⎞

⎜⎝⎛−

⎟⎠⎞

⎜⎝⎛+

=

966613025012501

30

20101

20101

1

1

2

2

2

2

2

2

,,,,

,

dd

dd

kB

=+−+

=

=+

⎟⎠⎞

⎜⎝⎛+

⎟⎠⎞

⎜⎝⎛+

=υ+

⎟⎟⎠

⎞⎜⎜⎝

⎛−

⎟⎟⎠

⎞⎜⎜⎝

⎛+

=

( )m,mm,

,,,,,

,,,Smin

μ===+⋅=

=⎟⎟⎠

⎞⎜⎜⎝

⎛⋅

+⋅

⋅⋅=

361101136000009365000006508010167

101296661

10123666110167 44

40


Fig.3 Assembly of a cogwheel on a tubular shaft

A.1; A.2; Determining the fit type and precision classes. Applying formula (7) for the given conditions:

So the fit is Ф10H4 / p4. The steps A4÷A10

are detailed in [10].

B. For the interference fit the following limits are set Smax şi Smin. The problem is solved using Table 4.

From Smax set as: Smax = es – EI = es – o (in basic hole, see fig.2), but es = ei + ITx, thus Smax = ei + ITx.and Smin = ei - ES = ei - ITx

(8)

Example: Smax = 106μm; Smin = 68μm for Ф =

55mm. Using formula (8) in the given example:

The resulting fit is 6655

uH

φ ; with the

following deviations: EI = 0; ES = 19 μm; ei = 87; es = 106μm.

Transition fits design

Transition fits (transitional or uncertain) make up a proportion which tends towards 1:

1→dD

because dD ↔ (9)

through this being created the conditions needed for clearance to appear and also interference in a certain percentage

As both clearance and interfence are relatively small (see formula 9), the excentricity (deviation from the position) of the geometrical axes of the two parts is small, towards 0, therefor we obtain concentrical assemblies, thus the conclusion that the transition fits are chosen to ensure a high assembly precision. Transition fits having, both, clearance and interference the insurance against relative movement is done through braces, with the exception of the tolerable fit (H/j) which in certain cases can be mobile.

In the diagram presented in fig 4 are depicted the variations of the assembly precision, the degree of stiffness and mobility, based on the assembly values (clearance or interference), for the groups and types of fit, in the interval (50...80]mm for the nominal diameter, for the tolerance steps indicated in [8].

Fig.4 The variation of the assembly precision, the

degree of mobility and stiffness based on the assembly characteristics

Given the formulas from [1]:

maxmin

minmax

minmin

maxmax

eS;eS;eS

;eJ;eJ;eJ

222

222

−=−=−=

===

(10)

for transition fits(with clearance) results that:

( ) eminmax

maxmax

minmaxS/J

TeeSJ

JJT

222 =−+==+=

=−= (11)

And for transition fits (with interference):

emaxmin

maxmax

minmaxS/J

TeeJS

SST

222 =+−==+=

=−= (12)

where Te – excentricity tolerance. The kinds of transition fits (including the formulaes to calculate (deducted by the author of [1]) emax) are presented in table no. 5 (Table 3.17 from [1]).

41


The fits from types 1 and 2 are used for assemblies that are subjected to frequent assemble/dis-assemble operations and those from type 3 for assemblies that are subjected to less frequent assemble/dis-assemble operations. Fits from type 4 are used in assemblies that are used for high static/dynamic loads, and are only disassembled in capital maintenances, and those from the 5th kind are used for assemblies using a cleat, when they are going to be overly braced.

When designing transition fits, knowing the nominal diameter or the assembly, the following data arrises [1]:

1 - The instructions refering to the assembly precision and the assembly/dis-assembly frequency are known.

2 - The majoritary maximum characteristic is set:

a - Jmax când Jmax >Smax; b - Smax când Smax >Jmax. 3 - The majoritary maximum characteristic is

set, as above, and the standard tolerance (Taj) or the average square deviation (σ).

4 - % is set vor the majoritary maximum characteristic (%Jmax sau %Smax) and t(sau he variation of the fit (or σ).

Table 5

Excentricity „e” [μm] Parameter for assembly imprecission Processing precision

a B c

Tran

sitio

n fa

mily

Assembly Characterist

ics J; S ei High Medium Satisfactory M

ount

ing

prec

isio

n

1 2 3a 3b 3c 4

1.

Jmax»Smax Jocuri; J > 90% ei < 0

Ф (1…500)mm

352 mmax ,e φ=

Ф (1…500)mm

363 mmax ,e φ=

Ф (1…500)mm

395 mmax ,e φ= Mod

est

Ф (1…120)mm 352 mmax ,e φ=

Ф (1…80)mm 33 mmaxe φ=

Ф (1…80)mm 35 mmaxe φ=

Ф (120…315)mm

252 3 m

mmax ,eφ

+φ=

Ф (80…315)mm

5233

,e m

mmaxφ

+φ=

Ф (80…180)mm

5253

,e m

mmaxφ

+φ=

2.

Jmax>Smax Jocuri; J > 80% ei < 0

Ф (315…500)mm

5252 3

,,e m

mmaxφ

+φ=

Ф (315…500)mm

5133

,e m

mmaxφ

+φ=

Ф (180…500)mm

5153

,e m

mmaxφ

+φ=

Satis

fact

ory

3.

Jmax=Smax Joc ≈ 50% Strâng. ≈50% ei=0 sau (ei=0+ε)

Ф (1…500)mm

341 mmax ,e φ=

Ф (1…500)mm

32 mmaxe φ=

Ф (1…500)mm

3753 mmax ,e φ=

Hig

h

4.

Smax>Jmax Strâng. >80% e i > 0

Ф (1…500)mm 3220 mmax ,e φ=

Ф (1…500)mm 3970 mmax ,e φ=

Ф (1…500)mm 342 mmax ,e φ=

Hug

e

5.

Smax » Jmax Strâng →100% e i > 0

emax < 0; J < 0 aj. cu strângere

emax < 0; J < 0 aj. cu strângere

Ф (1…500)mm 331 mmax ,e φ=

Choice criteria:→ Second preference First preference Third preference

[Pre

f.I şi

II

]: v

ery

huge

42


In [1] the algorythm steps for designing the type of the fit using the “key” proposed by the author.

If in [1] the design algorythm of the type of fit based on basic hole is presented, in [3] the design of the transition fit based on basic shaft is presented.

Calculus Example

1. Design the fit for a cogwheel used assembled on the shaft of a gearbox (Ф = 75mm).

For the given example is demanded the realisation of the montage with small forces.

From Table no. 5 the 2nd kind is considered (Jmax > Smax; J > 80%), choice I (for Ф = 1...80), ( ),e mmax

33 φ=

6320638050 ≅=⋅=φ ,m mm,

941198336333 33 ,,e mmax =⋅==φ= μm knowing the value of the maximum excentricity, you can determine the maximum clearance: Jmax = 2emax = 2 · 11,94 = 23,88μm = 24μm

Using one of the fundamental formulas Jmax= ES-ei, and using fig. 4 and 6th table, you can determine: Jmax = ES-ei = ITx-ei.

Considering ITxd = ITxD = ITx şi ei<0 in the “key” formula for using the nomogram is:

(13)

In other words, the maximum clearance is equal to the tolerance zone Itx, which is found in frame I of the 6th Table, and for which a digit corresponds vertically that will represent the grade of tolerance(class of precision, tolerance step) of the projected fit minus the lower deviation (with ei<0) (value from the frame II from table 6, which corresponds vertically to a letter), this will be the symbol letter for the type of projected fit.

For Jmax = 24μm, you can create the “key” formula:

Considering the assembly in the fit system

with basil hole, the projected fit will be Ф75H6 / j5. In machinery construction transition fit and precision classes 5,6 and 7 (with the following values IT5, IT6 and IT7)are exclusively used .

It’s worth mentioning that the “key” formula above could be fulfilled by other combinations of values, but you will choose the variant left after eliminating all the incompatibilities (between the precision class of the hole and that of the shaft there has to be a parity or a difference of maximum ±1), and he existence of the parity of the smallest difference between the value previously determined and that resulted by using the “key” formula (13). In [10] there are calculus examples for 2); 3); 4).

Table 6

Fig.5 Location field of tolerance depending on the fits (transition fits)

Conclusions

If the usage of a standardized fit for which calibers exist [2] is recommended for small volume

production, for large volumes production, if the parts are verified based on calibers then it’s worth creating non-standard calibers.

43


Transforming from the fit system using basic shaft to the fit sistem using basic hole in the case that the two precision steps are not equal, the part woult retain its grade of tolerance. With the purpose of eliminating routine tasks(simple math operations, consulting deviation tables, fundamental tolerances etc.) and substantially reducing the time required for these operations, the problem of fit designing can be easily solved using an electronic calculator[1],[9].

After chosing from the fit list the most convenient one, the limits of deviation and the assemply characteristics will be determined.

References

1. Bagiu L. Toleranţe şi ajustaje, Editura Helicon, Timişoara, 1994. 2. Drucean A., ş.a. Maşini-unelte şi control dimensional, Partea a II-a. Lucrări de laborator, Litografia I.P.”Traian Vuia”, Timişoara, 1991. 3. Niţescu N., Stoian A-M. Unele aspecte privind proiectarea ajustajelor intermediare., Lucrările ştiinţifice ale Simpozionului Multidisciplinar Internaţional „UNIVERSITARIA SIMPRO 2005”, Tehnologie, Mecanisme şi Organe de Maşini, Editura Universitas Petroşani, pag.43-48. 4. Niţescu N., Stoian A-M., Niţescu Al. Some Aspects in Regard to the Designing of Fits. Annals of the University of Petroşani, Mechanical Engineering, vol.7 (XXXIV), pag.75-86, Universitas Publishing House, Petroşani, România, 2005.

5. Niţescu N., Stoian A-M. Unele aspecte privind proiectarea ajustajelor cu joc. Lucrările ştiinţifice ale Simpozionului Multidisciplinar Internaţional „UNIVERSITARIA SIMPRO 2006”, Tehnologie, Mecanisme şi Organe de Maşini, Mecanică şi Rezistenţă, pag.62-72, Editura Universitas Petroşani, România, 2006. 6. Niţescu N., Stoian A-M. Some Aspects in Regard of Interference Fits., Annals of the University of Petroşani, Mechanical Engineering, vol.9 (XXXIX), Part.II, pag.73-78, Universitas Publishing House, Petroşani, România, 2007. 7. Niţescu N., ş.a. Unele aspecte privind alegerea preciziei, grupei şi felului de ajustaj în construcţia de maşini. Simpozionul „Durabilitatea şi fiabilitatea sistemelor mecanice”, Universitatea „Constantin Brâncuşi”, Târgu-Jiu, iunie 2008. 8. Niţescu N., Poanta A., ş.a. The computer Assisted Design of The Transition Fit. Simpozionul ştiinţific internaţional multidisciplinar „Universitaria Simpro 2008”. Lucrările ştiinţifice „Technology, Mechanisms and Machines, Mechanics and Resistance, Editura Universitas, Petroşani, 2008. 9. Poanta A., Niţescu N., ş.a. The computer Assisted Design of The Clearance, Interference and Transition Fits., 17th Internaţional Conference on Control Systems and Computer Science, Proceedings CSCS, Vol.1, pag.161-165, Editura Politehnica Press, 26-29 May 2009. 10. Niţescu N. Toleranţe şi ajustaje, măsurări, verificări şi control dimensional – îndrumător de laborator. Editura Universitas, Petroşani, 2010.

44


FAULT ANALYSIS IN HIGH VOLTAGE NETWORKS THROUGH MODERN NUMERICAL RELAYS

Dragoş PĂSCULESCU*, Andrei ROMĂNESCU**

Abstract Modern digital protections, provides comprehensive data in the event of a defect in equipment, data that can be used for the analysis of defects and to remove weaknesses in the system, namely the primary apparatus. Keywords fault, modern digital terminal equipment, software.

General considerations

Recorder function allows you to store disturbance events that took place in the primary network distribution system through continuous data collection. Such stored data can be used for various tests. Facilities included in the disturbance report function on a modern terminal the following: indications event recorder and fault locator, enabling the saving of many events. All events are recorded in chronological order with the actual times at which they occurred. Information is stored in non-volatile flash memory, avoiding data loss in case of interruption of the supply voltage terminal.[1]

Also new is the advantage of digital terminals providing information on the defect to reduce the cut-off time, and also speed up the recharge function of the electrical equipment. Interruption to electricity supply is characterized by two index:

SAIFI – System Average Interruption Frequency Index

entatilima

rerupereint

NN

SAIFI ∑= (1)

Number of consumers affected in each loss is added to all interrupts in one year and the result is divided by the average number of customers, providing the average number of interruptions that has a single customer. [4]

CAIDI – Consumer Average Interruption Duration Index

( )∑

∑ ⋅=

rerupereint

rerupereintreruptiint

NDN

CAIDI (2)

Interruption duration is mainly a long period of time required to locate the fault, together with the ____________________________________ * Lect.eng. Ph.D – University of Petroşani ** Eng. Ph.D. Transelectrica Alba-Iulia

short time necessary corrective measures power refueling. Such a calculation offline fault location can help, therefore, improve CAID index. [5] Obstacles to a precise fault location

Most faults are single-phase earth faults. Most often, the fault is calculated by measuring the loop impedance fault, either directly by the absolute value of phasors, or with changing delta between phasors before and after defect defect, also sometimes supply network is considered as a fault source model affected loops. But all these approaches are limited in precision due to system parameters.

- residual compensation ( )0LG k,Z/Z : most faults that occur in the electricity transmission system are earth faults. Precision "single ended" fault location depends largely offset by terminal sequence distinct set numerical zero when a fault involving ground. In most cases the exact value of this factor compensation is not known. Thus impedance fault has not often a proportional distribution along the length of the line, because it can vary widely depending on soil composition (sand, stones, water, snow) and type of applied earth (earth tower, cable screens parallel metal pipes). - parallel lines: In the case of parallel lines, inductive coupling of the current circuits is present. On transposed lines, only the zero sequence system is negatively influenced by this coupling. For load and faults that do not involve ground, the influence of the parallel line may be neglected. With ground faults in the other hand, this coupling may cause substantial errors in the measurement. On a 400 kV double circuit overhead line measuring errors at the end of the line may for example be as large as 35%. Some devices with distance protection functionality have a measuring input that may be applied to measure the ground current of the parallel line. With this measured ground current of the parallel line the impedance calculation may be adapted such that the parallel line coupling is compensated. This parallel line compensation can however frequently not be implemented. The reasons for this are that only a section of the line is in parallel to another line, two or more parallel lines exist or the connection of current transformer circuit between individual feeder bays is not desired by the user for operational reasons. While the selective distance

45


protection function can still be implemented by appropriate zone setting in combination with teleprotection systems, the results of the fault locator without parallel line compensation is often not satisfactory.[6] - tower geometry and transposition of the conductors - The geometry of the overhead line towers as well as the phase conductor transposition technique may introduce impedance measuring errors of up to 10%. Extra high voltage lines in transmission networks are often symmetrically transposed with 3 sections. In total, the same impedance for each phase is then approximately achieved for the whole line length. This influencing factor on the accuracy is in this case kept within an acceptable range. - another factor is the distribution lines that are usually heterogeneous, built as a chain of several segments for both economic reasons and environmental reasons. A typical example is a line that begins with one basic cable with some length, which is maintained by a transposed overhead line conductor arrangement whereby the horizontal. - also even if all the data line are known, there remains a significant influence on the measured impedances: how they would be different fault resistance seen at the ends of a transmission line, the phase shift due to stress, it can be seen in figure number 1.

Fig.1 Simple model for the effect of fault resistance at double-ended infeed (load flow from left to right)

At the line end that is exporting the load, the measured reactance is reduced, the phasor ( ) f12 RI/I ⋅ is rotated downwards (figure 3). At the line end that is importing load, the measured reactance is increased, the phasor ( ) f12 RI/I ⋅ is rotated upwards. The smaller the phase displacement between the currents

1I and 2I is,

the smaller the influence on the measured reactance will be. This assumed that the angles of the fault impedance loop are equal on both sides of the fault, which is on transmission lines normally fulfilled. On faults without ground, the fault impedance will be measured only with an additional resistive part what will not effect the result of the fault locator.[4][5]

Fig.2 Double infed fault resistance affecting the measured reactance

- other influences in the impedance measurement can be considered: capacitive line/cable charging current, CT and VT errors, transients of the voltages, declining DC component of the currents, load taps along the faulted line.[3]

How to obtain the precise fault location

If the fault location is known so due solely to the high degree of precision, specialized staff from the operation of power lines and stations can save time during the electrical control defective. Thus the supply of electricity to other parts of the energy system can be restored quickly, providing higher revenues for utilities and also helping to improve outage times CAID index.

Fig.3 Fault oscillogram, phasor diagram and impedance locus derived from one fault record

An accurate fault location is now available for all those who have implemented modern digital relay equipment that exploits them.

Modern numerical relays also allow you to download data and oscillograms on the fault, which

46


helps the interpretation of the defect, so we obtain release time, during the outburst, the amplitude, some phasors, as can be seen in Figure 3.

Positive sequence algorithm

The idea of installing the fault recorders at both ends when a line power appeared along with marketing and terminal deployment of protection in power systems. The reason is to use a set of redundant information about the defect to remove some harmful effects that may occur in measurement.

But this must be complemented with the other criteria namely, to restrict the calculations to the positive sequence system. The main advantages of this combination are:

- the data for the positive sequence system are the best and most precisely known grid data, as it can be validated by a three-phase load measurements

- the algorithm is invariant to fault resistance, as the fault is represented by a current source only.

- the signals of the positive sequence system are invariant to mutual coupling to adjacent circuits (2 or more

The voltage at the fault location “x” along an ideal line (length L, impedance Z, wave length Ι) is induced by the quantities from either of both line ends l=left and r=right:

( ) ( ) ( ) lllf IxhsinZVxhcosxV ⋅⋅γ⋅−⋅⋅γ= (3)

( ) ( )( )

( )( ) r

rrf

IxLh

ZVxLhxV

⋅−⋅⋅

⋅−⋅−⋅=

γ

γ

sin

cos (4)

At the fault location “x” the difference between these voltages has to be zero.

( ) ( ) ( ) 0xVxVx rflf =−=ε (5)

Also we now switch from solving the fault location analytically at one equation to estimate the most likely fault location at two equations. The voltage condition (5) applies for the positive sequence system as well as for the negative sequence system. Combining the information from both systems with the least-square criterion we get to a one-dimensional function:

( ) ( ) ( ) 2

neg

2

pozdefect xxxk ε+ε= (6)

The minimum of “k” is solved for the fault location “x” using a one-dimensional minimization featuring both a golden section search and a parabolic. This estimation is quite robust even

against line data errors not only in the zero-sequence system, but also in the positive-sequence system.[2]

Fig.4 Power Line fell to the ground 220kV Brazi Vest – Fundeni

Conclusions

As the algorithm has by principle excluded a lot of the causes for the common errors in fault location, the results obtained are significantly more precise than ever known in the past. The major advantage lies not in optimizing the precision for one special condition only like load compensation or mutual coupling. Instead the algorithm shows a high robustness against all usual causes for errors. All zero-system related influences (data errors, fault resistance, mutual coupling) are excluded by the principle. Even a data error of the positive sequence impedance only reduces the estimation quality and therewith enlarges the interval of confidence, but the indicated location remains correct. References

1. Duşǎ V. Sisteme moderne pentru comanda şi controlul funcționǎrii rețelelor electrice, Editura Politehnicǎ Timişoara, 2006

2. Vasilievici A. Implementarea echipamentelor digitale de protecție şi comandă pentru rețele electrice, Editura Tehnică, Bucureşti, 2000

3. Fotǎu I. Electroenergeticǎ, Ed. Universitas, Petroşani 2003

4. Saha M. Fault location method for MV cable networks. 7th International Conference on Developments in Power System Protection, IEE Conf. Publ. 2001

5. Kiessling G. Software solution for fault record analysis in power transmission and distribution. 8th International Conference on Developments in Power System Protection DPSP, IEE Conf. Publ. 2004

47


POSITIONAL SYNTHESIS OF FOUR-BAR MECHANISM

Vasile ZAMFIR*, Horia VÎRGOLICI**, Olimpiu STOICUŢA***

Abstract In the paper we present the positional synthesis of the four-bar linkage as part of mining machines and equipment.

Introduction

At the synthesis of four-bar mechanism it is

required to determine the relative lengths 0

1

lla = ,

0

2

llb = and

0

3

ll

c = and the angles φ0, ψ0 so that

element (3), considered working element, should generate the function ψ=F(φ) on the interval [φ0, φn], figure 1.

Fig. 1 The four-bar mechanism and the parameters

which defines it

To this end, five positions of the working element are chosen on the approximation interval [φ0,φn]. They are defined by the abscissae φ1, φ2, …, φ5, to which correspond the positions ψ1=F(φ1), ψ2=F(φ2), …, ψ5=F(ψ5) of the working element (3).

The function ),,,,;( 00 ψϕϕψ cbaf= is expressed analytically, obtaining the equation system:

5,...,2,1);,,,,;( 00 == icbaf ii ψϕϕψ (1)

from which the five dimensional and positional parameters of the mechanism a, b, c, φ0, ψ0 can be obtained.

From calculations, the system of implicit equations (2) is preferred in place of system (1):

5,...,2,1;0),( == if ii ψϕ (2) ____________________________________ * Prof.eng. Ph.D – University of Petroşani **Lect. Ph.D - Univ. „Spiru Haret” Bucureşti *** Asist.eng. Ph.D – University of Petroşani

The implicit function f(φ,ψ) is obtained squaring the mechanism vectorial contour equation:

1++= cab (3) obtaining the position function of the four-bar mechanism, of the form:

01)cos(2

)cos(2)cos(2222

0

000

=−−−++−

−++−−+

cabc

aac

ψψ

ϕϕϕϕψψ (4)

Equation (4) gets various appearances, depending on parameter number (three, four or five) chosen to be calculated; it will appear as a generalized polynomial, as it will be shown in what follows. Three parameter calculation

For the calculation of three parameters of the mechanism structure, equation (4) is written as the following polynomial:

0)()()( 221100 =+++ ϕϕϕ fpfpfp (5)

The parameters a, b, c (parameters φ0 and ψ0 are chosen arbitrarily) are to be found. By identification with equation (4) the following expressions are obtained for coefficients pj and functions fj, j=0,1,2:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

=

=

−−−=

apcapc

cabp

2

1

222

0 21

(6)

⎪⎩

⎪⎨

⎧

−−+=+=+=

)cos()()cos()()cos()(

002

01

00

ϕϕψψϕϕϕϕψψϕ

fff

(7)

The interpolation nodes in the interval [φ0,φm] are chosen, by abscissae φ1, φ2, φ3, either arbitrarily or as it will be shown further, by Chebyshev spacing for example.

The functions ψi=F(φi), i=1,2,3 are calculated in the three positions of the approximation interval, getting the following linear system of three equations with three unknowns pj, j=0,1,2:

⎪⎩

⎪⎨

⎧

=+++=+++=+++

0)()()(0)()()(0)()()(

322311300

222211200

122111100

ϕϕϕϕϕϕϕϕϕ

fpfpfpfpfpfpfpfpfp

(8)

48


from which the unknowns p0, p1 and p2 are found and by means of the relations (6), the unknown dimensional parameters a, b, c of the four-bar mechanism are established.

After having found the parameters a, b, c, the function (8) is written as the following equation in sin(ψ0+ψi) and cos(ψ0+ψi), after the function cos(ψ0+ψi-φ0-φi) is developed adequately:

0)cos()sin( 00 =++++ iiiii CBA ψψψψ (9) from which is found:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

−+±=+

ii

iiiii CB

CBAAarctg

222

0 2ψψ (10)

where:

⎪⎪

⎩

⎪⎪

⎨

⎧

=−++−

=

+−=−=

nica

ccbaC

aBaA

ii

ii

ii

,...,2,1;cos2

11cos

sin

222

ϕ

ϕϕ

(11)

Taking several values, inclusively the values of the nodal abscissae of angle φi on the interval (φ0,φm), with relation (10) the value of corresponding angle ψi can be determined and then is found the value of deviation Δψi, i=0,1,2,…,n, whose magnitude is compared with the values of allowable deviation Δψad:

adii ψψψψ Δ≤−=Δ maxmax (12)

The calculation of four parameters a, b, c, ψ0 (φ0 is chosen arbitrarily)

In this case, the mechanism position function (4) can be written (after the adequate development of cos function) like this:

0)()()()()(

4433

221100

=++++++

ϕϕϕϕϕ

fpfpfpfpfp (13)

where:

⎪⎪⎪⎪

⎩

⎪⎪⎪⎪

⎨

⎧

====

=

−−−=

3204

3

02

01

0

222

0

cos

cos21

pptgapaptgpc

ap

cacbp

ψ

ψψ

ψ

(14)

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

−+=−+=

=+=

−=

)sin()()cos()(

sin)()cos()(

cos)(

04

03

2

01

0

ψϕϕϕψϕϕϕ

ψϕϕϕϕ

ψϕ

fffff

(15)

It can be noticed that coefficient p4 is a combination of coefficients p2 and p3, therefore the system will be non-linear.

The calculation of four parameters a, b, c, φ0 (ψ0 is chosen arbitrarily)

In this case, developing the functions in equation (18), we come to the form (13), where pj and fj(φ) have the appearance:

⎪⎪⎪⎪

⎩

⎪⎪⎪⎪

⎨

⎧

====

−=

−−−=

3204

3

02

01

0

222

0

cos

cos21

pptgcpcptgp

acp

cacbp

ψ

ϕψ

ϕ

(16)

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

−+=−+=

=+=

−=

)sin()()cos()(

sin)()cos()(

cos)(

04

03

2

01

0

ϕψψϕϕψψϕ

ϕϕψψϕ

ϕϕ

fffff

(17)

As in the previous case, coefficient p4 is a combination of coefficients p2 and p3, therefore the system will be non-linear.

The calculation of five parameters

After developing all cos functions in equation (18), the equation is written under the form:

0)()()()()()(

554433

221100

=+++++++

ϕϕϕϕϕϕ

fpfpfpfpfpfp

(18)

where:

⎪⎪⎪⎪⎪⎪⎪

⎩

⎪⎪⎪⎪⎪⎪⎪

⎨

⎧

+−

=

−=

−−=

−=

−−=

−−−−

=

3142

41325

00

04

00

03

00

02

00

01

00

222

0

)sin(sin

)sin(cos

)sin(cos

)sin(sin

)sin(21

pppppppp

p

ap

ap

cp

cp

accabp

ψϕψ

ψϕψψϕ

ϕψϕ

ϕψϕ

(19)

⎪⎪⎪⎪

⎩

⎪⎪⎪⎪

⎨

⎧

−=====

−=

)cos()(sin)(cos)(cos)(sin)(

)sin()(

5

4

3

2

1

0

ϕψϕψϕψϕϕϕϕϕ

ϕψϕ

ffffff

(20)

49


Due to coefficient p5, the system is non-linear.

After finding coefficients pj, j=1,2,…,5 the same steps are covered in the case of calculation of three parameters.

Supplementary conditions at the positional kinematic synthesis of the four-bar mechanism

The mechanism designed has to ensure the generation of function ψ=f(φ) on the interval [φ0,φm]. Besides, the mechanism has to fulfill certain supplementary conditions: the crank existence (the rotability of the driving element 3600), the maximum lengths of the elements have to surpass a certain value, respectively their minimum lengths have to be below a certain value, the observance of the transmission angle etc.

Crank conditions

In case there is a rotating crank, two extreme conditions of the mechanism appear, called critical points or dead points, figure 2.

Fig. 2 Dead points of the four-bar mechanism,

where there is a crank

The following relation is valid for figure 2.a: 4321 llll +≤+ (21)

and the following relations for figure 2.b :

4312 llll ≥+− (22)

4123 )( llll ≤−− (23)

Relation (23) can also be written: 4231 llll +≤+ (24)

Supposing crank l1 is the shortest element. Three cases are possible: a) If l4 is the longest element, relation (24) must be fulfilled, because l4 is the longest element and if relation (23) is fulfilled, even more so is relation (22); b) If the connecting rod element l2 is the longest, relation (21) has to be fulfilled, which also includes relation (23), and is no account which of the elements l3 or l4 is the longer; c) If the lever element l3 is the longest, the inequality (24) has to be fulfilled, and is no account which of the elements l2 or l4 is the longest.

From the three cases it can be seen that relation (21) represents the crank condition for all the three cases.

This condition was given by Grasshof in the theorem saying that the necessary and sufficient condition for a four-bar mechanism to admit a crank is that the sum between the length of the shortest and the longest element should be less or at most equal to the length sum of the other two. The four-bar mechanisms that comply with Grasshof theorem are called of complex type. Out of these, by making one of these four links stationary, the same four-bar linkage will yield the following types of four-bar linkages:

- Double crank mechanism, when the shortest element is stationary;

- Double rocker mechanism, if the stationary element is opposite to the shortest element;

- Crank-and-rocker mechanism, when one of the elements adjacent to the shortest one is stationary.

The other mechanisms that do not comply with the conditions of Grasshof theorem are called of simple type, they all being double rocker mechanism, regardless which link is stationary. The maximum and minimum length of the links

The links relative length has to be between

the limits L and L1

(usually L is taken 5).

Fig. 3The transmission angle for the four-bar

linkage The following 12 inequalities are given for the

four-bar linkage (see figure 3):

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

⋅≤≥⋅≤≥

≥⋅≤⋅≤≥

⋅≤≥⋅≤≥

cLbL

cbLaLba

LcbLbcLa

Lca

LcL

bLaL

a

;1;;

;1;;

1;1;1;1

(25)

The transmission angle

The transmission angle γ at the four-bar mechanism is made between the absolute velocity direction of point C and the relative velocity direction of point C in relation to point B (figure 3).

50


Between the transmission angle γ and the pressure angle θ there are the relations (these two angles being complement):

⎪⎩

⎪⎨

⎧

≥+=

<−=

00

00

90,90

90,90

γθγ

γθγ

if

if (26)

For the mechanism to have good transmission characteristics between the connecting rod b and the working element c, the transmission angle γ should be comprised between the limits:

adad si γγγγ −≤≥ 0maxmin 180 (27)

The transmission angle γ can be expressed depending on the mechanism parameters and on the input variable φ and the output one ψ, applying the cosinus theorem in the triangles ABD and BCD: ( ) )cos(21cos2 0

2222 ϕϕγ +−+=−+= aabccbBD (28) or

)cos(2

1cos 0

222

ϕϕγ ++−−+

=bca

bcacb

(29)

If the driving element AB takes up positions AB’ and AB’’ shown in figure 4, the transmission angle γ has the value minγγ = for φ0+φ=0 and

maxγγ = for φ0+φ=1800, that is when element AB can be crank.

Fig. 4 The limit transmission angles at the four-bar

linkage that allows a crank

The expressions of the boundary transmission angles can be written with the notations in figure 4:

bcacb

2)1(cos

222

min−−+

=γ (30)

bcacb

2)1(cos

222

max+−+

=γ (31)

For the transmission angle in a four-bar linkage to be comprised between the boundaries (27) and the driving element AB to be a crank, the following inequalities should be fulfilled:

⎪⎩

⎪⎨

⎧

−−+≥

−−+≥

222

222

)1(cos2

)1(cos2

cbabc

acbbc

ad

ad

γ

γ (32)

For the mechanism to be of the crank and rocker type, the crank AB has to be the shortest element. In this case, the last three columns of the inequalities (25) have no longer meaning and therefore, besides the relations (32) referring to the transmission angle, the following conditions have to be fulfilled, referring to the relative minimum and maximum length of the links and the crank rotability:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

<≥

<≥

<≥

1;

;

;1

aLba

caLca

baL

a

(33)

For the four-bar linkage to have two cranks, as it was seen above, the stationary link should be the shortest element. In this case, besides inequalities (32), the following three inequalities out of the 12 inequalities (25) has to be fulfilled:

⎪⎩

⎪⎨

⎧

≤<≤<≤<

LcLbLa

111

(34)

In the case when for a four-bar linkage one or both inequalities (32) are not fulfilled, then the mechanism is of the two rockers type.

In the first case the connecting rod is the shortest element. In this case the following inequalities have to be fulfilled:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

≤≤

≥≤

≥≤

LcLcaLcbLba

LbLa

;

;

1;

(35)

In the case when both conditions (32) are not fulfilled, the relation (29) has to used, by means of which the corresponding magnitude of the transmission angle γ is determined for a run of successive values of the input angle φ (corresponding to the oscillation interval of the rocker). In the case when the obtained values for the angle γ are within the prescribed limits, then it is checked if the relations (25) are fulfilled. The above calculations, given with the aim of finding three, four or five parameters, with optimizing conditions regarding the links lengths, the transmission angle and the crank conditions can be easily programmed on the computer.

51


Numerical example

Let us synthesize the four-bar mechanism (five parameters) for approximation of the interval

0 0; 115 ;mϕ ϕ= = in all possible combination cases of samples and multiple interpolation nodes, function:

( ) ( ) 21250

F ϕ ϕ ϕ= Ψ = ⋅ (36)

in the next cases: admissibil error ( ) 20adψ ϕ ′Δ = ; the admissibil transmission angle

60adγ = ; the raport between maximal and minimal length of the ellements 5L = .

Solution: There are 10 possible combination for the four-bar mechanism:

P-P-P-P-P;PP-P-P-P;P-PP-P-P;PP-PP-P; PP-P-PP; PPP-P-P; P-PPP-P; PP-PPP;

PPPP-P; PPPPP

Appling the relation available at subchapter four, we can realise the next diagrams, of the aproximant and aproximated functions, and the aproximate error diagram.

Fig. 5 P-P-P-P-P case

Fig. 6 PP-P-P-P case

Fig. 7 P-PP-P-P case

52


Fig. 8 PP-PP-P case

Fig. 9 PP-P-PP case

Fig. 10 PPP-P-P case

Fig. 11 P-PPP-P case

53


Fig. 12 PP-PPP case

Fig. 13 PPPP-P case

Fig. 14 PPPPP case

Conclusions

The choice of the approximation function depends on circumstances – these being largely determined by the aspect of the function to be approximated, by the desired accuracy, by the preferences and mathematic ability of the person who solves the problem.

The function to be approximated has two aspects:

- the empiric aspect (the function is given by the values table it takes up for certain values of the variable);

- the analytic aspect. Generally speaking, the functions that are

used to approximate the given function can be expressed by n-degree polynomials. The polynomial is chosen so that for the same values given to the variable, it should have the same values as the given function. That is to say, the given function curve has (n+1) common points with the representative curve of the n-degree polynomial.

However, many times the approximation is done by p-degree polynomial, where p < n.

In this case, the representative curves will no longer have any common point, but the choice of p-degree polynomial is done, setting the condition that the generated diagram should pass as close as

54


possible to the (n+1) points on the given function diagram.

In solving the two aspects of the problem, the number and type of points where the diagrams of the two function touch are of great importance.

If the number of common points is small (small number of parameters) the interpolation method is not satisfactory.

Generally speaking, the interpolation method is used when the approximation is done in several discrete points in the interval. It is recommendable to use the multiple nodes interpolation to diminish the amount of work.

Nowadays, when we can use last generation software, the analytic synthesis has no limits. We can adopt that calculation method that leads most easily to a general equation that can be applied in programming.

Along with the problem of positional kinematic synthesis, a series of supplementary conditions arise; they ensure obtaining the most suitable, simple and operational structural diagram with a low number of elements, so that the designed mechanism should render the demanded motion law as faithfully as possible.

References 1. Zamfir V., Vîrgolici H. Condiţii de sinteză prin metoda interpolării Revista Minelor, vol 17, nr. 1 / 2011

2. Lazăr M., Pandrea N., Popa D. Obtaining Cebâşev-type mechanisms through optimal synthesis based upon some caalculus programs Mec. Apl., Bulletin of the University of Piteşti, 2001

3. Georgescu T., Lazăr M. Cebâşev-type mechanisms obtained through the optimum synthesis based on some calculus programs Scientific Bulletin automotiveAutomotive, no. 19, vol 1., University of Piteşti, 2002

4. Artobolevski I.I., Levitski N.I., Cercudinov S.A. Sintez ploskia mehanizmov Fizmatigiz, Moskva, 1959 5. Beleţki V. Rasciot mehanizmov maşin avtomatov piscevâh proizvodstv, „Vişa scola”, Kiev, 1974

6. Cercudinov S.A. Sintez ploskih şarnirnorîciajnîh mehanizmov Iz-vo Academii Nauk S.S.S.R., Moskva, 1959

7. Dancea I. Programarea calculatoarelor numerice pentru rezolvarea problemelor cu caracter tehnic şi de cercetare ştiinţifică Ed. Dacia, Cluj-Napoca, 1973

8. Hartenberg R.S., Denavit I. Kinematic Synthesis of Limkage McGraw-Hill Series in Mechanical Engineering, New York.

9. Lazaride Gh., Stere N., Niţă C. Mecanisme şi organe de maşini Ed. Didactică şi Pedagogică, Bucureşti, 1970.

10. Sarkisean Iu.L, Cecean G.S. Optimalnîi sintez peredatocinovo cetîrzvenika Maşino-beledenie, nr.3, 1969.

11. Tesar D. The Generalized Concept of Three Multiply Separated Positions in Coplanara Motion Journal of Meechanisms, vol.2, 1967, p.461-474

12. Tesar D. The Generalized Concept of Four Multiply Separated Positions in Coplanara Motion Journal of Meechanisms, vol.3, 1968, p.11-23

13. Zamfir V. Sinteza mecanismelor cu bare articulate plane (Note de curs), fasciculele 1-5 Litografia Institutului de Mine, Petroşani, 1976, 1977.

55


Instructions for authors

• Papers must be written using the program MS Word (or equivalent).

• Authors need to have the following page settings: A4 page format,

Up/Down/Left/Right - 2cm, Header/Footer - 1,25 cm.

• The font used is Times New Roman.

• Title is centered, capital letters, 14p. After title one free line 12p, then the name

of the authors centered, italics, 12p, surname with capital letters. Author

affiliation is written as footnote.

• Main body text is written with 11p letters, on two equal columns size 8,1 cm.

Chapter titles are written without alignment, bold, while chapter subtitles

without alignment, bold, italic. One free line after every chapter title. Paragraph

alignment is 0.7 cm.

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Mining Revue 2/2011 EN

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