VENTILATION IMPROVEMENT BY RE-ORGANISATION -A case study in SCCL

MD. Suresh Kumar Additional manager, UG mech cell, CP&P, SCCL. NIM-RG-II, Karimnagar dist. AP. Email: MDS_ROOJI@yahoo.co.in,

ABSTRACT

Safe, sustainable underground mining of any scale is not possible without an effective ventilation system. An efficient and effective mine ventilation system is not achieved by accident. It requires incorporation of a sole understanding of scientific ventilation principles into the planning stage itself and the sole understanding of scientific ventilation principles in further execution process. Important lessons can be learnt from history which has emphasized time and time. The knowledge require to implement effective mine ventilation has often been significantly more advanced than the practice adopted in the mine at the time. The terrible loss of life in the coal industries in the 19 th

Century is a sobering example. The mine disasters in 1980’s and 1990’s have drawn attention on mine ventilation. In all those examples, the health and safety risk were well known, as were the necessity of engineering of ventilation in ordered to minimize the risks. The cost of installing and managing effective ventilation system must have been minuscule compared with the subsequent outlay for compensation. One inference can be drawn from all of these is that ignorance and indifference are the important factors. The basic requirement for the mine ventilation system is to Dilute gaseous and particulate pollutant to concentration which are not injurious to

the health and safety of the workforce Maintain thermal comfort through the provision of adequate air velocity Assist with maintaining workforce morale and productivity through the provision of

high quality underground environmental conditions. In the processes of the mining, if positive airflow to the workings is not provided, the air will become stale, contaminated and unfit for human consumption. The ventilation must therefore be sufficient to deal with the contaminants such as dust, heat, gases and water vapor released during mining. If it is not adequately dealt with, it may become best discomfort to mine workers, and worst cause of serious or even fatal illness.This paper deals with the scientific study made to find out the effect of environmental conditions on health and chronological effort put to improve the ventilation standards in the mine Gdk-10A Incline and the proportionate improvement on production and productivity.

KEYWORDS: annual average temperature; sub surface temperature; heat transfer; LVCs; quality of air; special care in long drivages

1. INTRODUCTION

Providing healthy working environment for the underground miner is the major challenge for mine management and regulatory authorities. This complex task will

become more difficult in the future because large, deeper and more complicated underground mines are being designed.Gdk-10A incline is one of the best examples for this due to its extensive and deep workings, increased depth, its moist roof condition and the degree of mechanisation. The single seam operation in the mine initially had turned advantageous and the same became main cause and culprit for total ventilation problem in the mine in terms of difficulties in heat dissipation. Moreover the limited galleries in the existing No 1 seam offering high resistance to ventilation circuit and the fall of sides and roof in some places in return air ways are added reasons. Further the abortive ventilation walls due to heightened and widened galleries and their numbers are the major contributing factors for poor volumetric efficiency in the mine.

2. ABOUT THE MINE

2.1. Location, technologies and extent of workingsThe mine is one of the mechanized underground mines of SCCL located in sector-III of Godavarikhani area in Karimnagar dist.AP. The different technologies like SDLs, road headers and long wall face are exiting along with their back-up arrangements like belts, haulers and substations in a closely crowded location. The mine is served with two intake inclines and one return shaft. There are three main intake headings from Pit bottom to boundary of the mine. Among these one is used for coal conveying other two for haulage. The populous of pumps ranging from 125HPs, 190HPs, 240HPs, and 350HPs are being located and operated along these intake air ways. Belt conveyors are being operated in the mine for the length of around 4 km apart from districts belts, which is one of the source of transmitting heat energy and dust into the atmosphere. The total installed capacity of all electrical equipments in the mines is 8985 HP.

2.2. Fan parametersThe mine is basically worked with 300 HP / 3 Lack fan Andreyule fan with stantage 200 HP / 2Lack fan. The Road headers drivages for Long wall gate roads are being worked with high water gauge auxiliary fan. The details are given in the table 1.

Table 1: Details of Main mechanical ventilator and auxiliary fansDATA WORKING FAN STAND BYFan make / motor A/Y / Crompton greaves Hooks pooning / BhaCapacity 300Hp 200HPAmps 32amps / 3.3kv 28amps / 3.3kvMotor RPM / Water gauge 750 / 66mm 750 / 38mmNo of blades & angle 18 / 5 degrees 12 / 5 degreesEvassee length/dia 10m/3.6-4.8m 10m/3.6-4.8mPower consumption 5369.04kwh/day 3528kwh/dayAuxiliary fansFemrill (125HP) 420-700 cum.metersAndreyule (125 HP) 500 cum.meters2.3. VEQThe overall ventilation efficiency for a mine is arrived at with a relation between the total intake quantities flowing into the mine to the sum of quantities reaching to the

LVCs in each district. The calculated VEQ for the mine was 73% prior to ventilation reorganization and it was shooted upto 86% after reorganization.

3. VENTILATION REQUIREMENT OF THE MINE

3.1. Statutory standardsAs per Indian coal mining Regulation 130 of CMR1957, the persons should be supplied with statutorily acceptable air in terms of quality and quantity as follows.

3.1.1. Qualitative Standards Air should contain at least 19% O2.CO2 content has to be kept below 0.5%. For diluting inflammable gases to safe concentration, the % of CH4 in the general body of the return air should not exceed 0.75 and 1.25% in any place in the mine. CO and nitrous fumes shall be less than 50 and 5 ppm. The wet bulb temperature should not exceed 33.50 C, when it exceeds 30. 50 C the velocity of air shall be more than 1 m/s. The Permissible dust concentration shall not exceed 3 mg/cum of air sampled.

3.1.2. Quantitative StandardsFor any ventilation district quantity of air required to be passed along the LVC is determined based on the number of men employed on the largest shift (6 m3/min/man) and on production (2.5 m3/min/tonne of daily output). As per CMR 136A the air velocities (m/min) should be as follows for degree I, II and III mines. Immediate out bye ventilation connection : 30 / 30 / 30 4.5m from face on intake side of partition : 30 / 30 / 45 7.7m out bye of the discharge end of an air pipe : 15 / 15 / 25 Maximum span of long wall face : 60 / 60 / 75

3.1.3. Quantity of air for long drivages In lieu of rate of gas emission, heat addition and dust production in long headings, at least 284 m3/ min has to be circulated within 4.5m of the face. Face velocity of 0.5 to 2.0 m/s is reasonable, velocity above 2m/s cause discomfort and raise dust.

3.1.4. The overall requirement of airKeeping the above statutorial requirements and comfort of workmen in mind the quantity of air to be circulated was calculated by summing up the requirements of all districts, engine hoses, pumping rooms, substations, non sectionalized workings, leakages from doors, stoppings and expansion of air in upcast shaft. The results so obtained demanded further improvement of quantities and supply of comfort air as faces were suffering from inconvenient quality of air.

4. QUALITY OF AIR

Air quality is mainly expressed in terms of air temperature and air humidity. Hot and humid conditions have significant effect on the miners. Fall of working efficiency, mental fatigue, changes in cardiovascular system, heat stroke might occur in extreme hot and humid condition. Safety of miners is also directly related to these conditions.

4.1. Air TemperatureTemperature should not confuse with heat. Heat is form of energy and is calculated whereas temperature is state and measured. The difference being the thermal capacity which is the ability to raise the temperature of 1kg by 1oC.There are two components of air temperature, the dry-bulb and wet bulb. Dry-bulb temperature is the actual air temperature, measured with a standard thermometer and the wet bulb temperature measures the cooling power of air. When the air is humid, very little moisture evaporates from the wet cloth, and cooling process slows down. The smaller the difference between the two temperatures, the higher the humidity.

4.2. Heat transferThe knowledge of mechanism of heat transfer is vital to learn the importance of air quality. “Mr. George Agicoda and Mr. Demetalica the Australian ventilation experts” have studied heat transfer between source and the environment and “The Environment engineering in South Africa mines published by the mine ventilation society of South Africa in1989”narrates the different way of heat transfer between human body and environment which are Respiration: in a typical hot environment, respiratory heat exchange accounts for about 5% of metabolic energy production. Radiation: the magnitude and direction of radiant heat transfer depends on the temperature difference between the human body and the air. This type of heat transfer is usually significant in mines with hot rock temperatures, and in vicinity of hot diesel equipment. Conduction heat transfer occurs when two bodies come into contact. In normal mining activities, conductive heat transfer to or from the human body is usually negligible. Convection: convection occurs when a layer of cool air comes in contact with warm skin. The air temperature increases and its density decreases. As the air becomes lighter, it raises taking the heat away from the skin. Evaporation: is the main cooling mechanism for the human body, contributing about one third of total cooling. Evaporation relies on latent heat of vaporization of sweat from the body. The effectiveness of heat transfer is depending on efficiency of sweating and the evaporative capacity of the environment (depends mainly on air temperature, humidity, air velocity). The ability of the body to sweat depends on physical fitness, acclimatization (training of body to sweat efficiently), and body fluid. More sweating is more heat release from the body. Fiber cloths can significantly reduce the amount of heat reject from the body. The evaporative capacity of environment can be increased by increasing the air velocity. Hence it is inevitable to lower the wet bulb temperature by reducing moisture pick-up in take air.

4.3. Pre-Eminent causes of air become hot and humidThe sources of heat and humidity for underground mines are given in the table 2. The ground water flowing from the rock into an airway acts to transfer heat from the rock to the air. The ground water temperature is almost and always the same temperature as it is of the virgin rock temperature. One of the noteworthy examples is that a hot water sprinkle with the temperature of 38 oC used to flow from a borehole intersection in the road header face of 117L at PVK-5Incline KGM area SCCL. The situation was brilliantly managed by laying HDPE pipes ranging more than a kilometer and the total water was coursed through it to sumps.

Table 2: Sources of generation of heat and humidity in underground mines

SOURCES OF HEAT SOURCES OF HUMIDITYThe heat from the strata Naturally wet roadwaysMachinery and crowd of persons Prominent water fissures into UG Adiabatic compression Underground open drainagesChemical process-oxidation, spontaneous heating fire, blasting

Moisture pick up in the DC shaft and intake tunnels

Rock movement Water leakages in pipe linesFriction on air ways Sweat of menHot water from strata Excess water spray in machineries

“Some advanced studies by foreign authors’’ expresses that the mines being worked with long belting circuits will face lot of heat generation due to friction in each and every roller, idlers. More interestingly, the report describes that around 10% of the blasting energy is only utilized for rock breaking; remaining 90% is converted into heat energy and injected into the underground air abruptly. In Gdk 10A, a prudent study by the authors in the above lines has revealed out the different sources of heat and humidity in the prominent intake airways and in the districts which are The substations -12L,22L,34L,43L,47L,51L and 52L pumping stations at 24L,49L,51L,56L and 58L Belts and gear heads 2000T strata bunker with coal handling arrangement and the district machineries. Besides, the entire mine was developed in the top section having highly moist sand stone roof adding lot of moisture into intake air in the initial stage itself and by the time the air reaches to the district entrances it become saturated. Thus the dry and wet bulb temperatures have risen beyond the normal limits in the working faces.

4.4. Annual average temperature, sub-surface temperature and geo-thermal gradient

The Literature “The Basic mine ventilation” by AMC consultants Australia has described about the annual average temperature and sub surface temperatures. Surface rock temperature is equal to annul average temperature and can provide either cooling or heating depending on the air temperature passing over the rock. The annual average temperature is the average temperature in different periods of time. It affects the sub surface temperature greatly but it is not much affected by local seasonal changes. The annual average temperature is vastly varying in the land of Equator, Tropic of cancer and Tropic of Capricorn and of course, it determines the sub surface rock temperature.In China, the sub surface rock temperature in the deepest mines is 16-18oC. The surface dry bulb temperature varies between 30oC and -24oC through out the year. It was observed during the visit to Chinese mines by the author that the net increase of dry bulb temperature between pit bottom and 4 km distant a Road header district entrance and 1.5km long face was 8-10 oC which resembles our conditions. But the shaft bottom temperature was only 16-18oC and temperature at the faces was 24 -28oC after the air travelled the length of around 6.0 km at 600-800 m depth. Here the surface temperature plays critical role in maintaining sub surface temperature and in turn the geothermal gradient. The sub surface rock temperature increases with the depth

20

22

24

26

28

30

32

34

ma

r

ap

r

ma

y

jun

jul

au

g

se

p

oc

t

no

v

de

c

jan

feb

ma

rMonths(2007-08)

Dry

bu

lbT

em

p(oC

)

surface temp

sub surface (12L)

sub surface(29L)

Annual average temperature & sub surface temperature in Gdk 10A

Figure 1: Annual avg temp, sub surface temp of Gdk10A for one year period

is known as geo-thermal gradient. It varies depending on many factors. However in our country theoretically, it is 1 deg per 30 m of vertical depth. The proportionate relation between the surface temperature and sub surface temperature of Gdk 10A measured for the period of one year is given in the graph (Ref fig 1).

5. HEALTH Vs VENTILATION

It is essential to acquire knowledge of effect of heat and humidity on the workmen. Fall of working efficiency, mental fatigue, changes in cardiovascular system, heat stroke might occur in extreme hot and humid condition. Rise in body temperature: Human body produces lot of waste heat by metabolism and this has to be dissipated into surrounding air. Heat dissipation takes place by evaporation to some extent, radiation and convection. At the same times the wet bulb temperature greatly influences the rate of cooling of the body. At high wet bulb temperature, the rate of cooling gets reduced and the body temperature rises. Moderate such rise is not harmful but when it exceeds 39 oC, it may lead to heat stroke. Heat Stroke is result of break down of temperature of the body when temperature shoots up. This happens with high dry bulb temperature. Mental excitement, restlessness, delirium, vomiting, muscular cramps, loss of body fluid are the symptoms. Loss of body water and loss of salts: takes place due to excessive sweating. Excessive loss of water cause de hydration and may lead to failure of blood circulation. Mental fatigue: Due to continuous under supply of blood to be brain. Studies said that the work efficiency would fall down when the wet bulb temperature exceeds 33oC.

6. VENTILATION IMPROVEMENT IN THE MINE

The requirement of ventilation to give comfortable condition in working places varied lot from actuals in the mine. Due to various reasons discussed earlier the temperature in the working faces shooted upto 34 oC with saturated humidity leading to development of heat stress on the workmen. Hence, thorough studies of pressure, quantity, temperature, and hygrometric survey have been conducted by the authors and

it was decided to re-organize and improve the existing circuits. The advices of senior officers had become a tool for executing the task. A time frame of 2-4 months was evaluated to complete the task. A bar chart illustrating critical activities was drawn up and continuous effort was put up to complete the works.

6.1. Improvement of Quantity of air.

6.1.1. LeakagesThe volumetric efficiency of air is mainly affected by leakages in ventilation appliances. In Gdk-10A, there are 61 nos of ventilation walls existing on the south side and 85 nos. on north side. Air leakages through these walls were slightly on high side because these stoppings loosing its strength in course of time due to weathering of shale. Hence, these ventilation stoppings have been strengthened in phased manner and the no of doors has been minimised.

6.1.2. Cleaning of return roadwaysOut of two main returns, one airway was completely choked at 5R/44LS, due to roof and side fall. Around 1000 Te of coal was cleaned manually in a period of two months taking required precautions in supporting and persons safety. Another return road way

Figure 2: Commissioning of an additional return (6L) to the mine

at the rise side of the mine (6L/24D-25D) which was completely choked with heavy fall near 60m down throw fault (near boundary between 9A mine) followed by running mass of sand stone Bracia. The adequate supporting was done and the fallen debris nearly 500 te lifted by deploying a SDL. But the Bracia continued to flow from the cracks of the fault plane to the equal quantum of debris lifted and was arrested by netting the entire area by wire mesh (Ref Fig 2). Widening and heightening was done with controlled blasting to increase the cross sectional area. Finally it was commenced as a third independent return to the mine with an air flow of 2070 m3/min after connecting 29R against waterlogged 7L an 8L.

6.1.3. Forming LVCs to RHs DistrictThe road header districts 60LS and 59LN were suffering from high temperatureproblem due to difficulties in forming LVCs to them. Two air crossings were constructed at 5D/58L & 5D/57L with a series of 7 ventilation walls between 5D and

Figure 3: LVCs to Road headers districts 60L ( left) and 59L ( right)

4D.Thus fresh air was carried up to entrance of the district 60LS/7D dip and connecting it to main return through 6R ( Ref fig 3 left ).

29

29.5

30

30.5

31

31.5

32

32.5

50 74 M 116M 208M 310.5M 427M 473M 538M 554.5M 567M

May-07 June July Aug Sep Oct Nov Dec Jan-08 Feb March

Prog(m)

Month

wet bulb

dry bulb

Te

mp

era

ture

in

oC

Temperature profile in 60L RHs district

Figure 4: Temperature reduction in road headers district after LVC formed

Likewise, in 59LN district the high water gauge fan had to pull the fresh air from 58LN longwall intake split resulting lesser quantity available at district entrance. The separate split to the district could not be possible due to minimize no of galleries. Hence a decision was taken to develop below 59L with SDL & belt loading system. Around 7 pillars were formed from 60L/2 dip to 61L/N 2 dip The entire 59L from the entrance of the district upto the main return (5R/59LS) was cleared off water and slush to form an independent return route by constructing four ventilation stopping & one air lock door. Further improvement was achieved by taking the fresh air with 26 oC upto N2D by relocating the high water gauge fan. Finally the face temperatures were brought to comfortable conditions (Ref fig 4)

6.1.4. Parallel return to Long wall districtThe return of Longwall panel 3A on north side had to travel nearly 300m to merge with south side main returns at 33D air crossings where heavy pressure drop experienced due to restrictions and obstructions. Wherefrom 1100 m3/min of air used to flow in the initial stage which was uncomfortable due to the rise of dry bulb temperature upto32 oC at midface. As an alternate measure, decision was taken to add a parallel return to it by constructing 3 air crossings at 1D, 2D, 3D off 45L. This additional return added nearly 1000 m3/min.Thus the airflow increased to 1900 m3/min (Ref fig 5) and the face temperatures reduced to 30 oC and 29 oC dry and wet.

Quantity improvement & Temperature reduction in the Longwall face

10001100120013001400150016001700180019002000

74

6.7

m

67

1m

60

3.3

m

54

7.9

m

47

0.1

m

40

1.9

m

33

9.7

m

27

5.7

m

20

1.8

m

15

0.2

m

66

mmay june july aug sep oct nov dec jan feb mar

face retreat

Period

28

28.5

29

29.5

30

30.5

31

31.5

32

32.5

Quantity

dry bulb temp

wet bulb temp

Qu

an

tity

in m

3/m

in

Temp

Figure 5: Temperature reduction in Longwall face after adding parallel return

6.1.5. Quantity improvement in 29LN by additional return airway to mineThe 29L district is located on north side of the mine, having two road headers and one SDL. The intake used to flow from 29L and return air flow back from the district along 28L.The LVC was 22D which is 320 m and 470 m from the district entrances.

Figure 6: Connecting waterlogged 8L to establish 3rd return

Therefore the quantity of fresh air reaching to district entrance is the quantity that fan can pull. Thus the heat created by belts and fans could not be dissipated with available quantity of air. The temperature at the faces had risen to 32 oC and 32.5 oC respectively.

The upper levels 6L, 7L and 8L had been developed three years before filled with nearly 8 lacks gallons of water. As a unique experience, a rise gallery was driven with advanced bore holes using Burn side boring apparatus at 64m of partition (Ref fig 6).

Temperature profile in 29L RHs District

28.5

29

29.5

30

30.5

31

31.5

32

32.5

33

122m 204.5m 264m 354m 503.5m 657.5m 779m 884m 1042.5m 1113m 1204m

May-07 June July Aug Sep Oct Nov Dec Jan-08 Feb March

Prog(m)

Month

dry bulb

wet bulb

Te

mp

era

ture

in

oC

Figure 7: Temperature reduction in a longest RHs district – 29L

Finally an additional independent return airway was commissioned directly upto Airshaft pulling an additional quantity of 1600 m3/min. The LVCs have been pushed inside, the HWG fans were shifted to the new sites and the comfortable conditions were achieved that the longest face temperature brought below 30 oC (Ref fig 7)

6.2. Improvement of Quality of air.

6.2.1. Steps taken to content wet bulb temperature

Figure 8: Contenting moisture in Longwall face

Based on the hygrometric survey, the sources of humidity and its exposure to the airwas prevented right from pit mouth to coal faces that the open drains along main inclines and other parts of the mine were deepened and closed with belts. The already

existing siphons were repaired, reconstructed and made effective. The seepage water and back balance water from sumps flowing along 3D were covered with belts and siphon arrangement was done (51L&56L).The unnecessary drinking water lines were dummied. The goaf water from long wall face was sent through pipeline by constructing 3m x 4m water pockets along bottom gate (Ref fig 8). The spray water at the belt discharge points were controlled to the requirement.

6.2.2. Steps taken to content dry bulb temperatureThe sub stations along intake air were closed with walls giving them separate splits. The heat added from the pumping stations was isolated from the circuit by providing a separate split of intake and return through ducts. (Ref fig 9). Pumping re-organization in the mine resulted in reduction of around 900 HP power which proportionately reduced the heat generation. A regular cleaning of loose coal and coal dust along belt roadways has tremendous impact on dry bulb temperature. All newly constructed ventilation walls between intake and return were constructed closer to the intake path so that the maximum coal pillar is exposed to the return air.

Figure 9: Extracting heat from a Substation (left) pumping station (right) through ducts

6.2.3. Special care taken in Long drivagesSpecial attention paid in laying of ducts for their straightness and air tightness. Location of high water gauge fans was reorganized in all the road headers districts that the fans were located in line to the air flow. The heat exerted by the fans was exposed to return air way by extracting the heat through duct and pipes. Care was taken that the fans were located nearer to LVCs but out bye of district entrances. The water formed inside the ducts due to condensation of air used to be cleaned and damaged ducts were cleaned at regular interval. At least 2 oC heat produced by Transwitches and the gear heads were coursed to dissipate into return air. A Ventury fan operated by compressed air was attempted nearer to faces which reduced nearly 2 oC temperature at working area but the overall temperature was unchanged. An air quantity of 2 to 3 times the maximum capacity of the auxiliary fans was planned to be circuited at their LVCs which achieved a distinct improvement in contenting temperatures at the districts entrances itself. The entrances of the districts were so curve-shaped by chipping it out as to reduce shock losses and turbulence of air. Roadways were frequently treated with incombustible stone dust.

7. PRODUCTION, PRODUCTIVITY AND SAFETY

The ventilation improvement in the mine has brought enormous changes in the ergonomics and general safety. The hastiness and hurriedness of workmen reduced and people used to effectively utilise their time for safe doing of operations which is obviously witnessed from reduction of serious and reportable accidents (Ref fig 10. It created conducive situation for production and productivity. It superseded the

Figure 10: Qty increase & temp drop at district entrances, Mine production performance and Reduction in accidents

strain of the people due to long walking and created lot of confidence and motivation amongst workmen. The electrical break downs such as lowering of insulation values of cuter motors, high water gauge fans and other accessories are drastically reduced. It lead to uninterrupted, continuous production throughout the year also helped in driving galleries at least 4.0 Km for further long wall faces. On the whole, the mine could able to surpass the set target of 0.867 Mte and made profits in the company.

8. CONCLUSION

Scientific ventilation principals were clearly understood, health and safety aspects were also studied. The various ventilation parameters were taken into account and the data were carefully analised. The activities pertaining to ventilation improvement were planned and scheduled in a systematic way and were executed in a chronological order.The cleaning of falls, Forming of LVCs to the Road headers districts, additional return circuit for Longwall face and adding third independent return to air shaft have brought improvement in the overall volumetric efficiency of ventilation system. Connection of 29R against water logged old workings of 7L and 8L with Burnside boring apparatuswas unique experience. Special attention was paid for long drivages which includes bringing cool air upto LVCs, bringing LVCs nearer to the district entrances, proper location of high water gauge fans and leak proof dustings in the galleries. All the possible sources of dry bulb temperature like substations, pumps and haulers were isolated from circuit and the heat released from those were adequately coursed into return air. Sincere effort put to content wet bulb temperature by covering open drainages, siphon arrangements and control on leakages and spray water etc., Having

done all these, the dry & wet bulb temperatures in the road headers districts could able to be kept below 30 oC even at the distance of 1.2 km. The overall ventilation efficiency (VEQ) was improved to 86% against 73% and the fan water gauge was reduced by 6mm. Thus the improvement in the environmental conditions has positive role on health, production, productivity and safety.

REFERENCEProcedingsHOWES MJ.(1998) Advanced ventilation workshopHOWES MJ, JONES, MJ Proceedings of 3rd International mineventilation congress, Harrogate, England 1984VS.VUTUKURI “V th Australian tunneling congress, Sydney 1984” the design of auxiliary ventilation system for long drivages BookAMC consultants Australia. Basic mine ventilation BURROWS J “Environmental Engineering in south African Mines”(1984)CP.Singh Occupational safety and health in industries and mines GV.Krishma Roa, KSM Osmania University, Optimisation in mine ventilation.HARTMAN.H.L Mine ventilation and air conditioning McPHERSON.MJ, Subsurface ventilation and environmental engineering ,NB.Krishnamurthy, Ex D, Mine ventilation practices.