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journa l homepage: www.e lsev ier .com/ locate / jmatprotec

nalysis of the ageing impact on the strength of thedhesive sealed joints of conveyor belts

ariusz Mazurkiewicz ∗

ublin University of Technology, Ul. Nadbystrzycka 36, 20-618 Lublin, Poland

r t i c l e i n f o

rticle history:

eceived 29 September 2007

eceived in revised form

6 November 2007

ccepted 9 January 2008

a b s t r a c t

The article is devoted to the presentation and analysis of laboratory test results and of indus-

trial measurements, for conveyor-belt bonded joint strength from the point of view of the

impact of aging on their durability and reliability. The purpose of this extensive research

was to obtain the strength parameters of conveyor-belt bonded joints during different peri-

ods of use, as well as to compare the laboratory tests results with long-term measurements

carried out under working conditions. The laboratory tests included a typical new joint as

eywords:

elt conveyor

onded joint

well as a joint used previously at the LW “Bogdanka” S.A. mine. Analogous joints were mon-

itored under a real dynamic load with the use of a measurement device intended to form

an element of a future intelligent diagnostic and control system.

© 2008 Elsevier B.V. All rights reserved.

In order to provide sufficient strength for a typical bonded

ong-term strength

. Introduction

ccording to Godzimirski (2002) and other authors, bondedoints may amount to 8–10% of all joints used in machineonstruction in the future. This is because of the increasinglymproved characteristics of adhesive materials as well as thedvantages that bonded joints have over other types of jointssed in engineering. Therefore, construction bonding tech-ology is increasingly used in aviation, machine and vehicleonstruction, building engineering and many other branchesf industry (Czowniuk and Matwijenko, 1994a,b; Godzimirski,002; Kuczmaszewski, 1990; Tong and Grant, 1999). One of thereas where this type of joint is used is for belt conveyors asn intra-factory transport system.

Belt conveyors are basic intra-plant transport machines,specially in the mining industry. Due to their numerousdvantages, belt conveyors are also used in other industries,

uch as in natural resource processing, smelting, cement andime production, pulp and paper production, sea and riverorts, civil engineering, agriculture, sugar factories, power

∗ Tel.: +48 81 5384 229; fax: +48 81 5384 229.E-mail address: d.mazurkiewicz@pollub.pl.

924-0136/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.jmatprotec.2008.01.012

plants and others. The reason for this is that belt conveyorsare simple in construction, flexible in transport system con-figuration and versatile in use, and they also may be usedto transport goods over considerable distances. Their mainadvantages include high efficiency, light construction, ease ofinstallation in variable landscape conditions, as well as minorrequirements as far as operation, maintenance and supervi-sion are concerned. With the use of belt conveyors, it is alsopossible to transport, quickly and permanently, loose materi-als of various physical and chemical characteristics providinglow degradation during their transition between the loadingand unloading points. The high reliability of belt conveyors isof no minor significance. Their only crucial elements are thejoints between belt sections, which in most cases are bonded,and these form one of the most frequent sources of unex-pected failures.

joint, a series of research and analyses investigations havebeen conducted on their use, on the technology of creatingjoints and on the possibilities to monitor their strength in

n g t

478 j o u r n a l o f m a t e r i a l s p r o c e s s i

operation (Ageorges and Ye, 2002; Czowniuk and Matwijenko,1994a,b; Kuczmaszewski, 1990; Lehocky et al., 2004; Liljedahlet al., 2006; Savage, 2007; Tong and Grant, 1999; Zur, 1979).The reasons for such failures are not particularly limited asthere is a wide range of factors concerning adhesive sealingtechnology, including adhesion theory, adhesive productiontechnology and the actual creation of the bonded joints.As Godzimirski (2002) indicates, in the analysis of bondedjoint strength, it is important that not only their short-term strength is taken into account but also their long-termstrength, fatigue strength, resistance to dynamic load, theimpact of aging on the joint load-carrying ability, etc. Theseissues are particularly significant in the case of conveyor beltjoints exposed to significant long-term dynamic loads.

Due to the need to provide high-strength conveyor beltjoints to guarantee failure-free use, the author has been con-ducting laboratory tests for a number of years, includingon-site measurements in order to assess the impact that jointconstruction, environmental conditions and duration of beltoperation have on joint strength. As part of this research,the author uses measurements conducted in accordance withrelevant international standards and compares them to long-term on-site measurements. The aim is to achieve long lifeand high reliability of conveyor belt joints as a result of usingeffective methods for diagnosing their condition, as well as ofcontrolling the operation of the transportation system in orderto prevent damage in the joint area. This paper presents theresults of the tests and analyses that have been conducted sofar.

2. Typical types of belt conveyor damage

Permanently operating conveyors (Fig. 1) can be mechanically,pneumatically or hydraulically-based means of materials han-dling, where the material is transported on a strictly definedroute between the loading and unloading point, with the

material being transported permanently at constant speed,variable speed, or in cycles. These conveyors, depending ontheir construction, may handle various types of materials withany angle between the horizontal and vertical orientations, in

Fig. 1 – A typical belt conveyor (Antoniak, 2004): (1) belt, (2)upper runner, (3) motion wheel, (4) return wheel, (5)diverting wheel, (6) tension wheel, (7 and 8) bottom runner,(9) weight, (10) cleaning device, (11 and 13) boosters, (12)transported material.

e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485

straight or curved lines. They may be constructed to be station-ary, slidable or transportable, and they are used for handlingloose materials or part-loads and in special cases, for trans-porting people (Antoniak, 1976, 2004).

The essence of transport in the mining industry, for exam-ple, is the continuous conveyance of rock material usingdifferent modes of transport. A characteristic feature of min-ing transport systems and other transport systems as well, isthe attempt to unify the various means of transport. If min-ing is carried out permanently, which is the most desirablecase, belt transport is used most frequently as it allows fordirect haulage of the extracted material. In such conditions,high reliability and durability of the transporting machine isrequired, although this is a particular source of problems inthe mining industry due to the often difficult working condi-tions. As has already been mentioned, the crucial elements ofthe whole system are the joints between the belt sections ofthe conveyor, and these require special attention.

Conveyor belts are selected so that with a sufficient safetyfactor, they are able to carry the largest tensile forces presentunder different states of conveyor operation. A user buying abelt receives its specification certificate stating the belt type,number, minimum longitudinal tensile strength, maximumbelt elongation (expressed as percentages) at a load amount-ing to 10% of the belt rated strength, as well as about theminimum belt elongation (expressed as percentages) at themoment of breakage. In this case, the actual values of thestrength parameters are compared with those quoted for thebelt, according to the requirements and currently applicablestandards. This information is to meet the requirements ofthe users, concerning belt durability, strength, incombustibil-ity, etc. While analysing typical conveyor belt constructions(Antoniak, 2004; Zur, 1979), it can be observed that a belt trans-mits longitudinal forces necessary to overcome movementresistance, and thus it must have sufficient longitudinal andlateral strength so that it can, without damage, withstand theloads created while the material falls into a booster and whileit is displaced by the runner sets. Equally important are thelarge forces transferred to the belt on the motion wheels bythe conveyor drive. The belt must be elastic enough to createa suitable trough shape while, at the same time, it should notbe so flexible that it bends between the rollers. It must alsobe sufficiently durable and resistant to punctures, mechanicaldamages and abrasion, as well as being insensitive to environ-mental conditions. The conveyor belts are also required to behighly resistant at the joints between their sections.

Conveyor belts are the main and the most expensive ele-ment of a conveyor, and are frequently damaged. This may bea result of stresses which occur during the belt’s operation ordue to the conveyor’s elements having direct contact with thebelt. Less frequent is damage resulting from the contact thebelt has with sharp pieces of the transported material and themovement of the material along the belt. The types of damagementioned above usually cause partial tears or breaking up ofthe belt, typically in the joint area.

Breaking up of the belt is the most critical state leading

to long periods of conveyor stoppages while complicated andtime-consuming repairs are made. Breaking up of the belt istypically caused by the concentration of stresses transferredby the belt core, having influence on further serious economic

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ffects. The belt is exposed to random, difficult to predict indvance overloads of the transported material. These loadsery often exceed the rated loads given by the belt manufac-urer and as a result, the tensile stresses are concentrated inhe belt and the belt breaks up. This critical situation causesasting immobilisation of the conveyor. The belt usually breaksp at the joint as this has a tensile strength lower than that ofhe belt itself. Thus, the joint is often the most critical part ofhe whole transportation system, having particular influencen its reliability.

Typical fabric-rubber belts used in the belt conveyors areoined using one of the three following methods: high tem-erature vulcanization, room temperature vulcanization (coldonding) or mechanical fastening. Mechanical belt joints,hich may or may not be permanent, must have a relative

trength of at least 60% of the nominal belt tensile strength.ulcanised and bonded joints of fabric-rubber belts are formedsing the same joint constructions but with the use of pro-ressive overlap joints. According to Antoniak (2004), theheoretical strength of such a joint, if compared to the nomi-al strength of a belt, is 67% in the case of three, 75% for four,0% for five and 84% for six interlayers.

Typical conveyor belts are manufactured in sections ofome specified length and delivered to the customer in thistate. The belt user joins all the sections during conveyorssembly in order to achieve an endless flexible transport con-ection. During this operation, both new and previously usedelts are joined, and information concerning the duration andther conditions of their previous use is usually unknown.hile in operation, permanent elongation or shortening takes

lace, which requires the constant creation of new joints.onveyors are moved to new locations and then have beltsonstructed of various belt sections. As a result, the numberf belt joints changes all the time and it is difficult to control.t the same time, the joints are expected to have the largestossible tensile strength with the least possible number ofections along the conveyor’s route. These requirements areifficult to achieve in industrial conditions, all the more soecause the number of joints increase with time as the belt

s used. For a joint strength to achieve the required value, theollowing conditions must be achieved: the tensile strength ofhe belts joint should at least equal to the nominal strengthetermined in accordance to some standard, the belt jointshould all be of the same type, the belt joints should have theame number of interlayers (more than two) and the joint itselfhould be made without defects. In practice, joints are madeccording to internal company instructions or the adhesiveanufacturers’ guidelines, often in a varied manner and using

arious materials and methods. Due to difficult weather con-itions, not all requirements guaranteeing high joint strengthnd durability can be met.

Despite all the disadvantages and problems discussedbove, the adhesive-sealing technologies are believed to be theost suitable methods for making joints of the conveyor bear-

ng element, as they guarantee belt continuity, high strengthnd durability and, moreover, they work well with the con-

eyor runners and wheels. One of their most often mentionedrawbacks is the low tenacity in comparison to the belt itself.hat is more, although the bonded joints are comparatively

heap, their strength varies significantly with temperature

h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485 479

and humidity during bonding. Varying states of joint work-manship is of no less importance; the joints are often madein difficult working conditions, and as a result, the conveyorbelts often break without previous indications to suggest animpending failure.

For this reason, the author has been conducting researchinto the strength and elongation of conveyor belt joints for anumber of years. The purpose of the research includes, butis not limited to, analysing typical belt conveyor operatingparameters which cause frequent failures due to breaking upof the belts, as well as designing a suitable system to allowthe monitoring of the machine working conditions and itsautomatic control in order to eliminate critical situations. Toachieve this aim, one has to analyse the durability of certaintypes of conveyor belt joints to find methods for increasingtheir durability, reliability and quality or to modify to thebonding technology without a lose of interlayer strength. Anadditional aim of this research is to analyse the causes ofworkmanship defects in joints and to compare the propertiesof adhesive materials used in terms of their ply adhesion andshear strength. Special attention has been paid to the scopeof strength analysis of bonded joints, which include not onlyshort-term strength measured in static laboratory tests butalso long-term strength, resistance to dynamic loads and theinfluence of aging on the joint carrying capacity—assessedwith measurements under working conditions.

3. Laboratory tests on conveyor belt joints

Conveyor belt joints are tested in laboratories using static ordynamic methods. Static methods consist of determining ten-sile strengths during a breaking attempt of a sample belt witha joint. The dynamic methods consist of applying a pulsat-ing load to a sample belt with a joint wound over two returnwheels. Conditions for testing conveyor belt joints are setby relevant international standards (Standard DIN 22110-2,1997; Standard PN-74/C-94143, 1974; Standard PN-75/C-05011,1975; Standard PN-C-94147:1997, 1997; Standard PN-EN ISO1120:2004, 2004; Standard PN-EN ISO 7622-2:2002, 2002). Nev-ertheless, these tests are rather complicated as they, in mostcases, require special devices and measuring methods, includ-ing horizontal testing machines, able to break a real-sizesample of a joined belt having a comparatively high elongationvalue at the point of destruction.

The laboratory research discussed here started with theassessment of strength and elongation of fabric-rubber beltjoints used by Lubelski Wegiel “Bogdanka” S.A., which coop-erates with the Lublin University of Technology. The scope oftests made in the Belt Transport Laboratory of the WrocławUniversity of Technology included but was not limited to: mea-suring joint elongation at belt breaking, measuring elongationof the whole sample (bonded joint + belt) at belt breaking,as well as analysing the course of joint elongation at loaduntil it breaks, in compliance with standard requirements.The course of the whole sample (bonded joint + belt) elon-

gation was also analysed at load until breakage occurred, incompliance with the standard requirements, and the break-ing force was measured (Anon, 2004; Mazurkiewicz, 2005).In the laboratory tests, two types of belt joints were used

480 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485

Fig. 2 – View of the joint division into measurementsamples A/1–A/4 (the first stage of laboratory tests).

for comparison—measurements were divided into two stages(stage A and stage B). During the first stage, the laboratory testswere carried out on a cold bonded joint with mechanical rein-forcements. The joint was made with a four-interlayer belt,B-1200 mm wide. The 3950 mm long joint used for the tests hadbeen previously used for a significant period of time in under-ground conditions in the LW “Bogdanka” S.A. mine and it hadnumerous areas with damage to the rubber covers as well as inbelt core. It was used to prepare samples marked A/1, A/2, A/3and A/4. Additional tests (the second stage) were carried outwith the use of three belt joints (without any mechanical rein-forcement) marked as B/I, B/II and B/III. The first two were newjoints, made according to the company’s internal instructionswhile joint B/III had been previously used for over 2 monthsin underground conditions on a typical mining haulage con-veyor. The joints used in the tests in this case had the followingdimensions—width: 1200 mm, length: 1900 mm (joints B/I andB/II) and width: 1200 mm, length: 2800 mm (joint no. B/III). Allthe joints were made using a cold bonding method using afour-interlayer belt. The tests were conducted both on jointswith and without mechanical reinforcements, and with differ-ent periods of previous use, to make a comparative analysis ofthe influence that bonding method and joint ageing have onits strength.

In compliance with the PN-C-94147:1997 (Standard PN-C-94147:1997, 1997) standard requirements, 200 mm widesamples were cut off the joint for the first stage tensilestrength tests (the A samples). Due to mechanical reinforce-

Table 1 – Results of strength and elongation tests on the bondewith mechanical reinforcements, previously used)

Sample number A/1

Sample width, b [mm] 242Breaking force, F [kN] 125.3Tensile strength, R [kN/m] 518Initial length of the joint, Lp [mm] 1100Joint elongation at break up, �Lp [mm] 167Joint elongation at break up, εp [%] 15.1Initial length of the sample’s tested part, L [mm] 2910Elongation of the tested length at break up, �Lp [mm] 383Elongation of the tested length at break up, εp [%] 13.1

Fig. 3 – Joint size marking.

ments, the joint was cut lengthways so that the cut did notcross the joints, as that could reduce the samples’ strength.This was also important from the point of view of the addi-tional purpose of the research, which was to determine howmuch the use of mechanical reinforcement influences thejoint strength.

For the above reasons, the widths of the individual samplesvaried, and were: sample A/1: 242 mm, sample A/2: 264 mm,sample A/3: 252 mm and sample A/4: 252 mm. Once the dam-aged edges of the belt were removed, four test samples wereobtained (Fig. 2); in one of them (sample A/2) the belt had apuncture approx. 400 mm from the joint edge. The markingsused for the lengths of the test samples are shown in Fig. 3.

In the second stage of the laboratory tests, samples of thesame width (200 mm) had to be cut off the joint (the B sam-ples). The length of the test samples was around 1900 mm,with small variations. To achieve the same testing conditions,all the samples were cut to a length of 1900 mm, which gavefive samples of each joint (marked as B/I/1 to B/I/5, etc.).

The laboratory tests were carried out using a ZP-40 testingmachine. The tension rate was 100 mm/min. The tension testwas recorded by the testing machine, equipped with a suitablecomputer program, while elongation of the Lp joint was mea-sured with the use of a millimetre gauge and a digital videocamera placed over the point of joint contact on the side ofthe immovable jaw of the tensile testing machine. The linesof contact were marked on the belt cover while the millimetregauge was fastened at the line of the second joint contact.Total elongation was measured using a second millimetregauge and a digital photo camera coupled with the video cam-era using the photo-flash-lamp. This allowed for simultaneousrecording of elongations of both measured values, simultane-

ously with the force gauge indications. The results of theselaboratory tests are shown in Table 1 (test stage 1) and Table 2(test stage 2).

d joint and the belt—the first stage of tests (bonded joint

A/2 A/3 A/4

264 252 252112.4 103.8 104.6426 412 413

1105 1110 1115152 154 163

8 13.75 13.87 14.622907 2903 2900

335 365 3426 11.52 12.57 11.79

j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485 481

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Fig. 4 – Diagram of breaking up an example test sample.

In the case of samples no. A/1 and no. A/4 (the first stageof tests), breakage took place at the point of contact of thefirst and second level. Sample no. A/3 broke up at the point ofcontact of the second and the third level while sample no. A/2broke up outside the joint, which was an effect of the previousoperational damage. A diagram of the test sample break up isshown in Fig. 4.

Fig. 5 shows joint elongation in comparison to elongationof the joint with a belt section depending on the force appliedduring the test. Fig. 6 presents the same dependence; in thiscase elongation is expressed as percentages. The results of thelaboratory tests provide much information on the analysedjoints in terms of its strength and they allow comparison totheoretical data on bonded joint strength.

The theoretical strength of a bonded joint with four inter-layers is 75% of the belt nominal strength. In the case ofmechanical joints, the strength of different types of suit-ably selected joints was 60% of the belt nominal strength,on average (Antoniak, 2004). The results of laboratory testswere, however, much lower than the theoretical values. For the

analysed samples (the A samples), their tensile strength wasbetween 25 and 32% of the belt nominal longitudinal tensilestrength. Slightly better results were obtained for the percent-age elongation at belt breaking. For the joint samples tested,

Fig. 5 – An example joint elongation in comparison toelongation of the joint with the belt section, depending onthe force applied at the test.

482 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t

Fig. 6 – An example joint percentage elongation in

comparison to the percentage elongation of the joint with abelt section, depending on the force applied at the test.

this was between 13.75 and 15.18%, which is more than thenominal belt elongation at breakage (according to the require-ments, it should be min. 10%).

An important quantity is also the percentage elongation atthe breakage of the joint section together with the surroundingbelt material. It is necessary to indicate the future locations ofmarking gauges for a monitoring system in order to performlong-term measurements under industrial conditions. If it wasnecessary to install a measuring gauge in the joint area, thiscould negatively influence the joint strength. From the oper-ational point of view, it would be much more useful to installthe measuring gauges in an area away from the joint, whichwould also give one a selection of places to install the gaugesin order to facilitate the further identification of joints. Duringtests, the percentage elongation of a measured joint length atbreakage was a little lower than the percentage elongation ofthe joint itself, which is a simple effect of the tensile strengthdifference between the joint areas itself in comparison withthe neighbouring belt sections. However, the results did notdiffer very much, and were mutually proportional (Fig. 6).

In the laboratory tests, samples of a previously used beltwere used; one of them (sample A/2) had a visible throughpuncture. Despite the damage, no significant reduction off thesample’s strength in comparison to the other samples wasobserved. The punctured joint sample achieved an elongationof 13.75% at breakage, a result almost identical to the one ofsample A/3 (elongation of 13.87%) and slightly less than thestrongest of the tested samples (15.18%). A similar situationwas observed for the tensile strength, which for damaged sam-ple A/2 was 426 kN/m and the breaking force was 112.4 kN.The other samples tested broke up at a load of between 125.3and 103.8 kN, while the tensile strength was between 518 and412 kN/m.

The results of the laboratory tests provide much informa-tion on the analysed joints and they allow for comparisonwith theoretical data on bonded joint strength. They also

strongly confirm the research thesis concerning the conceptof monitoring the elongation of conveyor belt joints in min-ing conditions in order to prevent their unforeseen breakageduring operation.

e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485

As mentioned above, theoretical strength of a bonded jointwith four interlayers is 75% of the belt nominal strength. In thesecond stage of the laboratory tests (the B samples), the resultsobtained were slightly lower than the theoretical values. Forthe analysed samples, their tensile strength was between 50and 57% of the belt nominal longitudinal tensile strength,while the lowest result was obtained in the case of sample B/III,which had been previously used for about 2 months. Such alow result (50%) could have been caused by partial wearing ofthe belt from which the sample was taken, although the factdid not influenced the results as much as the results of testson new samples were similar, being only a few percent higher.

Slightly better results were obtained for the percentageelongation at break up. For the joint samples tested (the B sam-ples), this was between 19.5 and 22%, which is more than thenominal belt elongation at breakage (according to the require-ments, it should be a min. of 10%). This parameter is almostidentical for used and a new belts. This proves the belt andthe joint retain good strength characteristics despite inten-sive, several-month-long use under mining conditions. Duringtests, the percentage elongation of the measured joint length(joint + belt sections outside the joint) at breakage was a littlelower than the percentage elongation of the joint itself, whichis a simple effect of the tensile strength difference betweenthe joint area and the area of joint with the neighbouring beltsections at both sides. Similarly to the first stage of tests, theresults did not differ very much and they were mutually pro-portional and amounted to between 19.5 and 22% for the jointand between 18.2 and 21.9%, respectively, for the joint withbelt sections on both sides.

If the results of tests on the A and B samples are com-pared, a significant difference between the measured tensilestrengths may be observed. The samples of bonded joints withmechanical reinforcements (A samples) had half the tensilestrength of the samples without the reinforcement (B sam-ples). This is an effect of the joint operation under tension. Inother words, it can be said that the mechanical reinforcementswork well for temporary reinforcing of a joint when there isa threat of breaking up, but they have much worse parame-ters at breakage. This also applies to the breaking force andelongation at breakage, which is much lower for joints with-out mechanical reinforcement. The analysis of laboratory testresults did not show any significant influence of the ageingprocess on the strength of the joints tested. On account ofthe above, the decision was taken to continue long-term testsunder industrial conditions.

4. Measurements under industrialconditions

Belt break-up results in a long downtime of the machine, aswell as the whole transportation system, and generates signif-icant financial losses. Because of the character and operatingconditions of a typical belt conveyor, as well as of the neces-sity to continue the research described above, it is necessary

to develop a concept for a suitable monitoring system. It ispossible to achieve this aim by constant measuring and com-paring the elongation of the indicated joints during operation.Thus, a system achieving this aim will have to diagnose the

t e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485 483

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achine condition on the basis of permanent measurements,hose results will be simultaneously analysed and indicated

o the operators.Developing a concept for the monitoring system in accor-

ance with the idea presented above required suitableesearch, analyses and construction works. The research andmplementation works undertaken in the Department of Pro-uction Engineering Fundamentals of the Lublin University ofechnology started with analysing the possibility of solving

n practice the problem of impossible-to-foresee under indus-rial conditions of the conveyor belt joints breakage. In thisase, the analysis was based on our long experience in theeld of strength analysis of different types of bonded joints.ur experience in operating mechanical devices in the mining

ndustry was also of great importance.To achieve this purpose, a suitable monitoring system was

esigned and is shown in Fig. 7. The method used to install

he monitoring device on the belt conveyor is shown in Fig. 8nd its detailed description is included in a few previous pub-ications (Mazurkiewicz, 2005, 2006a,b, 2007). The monitoringystem, which has been in use on one of the haulage conveyors

ig. 7 – A scheme of a system monitoring elongation ofonveyor belt joints: (1) conveyor belt, (2) joint area, (3)arker, (4) sensor, (5) measuring device, (6) microprocessor

ontroller, (7) digital data transmission unit, (8) computerystem.

Fig. 8 – The monitoring system installed on the beltconveyor.

at the “Bogdanka” mine for almost 2 years, has the possibil-ity of recording continuously a large number of measurementdata and, if needed, to indicate in advance the presence of con-ditions accompanying impending belt breakage in the jointarea.

Appropriate construction gives also the additional benefitsof using the device, and the extended possibilities it gives toanalyse data, including but not limited to:

• analysing operating parameters of a typical belt conveyorwhich cause frequent failures due to breaking up of thebelts, as well as working out a suitable intelligent systemthat would allow for monitoring the machine working con-ditions and the automatic control in order to eliminatecritical situations;

• analysing, on the basis of measurement results in opera-tion, the durability of certain types of conveyor-belt bondedjoints in order to improve the joint quality or to developmodifications to the bonding technology;

• analysing the reasons for the existence of joint workman-ship faults;

• practical comparison of the characteristics of adhesivematerials used in the aspect of their ply adhesion and shearstrength.

In the currently tested version of the system, which usesa computer program, it is possible to visualise changes inthe length of a selected joint during operation, to visualisechanges in the length of each belt section between the joints,as well as to present the overall results for all the joints ofa certain conveyor and all belt sections between them. It isalso possible to analyse statistically the recorded values, aswell as to export the measurement data, graphics, etc. Dataobtained in this way make it possible to monitor continu-ously the condition of all joints and belt sections betweenthem, to indicate exceeded defined values, to assess the con-veyor working conditions, to identify a single joint during each

moment of conveyor operation, as well as to assess the effi-ciency of any service works, such as reinforcing the joint withmechanical elements. In the example presented here (Fig. 9),after intervention by the operators (correction of the joint

484 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485

durin

on the practical application characteristics of intelligent sys-

Fig. 9 – Changes in the length of an example joint recordedand after reinforcing (the right-hand side).

stitching on the maintenance shift on 11 February), a decreasein the dynamic changes of the joint length during operationwas observed. At first, the length was between 2.82 and 2.98 m(the left side of the diagram) and later it was between 2.87 and2.94 m after reinforcement (the right side of the diagram). Thismeans that the range of dynamic changes in the joint lengthdecreased from 16 to 7 cm, which in percentage terms equalsto a fall from 13% (close to the boundary value) to the safevalue of 5%.

During long-term measurements under industrial con-ditions, no significant impact of the aging process on thestrength of the joints measured was noticed. The joints anal-ysed retain unchanged strength characteristics for a longperiod. Regardless of the time when the bonding took placeor the period of belt operation and dynamic load condi-tions, all the recorded results of strength parameters havebeen almost identical. However, the monitoring system underdevelopment has shown the possibility for continuous analy-sis of the bonded joints over long periods of time, in relationto the possibility to convert the currently used construc-tion into a diagnostic and control system which is able topredict intelligently the moment of potential joint breakup.

5. Summary

The laboratory tests and measurements under operating con-ditions provided us with some interesting information on

belt joint elongation and strength. The results are neces-sary to determine warning values of a future monitoringsystem that will help prevent belt breakage in the jointarea through permanent measurements and assessments of

g 24 h of operation—before reinforcing (the left-hand side)

the changes in the length of each joint, regardless of itstype.

The purpose of the planned future work is to establish amonitoring method and to control the working parametersof a typical intra-factory transportation system, hence mak-ing it possible to predict critical states and, in this way, toavoid a failure. As a result, it will be possible to determinethe construction and use conditions of such a device thatwill influence the frequent failures due to belt joints break-ing up. Following on from this stage, a suitable intelligentsystem will be established which will allow for the monitor-ing of the working conditions of the machine and to controlit so as to eliminate critical situations. Such a system willbe established on the basis of an intelligent model of theobject under analysis. To achieve this aim, it will be neces-sary to collect a set of data characterising the object and tocarry out an analysis of the intelligent system modelling tech-niques available with regard to the possibility of using themon various real objects, depending on their construction speci-ficity and operating conditions. Having analysed the operatingconditions of the object in question for elimination of unfore-seen loads, as well as having established the mathematicalmodel, it will be necessary to establish the control algorithms.These algorithms will help to implement the control proce-dures. In order to achieve this aim, it is necessary to continueresearch on a real object, while simulations and verificationtests as described above will also be carried out. Conclusions

tems and models which describe them will make it possibleto transfer the results easily to other real objects of this typewhich require intelligent real-time monitoring and controlsystems.

t e c

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cknowledgement

he research work is financed with the means of the Stateommittee for Scientific Research (Poland) in the years007–2009 as a research project.

e f e r e n c e s

georges, C., Ye, L., 2002. Fusion Bonding of Polymer Composites.Series: Engineering Materials and Processes. Springer Verlag,Berlin.

eport from Research Project nr 620004/1, 2004. Testingendurance and extendability of textile rubber belt joints.Wrocław.

ntoniak, J., 1976. Underground transport facilities and system incoalmines. Slask Publishers, Katowice.

ntoniak, J., 2004. Belt Conveyors. Introduction to the Theory andCalculations. Publishing House of the Silesian TechnicalUniversity, Gliwice.

zowniuk, J.W., Matwijenko, W.A., 1994a. Analytical dependencesfor determining parameters of adhesive-rivet joints.Technologia i Automatyzacja Montazu 2, 38–40.

zowniuk, J.W., Matwijenko, W.A., 1994b. The rheological modeland the mechanism for adhesive layer constituting inadhesive and adhesive-mechanical joints. Technologia iAutomatyzacja Montazu 2, 35–38.

odzimirski, J., 2002. Wytrzymałosc dorazna konstrukcyjnychpołaczen klejowych. Wydawnictwo Naukowo-Techniczne,Warszawa.

uczmaszewski, J., 1990. Technologia smigłowcow. Teoria itechnika klejenia. Wydawnictwo Uczelniane Politechniki

Lubelskiej, Lublin.

ehocky, M., Lapcik, L., Dlabaja, R., Rachunek, L., Stoch, J., 2004.Influence of artificially accelerated ageing on the adhesivejoint of plasma treated polymer materials. Czech. J. Phys. 54,C533–C538.

h n o l o g y 2 0 8 ( 2 0 0 8 ) 477–485 485

Liljedahl, C.D.M., Crocombe, A.D., Wahab, M.A., Ashcroft, I.A.,2006. Damage modelling of adhesively bonded joints. Int. J.Fract. 141 (1–2), 147–161.

Mazurkiewicz, D., 2005. Monitoring the condition ofadhesive-sealed belt conveyors in operation. Eksploatacja iNiezawodnosc. Maintenance and Reliability 3,41–49.

Mazurkiewicz, D., 2006a. Computer system for monitoring thecondition of conveyor belt joints. Mechanizacja iAutomatyzacja Gornictwa 4 (423), 14–22.

Mazurkiewicz, D., 2006b. A computer system to monitor thecondition of conveyor belt joints. In: International CarpathianControl Conference ICCC’2006. Roznov pod Rahostem, CzechRepublic. Conference Proceedings, pp. 361–364.

Mazurkiewicz, D., 2007. Computer system for monitoringconveyor belt joints. Can. Min. J. 5, 24.

Savage, G., 2007. Failure prevention in bonded joints on primaryload bearing structures. Eng. Fail. Anal. 14 (2),321–348.

Standard DIN 22110-2, 1997. Testing methods for conveyor beltjoints—part 2: Endurance running tests, determination ofrunning time belt joints at conveyor belts with textile plies.

Standard PN-74/C-94143, 1974. Textile rubber belts for generalpurpose conveyors.

Standard PN-75/C-05011, 1975. Testing methods for conveyorbelts. Determination of tensile strength as well as of relativeand permanent elongation.

Standard PN-C-94147:1997, 1997. Rubber products. Conveyor beltjoints made using the vulcanisation method.

Standard PN-EN ISO 1120:2004, 2004. Conveyor belts.Determination of strength of mechanical joint. The staticmethod.

Standard PN-EN ISO 7622-2:2002, 2002. Conveyor belts with steelcords. Testing traction properties. Part 2: Measuring tensile

strength.

Tong, L., Grant, St.P., 1999. Analysis and Design of StructuralBonded Joints. Springer Verlag, Berlin.

Zur, T., 1979. Belt conveyors in mining. Slask Publishers,Katowice.