Development of methodologies for the evaluation of wear-resistant materials for the mineral industry

WEAR ELSEVIER

WearZO3-204

(1997)

671-678

Case study

Development of methodologies for the evaluation of wear-resistant materials for the mineral industry I.R. Sare ‘, A.G. Constantineb

The paperreportsthe firstpartof a pro&t aimed at developingmethodologiesfor the evaluationof wear-resistant materialsin miningasd mineral processingoperations.A review of the literaturerevealedthatalmost no systematicstudieshave been made of wear phenomenain operatingmining and mineralprocessingplants.There have been a multitudeof laboratorystudiesof abrasivewar pbctmtncnawhichp11rp0n to have some relevanceto field applications,but very few of thesehave producedmeaningfulinformation. Thcrc is littledoubt thatsubstantialcost bcncfitscan be dcrivcdfrom a more systematicapproachto wearprobkms. It was conckded that a detailedstudy needs to be.tmdetrakento determinethe totalcosts associatedwith wear.includingnotonly the cost of the rcpkccmcr?titems themselves, but also the cost of labourassociatedwith replacingworn componentsand the cost of lost production.TotereaIis&ottof the savingswhich can accruethroughrelativelymodestoutlaysshouldthenbecome apparent.Techniquesof experimentaldesign and statistical analysisof data, combined with improveddata collectionand monitoringof field trials,have a key role to play in realising these savings. 0 1997 Ekevier Science S.A. All tightsreserved.

1. IntrtJductIon

existing evaluation techniques might not be providing site ti~i%OrS

bvirfr

appropimte mtormatton f0r the s&&m

Of

The costs associated with wear processes place asignificant

the most cost-effective materials, and that alternative tieId

burden upon many sectors of industry and the community. The magnitude of this burden is dramatically illustrated by

cally-based methodologies could be developed. At the same

the savings which can be real&d if proper attention is paid

time it was also felt that the very small scale

to tribology. Studies made in a number of countries have

sion testscommonly usedto assessmaterials for field applications probably did not give valid simulations of material

indicated that economic savings of between 1.3% and

I.6%

of GNP may be realiscd [ I], and, importantly. that the first 20% of such savings can normally be obtained without any significant investment. Of particular significance to the owners/operators

test procedures based on a bcttcr undcrstattding of statisti-

abra-

I

performance in the real wor!d, and therefore that an investigation of the validity of these tests was needed. The present study formed part of a larger project whose

of min-

ing and mineral processing plant is the likely return which can be achieved through expenditure on reducing lnsses

causedby tribological phenomena.Hard data are difficult to come by, but a 1986 report from China cited by Jost

! 1J

showed that costbenefit ratios of I:40 in the coal mmmg industry and I :76 in the metallurgical industty could bc achieved.

objectives were: 0 to evaluate the methods currently used in the mining and mineral processing industries for determining

the wear

performance of plant and equipment components: ?? to

develop statistically-based

procedures for efficient and

cost-effective performance assessment of components in operating plant and equipment;

It was against this background that tbe present study was

6 to determine the physical and metallurgical detail of how

initiated, which had as its aim an evaluation of the methods

components used in operating plant and ~uj~rnent degradefrom abrasivewear,

currently used in the mining and mineral processing industries for determining the wear performance of plant and equipment components. It was the view of the authors that O4343-1648/97/S17.OO Q 1997 Elsev~er SctenceS A All nghtsreserved PtISOO43-1648(96)07398-X

* to assess the mechanisms of wear produced by existing laboratory-scale abrasion tests;

672

??to develop alternative

laboratory-scale tests if some of the abrasive wear mechanisms identified in operating plantand equipment are not reproducedby existing tests: This paper presentsa review of general aspectsof wear evaluation in the mining and mineral processing industries, with particular reference tr, the relationships of laboratory and field abrasion tests to industrial practice, and to statistical aspects of wear assessment in the field. It also draws together tbc major findings of visits to a number of mine sites and discusses how alternative performance assessment strategies may be developed for particular items of equipment.

2 Wear evaluation

in mining and mineral

processing

In this section the merits and shortcomings of laboratory and field abrasion tests are considered. drawing in particular on previous work which relates to, or putports to relate to, mining and mineral processing operations. 2.1. Laborarory Laboratory

abrasion tests

abrasion

test rigs range from very simple

devices which cause Ihe material

under test to rub against abrasive grit in the absence of any impact loading (e.g. pin on abrasive paper) through to machines which perform a unit operation in the same manner as occurs in the field (e.g. jaw crusher plate test). The tests are, in general, relatively inexpensive and easy to control, and many different materials can bc evaluated in a short period of time. Some of these laboratory abrasion tests have received endorsement from standards or testing audmrities 2-41; their basic features are summarised in Norman’s comprehensive review IS]. 4 number of )ovesi;gat.or, h~vs at&mpt& to &miri,state dte validity of laboratory tests by attempting to establish correlationswith field testdata. althoughnone seems to have questtoned wbetber the existence of a correlation is sufficient to validate the resultsof the laboratorytests.In one suchstudy Swamon !61 compareddmresultsofadty sand rubber wheel laboratorytest (in which a rubber wheel is rotated against the ma:erial of interest in the presence of silica sand) with those obtained from a specially instrumented wear probe pulled by uactor through various types of soil. A reasonable correlation was established between the laboratory test results and field tests in sandy soil (but not in silt loam soil), but wear scar evaluation revealed that quite different abrasive particle motions were associated with each test. Thus. despite the extstence of a good correlation, the mechanism of wear induced by the laboratory and field tests was quite different, and the laboratory test ought really to have been discounted as having relevance to the field application. One of tbc most illogical, but unfortunately all too common. laboratory/field test comparisons arises in situations

[

wbcrc the field apphcatlon mvolves considerable impact (or repeated Impact).

but the laboratory test does not. Forexampie. in aa invesugauon of high carbon hardfacing alloys.

[

Borik and Majetich 71 compared laboratory testdataderived from rubberwheel and pin testswith weight lossresultsfrom striker plates in a rotary coke pulveriscr. They established correlations described as “unmistakable”, but then concluded that the correlationswere “not strongenough to predict well the performance of hardfacings operating in a coke pulverizer”. They attributed dte lack of strong correlation to “the absence of impact in the laboratory tests”. In carrying out a similar type of investigation, Mashloosh et al. [S] at least tried to take intoaccount the surface features of a worn field component in devising a suitable laboratory test. Their concern was with digger teeth. but after evaluating the nature of the surface of a worn toodr they then opted for simplicity (a steel pin on abrasive disc) rather than any semblance of realism in the development of a laboratory test. Their laboratory test reproduced “most of the features observed on worn digger teeth”, but again, since it involved no impact, it cannot really be considered to be relevant to the field application. ‘llte extent to which investigators have gone to simplify laboratory tests in order to make the test data easy to understand and handle, despite the lack of reality introduced, is well illustrated by a study reported by Perez and Moore [9]. Their work claims to look at the influence of grinding ball composition on wet grinding of a copper sulphide mineral, yet they chose to use a porcelain mill rather than a metallined one “as this would not produce any galvanic effects with the grinding balls or mineral slurry”. The deliberate introduction of artificial conditions hardly inspires confidence that the test data would have great relevance togrinding media performance in practice. The net conclusion which can be drawn from these and many other similar types of investigation is that laboratory tests are seidom able to predst with any accuracy the actual wear of materials in the field, despite what the authors of those investigations actually claim. Other workers have recognised the severe limitations of laboratory tests: for example, Hocke [ IO] found such little correlation between three different types of laboratory wear test and field trials with wear-resistant materials for coke and sinter handling plant that he abandoned the former, whilst Bruner [ I I] concluded that laboratory tests have no part to play in the assessment of materials for grinding media. Notwithstanding the many conceptual problems which arise in respect of laboratory tests, there is still scope for their use provided that their validity is checked for each field application that they purport to simulate [ 121. However, virtually no studies have been undertaken IO compare the mechanisms of abrasion produced by laboratory tests with those evident in components drawn from the field. The type of investigation reported by Mashloosh et al. [ 8 where the wear scars on a worn field component were evaluated, represents the extent to which mechanistic studies appear to have been carried out. However, in order to obtain a more complete picture of the mechanism of material loss. both surface and subsurface observations need to be made ] 13.141. If, from such obser-

1,

I.R.Sure.A.G. Cmmmrmne/Wear203-204(1997)67147X vations, it can be shown that the manner in which material is removed from the surface is essentially the same in both laboratory and field test components, then one can have some confidence that at least the rankings produced in the laboratory test will be the same as those derived from field evaluations. Another very important factor which must be borne in mind in assessing the utility and validity of laboratory tests is whether they use an idea&d “synthetic” abrasive or one which is actually encountered in service. The most widely used standard laboratory tests dry or wet sand rubber wheel tests and the pin on abrasive paper test) utilise relatively fine, homogeneous, pure minerals as the abrasive (typ ically silicasand,garnet,aluminiumoxideorsiliconcarbide). which are very different from the abrasive materialsencountered in practice. Since the type of abrasive encountered in the field probably exerts a greater influence on wear than any of the parameters associated with laboratory tests [ 151, it is clear that laboratory procedures must employ realistic abrasive species if they are to have any hope of producing meaningful results. It is interesting that laboratory tests oeveloped by some of the mineral processing equipment manufacturers (such as the Bond testdevelopedat Allis Chalmers I61 and the slurry erosion test developed at Wanr~an International 171) do userealistic abrasivespecies.Perhapsit is time that those types of test be consideredfor adoption as standards, rather than the much more idealised tests which use only “pure” abrasives.

(the

[

[

2.2. Field abrasion tests 2.2.1. Some concepts Field tests do not suffer from the many deficiencies assoelated with iaboratory wear tests 181. In partsular, with appropriate care, real service conditions are exactly duplicated. These are not only those relating to wear but also to other environmental factors, and loading patterns and frequencies. Furthermore, the data need not be comparative, as is the case with laboratory test results. Absolute data can be obtained, which may be used to predict or estimate real component/product life in service. A thorough examination of the principles of field wear testing was published by Blickensderfer I91 of the US Bureau of Mines. He described the essential features of what constitutes a field wear test, and noted, in particular, the importance of its being a “critical evaluation” of the loss of material. New or different materials are frequently placed in service with the expectation of finding improved wear resistance, but since the evaluation is not critical then the procedure does not constitute field wear testing according to Blickensderfer’s definition. The critical evaluation should include statistical analyses that enable the standard deviation or variance of the measurements to be determined. He claims. therefore, that lifetime service trials in which an item is used until it is worn out and then is replaced by items of different materials until improvements eventually evolve, are not

[

[

673

proper field tests. However, systematic appliiation ofaseries of materials for lifetime service measurements can qualify as a proper field test provided that the lifetime of the is sufficiently short that parts made of different materials can be tested in a reasonable time. In order to qualify as a field wear test, certain criteria have been proposed by Blickensderfer [ 191: 0 the test specimen must constitute all or part of the actual hardware of concern; 0 the wear conditions must be those of concern; ??the test specimens must cause little or no disturbance of the wear conditions; 0 the time of the test must be relatively short compared with the time for the part to become obsolete. He notes that reproducibility among various field tests is not an important criterion, as it is for laboratory wear tests, because field wear conditions are not identical. However, duplicate specimens in any one field test should give similar wear values. Two of the factors which make field tests very different from laboratory tests are wear intensity and wear gradients 191. The wear intensity w is defined by Blickensderfer as the instantaneous potential to produce wear at a given point on a wear surface, and is given by:

[

w=kp where k identifies the wear parameters of the counterface aud environmental factors, and p is the applied pressure at that point. In laboratory tests, every effort is made to ensure that k audp are constant and reproducible. so that the wear intensity at any point is constant. In field service, however. the wear intensity generally fluctuatesin unknown waysover the surface Thus. meaqxements of vo!ume lnrs in geld tce!~ often fail to give reproducible values of the susceptibility of a material to wear. The related concept of wear gradient describes the nonuniformity of wear intensity over a counterface. It is the unknown wear gradients that make field wear conditions so difficult to reproduce in rhe laboratory. A common practical example of an item which experiences a wear gra&ent is the side wall of a bin filled with moving ore. The loading pressure from the weight of the ore increases towards the bottom of the bin, giving rise to a gradient in wear intensity from the top to the bottom of the side wall. A further complicating factor in field situations is that the wear at any place in a system may vary with time, giving rise to time-dependent wear gradients. For example, as the feed rate of au ore increases, a gradient occurs along the direction of motion until a new steady-state feed rate (and hence wear rate) is established. This type of gradient may be cyclic. with periods ranging from fractions of a second to days. 2.2.2. The utility of somefield tests Probably the most widely used held test is the marked ball procedure. first described by Norman and Loeb [XII. to assess the relative performance of grinding balls in commer-

I R &we, A G. Conr:anrmc/

Wear 203-204

(1997) 671-678

Yet another field application which allows for the simultaneous evaluation of components under identical conditions involves the wear of teeth on buckets. Again, though, it would seem that investigators have failed to appreciate the importance of designing tests to facilitate subsequent data analysis. Matsunaga et al. [ 291 evaluated three different tooth steels in an eight-tooth bucket performing normal digging. Lao.ng and carrying tasks, but utilised differing tooth designs for each material and a biassed or&r of placement of the teeth on the bucket. More appropriate as a field application for toothtrials wouldbeabucket wheelexcavator.but,aspointed out by Blickensderfer [ 191, although it is a good test conceptually it is very difficult to monitor and control in a production situation. The field applications outlined above have particular attraction because of their ability to accommodate simultaneously several test specimens, whicharecompletepiccesof hardware, expose themto nominally identicalconditions. Variants of this form of testing have been used in other applications where sections of the one item of hardware made from different materials are tested at the same time. Examples reported have included pipe linings for power station ash handling and ore tailings transport 301, shaker conveyors for rock transport 311 and chutes in coal preparation plant [ 321. Unfortunately, studies in all of these areas reported to date have probably not extracted the maximum information possible because of deficiencies in the ways in which the tests have been designed and hence their lack of amenability to statistical analysis. Many other types of field trial have the added complication that sequential rather than simultaneous evaluation must be employed. If the service conditions are relatively constant or cycucatiy repeatable this may not be too much of a problem, although without careful monitoring even nominally constant conditions may fluctuate in an unknown way which can confound the test results. Applications for which tests may be conducted in this way include slurry pumps. piping systems and chutes, where the material being transported is uniform over time, and where constant operational conditions such as velocity, temperature and pressure obtain. A good example was a comprehensive evaluation of 64 different wear-resistant materials tested as chute liners in a sequential testing program [ IO]. Two very different abrasive materials, coke and non ore sinter, were used in this study; the former only under sliding conditions and the latter under both sliding and medium impact. The study revealed the importance of assessing materials under the actual conditions which exist in service. for it showed very clearly that ceramic materials performed best in chutes handling coke, whil: white cast iron performed best in the chutes which handled sio!er. This study, however, despite its comprehensiveness in terns of the number of materials tested and the quantitative manner in which lining material performance was measured, suffered from the shortcoming that only one test was conducted with most materials. Reproducibility was said “to be good from the few duplicate tests that were made”, but the results must he

and

[

[

I.R. Sore. AC.

Con.ttantinr/ Wear 203-204

tmated with some caution because of the general absence of replicate determinations. Very few field trials reported to date have employed totally adequate experimental designs and data analysis techniques. The importance of ensuring that a test design is amenable to statistical analysis is outlined in the next section.

3. statlstlcalasp&sofwearrtsWmWt

tis*kId

3.1. Introduction When assessing the relative wear performance of different materials. it is essential that the variability of their wear rates be taken into account. Sound prediitions of the long-term properties of materials, such as their mean lifetimes in use, can only be based on proper statistical analyses of data from field trials. The precision of estimation of mean lifetimes is inversely proportional to variability, and for cost efficient testing it is necessary tobeable tocontrolorreducevatiability by both the collection of appropriate data and the selection of efficient test designs or plans. Due regard must be given, of course, to the constraints imposed by the normal operating procedures of mines and plants, and the conditions specific to various sites. Variability is usually measured by the standard deviation of a series of test results or by the coefficient of variation, which is the ratio of the standard deviation to the mean of the test results. Assessment of a material under test is often measured by a 95% confidence interval

i*

ts/+l

(1997)

671-678

675

one can test up to four materials simultaneously in each run, two on each jaw. A test plan can be selected wbiih will eliminate the effect of jaw differences (fixed and moving) and even eliminate side effects (left and right) which might arise due to unbalanced feeding of the abrasive rock In tion. the rock flow is controlled carefully by achoke feed and the jaw gap can be adjusted as necessary. Equal :moums of accurately measmed by recording the weight cr volume loss of each test specimen. As an example, consider a series of split-plate jaw crusher tests in which four materials, labelled A, B, C and D, are to be tested. An efficient basii test plan is as follows: Test number I 2 4 3 Stationaryjaw DA AC BD CB BC Movable jaw DB CA AD This basic plan can be repeated for 8,12, etc. tests, if needed. Note that each material is tested four times, twice each on the stationary and movable jaws, and twice each on the left and right hand sides of the jaws. An analysis of variance can be carried out to eliminate the effects of variability of: 0 test tuns (rock changing in time); ??jaw differences; and ?? side effects (left or right). The residual variation then gives the component of not associated with these three systt effects. Its value will be.sigttilicatttly smallerthattthatobtainediftheseeffects were not eliminated. Details of the analysis can be found in thereportofElallandSare[?4]. In a field testing environment, this level of control is usually difficult, if not impossible. to ohtain. Nevertheleris,ther

t

where is a quantity that depends on the number of samples tested but can, for practical purposes. usually be taken as having the valw 2 unless the number of samples is less than about 20. The quantity s is an estimate of the standard deviation obtained from the test results. The precision of estimation of the average lifetime can therefore be improved by either: 0 increasing the number of test results; or 0 reducing the value of the standard deviation; or ?? both of these. For cost-efficient assessment of materials it is desirable to reduce the magnitude of the standard deviation by suitable test procedures. The magnitude of the standard deviation will depend on all of the sources of variability inherent in a given situation. It is usually possible to eliminate, or at least reduce, some of these components of variation by appropriate &sign of test procedures. This is most clearly demonstrated by consideration of laboratory wear testing. In laboratory-scale wear testing, materials are subject to abrasive wear under carefully controlled conditions such as homogeneity of the abrasive used, constant monitoring of the test procedure, etc. In addition, it is relatively easy to apply efficient statistical designs to eliminate many sources of variability. For instance, in split-plate jaw crusher testing [ 33

I,

variation may be achieved. 3.2. Mainsourcesof variation The sources of variability in field testing are many, but the following ones are seen as being the most important. ?? Operating constraints. Many components, particularly larger ones such as jaw crusher plates, chute liners, and mill liners can be conveniently changed only at tbe time of regular maintenance shutdowns. Such components may be discarded before they are fully worn if it is decided that they will not last until the next shutdown. Tbe (incomplete) lifetime of tbe component will he recorded. not weight loss, and often tonnes of ore processed may not be recorded. 0 Variability within ore bodies. It is common for the abrasiveness of the ore to vary within the ore body, thus adding to the variability of lifetimes. 0 Equipment effects, such as age and uneven feeding. ?? Operator effects. For components such as front-end loader buckets and drill bits, tbe operator effects may be marked. In general, then, field test results will be expected to be more variable than those from laboratory-scale testing. For

,.R

676

Sm.

A C

Comrmr,nc/

instance, the ore handled would usually be less homogeneous tian the screened and blended rock used in jaw crusher tests. In the next section an indication is given of how some, al least. of Ihe above sources, of variation may be controlled, if not completely eliminated. by judicious choice of lest plans and by the collection of appropriate subsidiary data.

4. Performance

assessment

strategies

4.1. Introduction During visits to a number of mining sites, rhe various areas of operation where wear was considered a problem were examined and discussed with operational and mainrenance SM. In this section an indication is given, in general terms. as 10 how, and when, appropriate experimental plans and statistical methodology can be used for cost-efficient assessment of tbe wear of different materials. In some areas, such ar primary and secondary crushing. field assessment appears difficult 10 carry out within a reasonable time frame and the use of realistic laboratory-scale testing methods is indicated. In other areas more detailed work is required, including the acquisition of data so that variability can be examined and opumum sample sizes for testing determined. 4.2. Componenrs 42.1.

Rock-cutting

tools

In general. drill bits are used in large numbers and the effective life of each hit 1%sufficiently shon that efficient teshng IS rclauvely suatghtfonvard. High precision of mean lifetimes can be obtained by testing large numbers of bits. Efficient estimates of the standard deviation and means can be obtained by appropriate, but simple. trial designs, which eliminate operator and site effects. For instance. all operators at each site should receive samples of all types of drill bit 10 be tested. Alternatively, all drill bits under testcould be allotted aI random if many bits are to be tested.Though simpler, Uus second strategy would require more bits for the same precision of testing, particularly if operator and site effects are large. The first sualegy is 10 be preferred and does not require complicated planning or increased manpower lo carry OKI. As a general rule in this and other component testing wheeze large numbers are involved. it is advisable 10 educate rhc operators as to the imponance of the testing program so as 10 minimize loss of components. In these circumstances, however. loss of some drill bits is not a serious problem and extra tnts can bc mcludcd 10 compensate for losses. Wear can be assessed by metres dnlled, or by hours of use. Thts would require some monitoring and record keeping.

Wcor

203-204

I/997)

671478

carried out by keeping records on individual teeth.This would require having a person dedica!ed to this task. To eliminate operatoreffects,simultaneoustestingof teeth on each bucket is required. A problem is the fact that if, say. Iwo different types of teeth are used and one wears mole rapidly than tbe other one initially. the other will wear more rapidly later on due to the fact that it protrudes more and will do more work. Ir this is so, regular examination of the teeth and assessment of their wear would need to be made. If different teeth are assigned todifferent bucketsandoperatots, quite large numbers may be needed for testing. Because large numbers of teeth can be used in testing, the design of appropriate trials does not represent a major problem unless many types of material need 10 be simultaneously tested. For instance. if only two materials are to be compared, each bucket would have half of its teeth made from one material and half tbe other. The materials could be arranged so that one was on the left side and the other on the right side of the bucket. Alternatively, they could be interspersed. For a large number of materials, “incomplete block designs” may be needed. These are very efficient statistically but do require management and planning to cm_ r.‘t. 4.2.3. Crushers On-site testing of jaw crushers and cone crushers presents real problems. The crushers are large and may have relatively long lifetimes dependent on site conditions. Generally, the number of crushers at any one site is very small, so that effective replication (using different crushers as replicates) is not possible. For jaw crushers, the wear on different sections of the jaws may be. markedly di.‘.erent. For instance. one jaw is stationary and the other moves in the crushing operation. High impact wear occurs where the ore strikes the jaws from the feed bins. The feed may be uneven, leading to more wear on one side than the other. In addition, only running time data rather than exact amounts of tonnes crushed may be recorded. The effective lifetimes of the jaws are therefore likely lo be very variable. This appears to be one area where realistic pilo&scale or laboratory-scale testing methods are needed. The problems for other types of crushers such as cone crushers and impact crushers are similar. 4.2.4. Chute liners The wear problems on chute liners are many and varied. Some problems are due 10 the “geomeuy” of the chute, the designs often being consuained by the operating conditions. Wear appears wolsl where impact occurs. There is also a problem in defining what is meant by lifetime: is a chute liner at the end of its life when the first hole appears, or is it before that when it wears very thin? Some simultaneous testing would be possible since chutes are often constructed in sec-

4.2.2. Bucket teeth Bucket recrb. parocularly for front-end loaders, are also t)p~ally used m large numbers. Testtng can bc performed by uamg large numbers of tnals. but could be more efficiently

:ions. Once again, data on ore tonnage is not always recorded, which makes comparisons difficult. For efficient testing, bctterdatacollection

(ifpossible)

is needed. Realisticlaboratory

testing procedures may also be needed.

1.R.Sore.A.G. Conrmnrmne/ Wear203-204 (1997) 671-678

4.2.5. Grinding mills ‘Ihe liners and lifters in ball and rod mills are constructed in sections, and so simultaneous testing of different materials should be possible. In addition, if a series of mills is being used in parallel, grinding the same type of ore, then effective replication can be obtained by treating each mill as a replicate of any other. An analogous problem to that described above fcr bucket teeth occurs, however. if one material wears faster than another initially. The second material will then wear faster at a later stage since it will protrude more and receive more impact and abrasion, This problem may be overcome by suitable experimental plans, but may also require periodic examination and assessment. The area requires further consideration. 4.2.6. Slurry pumps Rumps are often used in parallel, each pump supplying a different grinding mill (for example). To achieve effective replication testing of different impellers and liners could be carried out by rotating different materials between different pumps. The collection of appropriate data and continuous monitoring is advisable. Electric power consumption readings can be a very good form of condition monitoring. 4.3. General comments

611

Specific conclusions arising from the observations of how wear is currently evaluated are as follows, could be carried out more efticiintly and systematically. F’rocedures often differ from one section to another in asingle mining/mineral processing Some sections systematically collect data on their operations, others do not. 0 There is a need for better data collection and processing. For cost-effective wear assessment. adatabaok is needed so that the sample sixes of components in trials can be detert..lned in advance. This is particularly im~t for larger and more expensive components, or for thoserequiring considerable manpower and downtime to change. 0 There is a need for realistic pilot-scale testing methods, particularly applicable to components such as jaw crusher plates, chute liners and, perhaps, bucket teeth, where efficient on-site testing is difficult and presents real problems. 0 In many operating areas, cost-effective improvements to wear assessment could relatively easily be implemented with some extramanpower for datacollection andanalysis, monitoring of wear and some extra measurement instrumentation.

??Wear assessment

plant.

AckuowIedgemeuts

With the exception of one or two problem areas, efficient wear test tg in mining and mineral processing operations would be easible. Appropriate data collection and experimental designs are needed, and, in some cases, extra monitoring of equipment would bc :equired. The extra resources needed, namely manpower and measuring equipment, should be more than compensated for by better cost-efficient testing. The data collected could easily be used for more efficient maintenance programs in addition to wear assessment.

The authors wish to acknowledge the financial support for this study provided by AMIRA, the Australian Minerals Industry Research Association, and the cooperatioo of the management of the various mine sites visited during its COIlIS

Refereuees

[11H.P. Josr.Tnbology-or&m

5. Couclusious Wear is a major cost factor in mining and mineral processing. although there are no hard data on ihe magnitude of these costs in individual plants. Whilst information is readily available from purchasing and/or production reccof the aggregate costs of replacement components, the related, and sometimes more significant, costs of labour and lost production associated with replacing worn items are not generally known. What is almost definitely certain, however, based on previously published experience, is that substantial savings are possible through the employment of known information about wear-resistant materials and products. In order to secure support for the implementation of appropriate programs to realise these savings, mine management is going to require convincing that wear is indeed a major cost. This will necessitate a detailed, systematic evaluation of wear problems and an assessment of the total costs (replacement items, labour, lost production) attributa’rie to them.

’;

andfuture.Wear.I36 ( 1990) I-17 (21 Wet sandlmbberwheel abnson te.s~method SAE Rccomn&d Pmcuce. Society of AutomotiveEngineers.New York. NY. 1977. [3] S~d~ceforcondudlngdrysandlnrbberwheel~wn~rs. ASTM GSS-81. Amenun Sooety for Testmg and Msenals. Phdaielphta.PA. 1981. [4] StandardpracticeforJaw crushergougmg&&on te.1.ASTM GRI83. AmencanSocietyfor Tcwng and Materials..Phdadeipkm.PA. 1982. IS] TE Nomw. Wear,“orepmcess,“gmachmcry.mlYI.B. pecersoOvld W 0. Wmer (eds.,. Wear Contrnl Handbook. AShE New Ywk. 1980.pp. 1009-1051. [b] PA. Sww. Comparisonof labontoryand bhi abcaron IQIS. m KC L&ma (ed.). Wearofrwarena/s 1985.ASME. New Yti 1985. pp 519-525. [7] F Bank and J C. MaJetich.iactors affectmgabrasionresstancsof commeraal hxdfasing alloys. m KC Ludema ted ). Wear of Moremds 1985, ASME. New York. 1985.pi 595604 [S] K.M Mashlwsh.FC. AkbssogluandTS Eyre.Wearofdwerreerh. rr~bolu~mrWtncrolExnamon- Warm Wear. 1. Mezh.E..Lwdon. 1984.pp. 29-34. (91 R. Perezand1.1 Moore. The mflvenceof gnndingball compozltron and wet grmdingconditronson metalwear. in KS. L&ma cd.). WearofhforenoL 1983. ASME. New York. 1983.pp 67-78.

I.R Sure.A G. Cunrrnn”nnr/ Wear20%204,199?)6?1-6?8

678

[101H Hocke.Wear res,sta”rm;ueri”lsfor coke“nd santerha”db”g pl”“1.

fm~~Sfe~/Inf, 50 ( 1977,361-371. [I I1 J P. Brwer. I” dlxussmn of paperby D.E Dlesburgand F. Bank. Opimrsrngabrasionresistanceand toughnw in steelsandironsfor the mining industry.Alarer~& for rhc hf~nmgIndwfry. Climax MolybdenumCo.. Greenwich.1974.p 39. [ 121R G Bayer (ed.). Sum-. Sclecmmand USCtf Wear Tesrsfor M-rub. ASTM Sp Tech PubI 615.ASTM. Philadelphxb PA. 1976. pp 110-111 1131J D W&on. P J. M&Rona”d I.R. Sam Abawe ww of whitecw.1 sons.Me!alsForum.3 ( 1980) 74-88 ( 141I R Sareand B K. Am&& Gougmgabnsion of wear-reststatalloy whitecastirons.Wear.13/( 1989) 15-38 I IS] R Bhckemderfer.B W Madsenand J H Tylczak. Comparisonof severaltypesof “bmwve wear tesb. in KC Ludema(ed ). Wearu/ hfarmsl.s1985,ASME. New York. 1985.pp 31M23. I61 F.C. Bwtd, Lab eqtipmmt and testshelp predwtmetalconsumption mcrusb~ngandgnndmgu”“s.Eng Mmmgl.. /65(6! (1964) l69175. I71 PC Hug@ axl C Walker.Developmentof a weartestto simulate shmyerosm”.Hjdrurraqon II - Proc. llthhtr Con/ onHydwdtc Trrzarponof Soluir m Ptpcs.BHRA. Cmnfield.1988.pp.495-506 I 181M A Moore. l&waxy s~mulatition testingfor sewwe &awe wear m-rrpllls.i” K.C. Ludema(cd.). WmrofMarerials 1987.ASME. New York. 1987.pp. 673-687 191R Bhckasderfer.Dcq” criteriaandcomxtm” factorsfor field wear tan”& Wear, 122 (1988) 165-182. [Ml T E NormanandCM. Laeb.Wear testson grindIngballs.Trans.Sot. MR Eng AIM&. 176 ( 1948) 490-526

I I

I

[

I211 I Iwas&. KA N&ua~an.SC RlemerandJ.N Grlich.Cormsrve;md abmswe wear in wz grinding. in KC. Ludenu (ed ). Wear nf kfarennls198.XASME. New York. 1985.pp. 509-518. I221J C FargeandGA. Baxctay.Ropemesandperformanceof cast-imn grmdrng~ls.Mu~crruls/urr~~~ninl:/~dusr~.Cl~m;u Molybdenum Co. Gwawich 1974.pi 189-199

[23] PJ. Moroz and J. Lorenzetti.The effecIs of m&ix hardnessand m~crostrticfllre on the wear of steelgrindingballs duringwet capper oregnnding.in SK Rhee.A W. Ruff sndK C L&em” feds.). W*ur ofMarerkds 1981,ASME, New Y.xk, 1981.pp.280-289. [24]PJ.MororTheelfensofmarixhardncssand~~suustu~~1the war of steelgrindingballsduringwet hw ore (magmtire) grhxhng. in RQ Bar. D.V. Doan and K.H. Miika feds.). /ntermorm&dn Minerob Sympowm. Cliw MolybdenumCo..A”” Arbor.MI. 1982. pp 63-77. [ 251T E Norma”. Factorsinfluencingthe resistaweof steelcastingsto highstressabrasion.M&m Cariings.33 f 5) 1958) 89-98. [26] R. Eamn,privatecommunicaion,1990. 1271D.J. Dunn.Metal removal mechanisms compnsmg wear in mineral processing.in K.C. Ludema ted.). Weorofllnioreriols1985.ASME. New York. 1985.pi. 501-508. 1281P.K. Mehmtm.A model for wearof conical aal miningbi(s. in KC. Ludenu(ed.). WewofMarerinls 1’3g5.ASME, New Ymk. 1985.pp. 491600. [ 291 M. Matsunaga. Y. ho yld H. Kobayashi,Wew lestof bucketteah. in I: C. Ludema,W.A. GlaeserandSK. Rbee (eds.). WeorofMotenols 1979,ASME. New York. 1979.pp. 336-342. 301 K.J.Oswald aI WE. Lasbx. The performanceof Iibmglasspiping systemsin abrasiveapplications.in KC Ludema W.A. Glaeserand SK. Rhea(eds.). WcarofMarcriafs 1979.ASME. New York. 1979,

[

pp. 601-Eu4.

1311R.E.J.Noel, C. Allen sod A Ball. The developmnt anduseof in-situ ixndlzdxxmmry testsar Bguideto thewlecdon of maaerialsfortbegold miningiadusuy.Tribologyin Mineral firracrion - War on Wear, 1. Mech.E.. London.1984.pp. 23-28. 1321G. Moreto” and E.D. Yardley. The evaluatio” of wear-resistant metallic“uwials for coal rmningapplicasions. Tribologyin Mmeral Ewacrrc~ - Waron Wear. 1. Mech.E.. London.1984.pp. 243-250. 1331I.R Sye and A.G Cons~~~~tine. Designand analysisofjaw ausher gougingabrasionta.s. 1. TesnngEva/uarron,19 ( 1991) Il5--122. [34] W.B.HallandI.R.~.Te~tplvuforajawcrwhrrgw%ngabrario” test. CSIRO Mmufnrtunng TechnologyTechwcal Report 83IUFB, 1983.