TRANSPORT and ROAD R ESEARCH LABORATORY

Department of the Environment Department of Transport

SUPPLEMENTARY REPORT 773

WEAR IN SLURRY PIPELINES: EXPERIMENTS WITH 38mm DIAMETER SPECIMENS IN A CLOSED-LOOP TEST RIG

by

J G James and B A Broad

Any views expressed in this Report are not necessarily those of the Department of the Environment or of the Department of Transport

Transport Engineering Division Transport Systems Department

Transport and Road Research Laboratory Crowthorne, Berkshire

1983 ISSN 0305- 1315

Ownership of the Transport Research Laboratory was transferred from the Department of Transport to a subsidiary of the Transport Research Foundation on 1 st April 1996.

This report has been reproduced by permission of the Controller of HMSO. Extracts from the text may be reproduced, except for commercial purposes, provided the source is acknowledged.

Abstract

1.

2.

.

Introduction

CONTENTS

Test equipment and procedure

2.1 General description

2.2 Tests with varied slurries

2.3 Tests with varied pipe materials

Description of test materials

3.1 Slurry constituents

3.2 Pipe materials

4. Slurry degradation and repeatability of results

5. Results of the first test programme: effects of slurry variables.

.

5.1 Tabulated results

5.2 Effect of concentration

5.3 Effect of velocity

5.4 Effect of particle size

5.5 Effect o f particle hardness

Results of the second test programme: comparison of 18 pipe materials

6.1 Tabulated results

6.2 Discussion of results

6.3 Conclusions

6.4 Economics and choice

7. Acknowledgements

8. References

9. Appendix 1. Chronological bibliography

Page

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© CROWN COPYRIGHT 1983

Extracts from the text may be reproduced, except for

commercial purposes, provided the source is acknowledged

WEAR IN SLURRY PIPELINES: EXPERIMENTS WITH 38mm DIAMETER SPECIMENS IN A CLOSED-LOOP TEST RIG

ABSTRACT

This report describes two programmes of wear testing, planned by TRRL but

carried out under contract by BHRA Fluid Engineering, Cranfield, Bedfordshire.

Abrasive slurry was circulated through 38mm diameter pipe in a closed-

loop test rig and the amount of wear was assessed by measuring the weight loss

of short removable lengths.

In the first programme (1979/80) the slurry was varied to study the

influence of velocity, concentration, particle size, and particle hardness on the

wear of ordinary mild steel pipe.

The following conclusions were reached:

i) Over the range investigated (2 to 6m/s) wear varied according to a power

between the square and cube of velocity.

ii) Over the range investigated (5 to 15 per cent by volume) wear varied more

or less linearly with concentration.

iii) Over the range investigated (0.015 to 1.5mm) wear varied more or less

linearly with particle size.

iv) Emery (Mohs Hardness 8 to 9) produced a wear rate several times greater

than that for silica sand (Mohs Hardness 6 to 7).

In the second programme (1980/81) the operating conditions were kept

constant (velocity 4m/s, 10 per cent slurry of 0.15mm emery) while 18 different

pipe materials were compared. Most of them proved to be more resistant to wear

than mild steel but no particular class was found markedly to outrank the others.

Somewhat surprisingly the best four materials comprised one from each main

category (metal, ceramic, rubber and plastics).

An annotated bibliography of 60 papers on other pipeline wear work is

given in an Appendix.

1. INTRODUCTION

Slurry pipelines are usually regarded as a "capital-intensive" mode of transport; i.e. their operating costs are

often secondary to the costs arising from the relatively high initial outlay and the periodic replacement of

capital items such as pumps. The cost and life of the pipe itself is obviously of great importance.

For very long slurry pipelines the solids are invariably ground to powder: this yields a slurry which

requires minimum energy consumption at the pumping station and also has minimum abrasivity so that

standard mild steel pipe can usually provide the required 20-year life or more without replacement. With

short pipelines however it is sometimes cheaper to pump coarser (i.e. more abrasive) material, trading off

pumping energy and the cost of the pipe against the expensive terminal processes of grinding and de-watering,

the latter being relatively costly for a very fine powder. In some situations such as gravel dredging it may be

necessary in any case to retain the solids in unground form. When relatively coarse solids are being pumped

the decision has to be made whether to use steel pipe and keep replacing it or to adopt some longer-lived

but initially more costly substitute. A bewilderingly wide variety of alternatives have been advocated,

ranging from ultra-hard ceramics or special steel alloys to plastics and rubbers. In the absence of adequate

and reliable published data from operating pipelines several researchers in recent years have sought to forecast

relative (and sometimes absolute) lives from laboratory tests.

Internal pipe wear, commonly expressed as mean loss of wall thickness per unit of time (or sometimes

per unit of solids throughput), is due to the combined effects of two distinct phenomena, erosion and

corrosion. Erosion losses result from the pipe being abraded by the solid particles in the slurry sliding or

bouncing along it. In centrifugal pumps erosion may also be caused by cavitation, but within a pipeline

velocities are too low for this to be a serious contributory factor. Corrosion losses result from chemical or

electro-chemical attack (mostly oxidation): methods sometimes used to combat corrosion are de-aeration,

adjustment of slurry pH and application of cathodic protection to the pipe.

With a slurry of very fine particles (say less than 50/am) erosion is generally negligible no matter what

the hardness of the minerals in the solids. Often the only precaution taken to protect such pipes from wear

is the addition of a corrosion-inhibitor to the slurry. A twenty-year life is then confidently expected from

normal steel pipe and its wall thickness is specified solely on pressure considerations.

In most long coal and ore pipelines, where the solids have to be specially ground to form the slurry

(unlike clay or chalk), the particles are commonly an order of magnitude larger (top size 1 to 2mm) because

very fine grinding and subsequent dewatering are expensive. If the solids contain hard minerals, and are

angular or harsh-textured, erosion may be no longer negligible and in such pipelines extra wall thickness is

often specified to ensure the required life. Corrosion may also be enhanced undesirably by erosion since the

latter tends to provide fresh chemically-active surfaces for attack.

With very large particles such as sand and gravel erosion is so rapid that no attempt is made to counter

corrosion which becomes the secondary effect. Steel pipes may last only one or two years and are treated

as expendable. They are not buried but left above ground to facilitate replacement. In many instances the

wear takes place largely on the bo t tom of the pipe and sometimes provision is made to rotate the pipe

through 120 degrees at intervals to maximise its life.

When wear is a problem non-metallic pipes or linings may prove to be more resistant to both corrosion

and erosion but, because they are more expensive initially, the economic choice may be far from clear cut,

depending on estimated lives of the alternative materials. Sometimes steel is used for the straight sections

with special material for bends where erosion is most severe. It is generally accepted nowadays that an ultra-

hard material may be best at resisting sliding particles although susceptible to brittle failure under impact

and, conversely, elastomeric materials may be best where particles are bouncing or impacting. Several

laboratory studies have been made on the effect o f impact angle on abrasion, showing that each material may

have its individual best and worst angles of attack while some are relatively unaffected by the angle. In

slurry pipelines, where the particles may move both in suspension and by saltation it is often difficult to

forecast which form of abrasion - sliding or impacting - will be dominant.

2

Finally, the choice of pipe material may not be made solely on cost-life considerations. Even wherea

frequently-replaced steel pipe may be correct on an economic basis, there may be environmental reasons for

wishing to bury the pipe below ground. The choice then has to be made of the best long-life substitute.

Most early slurry pipeline research (in the 1950s and 1960s) was concerned with the problems of slurry

flow characteristics. It was only in the I970s, after reasonable working solutions to that primary aspect o f

pipeline design had been established for most types of slurry, that much attention was turned to the assess-

ment of wear-resistance and the problems of predicting the lives of relatively uncommon pipe materials in a

wide range of operating conditions. Much of this work has been funded by producers of specific pipe materials

and it is not surprising that reports often appear contradictory since it is possible to select test conditions

favouring one or another. The TRRL work Was undertaken with the object of contributing data towards a

better understanding of the subject, firstly by varying the basic parameters (v~elocity, concentration and

particle size) under controlled conditions, using one type of steel pipe ; and secondly by then standardizing

operating conditions and comparing several types of pipe. For economy this work was undertaken on a

laboratory scale using relatively small pipe specimens (38mm bore). It was intended to complement the

resultsof these tests with full-scale trials, and 150mm bore specimens of a similar range of materials were

installed in a commercially-operating sand-dredging pipeline. Unfortunately this third stage of the work was

brought to a premature end due to closure of the plant by the owners for reasons connected with the trade

recession.

A chronological bibliography of papers on related pipeline Wear research, mainly since 1970 is given

in Appendix 1.

2. TEST EQUIPMENT AND PROCEDURE

2.1 General description

All tests were made using the closed4oop slurry-circulating test-rig depicted diagrammatically in Fig. 1.

This has been described in detail elsewhere 1.

From the main tank slurry may be sent by means of a centrifugal pump around one of two loops of

steel pipe having internal diameters of 38.1 and 76.2mm. In this work the 38.1mm loop was used exclusively.

Each loop includes a stainless steel pressure-measuring section and a perspex viewing section. Mean

flow velocity is measured with an electro-magnetic flow-meter located on a vertical part of the loop. The

Relative Density (Specific Gravity) of the slurry and hence the concentration, is measured with an in-line

density meter which directly weighs a short length of the pipeline. A cross check on this meter may be

obtained by diverting the flow into a weigh tank. Velocity is varied by means of the thyristor-controlled

DC motor driving the pump.

The wear-resistance of some plastic pipe materials is dependent on temperature and in work reported

by certain other laboratories refrigeration has been used to keep the temperature below a certain critical

level. However, the thermal capacity of the BHRA test rig is such that, under the operating conditions

adopted, little increase in temperature occurs and this precaution is consideredunnecessary.

At the start of a test the required slurry is constituted by gradually adding solids to wafer in the main

tank while circulation is in progress. Relative Density is monitored continuously by the in-line meter and

3

solids are added until the required concentration has been reached. Before starting the actual test run this

density is checked via the weigh tank. The required velocity is then set and circulation continued for the

specified time.

The pipe wear is determined by measuring the loss of weight of removable sections of pipe 152.4mm

long. Pipes obtained for testing may not be perfectly round, may not have exactly the right diameter, and

may not have a perfectly concentric bore: therefore they may not align perfectly with the main pipeline.

For this reason three specimens of each material are used, set end to end, accurately aligned with each other

in a special jig. The weights of all three specimens are recorded but, since the end pieces are there primarily

to provide transition from the main pipe, only the middle specimen is considered in the final evaluation.

Fig. 2 shows how the three specimens are butted together, held with tie-rods and sealed with O-rings.

From the measured weight loss after the specified test period the mean loss of wall thickness can be

calculated. This is expressed in mm/year and referred to as the Wear Rate.

Wear Rate in ram/year - W 8760 . 103 sTr LD T

where W = measured weight loss (kg)

S = Relative Density of pipe material

L = Length of test specimen (m)

D = Mean internal diameter of test specimen (m)

T = Duration of test (h)

2.2 Tests with varied slurries

In the first programme of work all of the test specimens were mild steel. A 7-metre length was

"condi t ioned" by installing it in the rig for 100 hours with a 10 per cent slurry of 0.15mm emery circulating

at 4 m/s to produce a uniform interior surface. It was then cut into 152.4mm lengths with accurately machined

ends. The outer surface of these was descaled and they were immersed in an ultrasonic cleaning bath with a

de-greasing agent for 2 hours prior to use. They were handled with gloves and dried at 50°C for 16 hours

(both before and after testing) before weighing with a balance sensitive to 0.0001g. With these mild steel

specimens a standard test time of 50 hours was found to be ample with all slurries at all velocities to obtain

readily measurable wear.

2.3 Tests with varied pipes

In the second programme, comparing pipe materials, various modifications of the test technique were

found necessary due to the characteristics of some of the materials. These involved (a) changes in the method

of preparing and mounting the test pieces, (b) extension of the test duration, and (c) more elaborate wetting

and drying techniques to cope with problems of water absorption. These are discussed in turn.

Several o f the test pipes had wall thicknesses much greater than the normal mild steel pipe. A new

specimen-holding jig was therefore designed to take the largest of all. Specimens with intermediate wall

thicknesses were then provided with specially made steel sleeves to ensure a close fit in the new jig.

Relatively flexible pipe materials (the rubbers) were also bonded into suitable metal sleeves.

Having two specimen jigs it was now possible to test two pipe materials simultaneously, one thick and

one thin. The 18 materials thus nominally required 9 test runs but in fact 11 were made. It was found that a

4

test duration of 50 hours, as used in the first phase of the work, was insufficient to produce measurable wear

with some of the pipes. Test times were accordingly increased to 100,200 and 300 hours as appropriate.

The tenth test was included as a repeat to extend the testing time with two of the materials by a further

200 hours. Finally, as three of the materials had still suffered only very slight wear, an eleventh test was

specially made for 1000 hours, additional arrangements being made to accommodate a third set o f test pieces.

For all of the longer tests the slurry was renewed after each 100 hours to minimise possible errors due

to progressive degradation of the solids in the slurry. To check that no errors arose from the use of varied

test times, "control" specimens of mild steel were inserted in the pipeline every time and checked for

repeatability of wear rate. This is discussed further in Section 5. These control specimens were mounted

in triplets as usual but, to save making any further special jigs, they were fitted into commercially-available quick-release pipe couplings (Viking-Johnson type). Hate 1 is a photograph showing both types of mounting

in place in the pipeline.

The most serious problem in this second programme of work arose f rom the fact that several of the'

non-metallic pipe materials absorbed water in an amount comparable with the weight lost due to wear.

Increased drying temperatures were out of the question for fear o f physical or chemical changes and hence

extremely long drying times were needed in order to obtain meaningful weight readings. This problem and

the technique adopted to minimise delay has been discussed in detail elsewhere 2. Examples of weight/time

drying curves for several specimens are given in Fig. 3 to illustrate the great variability.

3. DESCRIPTION OF THE MATERIALS

3.1 Slurry constituents

In the first test programme the pipe specimens were all mild steel but the slurry constitution and flow

conditions were varied.

In order to obtain readily measurable amounts of wear without running tests of inordinately long

duration it was decided to use very abrasive solids in the slurry for most of the work. Turkish emery was

chosen. This is a naturally-occurring rock rich in corundum (Mohs Hardness 9, specific gravity 3.9) which

is commercially available in a wide range of closely graded sizes (complying with British Standard BS 871

"Abrasive papers and cloths") and is commonly specified for standard abrasion tests of various sorts.

Because of the relatively small bore of the test pipe the upper size of particle was limited. In order to

range over three orders of magnitude, three grades with mean particle sizes of 1.5, 0.15 and 0 .015mm were

selected, hereafter often referred to as coarse medium and free for simplicity. All of these materials were

comparatively single-sized as can be seen from the actual measured gradings given in Fig. 4. Photographs of

all three are given in Plate 2.

At first it was proposed to test each size of emery at three velocities, 3, 6 and 9 m/s, and at three

concentrations, 10, 20 and 30 per cent by volume, but due to limited pumping capacity more modest ranges

had to be accepted. After some preliminary trials velocities o f 2, 4 and 6 m/s and concentrations of 5, 10

and 15 per cent were used. It may be noted that in some comparable work reported at Toulouse 3 velocities

of 7, 12 and 16 m/s were used to obtain rapid results but they were very far removed from practical operating

velocities which are usually in the range 2 to 5 m/s.

5

It was also proposed at first to investigate solids with three widely different hardnesses e.g. limestone

and flint in addition to the emery. However, relatively soft particles create testing problems. To obtain measur-

able amounts of wear the test time has to be prolonged while, at the same time, the particles degrade

relatively rapidly (reducing the slurry's abrasivity) so that very frequent renewals of the slurry become

necessary to achieve meaningful results. Merely to establish satisfactory test routines would have required

extensive preliminary testing. In the end it was decided to make only a few tests with one material other

than emery, at all three velocities, but at only one concentration (10 per cent). The material chosen was a

medium-sized naturally-occurring flint sand (100 per cent silica) with Mohs Hardness between 6 and 7 and

Specific Gravity 2.7. The grading of this sand is included in Fig. 4. The mean particle diameter was about

0.25mm.

3.2 Pipe materials

In the second programme the slurry was kept constant (medium sized emery, middle velocity and

middle concentration) while various pipe materials were compared. From the wide range of possibilities

a list of about 30 was compiled but many could not be obtained in the required small-bore size. Eventually

18 were tested: four types of steel, one steel with a special coating, seven plastics, three rubbers, two ceramics

and one asbestos/cement. Brief notes on these are given herewith:-

Mla. Mild steel 'a'.

This was a standard grade of drawn mild steel tube (S.G. 7.86) obtained by TRRL from a local stockist

and said to be ASTM Grade A106.

Mlb. Mild steel 'b ' .

This was another mild steel tube obtained by BHRA from a different source. Its inclusion here provided

reassurance that one mild steel behaves much like another in this context.

M4. 'NIHARD' steel.

This well-known alloy of exceptional hardness (S.G. 7.6) is commonly used in the dredging industry for

certain parts of centrifugal pumps and pipe bends. It contains typically about 6 per cent nickel, 0.5 per

cent manganese and 3 per cent carbon. These specimens were cast by a specialist founder. The bore and

the ends were then turned accurately at TRRL using a special diamond-impregnated tool.

M6. Stainless steel.

This was obtained from a local tubing stockist and said to be drawn from an Austenitic stainless steel

Type 316 (S.G. 7.7) containing 17 per cent chromium, 11 per cent nickel, 2.5 per cent molybdenum

and 0.07 per cent carbon.

M7. Nickel/diamond coating.

During enquiries about problems of machining some of these special pipe materials, a firm of industrial

diamond dealers offered to coat the interior of a set of mild steel specimens with a relatively new wear-

resistant system.• This consisted of a layer of nickel deposited by the 'Electroless' process and impregnated

with diamond dust (25 per cent by volume of the coating) 3. The diamonds had a mean diameter of

0.005mm and the coating thickness was 0.025ram. The mean S.G. of the coating was 7.55.

P1. Unplasticized polyvinyl chloride ('UPVC')

T~tis was a standard grade used for water-pipes (S.G. 1.42) obtained from a local stockist.

• P3. High density polyethylene 'a'.

This was obtained from a German-based supplier who had published test data in recent years reporting

this material's superiority over steel for slurry pipelines although it is mostly used for other purposes 4.

S.G. was 0.95.

6

P15. High density polyethylen 'b ' .

This was a material of similar type to P3 but obtained from a British extruder. S.G. was 0.96.

P4. Polypropylene.

This material is primarily recommended for corrosion-resistant pipes. These specimens were obtained

from the extruder. S.G. was 0.91.

P7. Acrylonitrile-butadiene-styrene co-polymer ('ABS').

This material is primarily recommended for its impact resistance. These specimens were obtained from

a local tubing stockist. S.G. was 1.06.

P8. Polyurethane 'a ' .

Polyurethanes have a reputation for abrasion resistance and these specimens were obtained from a firm

specializing in manufacture of polyurethane-lined pipes for slurry transport 5. It was cast as a 6ram

layer inside 50mm steel tube. S.G. was 1.15. Dunlop Hardness 70, and Lupke Resilience 50.

P9. Polyurethane 'b' .

This was provided by the same firm as P8 but the constituents came from a different chemical

manufacturer. P9 was dyed red to distinguish it from P8 which was dyed blue. S.G. was 1.15, Dunlop

Hardness 73, and Lupke Resilience 45.

P10. Rubber 'a'.

These specimens were provided by a Swedish firm specializing in manufacture of slurry hose 6. For these

small-bore specimens the rubber (natural rubber 6mm thick) was bonded inside 50mm steel tube. It is

claimed to be particularly suited to slurries with particle sizes of less than 3mm and sliding abrasion

conditions. It was light brown with an S.G. of 0.98, Dunlop Hardness of 35, and Lupke Resilience of 60.

P11. Rubber 'b ' .

These specimens were made and provided by the same firm as PI0 in a similar manner but with carbon

reinforced rubber, claimed to be more suitable for large-particle slurries e.g. gravel, where impact

conditions predominate, It was black in colour, with an S.G. of 1.12, Dunlop Hardness 56, and Lupke

Resilience 32.

P12. Rubber 'c'.

These specimens were provided by a British dredging hose specialist. In this case a length of pipe with

the appropriate bore was available and the specimens were fitted with steel sleeves at TRRL. This

rubber, carbon-reinforced and black in colour, had an S.G. of 1.1, Dunlop Hardness of 54, and Lupke

Resilience of 33.

(Note: The Hardness and Resilience of these last five materials were measured at TRRL, the

quoted values being at 15°C. For the Resilience measurements the thickness of these

specimens was rather less than the standard test required and the values are therefore

only comparative.)

C3. Zirconfa/alumina ceramic ('ZAC 1681 ').

These specimens were fusion-cast by the specialist suppher of this material which is marketed

sPecifically as an abrasion-resistant ceramic (S.G. 3.8) 7. Its constitution is stated to be 50 per cent

alumina, 33 per cent zirconia and 16 per cent silica. The ends of these specimens were encased in

steel sleeves.

C4. Sintered alumina ('DERANOX 975').

These specimens were moulded and sintered by the speciahst supplier of this material which is also

7

marketed as an abrasion-resistant ceramic (S.G. 3.78). It consists almost entirely (97.5 per cent) of

pure alumina. The supplier stated that this material is more suited to sliding abrasion than to impact

conditions and it appears to be more brittle than C3.

C5. Asbestos/cement.

Asbestos/cement pipes are not regarded as being very abrasion-resistant but they are nevertheless used

in many situations for fine slurries where corrosion-resistance is important e.g. for pulverised fuel ash

at power stations. Although small-bore pipes are no longer made with asbestos/cement, the major

supplier was able to produce a 10-year old length with the correct diameter and the specimens were

cut from this. The interior had a coating of bitumen but this was dissolved away before the tests were

made. The S.G. was 2.3.

A photograph of a selection of the test specimens is given in Plate 3 . It will be seen that the Ni-hard

specimens are shorter than normal and have a waist turned on them: this was necessary to reduce their overall

weight to within the capacity of the weighing equipment.

As noted earlier several of the materials which had been mooted for test proved to be unobtainable

here despite strenuous appeals to manufacturers and suppliers. Regretted omissions include the plastics

polyamide and polybutylene which are often referred to in the slurry pipe literature of Germany and U.S.A.

respectively but could not be obtained in the U J( . Another plastics material sometimes advocated for slurry

pipes is ultra-high molecular weight polyethylene: this was ordered from the German supplier but, due to

some misunderstanding, was not received. Cast basalt is sometimes used in abrasive situations but the British

agents for this material declined to make small-bore test specimens or to provide very thick blocks which

could be suitably cored. Several specially-made experimental materials were considered but abandoned from

lack of available research time and effort: these included ultra-high-density concretes and dense mastic

asphalts made with abrasion-resistant aggregates and perhaps polymeric additives such as epoxy/asphalt

mixtures.

4. S L U R R Y D E G R A D A T I O N AND REPEATABIL ITY OF RESULTS

To obtain measurable amounts of pipe wear the longer the test duration the better. However, a constraint

arises because of progressive attrition of the solid particles in the slurry which reduces their angularity and

diameter, and hence their abrasivity.

It was found in previous TRRL slurry experimentation that very large angular limestone particles

(10 to 20mm diameter) become noticeably rounded, with consequent generation of much limestone dust,

after only a few hours circulation in a test pipe, but that this degradation is much less severe with time

particles and neghgible with very fine particles.

At the outset of the present work it was proposed that a test duration of 100 hours in the first phase

o f the work would be sufficient to produce measurable pipe wear but it was not known how severely the

emery would degrade over that period. It was decided to take samples of the slurry for particle-size

analyses after various times during the 100 hour preliminary run made to "condit ion" the length of steel

pipe f rom which the test specimens were to be cut (see 2.2). In this conditioning run the medium grade

emery was used. The degradation was found to be not very severe after 100 hours but not negligible and,

as a result of this, it was decided to make the test duration for all of the runs in the first stage of the work

only 50 hours.

8

To check on the degradation of the other grades of emery, slurry samples were also taken for particle-

size analysis during some of the actual test runs. It ~vas found, as expected that the t-me emery was unchanged

by 50 hours circulation but, unfortunately, it was found that the coarse grade degraded very severely. The

fact that this was so, and that the degradation had caused anomalous results with the coarse emery, was only

appreciated towards the end of the first test programme, too late to enable tests to be repeated With a

modified procedure. Typical grading curves illustrating the particle degradation are given in Fig. 5 from

which it will be seen that over 25 per cent of very fine emery flour was rubbed off the coarse emery after

50 hours at a velocity of 4 m/s. Photographs of these samples are given in Plate 4. With hindsight it would

clearly have been necessary to renew the coarse emery slurry every few hours to obtain meaningful results,

or else to have adopted a much shorter test duration.

A similar problem with degradation arises when studying the effect of velocity since the rate of

degradation may be expected to increase with velocity. Furthermore it is possible that the relationship

between degradation rate and slurry velocity is not a simple one because of changes in particle trajectory.

As velocity increases there is a tendency for the larger particles, transported by saltation, to be transported

in suspension with a consequent change from impact to sliding conditions.

The magnitude of these effects and the degree of reliance which can be placed on the results of the

first programme of testing is discussed further in section 5 .

For the second test programme, comparing different pipe materials, it was expected that several of

them would suffer relatively little wear and it was certain that much longer test durations would be necessary.

Fortunately these were all to be made with the medium emery at only one velocity. In the event test

durations of up to 1000 hours were required to obtain measurable pipe weight loss and a routine was adhered

to of renewing the slurry every 100 hours.

Since there was still an element of doubt about the likely reliability of results obtained from tests of

widely varying duration, it was also made part of the routine to include a triplet of mild steel specimens in

every test run as a control. On completion of this second programme the calculated rates of wear from all

of these control specimens, from eleven different test runs with durations ranging from 50 to 1000 hours,

were compared and found to be gratifyingly similar. As shown in Fig. 6, all are within about 7 per cent of

the mean value and all but two are within 5 per cent. When it is recalled that these control specimens were

coupled together Jess precisely than the actual test specimens (see third paragraph of 2.3) it may be

expected that the experimental results are probably reliable to plus or minus 5 per cent in the second

programme.

Also included in Fig. 6 are the results for the 'lead-in' specimens for each of the control triplets, i.e.

the pieces used to align the central specimen with the incoming flow. It is interesting to note that in all cases

but one the wear was greater than the wear on the central specimen, testifying to the value of the triplet

procedure. The sole exception is so anomalous (Test run 2) that it seems possible some error occurred in

recording the weight on that occasion. A photograph showing the leading edges of the first and the central

specimens in a triplet which had a bore slightly less than that of the BHRA test loop is given in Plate 5.

5. RESULTS OF THE FIRST PROGRAMME: EFFECTS OF S L U R R Y V A R I A B L E S

5.1 Tabulated results

Most of the first programme was devoted to examining the effect on pipe Wear Rate (W) of volumetric

9

concentration of solids (Cv) , velocity (v), and particle diameter (d) using emery, although a few tests were

also made to examine the effect of particle hardness, using silica sand.

A total of twenty tests were made, all of 50 hours duration using mild steel pipe. Details of these tests

and the results obtained are summarised in Table 1 below.

T A B L E 1

Results of first programme: investigation of slurry variables

Velocity Concentration Duration Wear Rate Solids Test No. (m/s) (% by volume) (hours) (ram/year)

Fine emery

(0.015mm)

Medium emery

(0 .15 mm)

Coarse emery

(1.5mm)

Medium grade

silica sand

(0 .25mm)

17

18

19

l a

lb

6

10

2

5

7

3

4

8/9

11

15

13

12

14a

14b

14

16a

16b

16

20

21

22

2

4

6

2

2

2

2

4

4

4

6

6

6

2

4

4

4

4

4

6

6

6

2

4

6

10

10

10

5

5

10

15

5

10

15

5

10

15

15

10

5

10

15

15

15

10

10

10

10

10

10

50

50

50

50

100

50

50

50

50

50

50

50

29

50

50

50

50

1 st 25

2nd 25

50

1 st 25

2nd 25

50

50

50

50

0.11

0.34

0.56

0.35 ) 0.34 )

0.47

0.58

1.84

2.66

3.64

4.55

9.02

13.62

13.54

1.80

"8.12

*11.31

"18.73 )

"10.28 )

* 14.49

"17.40 )

* 5.00 )

* 11.20

0.20

0.74

1.30

Comments

Degradation trial

Terminated because of technical fault

Consecutive periods

with same slurry

Mean of a and b

Consecutive periods

with same slurry

Mean of a and b

* Results marked with asterisk are known to be erroneous. Due to slurry degradation the Wear Rates are

much lower than they should be.

1 0

5.2 Effect of concentration (C v)

At relatively low concentrations, i.e. in the unhindered state, it is to be expected that pipe Wear Rate

(expressed in mm/year, as in the present paper) will increase linearly with slurry concentration due to the

increasing number of particles passing in a given time.

The results obtained with the medium-sized emery are plotted at each velocity in Fig. 7 and they appear

to confirm that, over the range studied:-

W = k.C v

However, the value of k is dependent on the velocity and at 2 m/s the effect of concentration is barely

noticeable. This may account for the fact that a few workers have reported concentration to have no effect

upon pipe wear. Of course, if the Wear Rate is expressed as mm/Mt of solids throughput this latter statement

is true.

In Fig. 7 the Wear Rates obtained with the coarse emery at a velocity of 4 m/s are also included for

completeness but, because of the severe degradation of particles which occurred, all three of these points

are too low and it is impossible to say where the line should be drawn.

5.3 Effect of velocity (v)

At relatively low concentrations, i.e. in the unhindered state, it is to be expected that the pipe Wear

Rate (expressed in mm/year) will rise withvelocity according to some power between 1 and 3. Firstly it

should rise linearly with velocity because of the greater number of particles passing in a given time. Secondly,

it should rise as the square of velocity if it is assumed that the erosion is directly linked with the kinetic

energy of the particles (my 2). In practice it seems likely that the power will be less than 3 because an

increasing amount of energy will be dissipated through turbulence and ~ter-particle collisions. Furthermore

it seems unlikely that the power will remain constant because of changes in the trajectories of the particles

and their distribution across the pipe section. With increasing velocity, the mode of solids transportation

changes typically from a bed sliding on the invert to saltation, then to a heterogeneous suspension, and

finally to a homogeneous suspension; i.e. from localised sliding abrasion to a mixture of sliding and impact,

and finally back to general sliding wear. Fig. 8a displays (on log/log scale) the effect of velocity on pipe Wear

Rate for three concentrations of the medium-sized emery. The graphs are straight lines and:-

Wc~ v 2"s to v 2"9

Unfortunately this simple conclusion does not hold when the other available results are examined.

In Fig. 8b the result for the middle concentration of all three .~izes of emery and for the silica sand are

compared.

The Wear Rate for the fine emery increases a s V 1.6 Possibly this lower value for the exponent is

explainable by the fact that all of these time particles are likely to be in suspension and there is no sliding

on the invert or saltation impacting.

The slope of the line for the coarse emery is uncertain because particle degradation has resulted in the

Wear Rate at 4 m/s appearing lower than it should be, while the Wear Rate at 6 m/s is even more erroneous.

Some measure of the great effect which particle degradation has on the wear was obtained in the 6 m/s test

11

run by weighing the pipe specimen after the first 25 hours as well as at the end of the 50 hour period. The

values for the first half and the second half are shown on the graph as well as the mean overall value. It

may be concluded with the coarse emery however that the exponent is likely to be greater than 2.7.

The most surprising result is the low exponent obtained with the medium-sized flint sand where

W a v 1.9. Perhaps this is due to the fact that the S.G. of flint is only 2.7 compared with 3.9 for emery and

that, in consequence, the flint sand tends to go into suspension at 4 and 6 m/s while comparable-sized emery

is still saltating.

The overall conclusion from this part of the work is that the Wear Rate is likely to vary with velocity

according to some power between 1.5 and 3, the lower value being obtained with smaller and lighter

particles and the higher value with coarser denser particles.

5.4 Effect of particle size

On the assumption that erosion wear is directly linked with the kinetic energy of the solid particles

(mv2), coarse particles will be individually more destructive than fine ones. On the other hand, for a given

concentration the total mass of solids is constant and it might be argued that the net effect of particle size

should be zero. However, due to viscosity and drag there will be no impact at all with very f'me particles,

and with the coarser particles the amount of impacting will vary as the flow regime changes, this being

interdependent on velocity as well as particle size. The pattern of Wear Rate change with particle size is

therefore likely to be complicated. This is confirmed by the limited results available, which are presented

(on log/log scale) in Fig. 9.

At 2 m/s a straight line is obtained with Wear Rate changing as d ° ' 6 i.e. the Wear Rate increases

rapidly at the fine end of the size range but less rapidly at the coarse end.

At 4 m/s and 6 m/s the picture is unclear due to the erroneous points obtained because of excessive

particle degradation. However, it may be noted that the first part of the graphs between the points for the

small and medium emery, which are reasonably reliable, have steeper slopes. At 4 m/s the slope is about 1

i.e. the Wear Rate increases linearly with particle size. At 6 m/s the exponent is 1.2 i.e. the Wear Rate

increases more rapidly as particle size increases.

5.5 Effect of particle hardness

The abrasivity of solids per se is a complicated subject, depending on the hardness (in Mohs' sense)

of the minerals present, toughness (which tends to be inversely proportional to hardness), angularity, specific

gravity, coefficient of restitution in impact conditions and so on.

In the slurry pumping field a variety of tests are used to provide an ad hoc assessment or index of

abrasivity of the solids which it is proposed to pump. The most widely used is the Miller Test, devised by

pump technologist J.E. Miller in 1967. In this a standard metal block is driven with a reciprocal motion

over a shallow bed of slurry contained in a trough and the weight loss is measured periodically. The "Miller

Number" is then calculated and, in the inventor's own words, "it consists of two values. The first is called

abrasivity and represents the weight loss from the metallic wear block. The second value is called attrition

and represents the effect of slurry particle breakdown as measured by loss of abrasivity as the test progresses:

this may be minus if there is a loss o f abrasivity and plus if there is a gain." The phenomenon of abrasivity

increasing with time is comparatively rare but it can dearly occur under certain conditions if the solids

12

tend to split with brittle fractures exposing fresh sharp edges. Typical results from more than eighty ad hoc

tests reported by Miller include the following examples:-

Potash 'A' 00 --00

Potash 'B' 10 +01

Iron ore 'A' 28 - 0 7

Iron ore 'B' 157 - 1 1

Coal 'A' 6 - 2 6

Coal 'B' 57 - 0 3

Sand 'A' 51 - 1 0

Sand 'B' 246 - 0 9

Mine tailings 'A' 24 - 0 8

Mine tailings 'B' 644 - 1 4

0.037mm fused alumina 241 +21

0.074mm fused alumina 1058 - 1 5

0.068mm silicon carbide 1284 - 1 5

The importance of particle size was recogrtised by Miller but only in the last three examples given above

did he bother to report the sizes of the materials he tested and it is therefore impossible to analyse his results

in detail to isolate the effects of mineral hardness and size. From the point of view of the present work it is

also unfortunate that he did not include emery in his tests.

As noted in 3.1 above, it was not possible within the time and resources available to conduct pipe wear

tests on an adequate range of different mineral particles. Only three tests runs were made with a naturally-

occurring silica sand of medium particle size, at medium concentration with three velocities. Due to the

moderate particle size and the fact that the particles were aleady well rounded, rapid degradation by attrition

was no problem and the results are considered reliable.

The Mohs Hardness of silica is about 6 or 7, much less than that of corundum, the main constituent o f

emery. As expected the Wear Rates were much lower than those obtained with the comparable sized emery,

as shown in Fig. 8b. No quantitative deductions can be made from this single comparison. What is needed

is the accumulation of a data bank of such tests results for a great variety of materials, as assembled by Miller

with his test, before some clear pattern can be seen.

6. RESULTS OF SECOND TEST PROGRAMME: COMPARISON OF 18 PIPE M A T E R I A L S

6.1 Tabulated results

In this part of the work the Wear Rates were determined for eighteen different pipe materials, details

of which are given in 3.2 above. Medium emery (O.15mm) at medium concentration (10 per cent) and

medium velocity (4 m/s) was used throughout. As noted earlier, test times had to be greatly increased for

several of the pipe materials to achieve readily measurable wear, but the slurry was renewed every 100 hours,

and there was no degradation problem. Mild steel control specimens were included in every test run a-9. d,

as was shown in Fig. 6, good reproducibility was established.

The results are given below in Table 2, listed in order of Wear Rate, best first.

13

TABLE 2

Results of second programme: comparison of pipe materials

P10.

C3.

M4.

P8.

P9.

P11.

M7.

C4.

P12.

P15.

P3.

P1.

M6.

Mla.

P4.

Mlb.

P7.

C5.

Material

Rubber 'a ' (Resilience 60)

Zirconia/alumina ceramic (ZAC 1681)

Ni-Hard steel

Polyurethane 'a ' (Resilience 50)

Polyurethane 'b ' (Resilience 45)

Rubber 'b ' (Resilience 32)

Nickel/diamond coating

Sintered alumina (DERANOX 975)

Rubber 'c ' (Resilience 33)

High density polyethylene 'b '

High density polyethylene 'a '

Unplasticised polyvinyl chloride

Stainless steel

Mild steel 'a '

Polypropylene

Mild steel 'b '

(mean of 11 runs with range 1.62 to 1.83)

ABS

Asbestos/cement

Wear Rate

(mm/year)

0.13

0.15

0.19

0.20

0.22

0.35

0.38*

0.40

0.61

0.67

0.87

1.27

1.29

1.57

1.59

1.69

2.52

94.68

Life expectancy of

a 5mm thickness

(years)

38

33

26

25

22

14

12

8

7

5

4

4

3

3

3

2 I

* Note. The figure for C7 was calculated on the assumption that only nickel has been abraded away in tiffs

100 hour test run.

6.2 Discussion of results

Two materials, asbestos/cement (C5) and the nickel/diamond coating (M7) require separate consideration

from the others and are here eliminated from further discussion.

(i) Asbestos/cement (C5). This material suffered extremely rapid wear, two orders of magnitude

greater than the others, and it must obviously be regarded as generally unsuitable for use with

highly abrasive slurries.

(~) Nickel/diamond coating (M7). This material differs from all of tile others in being applied as

a coating only 0.025mm thick. Since the calculated Wear Rate was 0.38ram/year it also seems

at first consideration to be unsuitable. However, this figure is based on a test of only 100 hours

duration, in which only about 20 per cent of the coating was worn away. It is possible that this

loss was virtually all nickel and that the high wear-resistance claimed by the suppliers only comes

into play when the diamonds have become extensively exposed. A much longer test, with

periodic weighing, would be necessary to evaluate this material more fully.

1 4

The remaining materials all had Wear Rates in the range 0.1 to 2.5 ram/year. Since it is technically

possible to supply any of these materials inside a suitable pressure casing as a lining 25mm thick, it might

be argued that they are all therefore potentially capable of providing a life of 10 years. However, with a

slurry pipeline designed for optimum performance it is undesirable that the pipe diameter should change

markedly from that for which the system was designed: for instance, i f a 200mm diameter pipe lost 10mm

wall thickness overall, the flow velocity would change by 20 per cent. On the assumption that 5mm wall

thickness change would be generally tolerable a second column has been added to Table 2 showing the

life expectancy of a 5mm lining.

It must be pointed out that various practical difficulties are presented by the adoption of lined pipes.

Continuous welding is not possible and suitable lengths have to be bolted together, requiring care in

alignment and special pressure-tight joints. Furthermore, with relatively soft elastomeric linings, instances

are known where these have parted from the steel in time: in the present work one of the polyurethanes

was found to have shrunk noticeably during storage for about a year after testing and was partially disbonded

as shown in Plate 6; (the other polyurethane remained satisfactory).

In considering the tabulated figures it should be borne in mind that they are based on work with

unusually abrasive solids and that in practice most minerals will be less aggressive. On the other hand the

tabulated figures are only based on overall mean rates of wear around the pipe: much higher Wear Rates

may occur locally at bends, at irregularities in the pipe-wall where turbulence is induced, or in the invert

if pronounced saltation is present.

6.3 Conclusions

On the basis of Table 2, neglecting materials C5 and M7 for the reasons given in 6.2, the following

conclusions may be drawn:-

. When a highly abrasive slurry is to be pumped many materials more durable than conventional mild

steel pipe are available, some ten times as durable.

. By choosing a suitable lining it is possible to envisage burying abrasive slurry pipelines for a typical

operational life of 20 years providing that secondary problems with jointing and lining-disbonding are

not insuperable.

. No particular category of material appears outstandingly better than any other from an abrasion

point of view. The best group in these tests included rubber, plastics, ceramic and hard steel alloy

-materials.

4. With rubbery materials, within the range tested, the softer and more resilient the better. However,

there is no doubt a limit to which this trend can be followed before tearing wear becomes a problem.

With plastics which are relatively elastomeric such as the polyurethanes, tests on a wider range are

needed to establish acceptable limits o f their properties.

6.4 Economics and choice

It is impossible to generalise about the economic balance of increased life and higher initial cost:

each potential installation of a pipeline requires its own calculations.

In arriving at the cost of an alternative to a continuously welded steel pipe it is not sufficient merely

to add the cost of a suitable lining 5mm thick to a steel casing. There is also the cost o f numerous joints

15

and probably extra care in installation. In any case, not all of the materials are readily available as 5 ram

linings: ZAC and Ni-hard for instance are not usually cast with thicknesses less than about 15mm.

The prevailing rate of interest on capital is an important factor, since the present high rates favour

cheap replaceable pipes over expensive more durable ones.

Finally, in addition to the cost/life question, several pipe materials offer other advantages over steel

which sometimes lead to their choice, i.e. high corrosion resistance, lightness of weight, and flexibility.

The last two apply mainly to the use of low-pressure plastic pipelines where no outer steel casing is necessary.

7. A C K N O W L E D G E M E N T S

This Report was prepared in the Transport Engineering Division of the Transport Systems Department of

TRRL. Acknowledgements are due to the staff of BHRA Fluid Engineering, Cranfield, Beds., for their

conduct of the tests, principally Barry Jacobs (Project Officer for this work), Vinod Mistry for the tests

in the first programme and Stuart Croshaw for the tests in the second programme. Thanks are also due to

TRRL colleagues Tom Williams and Dave Jacklin for carrying out the measurements of Hardness and.

Resilience on the elastomeric materials. The cooperation of several firms in providing materials for testing is also appreciated.

8. REFERENCES

1. BOOTHROYDE J. Investigation of pipeline abrasive wear using existing slurry facility, BHRA

Technical Report TRC 1075, Cranfield, 1976 (BHRA Fluid Engineering).

2. JACOBS B.E.A. Measurement of wear rates in pipes carrying abrasive slurries, Paper C2, pp 145-60,

Proceedings of the 8th Annual Conference on the Hydraulic Transport of Solids in Pipes (HYDRO-

TRANSPORT 8), Cranfield, 1982 (BHRA Fluid Engineering).

. WAPLER H., T.A. SPOONER and A.M. BALFOUR. Diamond coatings for increased wear resistance,

Industrial Diamond Review, 1979 (July), 251-255 .

4. MELDT R. Feststoff-Transport in Kunststoff-Rohrleitungen (Transportation of solids through

plastics pipelines), Kunststoffe, 1978, 68 (10), 642-644: and MELDT R. Kunststoffrohre fur den

hydraulischen Feststofftransport (Plastics pipelines for hydraulic transport of solids), VDI-Bedcht

Number 371 "TRANSROHR 80", 1980, 45--50.

. MUNRO C.E. Polyurethane-lined pipelines, Pipes and Pipelines International, 1974, 19 (March-April), 16--18,33.

. TRELLEBORG RUBBER LTD. A study of wear-resistant rubber, Colliery Guardian, 1979 (February), 8 1 - 8 6 .

. OLSEN E. Wear-resistant ceramic lining for piped materials handling, Proc. 1st. Intemat. Conf. on the

Protection of Pipes, Durham 1975, Paper G5.

16

Weigh tank

Flow meter

See below for details of test loop

hopper

pump

(a) Slurry circulation arrangement

4 Return to hopper •

Entry from pump

76mm line I I

38mm line

Pressure tappings 6 7 8

1 2

U.V. recorder

Pressure transducer

TO manometer

t ~ Drain valve

~ / w ~ i = t a ~ "1>~1-- - - = I

sWpeeca, mens Density meter

(b) Details of test loop

Fig. 1 Schemat ic layou t of small s l u r r y r ig at BH RA Labora tory , Cranf ie ld

1'

c ~ 0 ~

~ D

c G~

E ° ~

Q~

B

° ~

"1o ° ~

Q~

i J

0 ~

C ° ~

0

0 ~ . m o , m q

r s J 4~ 4 - J

o~ ° ~

LL

A

" O

e -

° - -

A

v

" O

( I )

e -

0.1

0.1[= 0

0.7

0.6 -

0.5 i 0.4

0 .3

0.2 -

0.1 - -

0 - - 0

1.3

1.2 -

1 . 1 -

1.0

0.9

0.8

0.7 1

0.6 ,

0 .5

0.4

0.3

0 . 2 - -

0.1 - -

0 J 0

~Po lyp ropy lene I i i I

0 1000 2000 3000

1000 2000 3000

PIO Rubber 'a'

1000 2000 3000

P8 Polyurethane 'a'

1000 2000 3000 Drying time (h)

Fig. 3 Drying curves for four non-metallic pipe specimens, il lustrating the great variability in water absorption and its,slow release at 50°C

S.

o o

\

Or) UJ > IL l

I - - U 3

~ot ui m

( :3 0

( :3

\ \ .

I o a~

C3 OD

I - - - e -

0

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[ I

o o o

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o o o o o

6ulssod a 6 " 0 ~ u a 3 J a ¢ j

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= ~ i l l I I m m I ~

o o

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o

\

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N

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. o o

\

0 • 0

0 o

~o U

~- -.,I D

tU J'~[ ~E in~"

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t~

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t L

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0 0

~E • -~ I - -

0 W~

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IT

=.

m

. E

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" o cL)

e-

o

{I=

t~

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"6 ° m , i ~

a .

o l ° l i i

B L A N K G - / ~ 2 0 8

0 0

6mssod ~ 6o),ua3JacJ 0 (:3 0 C) C) 0 C) 0 C)

I I i 0

LU

UJ

i f )

II1

\ \

\

o

o o o ..E r" .,E

: : O L O O - -

f,-)e

0 0 0 tU c - c - e - ~

>_ E ~ " ~

\

IJ.

t ~ i o

:\

e-

c ° ~

0 " 0

' ~

O 0

IDG,~

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_ ~ .u "E

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0 C)

C) ( 3 0 o o o o

6mssod a6o)sua3Ja~

c ) o

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B L A N K G . L 2 0 8

Test run no°

Duration (h)

1 50

2 100

3 100

4 200

5 200

6 100

7 100

8 200

9 300

10 200

11 1000

Wear rate (ram/year)

Centre Lead-in (definitive) specimen specimen

• "

1.937 1.804

1.373 1.642

1.764 1.693

1.745 1.628

1.735 1.620

2.030 1.623

1.886 1.825

1.800 1.698

1.722 1.647

1.810 1.692

1.808 1.756

¢o

E E

v

P

2.0

1.0

m

Z~ Z~

• _ ~ Z~ z~ - - J - z ~ - - - - z £ ~ z~ ~ - - - - +5% A A A Mean

v v

_ e _ _ _ - _ _ e _ - - e ~ - ~ - • 5%

A

i ! I | I I I ! I I I 1 2 3 4 5 6 7 8 9 10 11

Test run number

Fig. 6 Wear rates o f m i l d -s tea l c o n t r o l specimens in a l l e leven tes t runs o f the second p r o g r a m m e , s h o w i n g good repea tab i l i t y desp i te var ied dura t ion

20

1 5 - -

%- t~ ¢D

E E

v

10 B P

¢D ¢Z

5 - -

0 0

I Z~ 0.15mmemery I"1 1.5mm emery at 4 m/s

J:

5 10

Volumetric concentration (per cent)

2 m/s

15

Fig. 7 Effect of concentration on wear rate of mild steel pipe

E E

20

10

8

6

m

m

m

1 .0 I

0 . 8 - -

0 . 6 - -

0.4

0 . 2 ~

0.1 1

Slope Cv 2.9 ~ ~ 15%

2.7

2.5

10%

5%

I ! I I I 1 11 2 3 4 5 6 7 8910

Velocity (m/s)

20

10

8

6

4

E E 2

h~

~. 1.0 0.8

0.6

0.4

0.2

0.1

• n Ist

t # ~ 25hrs -- 17 mean

/I/ od Slope [ ] 25 hrs

_ ~ 2.7 ~~.~"'~/ - j

~ ~~" 1.6 I I I I I I I 3 4 5 6 7 8 9 1 0

Velocity (m/s)

(a) 0.15mm emery at three concentrations (b) All materials at one concentration (10%)

Fig. 8 Ef fect o f ve loc i ty on wear rate of mild steel pipe

50

4 0 m

3O

/ 7 20

p ~ Velocity

t Is 10

6

2

1.0

0.8 "

0 .6

0 .4

0.6 ,.

0.2

0.1 *Y I I 0.015 0.15 1.5

Mean particle diameter (mm)

Fig. 9 Effect of particle size on wear rate of mi ld steel pipe

~:

C ,

!! .....

J

A

..1

C

E U.I

U . .

e -

:~ 0

e-

X ~ U

~ ' - - . _

"6 "~ E , - ~ , E .o_ ~8 ~ e- C

• ~ ° ~ ~ " 0 " 0

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o E E

W / '~ll~l"tlrINf=*'l',=llll1,1T,lltll~l~l~lll~*l~ I I m 1.0 20 30 40 5 0 ~

IIII I II

Neg. no. R562/82/6

Plate 2 The three grades of emery used in the first test programme

I f •

Neg. no. B905/82

Plate 3 Specimens of various pipe materials used in the second test programme. The M4 specimens had to be cast relatively thick and, to keep the weight down, they were made half the normal length

- ° 0 h o . ~ s 5 0 h o ~ s

~ b

Neg. no. R562/82/9

Plate 4 Photographs of the coarse emery at various times during a test showing excessive particle degradation

Neg.no.R 562/82/5

Plate 5 Photographs of the leading edges of the lead-in specimen of a triplet (left) and the central specimen (right),, demonstrating the importance of obtaining an accurately matched bore

Neg. no. R562/82/2

Plate 6 The polyurethane specimens P8 (left) and P9 (right) after about one year storage: P9 has shrunk away from the steel noticeably

1.

2.

3.

4.

5.

6.

7.

.

.

10.

11.

9 . A P P E N D I X 1

CHRONOLOGICAL BIBLIOGRAPHY

WELLINGER K. and H. UETZ. Sliding and impact wear under the action of granular solids (in German),

V.D.I. Forschungsheft, 449, 1 --40, 1955. Discusses, inter alia, the effect of impact angle on wear as

shown by laboratory tests.

NEKRASOV S.S. and N.E. OFENGENDEN. Study of the abrasion resistance of plastics, cast basalt

and rubbers in hydraulic mixtures, Soviet Plastics, 1961, (11): English translation from Russian in

JAMES D.I. and M.E. JOLLEY (editors). Abrasion of rubber, 1967 (Maclaren & Sons), 317-21 . From

laboratory tests on 7 plastics, 3 rubbers and cast basalt it is concluded that the plastics and basalt have

inferior resistance to steel but that the rubbers are all greatly superior.

BITTER J.G.A. A study of erosion phenomena, Wear, 1963,6~ 5-21 and 169-90. From experimental

and practical data a theory is derived to explain erosion wear in terms of two components, one arising

from deformation and one from cutting action.

BRAUER H. and E. KRIEGEL. Wear on pipes in the hydraulic transport of solids (in German), Stahl

und Eisen, 1964, 84 (21), 1313-22 . Discusses wear patterns and wear mechanisms in the light of

laboratory tests (steel pipe, 20 per cent iron ore slurry).

BRAUER H. and E. KRIEGEL. Pipe-wear problems in pneumatic and hydraulic transport (in German),

Maschinenmarkt, 1965,71 (68), 2 0 - 3 1 . More extensive than Ref. 4.

BRAUER H. and E. KRIEGEL. Wear of pipe-bends in pneumatic and hydraulic transport (in German),

Chem.-lng.-Tech., 1965,37 (3), 2 6 5 - 7 6 . Variant o f Ref. 5.

JACKSON L.D.A. Slurry abrasion, Trans Canad Inst Min and Met, 1967, 70, 219-24. From laboratory

tests using steel pipe and silica sand slurries it is concluded that wear varies with v 2"6, Cv,d"

ANON. What about using a portable dredge, World Construction, 1967, 20 (March), 24 -7 .

Practician's discussion of pump and pipe life including an empirical formula for pipe life.

BA1N A.G. and S.T. BONNINGTON. The hydraulic transport of solids by pipeline, 1970 (Pergamon).

Discusses (on pp 131 --6) the variable results reported by several workers in France and Russia in which

wear varies with v ~ to v 4"s, Cv,d"

WIEDENROTH W. The influence of sand and gravel onthe characteristics of centrifugal pumps, some

aspects o f wear in hydraulic transportation installations, Proc I st lnternat Conf on the Hydraulic

Transport of Solids in Pipes (HYDROTRANSPORT 1), 1970, (BHRA, Cranfield), Paper El, 1-27.

Reviews experimental work by the author and others (mainly German) illustrating, inter alia, the good

performance of rubbers and the poor performance of several plastics and basalt at high impact angles.

ROHNISCH A. and E. VOI_LMER. A method for the uniform evaluation of resistance to erosion of

materials used for hydraulic structures. Proc HYDROTRANSPORT 1, 1970, Paper E2, 29-40 .

Describes a simulative laboratory test (using 16mm particles in a relatively high-impact condition)

comparing 12 pipe materials: all proved worse than steel.

3 0

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

PRUDHOMME RJ. , J.E. MILLER et al. Reciprocating pumps for long-distance slurry pipelines. Proc

HYDROTRANSPORT 1, 1970, Paper E4, 49 -59 . Includes description of the Miller abrasion test.

LINK J.M. and C.O. TUASON. Pipe wear in hydraulic transport of solids, Mining Congress J., 1972,

5__88 (7), 38-44 . Reports laboratory tests with various slurries in steel pipe showing that wear varies as

v 2.1, d and C v although above 20 per cent the effect of C v diminishes.

TARJAN I. and E. DEBRECZENI. Theoretical and experimental investigation on the wear of pipeline

caused by hydraulic transport. Proc HYDROTRANSPORT 2, 1972, Paper G 1 , 1 - 1 3 . Reports tests on

pilot-scale test-loop using sand slurry with three different metal pipes. Wear increased with C v at low concentrations (less than 9 per cent).

POSTLETHWAITE J., E.B. TINKER and M. HAWRYLAK. Corrosion studies in slurry pipelines, Proc

HYDROTRANSPORT 2, 1972, Paper G2, 15-24. Reports results of test-loop studies using various

slurries in steel pipe with and without corrosion protection, showing the important role played by this

aspect of wear.

ARUNDEL P.A. et al. The rapid erosion of various pipe-wall materials by a stream of abrasive alumina

particles. Proc PNEUMOTRANSPORT 2, 1973, Paper El , 1 -15 . Reports laboratory studies of varied

impact angle using sand-blasting techniques (very high velocity) on steel, nylon and two rubbers. Wear was found to vary as v 3 .a

LANCASTER J.K. Basic mechanisms of friction and wear of polymers, Plastics and Polymers, 1973,

(Dec), 297-306. Largely theoretical discussion of sliding wear mechanisms.

POSTLETHWAITE J. and E.B. TINKER. Experimental studies of solids pipelining o f Canadian

commodities, Report No. 8. Erosion-corrosion studies in slurry pipelines, University of Saskatschewan,

1973. A more detailed report (75pp) than Ref. 15.

TURCHANINOV S.P. The life of hydrotransport pipelines (in Russian), Moscow, 1973, translated

into English by A.L. PEABODY, Maryland, 1979 (Terraspace Inc.). Detailed review mainly of Russian

work, with bibliography of 87 refs.

MILLER J.E. The Miller Number - a new slurry rating index. Society of Mining Engineers of AIME,

Preprint No. 73-B-300, 1973. Description of the Miller test with table of ad hoc test results on numerous

slurries.

JACKSON L.D.A. Controlling abrasion in slurry pipeline systems, Canadian Mining J., 1974, 95 (11),

42-45 . Describes a simulative laboratory test. Reports that wear varies as v 2"6.

SAMBELLS D.F. A practical solution to pumping an abrasive slurry, Proc HYDROTRANSPORT 3,

1974, Paper J 1, I - 15. Advocates polyurethane pipe linings on basis o f experience.

MUNRO C.E. Polyurethane lined pipelines. Pipes and Pipelines International, 1974, 1_99 (March-April),

16-18, 33. A complementary paper to Ref 22, giving some case histories.

HUGHES R.C. et al. Steel pipeline design, Civil Engineering-ASCE, 1974, 44 (3), 6 4 - 7 . Brief discussion

only, but includes graphs of wear rate- v- velocity from test-loop measurements with sand slurry in steel pipe.

31

25. BARKER M.L. and G.F. TRUSCOTT. The development and operation of a test facility for pipeline

abrasive wear measurement. Proc HYDROTRANSPORT 3, 1974, Paper J3, 33-50 . Describes the test-

rig at BHRA laboratories, Cranfield.

26. GOCHITASHVILI T. Sh., M.N. GELENIDZE and N.G. ARAKELASHVILI. Procedure for calculating

the hydro-abrasive wear of hydraulic transport pipelines (in Russian), 86 -90 , in DZHVARSHEISHVILI

A.G. (editor) Long-distance hydrotransport o f granular solids by pipeline, 1974, Tbilisi (Georgian SSR

Academy of Sciences). Presents formula for wear rate in which it varies as v a , C v and d.

27. MILLS D. and J. S. MASON. Learning to live with erosion of bends, Proc 1st Internat Conf on Protection

of Pipes, Durham Sept 1975, Paper GI , 1-20 . Reviews wear theories.

28. LEHRKE W.D. and F.A. NONNEN. Internal protection of pipes against abrasion and corrosion by fused

cast basalt, Proc 1st Internat Conf on Protection of Pipes, Paper G2, 21-28 . Commercial advocacy of

basalt pipelinings.

29. FADDICK R.R. Pipeline wear from abrasive slurries, Proc I st Internat Conf on Protection of Pipes,

Paper G3, 2 9 - 3 7 . Suggests wear is proportional to v 2 when expressed as mm/tonne throughput.

30. GANDHI R.L., B.L. RICKS and T.C. AUDE. Control of corrosion-erosion in slurry pipelines, Proc 1st

Internat Conf on Protection of Pipes, Paper G4, 3 9 - 5 2 . Discusses corrosion inhibitors.

31. OLSEN E. Wear-resistant ceramic lining for piped materials handling. Proc 1 st Internat Conf on Protection

of Pipes, Paper G5, 53--64. Commercial advocacy o f ceramic ZAC 1681, reporting test cases.

32. TRUSCOTT G.F. A literature survey on wear on pipelines, BHRA Fluid Engineering Paper TN 1295,

1975. A bibliography of 51 papers with summarised Findings.

33. BOOTHROYDE J. Investigation of pipeline abrasive wear using existing slurry facility and design of

a large-scale slurry test facility, BHRA Fluid Engineering Paper TRC 1075, 1976. Description o f the

test rig used for the experiments reported in the present paper.

34. BAKER P.J. and B.E.A. JACOBS. The measurement of wear in pumps and pipelines, Proc HYDRO-

TRANSPORT 4, 1976, Paper J1, 1 -16 . Brief description of recent work at BHRA.

35. POSTLETHWAITE J., B,J. BRADY and E.B. TINKER. Studies of erosion-corrosion wear patterns in

pilot plant slurry pipelines, Proc HYDROTRANSPORT 4, 1976, Paper J2, 17-26. Shows value of

cathodic protection against corrosion.

36. JAQUES R.B. and W.R. NELL. Internal corrosion of slurry pipelines, Proc 2nd lnternat Tech Confon

Slurry Transportation, 1977, 124-35 . Commercial advocacy of corrosion inhibitors.

37. GLAESER W.A. and T.A. DOW. Mechanisms of erosion in slurry pipelines, Proc 2nd Internat Tech

Conf on Slurry Transportation, 1977, 136-40 . Offers an empirical formula for pipeline wear.

38. HOCKE H. Wear-resistant materials for coke and sinter handling plant, Iron and Steel International,

1977 (Dec), 361 -71 . Presents results obtained in practice with 64 materials under impact and sliding

wear on shutes.

32

39. HOCKE H. and H.N. WILKINSON. Testing abrasion resistance of slurry pipeline materials. Tribology

International, 1978 (Oct), 289-94. Presents test results on 15 materials using protruding inserts in a

slurry pipeline i.e. under impacting conditions: all wbre better than mild steel except PVC.

40. MELDT R. Transport of solids through plastics pipelines (in German), Kunststoffe, 1978, 68 (10),

642 44. From test results advocates plastics, particularly high density polyethylene.

41. GLAESER W.A. and A.T. HOPPER. Erosion life in slurry pipelines; possible sources of error in

prediction. Proc 3rd lnternat Tech Confon Slurry Transportation, 1978, 179-82 . Discusses effect

of impact angle.

42. MISTRY V.R. Wear of slurry system components due to abrasion. BHRA Fluid Engineering Paper

RR 1494, 1978. Reports on current work at BHRA.

43. POSTLETHWAITE J. The evaluation of slurry erosion-corrosion inhibitors in pilot plant test loops.

Proc 3rd Internat Tech Conf on Slurry Transportation, 1978, 189-194. Reports tests on various

corrosion inhibitors.

44. KARABELAS A.J. An experimental study of pipe erosion by turbulent slurry flow, Proc HYDRO-

TRANSPORT 5, 1978, Paper E2, 15-24 . Reports results from closed loop tests using sand slurries

and brass inserts flush with pipe wall. At 30 per cent concentration wear varied with v 2"3 v 2.8 and v 3 .a

for top middle and bottom respectively. Wear also increased with d 2"I s.

45. KAWASHIMA T. et al. Wear of pipes for hydraulic transport of solids, Proc HYDROTRANSPORT 5,

1978, Paper E3, 25--44. Analysis of practical and experimental data obtained from various sources

(mainly Japanese) by a Japanese committee on pipe wear. In a table summarising results from 26

workers wear was reported to vary with v to powers ranging from 1 to 4.6.

46. WANT F.M. Wear in slurry pipelines. Inst of Engineers Australia, Mech and Chem Eng'ng Trans, vol

ME4, 1979 (Nov), 17-27. Reports tests with bauxite sand slurry and 14 pipe materials: all better

than mild steel except cast basalt. Reviews data reported from actual pipelines.

47. TUFT P.R. Wear in slurry pipelines - a survey. Proc 7th Australian Conf on Chern Eng'ng, 1979,

196-201. A review of the literature (45 refs), including several lesser known papers.

48. PATERSON A.C. and N. WATSON. The National Coal Board's pilot plant for solids pumping at

Horden colliery, Proc HYDROTRANSPORT 6, 1979, Paper HI, 353 -66 . Details o f a 250ram

diameter pipeline pumping coarse solids (up to 75mm stones) which is being used also as a practical

test bed for pipe wear. See Ref. 51 for results.

49. NGUYEN V.T. and F. SAEZ. Design of pipeline for a highly abrasive and corrosive slurry, Proc

HYDROTRANSPORT 6, 1979, Paper H 2 , 3 6 7 - 7 8 . Describes wear tests for a proposed copper

tailings slurry line and method of estimating pipe life from the results. To achieve rapid wear in

the tests ultra-high velocities were used (7 12 and I6 m/s).

50. GITTINS L. (editor). Wear in slurry pipelines, BHRA Information Series No. 1, Cranfield, 1980.

A collection of nine papers and a bibliography of a further 31. The nine include Refs. 29, 30, 32 ,42 and 44 as listed above.

33

51. PATERSON A.C. Pumping solids, Presidential address to the Societe des Ingenieurs et Scientifiques de

France, British Section, 1980. Fuller details of tests in Ref. 48 and report on the results to date. ABS,

grey cast iron, and basalt worse than mild steel. Best results given by ZAC and polyurethane.

52. DUCKWORTH R.A. Hydraulic Transport of Materials, Proc Inst Mech Engrs Conf on Hydraulic

Transport, London, 1980, I - 5 . Includes results of laboratory tests on five materials used as inserts

projecting into a test loop carrying silica sand slurry. Polyurethane and ZAC proved better than steel,

basalt worse.

53. HAY E. and L.D.A. JACKSON. Rubber lined pipelines - an overview. Amer Soc Mech Engrs Paper

No. 80-WA/MH-8, 1980. Review of rubber pipelinings.

54. MELDT R. Plastics pipes for the hydraulic transport of solids (in German), Proceedings of Conference

"TRANSROHR '80", VDI-Berichte No. 371, 1980, 45-50 . An updated version of Ref. 40. English

translation in Bulk Solids Handling, 1981,1 (2), 307-12 .

55. WANT F.M. Centrifugal pump wear: plant experience. Proc HYDROTRANSPORT 7, 1980, Paper HI,

301 -14 . Compares various impeller materials in practice.

56. MURAKAM1 S. et al, Wear test of pipe linings for hydraulic transport of dam deposit, Proc HYDRO-

TRANSPORT 7, 1980, Paper H2, 315-30 . Progress report on laboratory tests and comparative trials

of various materials: polyurethane best.

57. SHOOK C.A., D.B. HAAS, W.H.W. HUSBAND and M. SMALL. Relative wear rate determinations for

slurry pipelines, Journal o f Pipelines, 1981,1 (4), 273-9 . Reports closed-loop wear tests using sand

slurries with four plastics and steel. High density polyethylene was best (polyurethane not tested).

Wear rate (in mm/Mt throughput) was found to be insensitive to velocity and concentration.

58. GAESSLER H. Steel pipe for slurry pipelines, Bulk Solids Handling, 1981,1 (3), 463-9 . Inter alia,

discusses wear of various steels.

59. DAYKIN K.W. An evaluation o f materials for use in coal preparation plants. Mine & Quarry, 1982,

!_[1 (May), 2 6 - 3 I. Experience with wear resistance of various plastics in National Coal Board plants

including the Horden pipeline (Refs. 48 and 51).

( 1 3 8 ) D d 8 0 4 1 3 1 8 1,400 2 /83 HP Ltd So ' ton G1915 P R I N T E D IN E N G L A N D

ABSTRACT

Wear in slurry pipelines: experiments with 38mm diameter specimens in a closed-loop test rig: J G JAMES and B A BROAD: Depar tment o f the Envi ronment Depa r tmen t o f Transpor t , T R R L Supplementary Repor t 773: Crowthorne, 1983 (Transpor t and Road Research Laboratory). This report describes two programmes o f wear testing, planned by T R R L bu t carried out under contract by BHRA Fluid Engineering, Cranfield, Bedfordshire . Abrasive slurry was circulated through 38ram diameter pipe in a c losed- loop test rig and the a m o u n t of wear was assessed by measuring the weight loss o f short removable lengths. In the first programme (1979/80) the slurry was varied to s tudy the inf luence o f veloci ty, concen t ra t ion , particle size, and particle hardness on the wear of ordinary mild steel pipe. The fol lowing conclusions were reached: (i) Over the range investigated (2 to 6 m/s) wear varied according to a power be tween the square and cube o f velocity. (ii) Over the range investigated (5 to 15 per cent by volume) wear varied more or less linearly with concent ra t ion . (iii) Over the range investigated (0.015 to 1.5mm) wear varied more or less linearly with particle size. (iv) Emery (Mohs Hardness 8 to 9) produced a wear rate several t imes greater than that for silica sand (Mobs Hardness 6 to 7).

In the second programme (1980/81) the operat ing condi t ions were kept cons tant (velocity 4 m/s, 10 per cent slurry o f 0.15ram emery) while 18 di f ferent pipe materials were compared. Most o f them proved to be more resistant to wear than mild steel bu t no particular class was found markedly to outrank the others. S o m e w h a t surprisingly the best four materials comprised one from each main category (metal , ceramic, rubber and plastics).

An annotated bibliograph o f 60 papers on other pipeline wear work ' is given in an Appendix.

I S S N 0 3 0 5 - 1 3 1 5

ABSTRACT

Wear in slurry pipelines: experiments with 38mm diameter specimens in a closed-loop test rig: J G JAMES and B A BROAD: Depar tment o f the Env i ronment Depa r tmen t o f Transpor t , T R R L Supplementary Repor t 773: Crowthorne, 1983 (Transpor t and Road Research Laboratory). This report describes two programmes o f wear testing, planned b y T R R L b u t carried out under contract by BHRA Fluid Engineering, Cranfield, Bedfordshire . Abrasive slurry was circulated through 38mm diameter pipe in a c losed- loop test rig and the a m o u n t o f wear was assessed by measuring the weight loss o f short r emovable lengths. In the first programme (1979/80) the slurry was varied to s tudy the inf luence o f veloci ty , concen t ra t ion , particle size, and particle hardness on the wear o f ordinary mild steel pipe. The fol lowing conclusions were reached: (i) Over the range investigated (2 to 6 m/s) wear varied according to a power be tween the square and cube o f velocity. (ii) Over the range investigated (5 to 15 per cent by volume) wear varied more or less linearly wi th concent ra t ion . (iii) Over the range investigated (0.015 to 1.5mm) wear varied more or less linearly with part icle size. (iv) Emery (Mohs Hardness 8 to 9) produced a wear rate several t imes greater than that for silica sand (Mohs Hardness 6 to 7).

In the second programme ( 1980]81) the operat ing cond i t ions were kep t cons tant (velocity 4 m/s, 10 per cent slurry of 0 .15mm emery) while 18 d i f fe ren t pipe materials were compared. Most o f them proved to be more resistant to wear than mild steel bu t no particular class was found markedly to outrank the others. S o m e w h a t surprisingly the best four materials comprised one from each main category (metal , ceramic, rubber and plastics).

An annotated bibliograph o f 60 papers on o ther pipel ine wear work is given in an Appendix.

I S S N 0 3 0 5 - 1 3 1 5