conveyor belt hand book

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CONVEYOR BELT

HAND BOOK

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This CONVEYOR HANDBOOK is provided by WE to allow designers to select the correctspecification belting for any particular installation. This is just a general guideline and finaldecisions are to be taken by the user based on actual working conditions.

Properties of fabrics used in Polyester Nylon multi-ply belting constructions are given in detail,while the general properties and application areas of special multi-ply constructions, solidwoven, Aramid and steel belting are also shown.

The use of various natural and synthetic rubbers with these reinforcements for handling

different service conditions is set out for the designer.

Design considerations affecting power demands, belt curves, transitions etc., are provided.

Whilst users are vitally interested in these design considerations for conveyors, there is aspecial section on fault diagnosis to enable users to identify causes of troubles which mayoccur and correct them before belt damage either occurs or becomes extended.

The layout of this manual and easy approach to belt design will be readily followed by beltdesign engineers.

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Reinforcements 1 - 1

General Properties .. 1 - 3

Capacity Calculations . 2 - 1Properties of Materials . 2 - 2

Belt Power Calculations Formulae . 3 - 1Calculation of Maximum Tensions ... 3 - 5Graduated Idler Spacings ... 3 - 7Feeder Belt Calculations . 3 - 9Acceleration and Deceleration .. 3 - 10Application of Forces .. 3 - 14Algebraic Signs of Conveyor Forces .. 3 - 15

Coasting .. 3 - 16Check List for Large Conveyor Systems ... 3 - 17

Belt Construction Requirements . 4 - 1Considerations . 4 - 1Procedure .. 4 - 2

Considerations 5 - 1Selection...5 - 1Pulley side cover 5 - 1

Parallel face pulleys.. 6 - 1Crown face pulleys 6 - 2Pulley face width 6 - 2

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Multiple Slope and Vertical Curve Conveyors ... 7 - 1Terminal Troughing Idler Arrangements . 7 - 4

Transitions ...7 - 4Take - Up Arrangements .. 7 - 5

Belt Mass and thickness... 8 - 1Shipping dimensions and roll sizes...... 8 - 1Length of belt on a roll.... 8 - 2Belt transport guidelines.. 8 - 3

Belt construction. 9 - 1Belt and cover thickness.. 9 - 2Operating temperature range.. 9 - 2Operating factor of safety. 9 - 2Safety 9 - 2

General Maintenance ... 10 - 1Loading point considerations... 10 - 2Random events . 10 - 4Troubleshooting ... 10 - 5

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1 0

Reinforcements .. 1 1General Properties 1 3

Table 1 Reinforcement Fabrics 1 2Table 2A Cover Compounds ... 1 4Table 2B Heat Resistant Belts 1 5Table 2C Oil & Chemical Resistant 1 6Table 2D Fire Resistant & Anti Static Belts .. 1 7

The composition of a conveyor belt can be considered in two parts:

A. The Carcass, whether ply type (textile) or steel cord construction, which must havesufficient strength to handle the operating tensions and to support the load.

B. The Covers, which must have the required physical properties and chemical resistance toprotect the carcass and give the conveyor belt an economical life span.

The general properties and the application usage of the more economical availablereinforcement fabrics and rubber compounds are discussed in this section.

REINFORCEMENTS

Fabrics

Fabrics that are commonly used as reinforcement in conveyor belts are shown in Table 1 ofthis Section

The fabric designation indicates the material used in both warp and weft, e.g. EP signifies thatthe fabric has Polyester warp fibers and Nylon weft fibers.

The ultimate strength of the belt in kilo newtons per metre width is shown along with thenumber of plies. EP1000/4 designates a belt with four plies of polyester warp, nylon weft fabricand an ultimate full-belt tensile strength of 1000 kN/m. Alternatively the belt can be oftendescribed as 4 ply EP250 where the strength of the individual plies is shown.

The allowable working tensions allocated are shown in tables 1 and 2 in section 4.

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GENERAL PROPERTIES OF BELT COVERS AND GRADES

The following tables give a comparison of general characteristics of polymers used in beltingcompounds.

Special compounding can result in substantial changes to these general polymer properties.

Generally conveyor belts are supplied with electrical resistance in the anti-static range andshould not be used for electrical insulation. Special non-conductive grades are available onrequest.

There are four separate tables:

Belts for Mining, Quarrying and General Service

Heat Resistant belts

Oil and Chemical Resistant grades

Fire Resistant and Anti-static belts

Notes referred to in these tables are:

1. Available with extended ozone resistance capabilities on special request.

2. The low temperature performance figures given in the table are representative of generalpurpose compounds in each classification. Belts for operation at lower temperatures thanthose given are available on request.

3. The high temperature performance figures given in the table are representative of situationswhere the belt is subject to relatively long exposures of blanketing heat. Considerably highertemperature bulk material can often be carried in ventilated situations or where the belt surfacecan be shielded to some extent by a protective layer of cooled fines.

4. Resist most acids except concentrated strongly oxidising ie., Sulphuric, Nitric and theirderivatives.

5. Fire resistant and anti-static grades:

GRADE S meets AS4606 for UNDERGROUND COAL MINING.GRADE E, F fire resistant and anti-static - mostly for ENCLOSED ABOVE GROUND USEGRADE K fire retardant and anti-static - meets MSHA 2G and ISO433 requirements

6. Resists most oils however resistance may vary greatly depending on the type of oil.

7. May have poor resistance to oils with low aniline points.

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4. Belt Carcass Selection

Belt Construction Requirements 4 - 1

Considerations .4 - 1

Procedure .. 4 - 2

Table 1A Allowable Working Tensions Standard constructions.. 4 - 3Table 1B Allowable Working Tensions Coal Master series.. 4 - 4Table 2A Load support table Standard constructions.. 4 - 5Table 2B Load support table Coal Master series 4 - 6Table 3 Belt troughability . 4 - 7

BELT CONSTRUCTION REQUIREMENTS.

To select the optimum plied belt carcass, five properties must be considered:

The belt width.

The service conditions under which the belt will operate.

The maximum operating tension (T max) both steady state condition and peak (seetable 1).

The minimum number of plies required to support the load (see tables 2).

The maximum number of plies beyond which transverse flexibility is reduced and thetroughing efficiency is affected. This varies with the belt width, trough angle and theidler roll arrangement (see table 3).

CONSIDERATIONS:

Operating conditions

The allowable working tensions shown on Table 1 that follow are applicable for reasonablywell maintained conveyors operating with moderate impact, infrequent starts and good loading.Peak tension on starting or braking, should not exceed 140% of the allowable workingtension.

For more severe operating conditions, moderate maintenance, short time cycles, frequent DOLor loaded starts, poor loading or severe impact, hot materials handling etc., reduce the tabledfigures by 15%. Tension on starting or braking should not exceed 150% of the resulting ratedtension.

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For severe service conditions, poor maintenance, very hot materials, chemically aggressiveenvironment, severe impact and short time cycles etc., reduce the tabled figures by 30%.Tension on starting or braking should not exceed 160% of the resulting rated tension.

Safety factors

The working tensions shown on these tables are based on the application of a safety factor of6.7:1 on the strength of the belt at the splice or fastened join. The safety factor is increased formore difficult operating conditions with further restrictions applying for starting and braking.

Starting and braking tensions

A check should always be made comparing the acceleration or braking tension with theallowable peak tension for the belt, i.e. 140% of rated working tension. If the peak tensionexceeds the latter figure, a stronger belt can be selected or the choice of control must be

changed to reduce peak tension.

Mechanical fasteners

WE always recommend hot vulcanised splices for plain weave plied belting. Otherconstructions including the Crows Foot Weave, Double Weave and Solid Woven PVC can besuccessfully operated at close to vulcanized joint tensions for long periods of time whereasplain weave constructions generally operate at reduced tensions when fitted with mechanicalfasteners

Recommended precautions including frequent inspection and monitoring, any Local Authorityrestrictions and greater than normal care should always be observed when using MechanicalFasteners. Belt cleaners should only be fitted if specifically suited to operation with mechanicalfasteners

If a conveyor belt is to be operated for any length of time with mechanical fasteners then theselected combination of belt and fastener should be statically tensile tested and a workingtension of not more than 15% of that result. Table 1 lists WE recommendations for its commonrange of belts.

Troughability and load support

This table provides a guide to the maximum width of belt that will support the load whencarrying material with the bulk density shown.

This table provides a guide to the minimum width of belt that will trough satisfactorily at thetrough angle shown. The widths shown above are a guide only and experience may dictate theselection of a ply more or a ply less.

Some factors that may influence the choice are:

Partially filled belt.

Idler trough angle Convex or concave curve radius and idler pitch

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Lump size of material

Installed pulley diameters

PROCEDURE:

Considerthe possible belt constructions.

1. Calculate working tension needed for the both steady state and peak (accelerating orbraking).

Required Working Tension (kN/m) = Tmax (kN)Belt width (m)

Where: Tmax. = Peak or Steady State tension in conveyor (kN).

2. Considering operating conditions and starting and braking tensions and determine suitablebelt constructions from tables 1A and 1B. Working tensions shown in tables 1A and 1B are

applicable for reasonably well-maintained conveyors with moderate impact, infrequent startsand good loading and are reduced where operating conditions are less favourable - seediscussion below.

3. Consider special needs and the use of special fabrics such as Crows foot or Doubleweaves.

4. Establish the various practical carcass/ ply number combinations to support the load for theconveyor working conditions under review - (Tables). Load support requirements may

dictate that the selected belt is operating at a fraction of its allowable working tension.

5. Check that the selected construction(s) are acceptable for troughing - (Table 3)

6.Check that the installed pulley diameters are adequate (refer section 6)

The final selection should be checked with WE since cost, availability and servicecriteria can be additional factors for consideration.

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Considerations 5 - 1

Selection... 5 - 1

Pulley side cover 5 - 1

Table 1 Top Cover Thickness 5 2

CONSIDERATIONS

There are a number of factors that must be taken into account when selecting the belt grade or

cover material, such as:

Fire resistance or anti-static properties

Resistance to oils or chemicals

Temperature of the operating environment or conveyed material

Resistance to ageing, weathering and ozone.

The type of material being conveyed

The lump size and shape of the material being conveyed

The mix of lumps and fines in the material

The abrasiveness of the material

The method of loading the belt The fall height of material to the belt

The cycle time of the conveyor for a single revolution of the belt

Performance or experience in a similar application

For replacement belts the performance of previous belts on the same installation

Availability and cost

SELECTION

Previous experience will always be the best guide to the optimum selection of both the type

and thickness of belt cover, however if this information is not available as will be the case fornew installations, the following steps should be followed.

From table 1 2 select the most suitable cover types of cover or belt grades for theapplication. In some cases statutory requirements or the operating conditions will limitselections to one or two possibilities.

Calculate the time cycle of the conveyor = (2 x L)S

Where:L = conveyor centres (m)S = belt speed (m/s)

Use table 1 as a guide to select the appropriate thickness of top cover. Considerationshould be given to the applicable properties of the cover in making this selection.

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For difficult applications such as belt feeders, or impact belts, heavier covers may be required.

PULLEY SIDE COVER

As a guide, pulley side cover should generally be not less than 1/4 of carry side cover forcovers up to 9mm and about 1/3 of carry cover thickness for covers heavier than 9mm.

Operating conditions can dictate that heavier pulley side covers are required.

For long centre, long time cycle conveyors, pulley side cover can be up to 1/2 of carry sidecover.

Parallel face pulleys.. 6 - 1

Crown face pulleys 6 - 2

Pulley face width 6 - 2

Table 1 Standard constructions operating at over 60% of allowable working tension 6 - 3

Table 2 Standard constructions operating at 30 - 60% of allowable working tension . 6 - 4

The minimum pulley diameter recommended for a particular belt depends upon three factors:

Carcass Thickness The wire rope diameter in the case of Steel Cord belts.- The overall thickness of all plies plus the rubber skims between

plies in the case of Ply Type belts.-The overall thickness of the thick woven fabric separating the top

and bottom covers in the case of Solid-woven belts.

Operating Tension The relationship of the operating tension of the belt at theparticular pulley to the belts Allowable Working Tension.

Carcass modulus The relationship between elongation of the carcass and theresulting stress.

Whatever the carcass type, Steel Cord, Ply Type or Solid Woven, when the belt is bent arounda small radius, tension stresses are developed in the outer fibers while compression stressesare built up in the inner fibers. At a given tension, if the radius is too small the elastic limit ofthe outer fibers may be exceeded and fracture, and at the same time, the compression of theinner fibers may cause severe crinkling and eventual ply separation.

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Since the elastic properties of the rubber or PVC cover material is so much greater than thecarcass material, the cover thickness of the belting is not a factor in determining minimumpulley size, and may be ignored.

The tables of recommended pulley diameters in the INFINITY handbook for Ply Type belting

are based on the three classes of pulleys defined in ISO 3684. viz.;

Type A High tension / tight side pulleys (T1) e.g. head, drive, tripper and shuttlepulleys

Type B Low tension or slack side pulleys (T2) such as tail and take up pulleys Type C" Low tension snub or bend pulleys with wrap angle of less than 30 degrees

Two sets of Pulley Diameter tables follow:

For belts operating at over 60% of allowable working tension Table 1 - for standard beltconstructions

For belts operating at 30 60% of allowable working tension Table 2 - for standardbelt constructions

For belts operating at less than 30% of the allowable working tension, the diameter of Type Apulleys can be reduced to the same as Type B.

PARALLEL FACE PULLEYS

With just a few special exceptions, all pulleys used with modern high strength, high modulusfabric belts should be parallel face types. It is absolutely mandatory that all pulleys used inconveyors fitted with Steel Cord belting be parallel face type. One notable exception to thisrule is in the case of Bucket Elevators which, lacking any other means of tracking the beltcentrally, may benefit from Crown Faced Pulleys.

CROWN FACE PULLEYS

A Crown Faced pulley can have the effect of centering the tracking of the belt, but only in thecase where there is a long unsupported length of belt leading into the pulley, as the belt mustbe able to bend longitudinally along its centre line to benefit from the crown. High modulus PlyType belts have very little ability to bend longitudinally and Steel Cord belts have virtually noability at all. Solid Woven belts are not quite so rigid but still need an unsupported distance of

something like 4 to 6 times the belt width to be able to react.

Apart from not serving much purpose in troughed conveyor systems, Crowned pulleys canseriously damage the belt by severely overstressing the carcass in the centre of the belt,particularly in the case of Steel Cord belts.

The few special cases where Crowned pulleys are useful include, Bucket Elevators, the Take-up pulley in long gravity Take-up arrangements and for some short centre - wide belt,reversing conveyors. In cases like this where there are no supporting idlers to train the belt,some benefit may be obtained from the installation of Crowned pulleys.

It is fairly common practice to crown a pulley by machining a taper of 1 in 100 from each pulleyedge

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towards the centre over a distance of 1/4 pulley face. It is more correct to relate the amount ofpulleycrown to the pulley diameter, not to its face width. Viz.; d = D - 0.008 x D

PULLEY FACE WIDTH

As all belts tend to wander a bit in operation, the overall face width of the pulleys shouldexceed thebelt width by the following minimum amounts, if serious edge damage is to be avoided;

Belts up to 650mm wide . . . . . . . . 100mm

Belts 750 to 1400mm wide . . . . . . . . 150mm

Belts over 1400mm wide . . . . . . . . 200mm

For conveyors built on unstable ground, as in underground coal mines and very long overlandconveyors, the above allowances should be increased by 50mm.

Multiple Slope and Vertical Curve Conveyors .. 7 - 1

Terminal Troughing Idler Arrangements . 7 - 4

Transitions ..... 7 - 4

Take Up Arrangements . 7 - 5

Table 1 Average Elastic Modulus E . 7 - 3Table 2 Transition Distances for Head Pulleys 7 - 4Table 3 Transition Distances for Tail End Loading Points .. 7 - 5Table 4 Gravity Take Up Travel .. 7 - 6

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Belt Mass and thickness..,,,,,,,,,,, 8 - 1

Shipping dimensions and roll sizes.... 8 - 1

Length of belt on a roll... 8 - 2

Belt transport guidelines. 8 - 3

Table 1 Belt carcass mass and thickness standard constructions 8 - 4

Table 2 Belt carcass mass and thickness CoalMaster series 8 - 5

Table 3 Belt carcass and cover mass factors.. 8 6

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MISSING TABLE

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Belt construction. 9 - 1

Belt and cover thickness.. 9 - 2

Operating temperature range.. 9 - 2

Operating factor of safety. 9 - 2

Safety. 9 - 2

Table 1 Belt Designations.. .... 11 2

BELT CONSTRUCTION

Fenaplast conveyor belting consists of three main components: -

Textile Solid Woven Carcass

PVC Impregnation

Cover Material

THE TEXTILE CARCASS

The solid-woven carcass is generally woven with nylon or polyester load bearing warp fibers and nylonor nylon/cotton weft. Synthetic binder yarns follow a complex pattern to give the carcass its solid-wovenproperties. Various combinations of synthetic, and natural fibers are chosen, together with the fabricdesign to meet the requirements of impact resistance, belt elongation, flexibility for troughing and smalldiameter pulleys, load support and fastener retention. The patented Fenaplast PVC impregnationmethod also renders the carcass impervious to attach from moisture, dirt, chemicals, bacteria, and oils.Cotton pile warp yarns may be included for improved impact resistance and special edge reinforcementcan be included where these are particular problems. The Fenaplast carcass design facility enablesusers to choose the properties of a custom-built belt.

All Fenaplast belts have a solid woven carcass where all layers of yarn are mechanically interlocked

during the weaving process and bound together by a self binding warp yarn interweave, thus makingsubsequent delimitation impossible. High tenacity continuous filament synthetic yarns are used for thewarp fie length direction), such yarns also provide most of the necessary strength in the weft(transverse/width) direction.

PVC IMPREGNATION

After weaving the roll of carcass is vacuum impregnated with PVC plastisol containing a careful blend ofpolymer, plasticizers, stabilisers, fire retardants, and special additives, with special attention being givento viscosity control in order to ensure full impregnation of the woven structure.

Whilst the textile elements fix many of the belts properties such as tensile strength and elongation inservice, the properties of the plastisol are equally important, and it's formulation will influence not only

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the fire performance properties but also operational factors such as troughability and the ability to holdfasteners.

COVER MATERIAL

PVC covers

PVC covers to meet numerous fire resistance specifications or for other properties such as resistanceto oils, chemicals, fertilizer etc., are generally available up to 3mm thick per side. They can also becompounded to give improved abrasion resistance or coefficients of friction.

Rubber covers

Rubber covers to a specified safety standard may be applied on one or both sides of a PVCimpregnation parent belt up to a maximum of 6mm + 2mm, dependent on belt width, tensile andconstruction. SR wear-resistant nitrile rubber covers are also available, single or double sided, up

to 6mm + 2mm maximum, dependent on belt construction.

BELT AND COVER THICKNESS

When considering cover thickness the user should be aware of the thick, high textile content ofFenaplast and the special solid-woven carcass properties. Consequently thinner covers may generallybe chosen than normal with rubber, plied belting; the Fenaplast carcass being more substantial andproviding the necessary load support and impact resistance.

OPERATING TEMPERATURE RANGE

Above 90C PVC softens and the belt properties change, therefore Fenaplast is not recommended for

conveying materials above this temperature. Standard Fenaplast can be used in cold climates at minus15C and special cover compounds are available for operation down to minus 40C. Cold weatherdetails should be supplied to ensure a belt with suitable coefficient and flexibility characteristics issupplied.

OPERATING FACTOR OF SAFETY

With good quality mechanical fasteners or vulcanized joints a factor of safety of 8:1 may be acceptable.

SAFETY

Fenaplast is used extensively in underground coal mines and as such it exhibits excellent FireResistant, Anti-Static properties.

In Australia it is manufactured to AS 1332 and is tested to AS1334.It meets or exceeds all of the requirements of AS 4606-2000.

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BELT DESIGNATION: Belts can be produced to various tensile specifications, using either polyamide orpolyesterbase warp yarn. Some markets still prefer to specify belt types based on tensile strengthexpressed in Ibs/in width(the Fenaplast Belt Designation uses this terminology), whilst others opt for thepreferred ISO types expressed inkN/m.

BELT WEIGHTS: The above table shows some typical figures for minimum warp and weft strengths, beltthickness and weight for a selection of belt types, based on In- PVC covers. For thicker covers, add 1.3kg/m2/mm for PVC covers and 1.4 kg/m2/mm for rubber covers. The nominal figures quoted for thickness andweight are based on specific belt constructions and PVC covers of l mm. Alternative belt constructions may varythese figures which are only for indicative purposes and establishing shipping capacities.

ALTERNATIVE CONSTRUCTIONS: Many alternative constructions are available which give values higherthanthose in the table. This is particularly relevant to weft strength, where special yarns designs may be

recommended for improved properties such fastener holding, load support, weft stability etc. The use of suchspecial yarns may increase the belt weight and thickness which may be critical for shipping purposes orunderground transportation. An APEX FENNER engineer should always be consulted where this information islikely to be critical.

PULLEY DIAMETERS: The drum diameters are the minimum recommended without complete application details.With information regarding wrap configurations, tensions, belt speeds, jointing methods, etc., it maybe possible toaccept smaller drums.

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General Maintenance ..... 10 1

Loading point considerations.. 10 - 2

Random events 10 - 4

Troubleshooting ... 10 - 5

GENERAL MAINTENANCE

Conveyor belting represents a very significant portion of the overall plant cost and as suchwarrants regular inspection and maintenance to protect this investment. Broadly speaking,apart from normal wear, rubber conveyor belting fails through chemical attack or mechanicaldamage in one form or another.

Chemicals such as all greases, oils, solvents and animal fats should be removed assoon as detected from belts not designed to handle these materials. Susceptible beltsincluding all natural rubber belts should be washed down with water and detergentimmediately after contamination.

Ozone is a common cause of premature failure in natural rubber and many syntheticand rubber belts, particularly when operating near the sea, enclosed near electricalmachinery or in a salty environment. INFINITY belts are supplied with high levels ofozone resistance, and this level of protection can be increased by special request at thetime of ordering for extreme conditions.

Mechanical damage is best prevented by clean design and erection, (no jagged edges)good path clearance, generous belt paths, frequent checking and prompt remedying ofall faults.

Belt cleaners perform a very important role in the protection of the belt. Properly sitedand fitted they protect the belt from damage through:

o Trapping of material between return belt flight and pulley.

o Belt wander through running off as material forms a crown on the pulley.

o Damage to pulley face through belt edge slapping and grinding at the pulley face

edges.o Spill from the return side building up under the belt to damage both belt and

return idlers.o Belt cleaners must be selected carefully and deserve frequent attention.

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Idlers - All noisy idler should be looked at immediately. All jammed orbroken idlers should be removed immediately. Hot idlers should be hosed down andremain under supervision whilst the conveyor is stopping and down to ambienttemperature. It must be removed immediately the conveyor is stopped. A jammed idlercauses increased friction resulting in excess cover wear higher power consumption andmay create sufficient heat to start a fire when the belt stops.

Pulleys - Material trapped between a pulley and the belt may cause beltwander and if hard lumps are present may rupture the belt. Plough cleaners should befitted wherever a spill onto the return belt is carried onto a pulley. This is crucial at hightension pulleys but can lead to tracking and loading problems after the tail pulley.

Take-up may be automatic or manual. The Automatic Take-up is the mostdesirable as properly maintained, it is able to maintain the correct tension in the belt under allnormal operating conditions including starting, running, stopping and changes in belt lengthcaused by changes in ambient and operating temperature .

If for any reason the Automatic Take-up travel becomes restricted or jammed, belt slippage at the drivemay occur, this will cause extreme damage to the belt.

The Manual Take-Up has the advantages of compactness and low cost, however it is unable tomaintain optimum tension through the normal operating conditions including starting, running, stoppingand changes in belt length caused by changes in ambient and operating temperature.

Be aware of abnormal or changed noises emanating from the conveyor as these, if left unattendedcould lead to a fire, gearbox or pulley / coupling failure to name just two items. The following plantitems should be frequently listened to and looked at. Analyse the problem and take maintenanceprecautions.

LOADING POINT CONSIDERATIONS:

Chutes, loading boots and skirts - These items are frequent trouble spots when fitted too closely tothe belt. They can cause rapid localised cover wear and in extreme cases, slit the belt.

Conversely when installed with too much clearance, material is allowed to spill over, often falling ontothe return belt and building up on the tail pulley causing tracking problems in the loading boot furtherexacerbating the problem. If the spilled material is hard, the belt may also be punctured.

Also to be considered is wedging between a chute wall and the belt. In the mildest occurrence, thiswill accelerate the cover wear, in more severe occurrences the belt carcass is permanently damaged.

Most wear and tear on the belt takes place at the loading point. The manner of loading may influencethe life expectancy of the belt and the components of the loading boot. Loading points should bearranged with particular care and the following points should be observed:

The material being conveyed should be fed onto the belt at belt speed in the running direction of thebelt.

The height of the drop from the feeding point onto the belt should be as small as possible.

Impact idlers should be installed at the loading points.

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The following sketches show some loading point arrangements.Loading Point Arrangements

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RANDOM EVENTS AND CAUSES OF BELT DAMAGE

TRAMP IRON

Most rips, some continuing the entire length of the belt, are caused by tramp iron becomingwedged into the belt at loading chutes. If this hazard is prevalent, the installation of amechanical or magnetic detector to stop the belt may be justified. Dangerous material can bemagnetically extracted or some reliable rip detection/protection device may be warranted.

Work practices and vigilance among all employees and contractors can also reduce thisproblem.

MINOR REPAIRS

Unless repaired, minor tears quickly become major repairs or catastrophic failure. Earlydetection and prompt attention is the best long-term strategy.

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INSTALLATION,

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M AI

STORAGE

New conveyor belt should be stored upright in the factory package until used. A cool dry room, free

from sunlight, steam pipes, oil and corrosive fumes is best. Under no conditions should rolls of belt be

laid flat on a concrete floor. Moisture will shrink any exposed fabric which gets damp from such storage

and the belt is liable to bow on one edge. Upright rolls on a dry wooden floor is recommended.

HANDLING THE ROLL

Conveyor belting is customarily packaged in cylindrical reels or rolls which may be rolled from place to

place. All rolls are marked with an arrow showing the direction in which they should be rolled. (Fig. 1)

Rolling in a direction opposite to that of the arrow tends to loosen and telescope the belt.

Reels or rolls should never be dropped from a freight car, truck, or other means of conveyance since

their weight will break the packaging and may damage the belt. Reels or rolls should always be rolled or

provision should be made for hoisting them. For hoisting, a bar is passed through the hole in the centerof the roll. Chains or cables looped around the bar ends should be provided with a spreader above the

roll to avoid damage to the belt edges.

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INSTALLATION

Once the roll of belting has been transported to the point of installation it should be mounted on a

suitable shaft for unrolling and threading onto the conveyor. Conveyor belting is normally rolled at the

factory with the carrying side out. Consequently, in mounting the roll the belt must lead off the top of the

roll if it is being pulled onto the troughing or carrying idlers but off the bottom of the roll if it is beingpulled onto the return idlers. When pulling the belt onto the conveyor, the roll will turn opposite the

direction indicated by the arrows on the crate. Fig. 2 illustrates a suitable method of mounting as well

as leading off the top of the roll for pulling onto the troughing idlers.

In some cases, such as in mines where head room does not permit maneuvering a roll, the belt may have

to be pulled off the roll and reefed. (Fig. 3) Extreme care should be exercised to see that the loops have

large bends to avoid kinking or placing undue strain on the belt, and no weight should ever be placed on

the belt when it is in this position. Another method of handling belting under such conditions is to lay

the roll on a turntable with a vertical spindle.

OOTING

INSTALLATION, MAINTENANCE & TROUBLESHOOTING

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TRAINING THE BELT

Training the belt is a process of adjusting idlers, pulleys and loading conditions in a manner which will

correct any tendency of the belt to run other than centrally.

When all portions of a belt run off through a part of the conveyor length the cause is probably in the

alignment or leveling of the conveyor structures, idlers or pulleys in that area.

If one or more portions of the belt run off at all points along the conveyor the cause is more likely in the

belt itself, in the splices or in the loading of the belt. When the belt is loaded off-center the center of

gravity of the load tends to find the center of the troughing idlers, thus leading the belt off on its lightly

loaded edge. (See Fig. 4)

These are the basic rules for diagnosis of belt running ills. Combinations of these things sometimes

produce cases that do not appear clear-cut as to cause but if a sufficient number of belt revolutions is

observed the running pattern will become clear and the cause disclosed. The usual cases when a pattern

does not emerge are those of erratic running which may be found on an unloaded belt that does not

trough well or a loaded belt which is not receiving its load uniformly centered.

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FACTORS AFFECTING THE TRAINING OF A BELT

Pulleys and Snubs

Relatively little steering effect is obtained from the crown of conveyor pulleys. Crown is most effective

when there is a long unsupported span of belting, (approximately four times belt width) approaching the

pulley. As this is not possible on the conveyor carrying side, head pulley crowning is relatively

ineffective and is not worth the lateral mal-distribution of tension it produces in the belt.

Tail pulleys may have such an unsupported span of belt approaching them and crowning may help

except when they are at points of high belt tension. The greatest advantage here is that the crown, in

some degree, assists in centering the belt as it passes beneath the loading point which is necessary for

good loading. Takeup pulleys are sometimes crowned to take care of any slight mis-alignment which

occurs in the takeup carriage as it shifts position

All pulleys should be level with their axis at 90 to the intended path of the belt. They should be kept that

way and not shifted as a means of training with the exception that snub pulleys may have their axis

shifted when other means of training have provided insufficient correction. Pulleys with their axes at

other than 90 to the belt path will lead the belt in the direction of the edge of the belt which first

contacts the mis-aligned pulley. When pulleys are not level the belt tends to run to the low side. This is

contrary to the oldrule of thumbstatement that a belt runs to the highside of the pulley. When

combinations of these two occur, the one having the stronger influence will become evident in the belt

performance.

Carrying Idlers

Training the belt with the troughing idlers is accomplished in two ways. Shifting the idler axis with

respect to the path of the belt, commonly known as knocking idlers, is effective where the entire belt

runs to one side along some portion of the conveyor. The belt can be centered by knocking ahead (in

the direction of belt travel) the end of the idler to which the belt runs. (See Fig. 5) Shifting idlers in this

way should be spread over some length of the conveyor preceding the region of the trouble. It will be

recognized that a belt might be made to run straight with half the idlers knocked one way and half the

other, but this would be at the expense of increased rolling friction between belt and idlers. For this

reason all idlers should initially be squared with the path of the belt and only the minimum shifting of

idlers used as a training means. If the belt is over-corrected by shifting idlers it should be restored by

moving back the same idlers, not by shifting additional idlers in the other direction.

Obviously such idler shifting is effective for only one direction of belt travel. If the belt is reversed, a

shifted idler, corrective in one direction, is mis-directive in the other. Hence reversing belts should have

all idlers squared up and left that way. Any correction required can be provided with self aligning idlers

designed for reversing operation. Not all self-aligners are of this type, as some work in one direction

only.

Tilting the troughing idler forward (not over two degrees) in the direction of belt travel produces a self-

aligning effect. The idlers may be tilted in this manner by shimming the rear leg of the idler stand. Here

again this method is not satisfactory where belts may be reversing. This method is illustrated in Fig. 6.

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This method has an advantage overknocking idlers in that it will correct for movement of the belt to

either side of the idler, hence it is useful for training erratic belts. It has the disadvantage of encouraging

accelerated pulley cover wear due to increased friction on the troughing rolls. It should therefore be used

as sparingly as possible especially on the higher angle troughing idlers.

Special, self-aligning troughing idlers are available to assist in training the belt. (Fig. 7) For a morecomplete discussion of these idlers refer to the Goodyear Handbook of Conveyor and Elevator

Belting.

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Return Idlers

Return idlers, being flat, provide no self-aligning influence as in the case of tilted troughing idlers.

However, by shifting their axis (knocking), with respect to the path of the belt, the return roll can be

used to provide a constant corrective effect in one direction. As in the case of troughing rolls, the end of

the roll toward which the belt is shifting should be moved longitudinally in the direction of return belt

travel to provide correction. (Fig. 5)

Self-aligning return rolls should also be used. These are pivoted about a central pin. Pivoting of the roll

about this pin results from an off-center belt and the idler roll axis becomes shifted with respect to the

path of the belt in a self-correcting action. (Fig. 8) Some return idlers are made with two rolls forming a

10 to 20 V-trough which is effective in helping to train the return run.

A further aid to centering the belt as it approaches the tail pulley may be had by slightly advancing and

raising the alternate ends of the return rolls nearest the tail pulley. (Fig. 9)

Assuring Effectiveness of Training Rolls

Normally, extra pressure is desired on self-aligning idlers and, in some cases, on standard idlers where

strong training influence is required. One way to accomplish this is to raise such idlers above the line of

adjacent idlers. Idlers or bend pulleys on convex (hump) curves along the return side have extra ressure

due to component of the belt tension and are therefore effective training locations. Carrying side self

aligners should not be located on a convex curve since their elevated positions can promote idler

juncture failure of the carcass.

Side Guide Rollers

Guides of this type are not recommended for use in making belts run straight. (Fig. 10) They may be

used to assist in training the belt initially to prevent it from running off the pulleys and damaging itself

against the structure of the conveyor system. They may also be used to afford the same sort of protection

to the belt as an emergency measure, provided that they do not touch the belt edge when it is running

normally. If they bear on the belt continually, even though free to roll, they tend to wear off the belt edge

and eventually cause ply separation along the edge. Side guide rollers should not be located so as to

bear against the belt edge once the belt is actually on the pulley. At this point no edge pressure can

move the belt laterally.

The Belt Itself

A belt having extreme lateral stiffness, relative to its width, will be more difficult to train due to its lack

of contact with the center roll of the carrying idler. Recognition of this fact enables the user to take

extra precaution and, if necessary, load the belt during training to improve its severability. Observation

of troughability design limitations will normally avoid this trouble. (Fig. 11)

Some new belts may tend to run off to one side, in a certain portion or portions of their length, because

of temporary lateral mal-distributions of tension. Operation of the belt under tension corrects this

condition in practically all cases. Use of self-aligning idlers will aid in making the correction.

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SEQUENCE OF TRAINING OPERATIONSInitial installation of conveyor equipment should ensure good alignment of all pulleys, troughing and

return idlers, i.e., they should be placed at right angles to the direction of belt travel, leveled and

centered on a straight line. First movement of the belt should be slow and intermittent so that any

tendency of the belt to run off may be quickly observed and the belt stopped before damage occurs.

When the conveyor is a long center installation, men should be stationed at frequent intervals to observe

the action of the belt. They should be provided with an effective method of communication so as to

report their observations and, if necessary, cause the belt to be stopped.

Initial movement of the belt will provide indication of where corrections of the types described arerequired. The first corrections must be those at points where the belt is in danger of being damaged.

Once the belt is clear of all danger points, a sequence of training operations can be followed. The best

procedure to use in starting the training sequence is probably to start with the return run and work

toward the tail pulley. This assures early centering of the belt on the tail pulley so that it can be

centrally loaded.

If the empty belt troughs readily, so that its running tendencies are not erratic, the training can and

should be completed. Should the belt tend toward stiffness and erratic running, getting some load onto

the belt as soon as the return run has been straightened up and the belt centered on the tail pulley will

help hold the top run.

Normally, the belt can be trained properly onto the tail pulley by manipulation of return idlers and with

the assistance of self-aligning return rolls. Seldom is any adjustment of snub or tail pulley necessary but

the snub can be used as a supplementary training means.

Training of the top run, with the belt empty, is usually no problem if the belt troughs readily. In this case

self-aligners on top are not required except as insurance against damage in the region approaching

the head pulley. There, two self-aligners, placed approximately 40 and 80 feet preceding the pulley, will

help re-center the belt if it is ever forced off due to some temporary disturbance.

It should not be necessary to use the head pulley for training purposes if it has been aligned properly.

Likewise, the snub following the head pulley should not be required as a training means. It is relatively

ineffective as a training device due to the strong influence of the head pulley.

The take up carriage has a strong influence on the running of the belt at that point and, due to its

movement as belt length changes, is subject to mis-alignment. A vertical take up carriage, hanging in a

festoon of belt, must be guided in its travel so that the pulley shaft remains horizontal. The belt cannot

be depended upon to center itself on the pulley and, once it moves off center, the pulley will tip out of

horizontal if not guided closely on its posts.

A horizontal take up carriage is subject to mis-alignment due to loose track gauge, fouled rails or even

jumping off the track. V-shaped rails will hold the gauge tight and, with the apex upward, are self-cleaning. Hold-down rails above the wheels with sufficient clearance so that they do not touch under

normal operation will help prevent jumping off the track. (Fig. 12)

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With the empty belt trained satisfactorily, good operation with load is usually assured. Disturbances

which appear with load are usually due to off-center loading or to accumulation of material from the

load on snub pulleys and return idlers.

When equipment is known to be properly aligned, training action should be taken slowly and in small

steps because the belt requires some time to respond to corrective measures. It should begin at some

point preceding that where run-off occurs and then gradually proceed forward, in the direction of belt

travel, until the run-off condition has been corrected.

Under some conditions of operation where the conveyor is not level, is extremely short or too wide to be

affected by permissible crowning, belts with a special guide strip have been used. This V-guide strip

runs loosely in grooved pulley and idler rolls. Guide strips are not recommended or necessary for the

long conveyors normally encountered in industrial use.

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CLEANINGSpecial care must be exercised to keep the return rolls and snub pulleys clean. Buildup of material on

this equipment has a destructive effect upon training with the result that the belt may run against the

structure and damage itself. It is adviseable wherever possible that return idlers be suspended far

enough below the structure so that any mis-alignment or dirty idlers can be easily seen.

Keeping the return rolls and snubs clean requires that the belt be clean when it enters the return run.

Scraping is the most common method of doing this.

Rubber scrapers can be made by clamping rubber slabs 1/2

to 1

thick (not old belting) between twometal or wooden bars. Extend the rubber about twice its thickness beyond the bars and suspend the

mechanism with a counter-weight to provide the pressure against the belt. (Fig. 13) Replace the rubber

when it wears down near the bars. Two or three such scrapers can be used in succession.

The most common steel scraper is a series of diagonally set blades mounted on the end of a leaf spring

to maintain pressure against the belt. These will scrape sticky materials which rubber scrapers may ride

over. (Fig. 14)

Washing the belt with a water spray before wiping with a rubber scraper will do a good cleaning job on

almost any material, including iron ores and mixed concrete.

Dry materials can be cleaned off the belt with rotating bristle or rubber vane brushes, driven at fairly

high surface speed, usually three to five times the belt speed. (Fig. 15) They wear rapidly, require

considerable maintenance and are likely to fill up solid if used with wet and sticky materials.

It is preferable to clean just after the head pulley and before the snub. An exception to this is that sticky

material often requires scraping on the head pulley. This is because a large part of the fine material

sticks to the belt and must be scraped into the chute.

In some cases the best possible cleaning is insufficient and steps must be taken to compensate for the

effect of a dirty belt. Snub pulleys can be kept from building up by the use of soft rubber lagging or by

scraping directly against the pulley. Diagonal grooving will distort and discharge accumulations onthese pulleys. Rubber disc or spiral type return rolls prevent build-up on themselves and thus save a

training problem. (Fig. 16 & 17)

The only cleaning required on the pulley side is removal of material, principally lumps, which may fall

or bounce onto the return run, and be carried between the belt and tail pulley if not removed. (Fig. 20)

Rubber faced plows immediately in front of the tail pulley are used for this purpose. (Fig. 18 & 19) they

are usually held against the belt by gravity and set at an angle to the direction of belt travel.

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LOADING

Receiving material off center will cause the belt to move sideways after loading as the center of the load

seeks the lowest point in the troughing idlers. This can be corrected by proper chute arrangement

provided, of course, that the belt is centered as it enters the loading point. (Fig. 4)

The loading point of any conveyor is nearly always the critical point, the life determining point of the

belt. Here the conveyor receives its major abrasion, and practically all of its impact. The ideal

condition is to have the material pass from chute to belt at the same speed and direction of travel as the

belt with a minimum amount of impact.

The subject of chute design and arrangement is too broad to be discussed in detail here. In lieu of such

discussion, the following suggestions are offered:

The width of the receiving end of the loading chute should be great enough to accept material lying on

the extreme edge of the preceding belt or feeder, and its position determined by the trajectory of the

material coming into it. At no place should the chute be less than twice the size of the largest lumps, if

fines are present, and 3 1/2 times the size of lumps, if uniform. The discharge width of the chute thus

determined should not exceed about 2/3 of the receiving belts width. (Fig. 21)

The slope of the chute is determined by the nature of the material, its entering velocity and length of the

chute. This value varies with each particular installation, but about 35 has been found satisfactory for

most dry industrial materials such as coal and rock.

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An attempt to approach the above ideal condition should be made continually by adjusting the chute

arrangement. Optimum loading and transferring through chutes still requires considerable experimental

adjustment in the field.

Skirt boards should be used to further center and settle the load as it leaves the loading point. The steel

structure of the chute and skirts never should be placed closer to the surface of the belt than 1 , thisdistance to be made increasing in the direction of belt travel to free any material trapped between the belt

surface and the skirt. (Fig. 22) Skirt boards are usually 4 or 5 times the belt width in length, but may

vary considerably due to belt speed, type of material and lump size. Sample skirt board arrangements are

shown in Fig. 23.

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Impact of material being loaded on the belt is often the cause of severe cuts and gouges. The degree of

impact can be lessened to some extent by providing a cushion in the form of rubber covered disc type or

semi-pneumatic idlers which also tend to prevent material from crowding under the skirt boards at the

instant of impact. (Fig. 24)

The use of a Grizzly, a slightly fanned row of bars, at the bottom of the transfer chute reduces wear on

the belt. It distributes the impact of large lumps by allowing the fines to fall onto the belt first to act as a

cushion. The fan shape of the Grizzly in the direction of travel prevents jamming of the lumps. (Fig.

25)

A V-slot cut in the bottom of the chute is another very satisfactory method of allowing fines to fall on

the belt before the lumps and thereby reduce belt wear at this point. (Fig. 26)

PULLEY LAGGING

Lagging is recommended for drive pulleys for the following reasons:

1. Improved co-efficient of friction. This permits a belt to be driven by lower slack side tension and

sometimes results in lower total tension.

2. Reduction of slippage due to wet conditions if grooved lagging is used.

3. Increased life for pulley and pulley cover of belt.

Other pulleys in the system, especially those contacting the carrying side of the belt, are often lagged toprevent build-up of material. Grooving improves cleaning action on the lagging and the belt.

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TYPES OF LAGGING

1. Bolted lagging is usually fabric reinforced, the fabric being necessary to give proper bolt-holding.

This type has no inner or pulley cover; where no grooving is intended, 1/8

top cover is the properminimum, but if the lagging is to be grooved a minimum of 1/4 top cover must be used.

Bolted lagging is usually applied in two or more circumferential strips, applied under tension with the

points in the different strips staggered around the pulley. (On flat-faced pulleys, one strip the width of

the pulley may be used.)

For open end pulleys 5/16 or 3/8 diameter flat head elevator bolts with nuts may be used. Alternate

methods include slotted bolts with tapped holes or self tapping screws for use in welded steel pulleys. It

is necessary that the bolt heads be sunk below the level of the surrounding lagging to prevent damage to

the belt as it passes over the pulley. This may be accomplished by counter-sinking the holes in the pulley

or, where the lagging cover is greater than about 1/8, it is possible to sink the heads merely bytightening the bolts.

Ends of the strips should be bolted in a dovetail joint as shown in Fig. 27. In addition, bolts should be

used in rows running across the face and around the circumference of the pulleys no further than 10

apart in either direction. Edges of all strips should be bolted down and it is recommended that all

exposed fabric edges be cemented to keep out moisture.

2. Vulcanized lagging is a sheet of rubber, usually 1/2 thick, bonded directly to the metal. No fabric is

used because no bolt-holding reinforcement is needed. It is much longer wearing, has better and more

uniform adhesion to the pulley and eliminates the hazard of serious belt damage due to a loose bolt.

This type of lagging can be applied in two different ways:

Spiral method generally used for lower tension applications. A 4 wide strip is recommended for ease

of handling. (Fig. 28) The length of the strip may be calculated by the formula:

In application by the sheet wrap method, a beveled lateral splice is recommended. (Fig. 29) The tie gumside should contact the beveled leading edge for maximum adhesion at the splice.

3. Grooved lagging should be used on drive pulleys if they are likely to be wet. The grooves break the

film of moisture between the belt and lagging thereby eliminating slippage. Either bolted or vulcanized

lagging can be furnished with grooves. Either type can be grooved in the field with a tire-groover if there

is sufficient rubber to prevent cutting into the fabric carcass or metal pulley. Herringbone grooving 3/16

deep and wide spaced 1 apart is recommended. (Fig. 30)

4. A modified type of bolted pulley lagging is also available which features replaceable rubber pads

that slip into metal guides bolted or welded to the pulley. (Fig. 31)

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conveyor belt hand book

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