dunlop ingenieria

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CONVEYOR BELT TECHNIQUE

D E S I G N A N D C A L C U L A T I O N


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Index

1 Introduction1.1 Foreword1.2 Development chronology, development aims1.3 Dunlop-Enerka test rig

2 Belt Conveyors2.1 Basic sketch, concept, description

3. Drive Systems3.1 Pulley arrangement, conveying systems3.2 Single pulley head drive, Dual pulley head drive, Head and tail drive,

general criteria3.3 Drive components

Pulley motor, Geared motor, Motor-gears-Couplings

4 Couplings4.1 Coupling types, fixed coupling, flexible coupling, fluid coupling,

hydro dynamic coupling

4.2 Start-up procedure4.3 Run back prevention (holdback)

5. Drive Pulley5.1 Force transmission, Eytelwein limitations, slip, creep5.2 Friction factor , angle of wrap

6. Take-up (tension) Systems6.1 General, fixed take-up, gravity weight take-up, regulated take-up

tension

7 Detection Devices7.1 Belt tension detection, off-track detection, belt slip detection,

longitudinal slitting safety device

8 Cleaning Devices8.1 General, ground rules8.2 Cable scraper, transverse scraper, fan scraper staggered scraper,

rotary scraper (vertical)8.3 Rotary scraper (horizontal) rapping roller, belt turnover, high pres-

sure water cleaning

9 Load9.1 General, bulk loads, piece loads, bulk density, angle of repose/sur-

charge, lump size, classification9.2 Temperature, moisture, chemical characteristics, pH value, angle of

inclination

10 Conveyor Belt10.1 General, belt construction10.2 Carcase, ply material10.3 Covers, cover qualities (DIN/ISO)10.4 Special qualities, cover thickness ratio10.5 Angle of inclination values, cover thickness values10.6 DUNLOP cover qualities, specifications10.7 Basic Materials10.8 Belt specification, DUNLOP belt types


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Index

11 Design11.1 Main data, belt speed, standard values, recommended values11.2 Belt widths, standard widths, minimum belt width, idler arrange-

ment, idler spacing11.3 Idler spacing (recommended values) idler rotation, idler roll diame-

ter, standard idler roll lengths L11.4 Photograph11.5 Cross sectional area of load, comparison various cross sections11.6 Conveyor capacity, load stream volume, load stream mass, degree

of filling, reduction factor11.7 Power requirement, electric motor type list11.8 Adjustment factors11.9 Belt types11.10 Pulley diameters, standard diameters11.11 Pulley rotation, pulley loading11.12 Average surface pressure, transmission capability, start-up torque11.13 Troughing transition, pulley lift11.14 Convex vertical curve values

11.15 Concave vertical curve, curve co-ordinates11.16 Belt turnover, turnover length, values11.17 Horizontal curve, values

12 Basis of Calculation12.1 Resistance to motion, main resistance, secondary resistance, slope

resistance, special resistances12.2 Peripheral force FU (working), summation12.3 Factor C (allowance for secondary resistance)12.4 Fictitious friction factor f12.5 Mass of rotating idler parts. Mass of belt12.6 Mass of material load. Peripheral force FA (start-up) friction cut-off

material/belt

12.7 Start-up factor KA, acceleration aA, take-off time, accelerationdistance12.8 Peripheral force FB (braking), delay, over-run distance, braking tor-

que of motor MM, drive power at pulley PT, motor power PM12.9 Degree of efficiency , nominal motor power (DIN) drive system12.10 Distribution of drive power with head and tail drive, distribution of

drive power with dual pulley head drive12.11 Factor x for various drive conditions12.12 Distribution of drive power with dual pulley head and tail drive12.13 Belt tensions T1 and T2. Belt tension correction, fixed take-up12.14 Correction of belt tensions moveable take-up12.15 Correction of belt tensions for minimum belt tensions12.16 Sequential calculation to ascertain belt tensions T1 to T4, force

distribution, individual resistances12.17 Sequential calculation for single pulley head drive12.18 Sequential calculation for tail drive and tail drive braking12.19 Sequential calculation for head and tail drive and dual pulley head

drive12.20 Section loadings12.21 Nominal belt strength, safety factor12.22 Selection of belt type (criteria)12.23 Selection of belt type (criteria continuation)12.24 Selection of belt type (criteria continuation)12.25 Belt reference to ascertain a belt type12.26 Determination of fall energy at the loading point12.27 Influence of stresses on belt selection

12.28 Photograph12.29 Determination of troughing capabilities12.30 Determination of cover thicknesses12.31 Determination of take-up travel, values


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Index

13 Calculation Example13.1 Duty data, short calculation13.2 Peripheral force FU and motor performance PM13.3 Individual resistances, sequential calculation13.4 Sequential calculation for various take-up systems

13.5 Belt safety, pre-tension, take-up travel13.6 Pulley diameter, troughing transition13.7 Convex and concave vertical curve13.8 Control of additional stresses13.9 Computer calculations13.10 Photograph

14 Slider Bed Belt Conveyors14.1 Supporting surface, belt widths, belt speeds14.2 Conveying capacity, resistance to motion14.3 Frictional resistance, friction coefficient G (belt/supporting surface)14.4 Slope resistance, special resistances14.5 Special Resistances (continued)

14.6 Drive power, belt tension, peripheral force FA14.7 Safety Factor S, nominal belt strength KN

15 Bucket Elevator Belts15.1 Conveying capacity, bucket contents, bucket shape15.2 Degree of Filling, speed15.3 Loading, discharging15.4 Bucket spacing, belt width, main resistance15.5 Loading resistance, secondary resistance, peripheral force FU,

motor power15.6 Start-up factor, determination of belt type15.7 Determination of belt tensions T1 and T215.8 Safety factor S, friction coefficient (belt/drive pulley)

15.9 Belt stress T1 (load dependent) pulley diameter, number of plies15.10 Individual resistances, peripheral force FU15.11 Values for degree of filling, bulk density, speed15.12 Bucket shapes and dimensions15.13 Bucket attachment, making endless joint


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Index

A Theoretical Volume StreamA.1 Flat carrying idlers, 2 roll troughing idlersA.2 3 roll troughing idlersA.3 Deep troughing, garland idlersA.4 Box section belt

A.5 Steep conveying beltsA.6 Corrugated edge belts without cleats

B Masses of Rotating Idler RollersB.1 Standard idlersB.2 Cushion idlers, disc idlers

C Conveyor Belt Thicknesses and weightsC.1 Belt types SUPERFORT, STARFLEX, DUNLOFLEX, TRIOFLEX,

FERROFLEXC.2 Steep incline belts CHEVRON, HIGH-CHEVRON, MULTIPROFC.3 Slider bed belts, DUNLOPLAST beltsC.4 Steel cord belts SILVERCORD

rubber cleats

D Secondary ResistancesD.1 Inertial and frictional resistance at the loading point

Frictional resistance from skirt plates (loading point)Frictional resistance from belt cleaners

D.2 Belt bending (flexing) resistance, pulley bearing resistance

E Special ResistancesE.1 Resistance due to idler tilt

Frictional resistance from skirt plates beyond the loading pointResistance due to sideways load dischargeResistance from trippers

E.2 Resistance to belt sealing strip beyond the loading pointResistance from motion of bunker drag-out belts

F Drive Factors c1 and c2F.1 Drive factors c1 and c2 value ea

G Safety Factor SG.1 Belt safety (definition) time/strength behaviour, reductionsG.2 Safety factors S for steady and non-steady state working and for

temporary localised peak stresses

H Stress-Strain CurveH.1 Elongation characteristics (hysteresis curve)

H.2 Stress-strain curve (diagram)

I Additional StressesI.1 Belt safety, elastic modulusI.2 Values for Smin, elongation value kDI.3 Troughing transition: safety and elongationI.4 Troughing transition with raised pulleyI.5 Concave vertical curvesI.6 Convex vertical curvesI.7 Horizontal curveI.8 Belt turnover

J Roll Diameter

J.1 Standard rolls, coiled roll, double coiled roll, `S form coiled roll, rollon oval core

J.2 Diameter of standard rolls (table)


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Index

K Pulley DiametersK.1 Pulley diameters for DUNLOP-ENERKA belt typesK.2 Pulley diameters for DUNLOPLAST PVG and PVC beltsK.3 Pulley diameters for steel cord belts SILVERCORD

L Crowned PulleysL.1 Dimensions, taper

M Arrangement of Rubber Supporting Idler DiscsM.1 Installation instructions, measurements

N Chemical ResistanceN.1 Resistance of the carcaseN.2 Resistance of the coversN.3 Resistance of the covers (continued)

O Steep Incline InstallationsO.1 Hints for the improvement of installation components

O.2 Hints for the improvement of installation components (continued)

P Endless SplicingP.1 Methods, hot vulcanisingP.2 Warm vulcanization, cold vulcanisation, mechanical fasteners

Q Material CharacteristicsQ.1 Material characteristicsQ.2 Material characteristics (continued)Q.3 Material characteristics (continued)Q.4 Material characteristics (continued)Q.5 Material characteristics (continued)Q.6 Material characteristics (continued)


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Dunlop-Enerka Belting Dunlop-Enerka France Sarl

P.O. Box 86 Z.I. des EbisoiresCenturion Way 78370 PlaisirFarington, Leyland FrancePreston, Lancashire PR5 2EY Tel. +33 (0)1 3055 5419United Kingdom Fax +33 (0)1 3054 0238

Tel. +44 (0) 1772 433 751 Telex 695608Fax +44 (0) 1772 623 967Telex 627080

Dunlop-CCT s.a. Dunlop-Enerka b.v.Boulevard des Combattants 64 Visokovoltnij Proezd, 17500 Tournai 127577, MoskowBelgium RussiaTel. +32 (0) 69 254 811 Tel. +7 095 901 8857Fax +32 (0) 69 226 270 Fax +7 095 901 2921Telex 57187

Dunlop-Enerka b.v. Dunlop-CCT s.a.Postbus 14 Ovnatanyana str. 49200 AA Drachten 340017, DonjetskThe Netherlands The UkraineTel. +31 (0) 512 585 555 Tel. +38 0622 955 038Fax +31 (0) 512 585 490 Fax +38 0622 323 977Telex 46116

Dunlop-Enerka GmbH Dunlop-Enerka S.L.

Friedrich-Bergius-Strasse 10 Pol. Ind. Les Comes41516 Grevenbroich C/Italia, Parc, 70 Nave 3Germany 08700 Igualada

Tel. +49 (0) 2181 2701 00 BarcelonaFax +49 (0) 2181 2701 30 Spain

Tel. +34 (9)3 80 55 446Fax +34 (9)3 80 54 269

All information contained in this manual has been assembled with great care. It represents up-to-date knowledge and techniques and is based on our long experience of theindustry. We would however advise you that modifications may be necessary to cater for new technical developments. All information, guide values, comments etc. are givenfor guidance purposes only and the ultimate responsibility for the use of this information in conveyor design and any subsequent liability rests with the end user, particularlywhere the suitability of our products for certain applications is concerned. The data and values given are based on average values.


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Introduction

1.1

C onveyor belts have been used for decades to transport bulk and unit loads.They have proved their w orth everyw here because belt conveyor installationscan be adapted to m eet nearly all local conditions. They are w ork-safe andeconom ical.

The dem and for ever increasing capacities and ever longer conveying lengthshas accelerated the developm ent of the belt conveyor technique, new m ate-rials are being developed, new conveying system s are being planned andtested especially those having regard to the environm ental.

The conveyor belt plays the m ajor part in the w hole system and has to over-com e the m any and varied stresses. In addition to this every conveyingproblem is different and needs careful planning and selection of the right ele-m ents in order to achieve the optim um conveying capacity in an econom icalw ay.

There are a num ber of practical rules, values and experiences w hich can beuseful during the planning stage. This m anual aim s to be of assistance tooperators, engineers and project people and provides a substantial am ount ofelem entary data. In addition there are a num ber of instructions and hintsoffered to enable accurate calculations or checks on installation com ponentsthat im pinge on the running of the belt.

In future there w ill be m ore and m ore use of the com puter for calculationsand dim ensioning of belt conveyors. W ith this often the correlation of thevaluation criteria w ill no longer be recognizable. This m anual should also helpto understand the background to a calculation, the selection criteria for anoptim um belt type and to recognize a special operating case.

A ll new standards D IN , EN , or ISO , have been taken into consideration asw ell as the results of individual research studies. The developm ents continue

and w e are grateful for all hints and practical experiences.

July 1994

Foreword


9/1611.2

Introduction

U ntil the m id 1970s conveyor belt developm ent and technology w as concen-trated on the search for appropriate m aterials for the belt and the solving ofdrive problem s. In the first instance transm ission of traction played a part. A sthe dem and grew for conveyors of larger capacity and longer length, addition-al requirem ents effecting the belt had to be considered and researched suchas greater w ork load, elongation, slit resistance and endless splice jointing.

from 1870 Trials w ith plain cotton belts.up to 1914 First rubber conveyor belts developed from drive belts.1921 Founding of the Enerka factory. M anufacture of drive belts

and later conveyor belts.1923/1924 First use of belts underground, not a success due to drive

problem s.1926 First belts w ith robust B alata reinforced covers.from 1928 U se of belts w ith M aco cotton plies.from 1933 D evelopm ent of R ayon/cotton belts and pure rayon belts.

Transition from natural rubber to synthetic rubber for protec-tion of carcase.

from 1939 Increased use of rayon and synthetic rubber.1941/1942 U se of PVC belts above ground.1942 Steelcord belts used for the first tim e for m ajor long haul

installations in the U nited States.from 1945 Further developm ent of rayon belts.

Introduction of m ixed m aterial fabrics includes synthetic w eft.1954/1955 D evelopm ent of high tensile strength belts e.g. plies from

rayon, polyam ide and polyester. C over rubbers w ith varioussurface designs. Steep incline belting w ith profiles and cleats.

from 1955 D evelopm ent and use of steel cord belting in E urope.from 1970 U se of A ram ide as reinforcing m aterial for the carcasefrom 1980 D evelopm ent of new conveyor system s e.g. the tube

conveyor, ham m ock conveyor.

This brief history illustrates the m ore im portant stages in conveyor belt deve-lopm ent. The search for new m aterials becam e necessary because of theever increasing dem ands to optim ise installation construction such as pulleydiam eters, vertical and horizontal curves etc. and the dem ands of newconveying system s.

Optimising conveyor belt reinforcing materials i.e. exploit to theirm axim um strength lim its to obtain optim um w orking life econom y.

Optimum dimensioning of installation com ponents e.g. pulley diam eters,idlers, bearings and shafts, troughing transitions, drive and take-up system s.

Adaptation of cover quality to each duty i.e. cover quality to provide

optim um solution at the m ost econom ical cost.M anufacture of conveyor belts and installation construction w ith the

environment in mind.

ChronologicalDevelopment

Development Goals


10/1611.3

Introduction

To assist in future developm ent of new belt types and splice joining techni-ques, D unlop-Enerka have developed and installed a new type of belt testingrig. The principal intention of the testing m ethods is to sim ulate actual opera-ting conditions encountered by a belt in service.

W ith this rig it is possible to sim ulate changing stresses, bending changes,apply m axim um pre-tension, use various pulley diam eters, observe belt slip tocapacity lim its etc. A nalysing the test data can enable optim um use to bem ade of conveyor belt m aterials and belt conveyors thereby providing m oreeconom ical operations.

DUNLOP-ENERKABelt Testing Rig


11/1612.1

Belt Conveyor

A n installation consists of a drive system , a take-up system , additional com -ponents and the principal item , the conveyor belt. In addition to the conven-tional conveyor there are other conveyor system developm ents in w hich thebelt is the conveying elem ent.

Construction

B asic Sketch

C om ponents

Explanation

16

24

25

17

B elt conveyor-fixed position

M obile conveyorW ith w heels

W ithout w heels

Flat conveying

Troughed conveying

34

33

1 M otor2 M otor C oupling3 B rake4 D rive Transm ission5 A nti Runback6 D rive Coupling7 Pulley B earings8 D rive Pulley9 Tail Pulley10 D eflection or Snub Pulley11 Im pact Idler Garland12 Carrying Side Idler13 R eturn S ide Idler14 G uide R oller15 Counter W eight Take-up16 Screw Take-up

17 Take-up W eight

18 B elt R un C ounter19 O ff Track Control20 Belt Steering Idler21 Pull W ire22 Em ergency Sw itch23 Conveyor Belt24 Brush R oller25 Scraper26 Plough27 D ecking Plate28 C ow l (H ead G uard)29 Baffle B ar30 D elivery C hute31 Chute Lining32 Skirt B oard33 Upper Belt Location

34 Low er B elt Location


12/1613.1

Drive Systems

A drive system consists of all com ponents that provide for driving, start-upand braking forces. The transm ission of traction pow er from the drive pulleyis dependent upon the follow ing factors:

Angle of wrap the belt makes on the drive pulleyFriction coefficient between belt and drive pulleyPre Tension Tv.

The above sketches of drive system s and belt paths are of the classical and

m ost frequently used types. A dditionally there are a num ber of new provendevelopm ents or those w hich are still undergoing trials, for instance, tubeconveyors, piggy-back conveyors, clam p conveyors, aerobelt conveyors, loopbelt conveyors and others.

H ere are som e exam ples:

Drive Systems

Pulley A rrangem entand B elt Path

C onveyor System s

Eintrommel-Antrieb mit direktem Abwurf

Eintrommel-Antrieb mit Schwenkarm und

Abwurfausleger

Eintrommel-Antrieb mit Abwurfausleger

Zweitrommel-Kopfantrieb mit Schwenkarm

und Abwurfausleger

Zweitrommel-Kopfantrieb mit direktem Abwurf

Eintrommel-Kopfantrieb

mit Eintrommel-Umkehrantrieb

Zweitrommel-Kopfantrieb

mit Eintrommel-Umkehrantrieb

Loop Belt C onveyor Aerobelt Conveyor(FM W System ) System

Conveyor belt M aterial

C onveyingThrough

Airinlet

A ir Film

D rive m otors

H angers

D rive R ollers

M aterial Load

Loop Belt w ith C lam p Edges

Single pulley drive w ith direct discharge

Single pulley drive w ith sw ivel arm anddischarge jib

Single pulley drive w ith discharge jib

Single pulley head drive w ith single pulleytail drive

D ual pulley head drive w ith direct discharge

D ual pulley head drive w ith single pulleytail drive

D ual pulley head drive w ith sw ivel arm anddischarge jib


13/1613.2

Drive Systems

The single pulley head drive is the m ost com m on and preferred drive. Forlight duty applications the Motorized Conveyor Pulley or V-rope Drive isoften used.

U nder norm al circum stances the drive unit com prises m otor, coupling andgear box located at the side of the drive pulley and connected by m eans of aflexible coupling, flanged coupling or extension gear box. W ith higher dutyapplications the drive units can be located on both sides of the drive pulley.

For the higher duty applications the dual pulley drive is used w hich enables anincrease in angle of w rap and traction transm ission. 2 to 4 drives are possiblew hich as a rule for reasons of standardization, w ould be of the sam e size.

B y distributing the drive pow er in the ratio of 1:1 or 1/3 : 2/3, the transm issioncapability of the first pulley w ould not be fully utilized. A ll m otors take approxi-m ately the sam e w ork load. A lm ost the sam e size w ork load can be achievedby selecting a fluid coupling w hose slip characteristic can be m odified byadjusting the volum e of fluid in the w orking circuit. If slip ring m otors are

used this can be achieved by adjusting the slip resistance.

The head and tail drive m ay be used for relatively long installations, reversibledrives or w here high return side resistance can occur. Start-up and braking ism ade easier on long installations. The tail drive overcom es the resistances tom otion on the return side run, the pre-tension at the head drive can beincreased.

The choice of drive system depends on the total w orking duty, the belt char-acteristics and general operating conditions. W ith the higher duties the drivepulley is driven on both sides. The pulley shaft is then sym m etrically used andable to take a higher loading.

W ith m ulti-pulley drives the belt should be so reeved that the pulley side isleading over the drive pulley. In situations of high belt stress additionaldeflection of the belt should be avoided thereby preventing unnecessarybending stresses.

O ne should be particularly aw are of dirt build-up. Prom pt cleaning can avoiddow n tim e and repair costs.

Single Pulley H ead D rive

D ual Pulley H ead D rive

H ead and Tail D rive

General Criteria

P1 P2


14/1613.3

Drive Systems

In principle there are three possibilities for conveyor belt driving system s.

For use on sm all to m edium duty applications. These are distinguished bytheir com pact construction. A s a rule in the range of approxim ately 20 kW toa m axim um of 100 kW w here pulley diam eters up to 1400 m m are used andbelt speeds in the range 0.02 to 5 m /s.The heat loss is m inim al particularly w ith lagged pulleys.

U tilized up to approxim ately 30 kW , special applications up to approxim ately120 kW . Possibilities are spur gearing, angle drive, w orm gearing. C om pactand frequently used for light duty applications.The geared m otor is connected to the drive drum by a flexible or fixedcoupling.

D rive units com prising these three com ponents are used the m ost. Typicalare w ork loads up to 600 kW w ith m axim um s up to approxim ately 1500 kW .

The advantage of this arrangem ent is the good accessibility and interchange-ability of com ponents and favourable spares inventory etc.

In m ost cases, especially on large installations, coupling and brake are builtinto the drive unit.

A s a rule a belt conveyor has to operate under variable load conditions. Thedrive capability has to take account of these changes, also m ust run at con-stant revolutions and even speed.

This type of m otor is sim ple to build, is robust and econom ical. The high tor-que w hen starting can be m inim ised and adjusted by m eans of flexible coup-lings, fluid couplings and slip couplings. Sm all installations up to approxim ate-ly 10-12 kW can run w ithout interm ediate coupling. The high stressesim posed upon the system during loaded start-up can be lim ited by step bystep increases in resistance or by the Star D elta reduced voltage system .

W ith this type of m otor the starting torque can be reduced by the increase ofresistances w ithin the electrical circuit.

The slip ring m otor is used on large installations if a quasi stationary gentlestart-up is required.

Drive Components

Pulley Motor

Geared Motor

Motor Gears Coupling

Drive Motor

Squirrel Cage Motor

Slip Ring Motor

M otor Co upling G earbox


15/1614.1

Couplings

W hen starting up a belt conveyor, for a short tim e forces result w hich are hig-her than those w hich occur during norm al running conditions e.g. start-up andacceleration forces. The m otor in contrast creates by far the greater start-uptorque. The difference betw een the load torque and the start-up torque of them otor, is the acceleration torque.

D epending on the size and type of m otor, a gentle start-up is provided w hena flexible or hydraulic coupling is used.

Rigid couplings are used only on sm allinstallations up to a m axim um of 30 kWand at slow speeds.

Flexible couplingsof diverse construction

are already built into 16-20 kW units.

Centrifugal and magnetic type couplings w ith controlled torque are hardlyever used because of their high cost and are no longer a significantly useditem for belt start-up.

Fluid couplings or hydraulic couplings are often used for larger drives incom bination w ith squirrel cage m otors. They perm it a load free accelerationof the m otor and consequently w ith increasing oil fill, provide a gentle quasisteady state start-up of the belt conveyor. The m axim um torque occurringduring the start-up process is restricted to low est possible level. The convey-or belt and splice joints are relieved and conserved.

Em pty at R est Full at Start-up Full W orking

(Principle of the VO ITH Turbo coupling w ith delay cham ber)

Coupling Types

R igid C oupling

Flexible C ouplings

C entrifugal C ouplings

H ydraulic C oupling

The principle ofa Turbo coupling


16/1614.2

Couplings

The electric m otor produces a variable torque w ith speed of rotation w hich isillustrated below by line M . The belt conveyor as a w orking unit opposes tor-que M M at the sam e rotational speed set against torque M L.

A t the m om ent of sw itch on, the electric m otor delivers the start-up torqueM

A. W hen this happens, the belt conveyor dem ands the break aw ay torque

M LB . A s rotation increases the m otor torque declines to saddle torque M Sand then increases to the brink torque M K. Thereafter the torque at the nom i-nal speed of rotation reduces to the nom inal torque of the m otor M N . Theload increases steadily.

The difference betw een the m otor torque M M and the load torque M L is theacceleration torque M B up to the torque intersection of both lines.

The start-up of the electric m otor occurs practically load free com pared w iththe coupling torque M K up to the cut-off point 1 of the graph line M K and theload graph line M L.

The m otor rem ains at point 2 and accelerates the belt conveyor up to syn-chronous speed. Thereafter the m otor, the coupling and the belt conveyorreach the drive speed of rotation at point 3. This type of coupling is onlyeffective on a high speed shaft.

The start-up torque is reached by a continuous filling of the coupling from 0 tobreak aw ay torque w ithin a period of approxim ately 10 to 20 seconds. Thusthe belt is slow ly tensioned and longitudinal vibrations are avoided.

Start-up Procedure

Squirrel C age M otor w ithFixed C ouplings

Squirrel C age M otorw ith H ydraulic C oupling

M A Start-up Torque M otorM S Saddle Torque M otorM K B rink Torque M otorM N N om inal Torque M otorM Lb B reak Aw ay TorqueM L Load TorqueM B A cceleration Torque

M M M otor TorqueM L Load TorqueM K C oupling Torque

M A

M S

M K

M NM B

M L

M Lb

M M

M L

M K

132

Revolutions n

Revolutions n

Torque

M

TorqueM


17/1614.3

Couplings

A holdback device is necessary if the force due to the loaded incline of a con-veyor FSt exceeds that of the peripheral force FH stem m ing from conveyingthe load over the horizontal distance. This is the case w ith all steeply inclinedconveyors and w ith those having a decline of approxim ately 6 to 10.

FSt (N ) Incline ForceFH (N ) Force due to Horizontal Conveyingm L (Kg/m ) M ass of Load Stream on Beltm R (Kg/m ) M ass of Rotating C arrying Idler R ollersL (m ) Conveyor Length

H (m ) H eight D ifferencef (-) Artificial Friction Factorg (m /s2) Acceleration due to gravity

D uring installation a check should be m ade as to w hether the direction of pul-ley rotation corresponds w ith the free w heeling direction of rotation and thatreverse travel of the belt is no longer possible.

Holdback

SU PER FO RT B elt in ServiceConveying O verburden

FSt> FH ( N )

FSt= H * g * m L ( N )

FH = f* L * g ( m L + m R ) ( N )

stands fast

free locked


18/1615.1

Drive Pulley

The belt tensions required for frictional transm ission of peripheral force FUare:

T1 = Entry side force = Tight side tensionT2 = Leaving side force = Slack side tension

B ecause of the friction coefficient betw een belt and pulley, T1 is greater thanT2. The difference betw een both forces is peripheral force FU .

O n braking the forces are reversed.

In the extrem e case of friction cut off that is, if the slip lim it is about to bereached and the angle of w rap is fully utilized, then at the lim it of slip

T1 decreases along the angle of w rap to the value of T2 over a logarithm icspiral.

From the form ulae for peripheral force FU and T1 the follow ing relationshipscan be derived:

c1 and c2 are the drive factors.

If the peripheral force FU is greater than the transm ission capability accordingto the Eytelw ein theory borderline conditions, then the drive pulley over runsand slip occurs.

D uring the reduction of tension from T1 to T2 along the service arc, a decrea-se in the belt stretch occurs. It is not proportional to the tim e it occurs at aslow er rate. C reep rem ains on the pulley circum ference and often creates aw histling sound.

Entry side speed = pulley peripheral speed.Leaving side speed < entry side speed.

Force Transmission

Eytelw ein Lim itations

Slip

C reep

FU = T1 - T2 or T1 = FU + T2

T1! e or T1 ! T2 * e

T2

1T1 = FU * ( 1 + ) = FU * c1

e - 1

1T2 = FU * ( ) = FU * c2

e - 1

T1

T2

FU

T2

Angle

of

w

rap

Spirale

log

.

Angleofrepose

N

T1

T1T1m ax


19/1615.2

Drive Pulley

The factors determ ining the transm ission of peripheral force Fu are the fric-tion coefficient, the angle of w rap and the pretension T2 e.g. Tv.

The num ber of drive pulleys, the pretension force as w ell as various otherinstallation components are dependent upon the friction coefficient . Inorder to assess the friction coefficient, full know ledge of the operation isdesirable. In practice the friction coefficient varies w ithin lim its w hich aredependent upon:

Surface condition of the pulleyLubricating m aterial such as w ateror load slim e betw een belt and pulley

Tem peratureSurface pressureSlip and creep speed

The friction coefficient declines w ith increasing surface pressure and increa-ses w ith increasing speed of creep for instance at start-up.

The angle of w rap can be increased by m eans of a snub pulley to a m axim umof 230. B y using tw o drive pulleys an angle of up to approxim ately 450 canbe achieved.

Friction Coefficient

Angle of Wrap

O peratingC ondition

Plain S teel(sm ooth)

Polyurethanelagging(grooved)

R ubber lagging(grooved)

Ceram ic lagging(porous)

Pulley S urface

D ry 0.35 to 0.4

W et(Clean)

0.1

W et (dirtym ud, clay)

0.05 to 0.1

0.35 to 0.4

0.35

0.2

0.4 to 0.45

0.35

0.25 - 0.3

0.4 to 0.45

0.35 to 0.4

0.35

! 180 ! 230

1 + 2 ! ca. 450

coefficient de frottem ent

Facteurs

de

com

m

ande

c1 c2

c1 c2

arc de contact

c1 c2

c1 c2

Angle of w rap

D

rive

Factors

Friction coefficient

From the graph the follo-

w ing relationships can bederived.

An increase in value over0.35 does not result in anygreat advantage from c1and c2.

W ith friction coefficient value less than 0.3 anincrease of the angle isan im provem ent from c1and c2.

Values and take into

account the values of and w ith the sam e valueof drive factors c1 or c2.


20/1616.1

Take-up Systems

B elt conveyors are equipped w ith take-up (tension) devices. These arenecessary to m ake it possible for the transm ission of force on the drive pulleyor to accom m odate changes in the length of the belt as the load changes andto provide a sm ooth start-up of the installation. The choice of take-up systemdepends on the general conditions of the installation, the elongation char-acteristics of the belt, the start up behaviour, climate and perhaps theconveying distance and the inclination of the installation.

D epending on the application one differentiates betw een:

Fixed take-upM oveable take-up w ith a constant pre-tension provided by a gravity w eightor w ith a pre-tension regulated by m otor

This sim ple take-up device is used for relatively short conveyor lengths orw ith belts having a low elongation such as steelcord. A fter tensioning thebelt, the length stays constant but the belt pull force changes according to

the change in load through perm anent or elastic stretch.

The level of pre-tension force can be determ ined practically by tensioning thebelt until the forces react at all parts of the installation. The belt is perm anen-tly tensioned sufficiently high as is necessary for full load conditions. It ispossible to ascertain and actually adjust the tension by m eans of a sensor.

O n longer installations a m oveable gravity w eight tension device is used.W ith this a constant pre-tension is achieved at all parts of the installation.The length changes of the belt are evened out in the take-up travel. It m ustbe determ ined in such a w ay as to accom m odate those changes i.e. addition-ally to perm anent belt elongation.

A value for take-up travel w ith textile carcase belts is approxim ately 1.5%based on conveyor centre to centre distance and w ith steelcord beltsapproxim ately 0.3% .

W ith especially long installations or to reduce start-up vibrations of belt, socalled regulated take-up w inches are used. B y m eans of electric sw itching apre-run of the take-up w inch, before the belt start-up, is achieved. D uringstart-up the pre-tension is kept above nom inal value. A fter reaching the ste-ady running condition the w inch is adjusted so as to provide the nom inalvalue of pre-tension.

General

Fixed Take-up D evice

G ravity W eight

R egulated Take-up W inch


21/1617.1

Detection Devices

For the operation of com plex belt conveyor installations a range of safetydevices w ere developed. They serve to prevent accidents, to guard theconveyor belt and to run and automize the com plete installation.

This device detects the belt tension changes during different w orking condi-tions such as starting, braking and load variations.

A tensiom eter m easures the changing belt tensions. A s soon as the definedlim its of the upper and low er belts tensions are exceeded a signal is transm it-ted to the take-up unit.

A n off-track of the belt can be lim ited or corrected by m eans of a num ber ofm echanical devices. A nother possibility is to track the belt w ith light beam s.If a deviation beyond the defined lim its is detected a m otorized steering sys-tem is set into operation. If the off-track is not adjusted the installation isbrought to a halt.

W ith the help of this device the overloading of a transfer point is registered.A contact probe is suspended in the chute and adjusted to the required m ate-

rial flow . W ith an overload, contact is m ade w ith the probe and the installa-tion is sw itched off.

This device detects the force transm ission betw een belt and drive pulley.Too great or too long a duration of slip leads to overheating of the pulley sur-face w hich can lead to fire. Slip can occur m ore often at start up as w ell asoverload conditions or w hen the pre-tension is too low .

Slitting open of conveyor belts is a relatively frequent cause of dam age w hichleads to prolonged interruptions and incurs great costs. In m ost cases itstem s from sharp edged pieces of m aterial being trapped in the transferchute.

To avoid such dam age the follow ing rem edies are possible.

Textile or Steel breaker ply em bedded in the cover rubberBunched steel cords are em bedded in the carrying side cover set at fixedspacing.

Rip detection loops at approxim ately 50 to 100m spacings vulcanised intothe belt.

Carcase w ith a high resistance to longitudinal slittings such as D unlopFER R O FLEX belt orD U N LO PLA ST belt.

Belt tension detection

Off track detection

Chute detection

Belt Slip detection

Longitudinal SlittingSafety Device

Illustration of the transversereinforcem ent in a FER RO FLE X Belt


22/1618.1

Cleaning Devices

B elt conveyors w hen operating need to be cleaned constantly depending onthe type and characteristics of the load residues w hich stick to the carryingside of the belt. The return idlers get dirty w hich leads to further encrustingof idlers and pulleys. The consequences are, am ongst others:

loss of loadsoiling of the installation

damage to the beltoff tracking of the beltdamage to idlers

The belt cleaning requires special m easures having regard to:

material characteristics such as, dry, damp, sticky, granulateddegree of cleaning, rough to clinically clean

Thematerial from which the scraper

is m ade has to be in accord w ith thetype of belt and the m aterial to be scraped off.

The follow ing need to be observed:

thehardness of the belt and scraper;In general the m aterial from w hich the scraper is m ade should not be har-der than the belt surface. The scraper should be designed in such a w aythat it m akes contact w ith the biggest possible area of the belt, perhaps adouble or staggered scraper.

the contact pressure of the scraper;A n excessive contact pressure increases energy consum ption and w earand tear of the belt. A sm all gap betw een the scraper and belt surface pro-vides a sufficient cleaning effect w ith m ost bulk loads, causing m inim umw ear and tear. S liding friction becom es rolling friction.

In nearly every case the m ost effective and econom ic solution has to be esta-blished, possibly by trial and error. Several w ell proven system s are listed asfollow s.

General

Basic rules

TR IO FLEX B elt in operationon G arland Idlers


23/1618.2

Cleaning Devices

Steel cords tensioned transverselyover the belt carrying side behind pointof discharge for coarse cleaning of stic-ky m aterial such as loam , clay and thelike.

Fixed or m oveable also possible as adouble bladed scraper.

U sed for m oderately sticky m aterialB ig contact area.

For cleaning the under side of the beltoften located before tail pulleys. Inspecial cases it can be used in doublebladed form . A lso prevents m aterialfrom running into the tail pulley.

U sed for rough cleaning im m ediatelyat the discharge pulley.A djustable versions are available.

U sed for nearly all non-sticky m aterials.C an be adjusted depending on the loadand desired degree of cleaning.

R otating, partly self driven brushesw ith rubber or nylon bristles. N ot suit-able for sticky m aterials such as clay orloam .

Piano Wire Scraper

Transverse Scraper

Fan Scraper

Plough Scraper

Scratch Action Scraper

Staggered Scraper

Rotary Scraper


24/1618.3

Cleaning Devices

H orizontally rotating scraper located onreturn run. R ing scraper in slightly tiltedposition - belt driven.

Situated on the belt running side loca-ted in the region of the discharge hop-per. For belts w ith a profiled carryingside and steep inclined belts.

Located at inaccessible areas such as bridges, tunnels or over-passes. Thebelt is turned over on the return side so that the dirty carrying side is upper-m ost.

G ood cleaning m ethod w here good w ater supply and drainage are available.

Rotary Scraper

Rapping Roller

Belt turnover

High Pressure Water

Pulley sideC arrying side

TurnoverLength


25/1619.1

Load

It is im portant to know the exact make-up and material component of theload w hen constructing a conveyor installation. The choice of conveyor beltis determ ined by the physical and chemical properties of the materialsand possibly by safety regulations and dem ands.

D usty, granular or lum ps. Loads for instance, stone, earth, sand, grain,cem ent. They are defined by their physical characteristics such as density,granulom etry, m oisture, oil and fat content, pH value, abrasiveness, angle ofsurcharge etc.

Piece loads com prise such as boxes sacks, blocks etc., and are defined byshape, m easurem ent and w eight.

It is the quotient of the m ass and volum e V of the bulk load

If a load is loosely poured a static angle of slope st w ill form . If the underlayer is m oved as w hen being transported on a conveyor belt, the angle ofsurcharge dyn is form ed. The particles of the bulk load interact and thelow er the internal friction of the m aterial the low er the surcharge angle dyn.

A pproxim ately:

The surcharge angle is only to a degree related to material size. It dependson the friction betw een m aterial and belt, how the m aterial is loaded and thegeom etry of the conveyor installation. The tabulated values in the A ppendixare approxim ate values. If exact values are necessary they have to be deter-m ined by practical trials.

A s a measure of granulometry or lump size the m axim um diagonal cornerto corner dim ensions k are used.W hichever is the predom inant granulation or lum p size decides w hether thebulk load is sized or unsized.

General

Bulk Loads

Unit Loads

Bulk Density

Angle of reposeSurcharge

Granulometry k

M easurem ent

m = ( t/m 3 )

V

dyn = (0.5 - 0.9)* st

Sized load km ax / km in ! 2.5

U nsized load km ax / km in > 2.5

G ranulom etry k = 0.5 ( km ax + km in )

B ulk Load D efinition G ranulom etry (m m )

D ust 0.5G ranular 0.5 - 10Lum ps 10 - 200Large Lum ps > 200

kk


26/1619.2

Load

It is im portant to have as near accurate as possible know ledge of the loadtemperature and ambient conditions in order to select the optim um coverquality and in certain circum stances the layout of particular installation com -ponents.

Further influencing factors are:

Granulometry of the material and hence the contact density m ade w iththe belt.

The speed of the belt and therefore the heating up and cooling offtimes.

Whether installation is open or enclosed.

The moisture content of the material has an influence on the surchargeangle dyn, the friction value betw een m aterial and belt and thus the m axi-m um angle of inclination of an installation. It is difficult to give an exactassessm ent and if necessary practical trials need be conducted. The m oistu-re content is m easured in percentage.

A sound know ledge of the chem ical characteristics of the load is necessaryw hen selecting the cover quality and also the carcase reinforcem ent.Im portant are the proportions of oils and fats (m ineral and vegetable) andacidity.

The tem perature of the chem ical m aterial as w ell as the proportion of acidityinfluences the level of attack m ade on the belt cover.

The pH value is the concentration of hydrogen ions w hich are present in asolution e.g. the negative exponent to base 10 of the concentration (hydrogenexponent).

The neutral point is pH = 7

U nder 7 indicates acidityO ver 7 indicates alkalinity (bases)The pH value indicates the degree of acidity or alkalinity and can be im portantin selecting the cover quality.

The m axim um angle of inclination of a belt conveyor depends on the frictionvalue betw een m aterial and belt and the form of material. Large lum p andm oist m aterial decrease the angle of inclination. The m ethod of loading suchas direction and rate of feeding are also im portant criteria. For m ost bulkloads and belts w ith a sm ooth carrying surface,the limit angle lies betw een18 and 20. For steeper inclinations up to 90, profiled belts, belts w ith cle-ats or elevator belts are used.

Temperature

Moisture

Chemical Characteristics

pHValue

Angle of Inclination

ca.90

ca

.85

ca.40

ca.35

ca.22

pH > 7 alkalis

pH = 7 neutralpH < 7 acid

Sm ooth B elts

Sidew all B elting: w ith Vertical Cleatsw ith Tilted C leatsw ith Bucket Cleats

Elevators

Steep Inclining B elts: M ultiprofC H E V R O NH IG H -CH EVRO N

Profile Belts: H erringboneRufftop


27/16110.1

Conveyor Belt

The conveyor belt is the most important element of a belt conveyor instal-lation. It has to be capable of doing num erous tasks:

Absorb the stresses developed at drive start-up.Transport the load.Absorb the im pact energy at the loading point.W ithstand tem perature and chem ical effects (heat, oil and fat containingm aterials, acidity etc.).

M eet safety requirem ents (flam e resistant, antistatic etc.).

The conveyor belt consists of the follow ing com ponents:

Carcaseconsisting of textile plies, steel w eave or steel cord.Covers in different qualities of rubber or PVC .Additional components (as required) such as edge protection, im pact pro-tection, longitudinal slitting prevention etc.

Special construction elements like profiles on steep incline belts, cleatsor corrugated edges etc.

A ll item s m entioned above should be considered carefully. The selection ofthe belt specification depends on the application.

Schem atic C onstruction of a Plied B elt

General

Belt construction

C arcase oftextile plies

Pulley SideCover

B reaker Ply orLongitudinal SlitPreventor

C arryingSide Covers

Full Rubber Edge


28/16110.2

Conveyor Belt

The carcase can be m ade from various m aterials and in different construc-tions. The m ost frequently used are textile ply carcases and Steel C ord.

D U N LO FLEX TRIO FLEX SU PERFO RT2 Ply 3 Ply M ulti Ply

D U N L O P L A S T

FERR O FLEX

SILVERC O RD

For textile, solid w oven or steel reinforced types the principal m aterials usedare as follow s:

Carcase

C arcase w ith one or m oretextile plies(up to a m axim um of 6 ply)

C arcase of the Solidw oven type. M onoply belts

C arcase of the S teelw eave type

C arcase w ith SteelC ords. ST-belts

M aterial

D unloplast Belts have a PVC im pregnatedtextile carcase of m onoply construction.D epending on tensile strength and duty thecarcase fibres are in polyester, polyam ide or

aram id.

The transm ission of force is by m eans of thelongitudinal steelcords laid next to one anotherin the sam e plain. A bove this carcase is atransverse layer also of steel w hich is held inplace by a polyam ide binder cord.

W ith this belt force is transm itted via steelcords of the appropriate strength. The cordsare transversely bound together by an inter-m ediate layer of rubber only.Transverse Elem ents serve to prevent im pactdam age or longitudinal slitting.

Sym bol Ply M aterials

B C otton (N atural fibre)P Polyam ide (Synthetic fibre)E Polyester (Synthetic fibre)EP Polyester-Polyam ide (Synthetic fibre)D A ram id (Synthetic fibre)

F Steel W eave (Ferroflex)ST Steel C ord (ST belt)

Cover

Core R ubberSteelcord


29/16110.3

Conveyor Belt

O f the textile ply types the wholly synthetic plies have proved to be thebest over the years e.g.polyester (E) in the warp (longitudinal direction)and polyamide (P) in the weft (transverse direction). The abbreviation ofthis ply construction is called EP.

C arcases from Aramid (D) are in developm ent and are high tensile and lowelongation carcases.Steel Cord belts have very low elongation and are used predom inantly onlong haul installations.

Evaluation of various Material Properties

The carcase is protected against outside influences by the covers w hich arenorm ally m ade out of either rubber or PVC . The carrying side cover shouldnot be m ore than 3 tim es thicker than the running side cover.

W ith w holly synthetic and rot resistant plies it is not necessary to have full

rubber edge protection, it is sufficient to have heat sealed cut edges.Exceptions are belts requiring special qualities such as oil and fat resistance.

The basic grades and principal properties are in accordance w ith ISO and D IN .

Various other special grades exclude laid dow n m echanical or other values.

Covers

C over Thickness R atio

B elt Edges

G rades

Key and evaluation of the pliesC haracteristics

B P E EP D F ST

Tensile Strength ++ ++ + + + + + + + + + +A dhesion ++ ++ + + + + + + + + +Elongation ++ ++ + + + + + + + + +M oisture R esistance + ++ ++ + + + + +Im pact R esistance + + + + + + + + +

= bad = m edium + = good + + = very good + + + = excellent

C arrying side : R unning Side " 3:1

D IN 22102 (A pril 1991)

C over grade W X Y Z

Tensile strength N /m m 2 m in. 18 25 20 15B reaking elongation % 400 450 400 350A brasion loss m m 3 m ax. 90 120 150 250

ISO 10247 (N ovem ber 1990)

C over grade H D L

Tensile strength N /m m 2 m in. 24 28 15B reaking elongation % 450 400 350A brasion loss m m 3 120 100 200


30/16110.4

Conveyor Belt

The carrying side surface depends on the load, the inclination of the installa-tion or depending on the use of the belt, sm ooth, profiled, cleated and w ithcorrugated edges.

M ultiprof Profile H IG H -C H EVR O N P rofile

Special Q ualities

C over Surface

C haracteristics Type

Flam e R esistant FA nti Static EFlam e Resistant, Anti Static S or K

H eat R esistant TLow Tem perature R esistant RO il and Fat R esistant GFood Stuff AC hem ical Products C

H erringbone Profile R ufftop Profile


31/16110.5

Conveyor Belt

The thickness of the carrying side cover depends upon the nature of the loadand loading conditions (type of load, gradient, height of fall etc.).

G radient values

C arrying sideC over thickness

C over Thickness G auges

C over S urface B elt Type M ax. G radient A pplication

U nit andSm ooth N orm al 18 - 20 bulk loads

all types

Profiled Fishboneup to 35

Piece andR ufftop bulk loads

Steep conveyor Steep conveyor B ulk loadsprofile C H EVR O N (non-sticky)

H IG H -CH EVRO Nup to 40

Piece loadsM ultiprof (sacks)

T-cleats B elts w ith Piece andw ith or w ithout corrugated side up to 90 bulk loadscorrugated edges w alls, w ith or

w ithout T-C leats

W ith Steel

Elevator B ulk loadsor rubberbelts

80 - 90all typesbuckets attached

Load

W ooden cratesB ricks

Paper SacksJute SacksPlastic B oxes-dryPlastic B oxes-w et

4040

35354025

3030

30353025

G radient angle for conveyor belt w ith

R ufftop profile H erringbone profile

C over Thickness (m m )C onveyor Load/D uty

C arrying Side Pulley Side

Light package C onveying 2 2G ravel, Earth, Potash etc. 2 - 4 2 - 3O re, B allast, C oal 4 - 8 2 - 3Slag 4 - 8 2 - 3C oarse ballast, coarse O re 8 - 12 3 - 5large lum p C oal 8 - 12 3 - 5


32/16110.6

Conveyor belt

Dunlop-EnerkaCover Qualities

B asic m aterials C ode R ubber type

N R N atural R ubberSB R Styrene-B utadiene R ubberN B R N itrile R ubberIIR B utyl R ubberE PD M E thylene-P ropylene-D iene R ubberC R C hloroprene R ubber

D unlop- Q uality Tem perature (C ) B asic CharacteristicsEnerkaQ uality D IN ISO . base Application

m in. duration m ax.

RA Y (N ) -30 80 100 SBR A brasion resistant, for norm al serviceconditions encountered in carrying

bulk and aggregate m aterials.

RE X (M ) H -40 80 90 N R Extra abrasion resistant and cutresistant for heavy duty service

cond itions (sharp m aterials and

adverse loading conditions).

RS W D -30 80 90 N R/SB R Super abrasion resistant, for he aviestservice conditions, abrasive m aterials

w ith a large proportion of fines.

BETA- T -20 150 170 SBR H eat resistant, for m aterials atHETE m oderate tem peratures.

STAR- T -20 180 220 IIR Very heat resistant, for m aterialsH ETE w ith controlled high tem peratures.

D ELTA- T -20 200 400 EPD M Very heat resisant, for heavy dutyH ETE service conditions including abrasive

m aterials, at tem peratures up to

400C (or m ore) at tim es, e.g. som e

isolated burning m aterials or red-hot

cores, such as em bers, sinter, coke

etc.

RO S G -20 80 120 N B R O il and grease resistant, for oilym aterials on m ineral oil base.

RO M G -30 80 90 SBR /N BR O il and grease resistant, forvegetable oils and anim al grease s.

M O R S G -20 80 90 SBR /N BR O il and grease resistant, forvegetable oils and anim al grease s,

and for heavy service conditionsof the cove r.

BV S/K -30 80 90 CR /SBR Fire resistant for conveyanceof m aterials w ith fire and

explosion danger, such as

fertilizer

BVO S/G -20 80 90 CR/N BR Fire and oil resistant forconveyance of oily m aterials(vegetable oils and anim algreases), e.g. fertilizer, cereals,derivates etc.

The values apply to the m aterials tem peraturesO ther qualities for special applications are available on request.


33/16110.7

Conveyor belt

Characteristics and areas of application

N atural rubber, because of its special properties is a good basic m aterial forbelt cover rubbers.

Technical CharacteristicsVery good tensile strength and elongationH igh heat resistance and elasticityH igh tearing and shear strengthG ood abrasion resistance characteristics

Temperature StabilityG enerally stable w ithin the tem perature range of -30 to + 80C . W ith specialrubber com pounding a w idening of this range m ay be achieved from -40C to+ 100C .

Chemical StabilityR esistant to w ater, alcohol, acetone, dilute acids and alkalis - lim ited resistan-ce to concentrated acids and alkalis w here com pounding and service tem pe-ratures are m ajor consideration.

Special characteristicsW ith special com pounding natural rubber based m ixes can be m ade antistaticand flam e resistant.B y adding antiozonants a substantial protection against harsh tem peratureeffects, sunlight and am bient w eather conditions can be achieved.

ScopeEveryw here w here high physical properties are called for and the chem icaland tem perature dem ands are not excessive.

SB R is a synthetic polym erisation product consisting of styrene and butadie-ne w hose characteristics are sim ilar to natural rubber.Tensile strength and cut resistance are good. A brasion, heat and ozone resi-stances are better than natural rubber.

N B R is a copolym er of butadiene and acrylonitrile. It is not resistant toKetones, esters arom atics and hydrocarbons. The physical property valuesare slightly low er than those of natural rubber. The tem perature operatingrange can be controlled betw een -40C to + 120C. N B R is relatively abrasionresistant, resistant to ageing and is used for oil and fat resistant belt covers.

B utyl rubber is a polym erisation product of Isobutylene and Isoprene. It has avery good ozone and tem perature resistance.

In addition to a very good resistance to ageing, depending on com pounding, itis able to w ithstand tem peratures of -30C to + 150C . It has a lim ited resis-tance to acids and alkalis, anim al and vegetable fats. B utyl rubber is usedm ainly for heat resistant conveyor belting.

EPD M is tem perature resistant sim ilar to B utyl but w ith a considerably higherresistance to w ear and tear. A dditionally EPD M has a better ozone resistancethan all other basic polym ers.

Basic Materials

N atural R ubber N R

Synthetic R ubber SB R

N itrile R ubber N B R

B utyl R ubber IIR

Ethylene Propylene R ubberEPDM


34/161

C R is a S ynthetic polym erisation product of Chlorobutadiene. The m echanicalproperties are sim ilar to natural rubber but significantly better in respect ofozone and oil resistance. The chlorine in C hloroprene gives the product a highdegree of flam e resistance.

The w orking tem perature range is -30C to + 80C .

The resistance to anim al and vegetable oils and fats is superior to natural rub-ber as is the ageing resistance.

The use of N itrile in C hloroprene rubber enhances the dynam ic properties.For cover rubber w hich requires a high oil and fat resistance w hether it beanim al, vegetable or m ineral and also requiring superior m echanical proper-ties. N C R is better than C R .

The foregoing basic materials are m ain ingredients of cover rubber com po-nents. They provide the principal characteristics of each quality but can beaffected by the addition of othercompounding ingredients to achieve requi-rem ents of standards and regulations.

C onveyor belting is described according to laid dow n International standards.A dditionally special types and qualities m ay be described by the m anufactureror in accordance w ith C ustom er w ishes.

The belt length is generally given in m etres either open or endless.Open Length is the length around the pulleys plus an allow ance for m akingendless.Endless Length is the inside circum ference of the endless belt.

This num ber gives the nom inal or breaking strength of the carcase in N/mmof belt w idth. The values are Internationally Standardized.

The nom inal strength of the carcase is m ade up by a num ber of plies. Them onoply belt has a solid w oven carcase.

The nom inal tensile strength of the full thickness carcase is the sum of the

ply strengths rounded up to the next nom inal tensile strength. The num berof plies is not indicated in specially described types such as D U N LO FLEX,TRIO FLEX orDU N LO PLAST.

D D U N LO FLEX 2 Ply B elt F FER R O FLEX Steelw eave B eltT TR IO FLEX 3 Ply B elt D LP D U N LO PLA ST M onoply B eltS SU PE R FO R T M ultiply B elt ST SILVE R C O R D Steelcord B elt

10.8

Conveyor belt

C hloroprene R ubber C R

N itrile C hloropreneR ubber N C R

N ote

Belt Description

B elt Length

DUNLOP types

N om inal Tensile Strengththe C arcase

N um ber of Plies

N om inal Tensile Strengthof Plies

O rdering Exam ple 100 m 800 m m EP 400/3 4+ 2 m m X

B elt LengthB elt W idthM aterial (carcase)N om inal Tensile StrengthN um ber of Plies

C arrying Side C over ThicknessPulley Side C over ThicknessC over Q uality

125 160 200 250 315 400 500630 800 1000 1250 1600 2000 2500

63 80 100 125 160 200 250 315 400


35/16111.1

Design

Main Data Values

Speed V

Standard Values

Recom m ended

Velocity (m /s)

A fter establishing the duty of the operation and the type of belt conveyor,the m ain data m ay be determ ined.

B elt Speed v (m /s)B elt W idth B (m ) or (m m )C arrying Idler A rrangem entC ross Sectional area of Load Stream A (m 2)C onveyor C apacity Q (t/h)

The belt or C onveying Speed V (m /s) m ust be appropriate for the materialcompositionand operation conditions.

H igh Speed - N arrow er belt w idthsLow er belt tensionG reater w ear and tear

Low Speed - G reater belt w idthsH igher belt tensionLess w ear and tear

The m ost econom ical installation is that having the highest belt speed consis-tent w ith the type of m aterial and operating conditions.

Speeds V (m /s)

0.42 - 0.52 - 0.66 - 0.84 - 1.05 - 1.31 - 1.682.09 - 2.62 - 3.35 - 4.19 - 5.20 - 6.60 - 8.40

D uty v (m /s)

U nit Loads, A ssem bly Lines ! 1.68

M obile C onveyors 0.52 - 1.68

Very dusty loads such as Flour, C em ent ! 1.31

A sh and R efuse ! 1.68

G rain, C rushed Lim estone 1.05 - 2.09G ravel, Sand R eadym ix

O res, B itum inous C oal, Sinter

S torage and transhipm ent, P ow er S tations 1.31 - 3.35

Long distance conveying, overburden 2.62 - 6.60B row n coal

Throw er belts # 8.40

Steep gradient belts 0.84 - 2.62Type CH EVRO N and H IG H C H EVRO N


36/16111.2

Design

W herever possible a standard belt w idth should be selected. Type and granu-lom etry of the m aterials determ ine the minimum belt width. A fter determ i-ning the belt type a check on troughability m ay be necessary under som ecircum stances.

W ith unsized m aterial the large lum ps are em bedded in the sm aller granula-ted m aterial.

The disposition of the carrying idler varies from application to application. Thenum ber of idler rolls in a carrying idler set and troughing angle determ ine thecross sectional area of the load stream and thus the conveying capacity.

In deciding on the carrying idler spacing one has to take account of the loadlim itation of the carrying idler (note: R efer to m anufacturers specification).A fter establishing the belt tension the belt sag betw een idler rollers has to bechecked.The roller spacing has to be selected in such a w ay that the sag of a loadedbelt is no m ore than 0.5% -1.5% of the centre to centre distance. W ith returnside idlers one m ay allow approxim ately 2-3% sag.

Belt Width B

Standard W idths (m m )

M inim um B elt W idths

Carrying Idler Disposition

D istance betw eenC arrying Idlers

300 - 400 - 500 - 650 - 800 - 10001200 - 1400 - 1600 - 1800 - 2000 - 2200

M in. W idth Lum p Size K(m m ) Sized U nsized

400 50 100500 80 150650 130 200800 200 300

1000 250 4001200 350 5001400 400 6001600 450 6501800 550 7002000 600 800

k

hTx Tx

lo

lu

Tx*

8

*

hrello = ( m )

(m L + m G )* g

Tx * 8 * hrellu = ( m )

m G * g

Tx ( N ) Belt tension at point Xm L ( kg/m ) W eight of load per m etrem G ( kg/m ) W eight of belt per m etreg ( m /s2 ) G ravitational acceleration (9.81 m /s2)hrel ( - ) Relative belt sag

Carrying run : hrel= 0.005-0.015

Return run :h rel= 0.020-0.030

Flat 2 Part 3 Part D eep Trough G arland

C arrying Side

R eturn Side


37/16111.3

Design

Idler rotation should not be greater than approxim ately 650 r.p.m .

The length of the m iddle idler roll determ ines the cross sectional area of theload and thus the conveying capacity.

The gap d betw een 2 adjacent rolls should not be greater than 10m m , w ithbelt w idths B > 2000m m d = 15m m refer to D IN 22107, carrying idler arrange-m ents.

Values for Idler Spacing

Idler Rotation

StandardIdler Diameter (mm)

C arrying Sidelo = 0.5 1.0 m Sm all installation or high im pactlo = app. 1.2 m N orm al installationlo = 1.4 4.0 m H igh tension installation

R eturn S idelu = (2-3)*lo M axim um approx 6 m

nR = 60 * v (r.p.m .) D R

D R ( m ) Roll diam eterv ( m /s ) B elt speed

C arrying Idlers 51 63.5 88.9 108 133 159 193.7 219

Im pact Idlers 156 180 215 250 290R eturn R unSupport D iscs 120 138 150 180 215 250 290

Standard length L (mm) of rollers

B elt Troughing TypeW idth Flat 2 roll 3 roll Deeptrough GarlandB

(m m )

300 380 200 - - -400 500 250 160 - -500 600 315 200 - -600 700 340 250 - -650 750 380 250 - -800 950 465 315 200 165

1000 1150 600 380 250 2051200 1400 700 465 315 2501400 1600 800 530 380 2901600 1800 900 600 465 3401800 2000 1000 670 530 3802000 2200 1100 750 600 4202200 2500 1250 800 640 460

l

B

l

d ld d

l

l

d


38/16111.4

Design

FER RO FLEX Conveying B roken Stone


39/161

Form e dauge A ngle Section de char- C om parai-dauge gem ent A (m 2) son

plat 0,0483 44%

20 0,1007 91%30 0,1145 104%

20 0,0935 85%30 0,1100 100%45 0,1247 113%

20 0,0989 90%30 0,1161 106%45 0,1284 117%

30/60 0,1329 121%

A uge profonde

G uirlande

11.5

Design

To determ ine the cross-sectional area of the load stream A , one m ay use as abasis the geom etric relationship w hich can be constructed from the troughingangle , the usable belt w idth b and the angle of surcharge .

For 1, 2 and 3 roll carrying idler sets, the part cross-sectional area can be cal-culated as follow s:

Cross Sectional Area ofLoad Stream

C ross-Sectional A rea ofLoad S tream

Part Cross-SectionalA rea

Cross Sectional AreaComparison for VariousForms of Troughing.

N ote:

The values for the cross sec-tional area and the com pari-son are for a belt w idth B =1000 m m and for an angle ofsurcharge = 15.

B

b

l

l1

A 2

A 1

A = A 1 + A2 ( m2 )

A 1 = 0.25 * tan * [ l + ( b - l )* cos ]2 ( m 2 )

A 2 = l1 * sin * [ l + l1 * cos ] ( m2 )

l ( m ) Length of m iddle carrying rolll1 ( m ) Loading w idth of outer rolls

l1 = 0.5 ( b - l ) for 3 roll idler setsl1 = 0.5 ( b - 3 * l )for 5 roll G arland sets

b ( m )U sable belt w idth (loadstream w idth)b = 0.9 * B - 50 m m for belts B ! 2000 m mb = B - 250 m m for belts B > 2200 m m

( ) Troughing Angle ( ) Surcharge A ngle

Troughing Form TroughingA ngle

Load C ross Sec-

tion A rea A (M 2)

C om pari-

son

Flat

D eep Trough

G arland

0.0483

0.1329

0.10070.1145

0.09350.11000.1247

0.09890.11610.1284


40/16111.6

Design

The conveying capacity is determ ined from the cross-sectional area A andthe belt speed v (m/s).

The effective or nominal load stream volume is determ ined from theeffective degree of filling. This takes account of w orking conditions and thegradient of the installation.

The degree of filling is dependent upon the characteristics of the load, e.g.,the lum p size, the surcharge angle and the w orking conditions, e.g, m ethodof loading, tracking or the reserve capacity etc.

1 = 1 for norm al w orking conditions;1 = 0.8 - 0.95 for adverse condition.

The reduction factor 2 takes into consideration the reduction in part cross-sectional area A 1 as a result of the conveying gradient.

The load stream Q m (t/h) is calculated thus:

For the calculation of the conveying capacity for unit loads the follow ingform ula applies.

Conveying Capacity

Load Stream Volum e

Effective D egree of Filling

D egree of Filling 1

Values for1

R eduction Factor2

for Sm ooth B elts

for Steep Incline B elts

For Bulk Loads

Load stream m ass

For Unit Loads

Q uantity conveyed

Load S tream

Q V = A * v * 3600 * ( m3/h )

= 1 * 2 ( - )

G radient 2 4 6 8 10 12 14 16 18 20 222 1.0 0.99 0.98 0.97 0.95 0.93 0.91 0.89 0.85 0.81 0.76

Q m = Q v * ( t/h ) Theoretical value

Q m = Q v * * ( t/h ) Effective value

3600 * vQst

= ( St/h - pieces per hour )lst+ ast

m st * 3.6 * vQ m = ( t/h )

lst+ ast

Q V ( m3/h ) Volum e (values see Appendix)

w ith v = 1 m /sv ( m /s ) B elt S peed ( t/m 3 ) Bulk density (see Appendix)m st ( kg ) Piece W eightlst ( m ) Piece Length in direction of travelast ( m ) Spacing of pieces

A ngle of inclination 15 20 25 30 35 40

Spharical rolling and coarse M aterial 0.89 0.81 0.70 0.56

Sticky m aterial 1.00 0.93 0.85 0.68 0.58 0.47


41/16111.7

Design

This section deals w ith estimated values and relevant matters prim arily toenable the Project Engineer to provide a speedy assessment of require-m ents from the given service data. To m ake an optim um selection of theconveyor belt and conveyor com ponents it is recom m ended that detailed cal-culations be done in accordance w ith subsequent sections.

W ith the aid of the follow ing form ulae,power requirements can be roughlyassessed. The accuracy is sufficient for norm al installations w ith sim plestraight-forw ard running conditions. From the pow er calculations, the belttype can be closely determ ined. The actual nom inal belt w eight can be usedin the m ore precise calculation of the belt.

P3 is the sum of additional pow er for trippers, skirtboard friction, ploughs.

Standard electric motors (kW)

Power Requirements

A dditional Pow er

Installed M otor

Width factor CB

PT = P1 + P2 + P3 (kW )

C B * v + Q mP1 = (kW )

C L * kf

H * Q mP2 = (kW )

367

R equired m otor pow er PM = PT / (kW )

Q m ( t/h ) m ass of load streamv ( m /s ) belt speedC B ( kg/m ) w idth factor (see table)C L ( m

-1 ) length factor (see table)H ( m ) conveyor elevation H = sin * LL ( m ) conveying length ( ) angle of inclinationkf ( - ) Service factor (see table) ( - ) efficiency of the drive

= 0.9 for drives w ith fluid couplings

1.5 2.2 3 4 5.5 7.5 1115 18.5 22 30 37 45 5575 90 110 132 160 200 250

315 400 500 630

D uty B ulk D ensity

(t/m 3)

Light

M edium

H eavy

U p to C a. 1.0

1.0 to 2.0

O ver 2.0

31 54 67 81 108 133 194 227 291

36 59 76 92 126 187 277 320 468 554 691 745

65 86 103 144 241 360 414 644 727 957 1033

B elt W idth B (m m )

300 400 500 650 800 1000 1200 1400 1600 1800 2000 2200

Pow er at D rive Pullley

Pow er for em pty Conveyorand Load over the H orizontal

D istance

Pow er for Lift (or Fall)

PN selected m otor from standard list.


42/161

Trippers(throw -off carraiges)

Scrapers(for installations L ! 80 m )

M aterial - skirtboard

D ischarge plough

B elt W idth B (m m )

! 500! 1000> 1000

11.8

Design

Length Factor CL

Working ConditionsFactor kf

Additional Power Values

L (m ) 3 4 5 6 8 10 12.5 16 20

C L 667 625 555 526 454 417 370 323 286

L (m ) 25 32 40 50 63 80 90 100 150

C L 250 222 192 167 145 119 109 103 77

L (m ) 200 250 300 350 400 450 500 550 600

C L 63 53 47 41 37 33 31 28 26

L (m ) 700 800 900 1000 1500 2000

C L 23 20 18 17 12 9

W orking C onditions

Favourable, good alignm ent, slow speed

U nfavourable, dusty, low tem perature, overloading,high speed

N orm al (Standard C onditions)

Extrem ely low tem perature

kf

1.17

1

0.87 - 0.74

0.57

Scraper Type

sim ple, norm al contact 0.3 * B * v

1.5*B*v

1.8 * B * v

heavy contact

m ultifunctional fac scraper

0.16 * v * lfbeyond loading point

1.5 * B * vB ulk density ! 1.2A ngle = 30 - 45

P (kW )

0.8 * v1.5 * v2.3 * v

B ( m ) Belt w idthv ( m /s ) B elt speedlf ( m ) Length of m aterial betw een skirtboard

L (m ) Conveying Length


43/161

Belt Type

N om inal B reaking Strength

N um ber of Plies

Friction Value Factor cR

11.9

Design

This form ula is to enable calculation ofbelt breaking strength and applies toinstallations w ith a single pulley head drive, an angle of w rap = 200, a safe-ty factor S = 8 to 10. B y using a dual pulley head drive or a head and tail drivea low er strength belt type can result.

The nominal Breaking Strength kN is obtained by rounding up to the nexthighest belt type.

The num ber of plies or thickness of carcase depends m ainly on the beltw idth, m aterial characteristics (bulk density, lum p size) and conditions suchas transitions, height of m aterial fall, installation path, troughing etc.

cR PTk = * ( N /m m )cv v

98 74 59 45 37 30 25 21 18 16 15 14

69 52 41 32 26 21 17 15 13 12 10 9

62 46 37 28 23 18 15 13 12 10 9 8

57 43 34 26 21 17 14 12 11 9 8 8

53 40 32 25 20 16 13 11 10 9 8 7

D U N LO P B elt Type

D U N LO FLEX 2 ply overlap 100%1 ply overlap 50%

1.000.50

TR IO FLEX 3 ply overlap 100%2 ply overlap 67%

1.000.67

FER R O FLE X Zig-Zag Splice Joint 0.90

D U N L O P LA S T Finger S plice Joint 0.90

Steel C ord B elts Splice 1 and 2 step3 step4 step

Various M echanical Joints: Refer to M anufacturer

1.000.950.90

SU PER FO RT N um ber of plies 12345

6

0.700.500.670.750.80

0.83

Splice Type Ply R ating Factor cvBreaking Strength Lossat J oint Factor Cv

B reaking Strength

0.15

0.25

0.30

0.35

0.40

bare, w et

rubber lagged, w et

and dirty

bare, dry,

lagged, w et

rub ber lagged, dry

Friction

Value

Belt W idth B (m m )

300 400 500 650 800 1000 1200 1400 1600 1800 2000 2200

D rivePulleySurface


44/16111.10

Design

The pulley diam eter for a conveyor belt depends upon the belt construction(belt type, carcase m aterial and thickness of carcase), the duty and themethod of splicing. O ne can differentiate betw een 3 pulley groups depen-ding on pulley location and angle of w rap .

To determ ine the pulley diam eter first ascertain the diam eter of the drivepulley w ith m axim um tension.

The calculated pulley diam eter is rounded up to the next higher standard dia-m eter or if w orking conditions are favourable m ay be rounded dow n.

Pulley Diameters

Value CTr

Standard Pulley Diameter(mm)

G R O U P A PPLIC A TIO N

A Pulleys in the areas of high belt stress. D rive PulleysB Pulleys in areas of low belt stress. Tail PulleysC Pulleys w ith an angle of w rap ! 90,D eflection or snub Pulleys

D Tr = CTr * d ( m m )

d ( m m ) Thickness of carcase (see Appendix C)C Tr ( - ) Value for w arp m aterial of carcase i.e. B elt type.

C Tr M aterial of Carcase in W arp or Belt Type

90 Polyam ide (P)80 D U N LO FLEX 2 ply B elt95 TR IO FLEX 3 ply B elt

108 SU PER FO R T M ultiply B elt (EP)138 FER R O FLEX Steel W eave Type145 SILVER C O R D Steel C ord B elt100 D U N LO PLA ST M onoply B elt

Tail Pulley

Snub Pulley B end Pulley Snub Pulley

D rive Pulley

Tension Pulley

100 125 160 200 250 315 400 500630 800 1000 1250 1400 1600 1800 2000


45/16111.11

Design

O nce the diam eter of the largest pulley has been determ ined to a standardsize the diam eter for pulley groups A , B , C can be obtained from the follow ingtable.

The diam eters show n in the above table apply to belts operating at 60% -100% of allow able tension.

W hen the rated tension of the belt is not fully utilized, it is perm issible toreduce pulley diam eter to 1 to 2 sizes sm aller.

For pulley diameters of the DUNLOP belt types: see Appendix K.

Pulley Revolution

Pulley Loading

Pulley D iam eter O f Pulley G roups (m m )

D iam eterD Tr (m m ) A B C

100 100 - -125 125 100 -160 160 125 100200 200 160 125250 250 200 160315 315 250 200400 400 315 250500 500 400 315630 630 500 400800 800 630 500

1000 1000 800 6301250 1250 1000 8001400 1400 1250 10001600 1600 1250 10001800 1800 1400 12502000 2000 1600 1250

Tm ax * SkA = * 100 ( % )

B * kN

Tm ax ( N ) M ax. belt tensionS ( - ) B elt safety factor w hen runningB ( m m ) Belt W idthkN ( N /m m ) N om inal breaking strength of belt

D egree of U tilization Pulley D iam eter

kA > 0.6 1 D iam eters as tablekA > 0.3 0.6 G roup A, B and C one size sm aller

kA < 0.3 G roup A and B 2 sizes sm allerG roup C one size sm aller

v * 60nT = ( T/m in )

* D

TA1 + TA 2FT = ( kg )

9.81

Utilisation Percentage


46/16111.12

Design

W ith rubber lagged drive pulleys the average surface pressure lim it is approxi-

m ately 70 N /cm 2. This lim it is only reached on heavy drives and relativelysm all pulley diam eters.

The transm ission capability p is not to be confused w ith surface pressure!The surface pressure is sum m ary calculated, the belt bending stresses beingignored. W ith high belt stresses the pulley diam eter becom es too largebecause of the low values for p.

p = 1600 - 2000 N /m m2 above ground

p = 3000 - 3500 N /m m 2 under groundThis form ula is no longer used to determ ine the pulley diam eter.

The distance betw een a term inal pulley and the adjacent fully troughed idlerset at either the head or tail end of a conveyor is know as the transition dis-tance. In this distance the belt changes from a fully troughed to a flat profileor vice versa respectively. The belt stretches additionally at its edge zone andbuckling in the m iddle of the belt is also possible.

To relieve the belt and edge stresses, the pulley m ay be raised slightly to thevalue h (m m ) (see Page 11.13).

The necessary transition length for tension distribution w ith or w ithout pulleyelevation w hen designing can be estim ated or taken from the table.

Average Surface Pressure

Transmission Capability

Torque at Start-Up

Troughing Transition

Elevation of Pulley

TA1 + TA 2pT = ( N /cm

2 )D * B

360 * FUp = ( N /m m

2 ) * D * * B

FA * DM A = ( N m )

2 * 1000

D ( m m ) Pulley diam eterB ( m m ) B elt w idthFA ( N ) Peripheral force at start-up ( ) A ngle of w rapv ( m /s ) SpeedFU

( N ) Peripheral force w hen running

LM

Lred

l

h

S

L1


47/16111.13

Design

The pulley lift should not exceed the value h (m m ) in order not to get a skijum peffect. Lift-off from the centre roller is not desirable as this w ouldhave an adverse effect on belt tracking.

Values apply to 3 roll idler sets.1) R educed lengths Lred apply to the raised pulley w ith the value h (m m )

according to the table.

Troughing Transition

Pulley R ise

R educed Transition D istance

Trough Transition Values

Pulley Lift h (m m )

LM = x * s * sin ( m m )

s2

h = * sin ( m m )

B

Lred = x * (s * sin - h) ( m m )

LM ( m m ) N orm al transition lengthLred ( m m ) R educed transition length w ith raised pulleyl ( m m ) Length of centre carrying roller (see page 11.3)s ( m m ) Portion of belt in contact w ith side idler roller, s = 0.5 * (B-l)x ( - ) Factor for carcase x = 8 for Textile belts

x = 16 for ST. belts ( ) Troughing angleh ( m m ) Pulley lift

Troughing A ngleTextile belts

LM (m m ) Lred1)(m m )

ST Belts

Lred1)(m m )

Troughing 20 30 30 40 45 30 45

B elt W idth(m m )

500650800

1000120014001600180020002200

410550665850

100011901370155017101920

600800970

1240147017402000226025002800

680860

102012001380155017201900

8701100131015401770199022002450

9501210144017001950220024302700

13501710204024002750310034323800

19002420287033803890439048605390

B elt W idth

(m m )

37485668788998

112

47627287

100114126143

52688096

110125138158

8001000120014001600180020002200

Troughing A ngle

30 40 45


48/161

In the transition from inclined to horizontal, the belt edge zone is subjected toadditional stretch. In order not to exceed certain lim its, as a rule 0.8% addi-tional stretch, the transition radius R e has to be dim ensioned accordingly.

M inim um radii for 3 roll carrying idlers.

11.14

Design

Convex Vertical Curve

Values of R adius R e (m )

l

S

R e

L

l0

Carrying side

R eturn side

R e = x * s * sin ( m )

s ( m m ) Portion of belt in contact w ith side idler rollerx ( - ) Factor for carcase

x = 125 for textile beltsx = 400 for steel cord belts

L = * * R e / 180 ( m )

z = / (Pieces)

lo = L / z ( m )

( ) D eviation per idler = approx 2 for 30 troughing = approx 3 for 20 troughing

( ) G radient of installation

C onvex R adius

C urve Length

N um ber of Idlersin C urve

Idler Pitch

Textile belts

20 30 45

500650800

1000120014001600180020002200

6.58.5

10.5

13.016.018.521.024.026.530.0

9.312.515.0

19.523.027.031.035.039.044.0

13.517.521.0

27.032.038.044.050.055.062.0

30.040.048.5

62.074.587.0

100.0113.0125.0140.0

--

68.5

88.0104.0123.0141.0160.0177.0198.0

ST Belts

30 45Belt Width

(m m )


49/16111.15

Design

W ith a concave vertical curve, the belt path goes from horizontal to incline.A t start-up or load change there m ay be a risk of the belt lifting off the car-rying idlers in this region. This can lead to a reduction in pre-tension. If dueto special circum stances a brief lift-off can be tolerated then the lifting beltcan be restrained by rollers m ounted above the troughing idlers. In any eventaction m ust be taken to ensure that the belt does not lose load m aterial.

W ith a concave vertical curve,buckling of the belt edges and overstress ofthe m iddle of the belt can occur. (To check calculation see A ppendix I.5.)

Concave Vertical Curve

Additional Stretch-buckling

R aLx

Tx

xa

ya

Tx ( N ) Tension at start of curve w hen fully loadedm G ( kg/m ) Belt w eight ( ) G radient angle, up to 18 use 18, cos 1

TxR a = ( m )

m G * cos * g

xa = Ra * tan horizontal distance

ya = 0.5 * R a * tan2 vertical distance

C oncave R adius

C o-ordinates ofC urve


50/16111.16

Design

O ne m ethod of solving belt cleaning problems on the return side run is theuse of belt turnover. This m ethod is em ployed in inaccessible areas such asconveyor bridges and tunnels. To avoid excessive strain in the edge regionof the belt, the turnover m ust be a certain m inim um length, depending on them ethod of turnover, belt type and belt w idth.

W ith textile belts up to a w idth of 1200 m mand a thickness of 10 m m , the belt m ay beturned over unguided and w ithout support.A t the entry and exit points of the turnoverlengths, the belt is fed through a pair of rol-lers.

W ith textile and steel cord belts up to 1600m m w ide to support the belt in the m iddle ofthe turnover length, a pair of vertical rollers isused. A t the entry and exit points the belt isfed through a pair of horizontal rollers.

W ith textile and steel cord belts up to 2200m m w ide. W ith this turnover the belt is fedover support rollers w hich run on a length-w ise axis.

For sm ooth running of the belt through the turnover stretch, a minimum belttension is necessary.

If Tx is > than T2 or T3 then belt tensions have to be corrected.

Belt Turnover

U n-guided Turnover

G uided Turnover

Supported Turnover

Turnover Lengths

Values for Turnover LengthsLW (m )

M in. B elt Tension at Turnover

Lw * m G * gm in. Tx = ( N )

8 * h

Lw ( m ) Length of Turnover Stretchh ( % ) D egree of sag 1.5% is recom m ended (h = 0.015)m

G( kg/m ) Load due to conveyor belt

B ( m ) Belt W idth

Lw

Lw = 1.36 * B * 71 = 11.5 * B ( m )

Lw = 1.55 * B * 245 = 24 * B ( m )

M ethod of guiding belt inTurnover Lengths

B elt Typefree or w ith guided w ith asupport rollers m iddle roller

EP belts 12 * B 13 * BD U N LO PLA ST 16

*B 19

*B

FER R O FLEX 17 * B 20 * BST. B ELTS 18 * B 22 * B

for EP belts

for ST belts


51/16111.17

Design

W ithin lim its, belts are able to negotiate horizontal curves. To do this the car-rying idlers on the inside of the curve are slightly raised by the angle R accor-ding to radius and belt tension by approxim ately 5-15.

The exact position has to be determ ined by adjustm ent.

For design purposes the follow ing radii m ay be selected being the smallerpermissible radii RH (m).

The values R H apply to a troughing angle of 30

Horizontal Curve

Value of C urve R adius

R H

R H

R

l

Inside of C urve

lR H = k * [ l + B * ( 1 - )* cos ] ( m )

B

l ( m m ) Length of m iddle carrying roller (see Page 11.3)B ( m m ) Belt w idth ( ) Troughing angleR ( ) Lifting of the carrying rollers (ca. 5 to 15)k ( - ) Factor (consider belt type and duty)

for EP belts k = 71D U NLO PLAST k = 150FER RO FLEX k = 225ST belts k = 245

B elt w idth(m m ) 300 400 500 650 800 1000 1200 1400

EP belts 20 26 33 42 52 65 72 91D U N LO PLA ST 42 56 69 89 110 137 165 192FER R O FLEX - - - 134 165 206 248 289ST belts - - - 146 180 224 270 314

B elt w idth

(m m ) 1600 1800 2000 2200 2400 2600 2800

EP belts 104 117 130 142 156 169 182D U N LO PLA ST 220 247 275 - - - -FER R O FLEX 329 370 412 452 - - -ST belts 359 404 449 493 - - -


52/16112.1

Basis of calculations

A fter the design of the installation and the m ain data has been determ ined anexact calculation can be undertaken. Established installation com ponentscan be checked and dim ensioned. The belt selection can be undertakenaccording to forces that have been established and other relevantcriteria.

The resistances to m otion w ithin a belt installation m ay be categorised thus:-Main resistance-Secondary resistance-Slope resistance-Special resistances

Resistance due to moving the mass of idlers, belt and m aterial on the car-rying and return runs. R unning resistance of idlers (bearing and seal fric-tion). Resistance due to impressions m ade in the belt by idlers and theflexing of the belt.

W ith gradients ! 18 C os = 1.

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dunlop ingenieria

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