Conveyor handbook

13. TABLE 2A - GENERAL PROPERTIES
Mining, Quarrying and General Service

14. TABLE 2B - GENERAL PROPERTIES
Heat resistant grades

15. TABLE 2C - GENERAL PROPERTIES

Oil and chemical resistant grades

16. TABLE 2D - GENERAL PROPERTIES

Fire Resistant and Anti-static belts

31. 3. Belt power and tensions

BELT POWER CALCULATION FORMULAE

Power requirements for belt conveyors may be calculated from the following formulae

Fels) (C+3609 , Ch

one E E]

own

FolltW3608 | Felle | CH

Pe. ES EJ 7

m

Fe = Equipment fiction factors = refer item 11) below,
Horizontal centre to centre distance Im).
Terminal friction constant express in metres — refer item (2 below.
Capacity CU.
+ Mess of moving parts expresad in kilograms par meto of centre to centre distance
{rater Table 3, Section 3, Pago 3-4).
S = Bett speed (mish
H = Nett change in elevaron (i
KZ Brive factor dependent on pulley surfoce, ac of contact and type of tensioning
Ares Tables 1 and 2 ofthis section)

The values ofthe main factors and constants are as follows
(1) Equipment friction factors

On snort centre conveyors using est quality equipment, ts often more convenient o use an
eras equipment friction factor (Fe) of 0225 for horizontal and incined conveyors and
Dh on detinorogeneratv systems,

On many systems, such as portable conveyors, “Chewon” sterp angle conveyors and
temporary insaiatons using ant fiction bearings, the following value for equipmer
Pe 090

On longer centre conveyors and individual component tension calculations as detailed below
equipment faction factors Fy and Fy are us) for empty and loaded bet conditions

ll Horizontal and elevating conveyors

Fe = 020 fo: empty caealtions
Eg = 025 for lod caution

Hi Regenerative decline conveyors
8 = 010 for empty calculations
FR =.017 for load aurions

(2) Terminal reton constant, y expressed in metes of cante to centre distance:

Horizontal and elevating conveyors

(0) Up 10300 m centres = 60m
fi) From 300 mto 1200 m = 45m
(ii) From 1200 m to 1800 m= 30m
(iv) Above 1800 m nis influence is disogarded.

32. (0) Regenerative decline conveyors
4290

(e) On the systems as described in para, (II). Le, where
Fee 090
ty = 45 m (except for “Chevron” belt conveyors, where values asin (2) re used

(4) On rare occasions it is posible 10 find long centre belts that re sit regenerative under
loaded conditions, but require more power forthe empty belt. When this condition is met
the termina friction allowance is varied as follows for empty tension calculations only
y= 260m.

‘Additional friction considerations. Whore the number of pulleys is age in relation tothe length of
the conveyor. 29. multi tipper conveyors, His necessary to make allowance for the additional
tension required 1 overcome thee pulley tions.

‘Aso where skirt board lengths ate long in elation 10 conveyor length, allowance should be made for
the additional friction involves

{Component frictions and tensions. Should it be necessary to calculate individual component tensions
for the asembly of tension diagrams on multiple slope conveyors, of for assessment ofthe eects of
acceleration or deceleration on a particular system, the following formulae wil apy

Return side friction
Fe x Ox Lx 04 x (981 x 103) (KN)

Total empty fiction
= Fe L+ 1) Q x (9.81 x 109) (KN)

Carrying side empty friction
Total empty friction return side fiction (kN)
Load trietion

FE «(981% 109) (kn)

Lod slope tension

LH (9.81% 109) (KN)
LH «19.81% 109)

Belt slope tension
+ BxHx (981 x 109) (kN) as

ere 8 is the belt weight per lineal metre (roer 10 Section 8), and al other symbols are as given

Etective tension, T= Tota empty friction + lad tion + loud slope tension
= [Freeware itn E + &] 981x109 (kN)

Slack side tension Tz = Tax K (kN

where K is the drive factor dependent on pulley surface, ate of contact and method of te
sted in Tables Vand 20 thie section,

33. Power is simply calculated rom Te by

Bone = TexS (kW)

a)

STANDARD DRIVE FACTOR "K" VALUES

es sre ur [a
‘oon! Bes | ee

The above values are calculated fom the base tension relationship formula

1
Tr

Tight sde tension
Sick side tension

= Naperan ioparithm base

= Costiciont of fiction

The“ values in Table 1 are calculated from

1

Kos

Coefficient of friction, bare play, dry conditions
# = 03

efficient of tition, lagged pulley. cr conditions:
“ + 035

Contient o friction, lgoed and grooved pulley, wet or dry conditions

34. Tatez
SPECIAL DRIVE FACTOR "K” VALUES
For ring to concn (a and counter ake

AVERAGE VALUES FOR 0” FOR FABRIC BELTS
(MASS OF MOVING PARTS, KILOGRAMS PER METRE)

he mass of belting and ¡ler spacing obviously allct ne above values considerably and therefore
this {ble gives conservative and average figures only. For closer determination each individual
installation should be checked using the following formula, and taking ito consideration belt mas

om 13)

35. 10” values for see cord applications should always be calculated accurately using above formula,

CALCULATION OF MAXIMUM TENSIONS

Because of the different tyoes of belt arrangement which may be required to suit a particular
Spotiation, various basic formulae are needed to determine the maximum tension, exprese In

‘he main components ofthe maximum operating tension, Tmax, re
To Effective tension KN)

To > Slack side tension (kN)
Te ‘See Note (3), page 6 of this section

1. Horizontal belts
Tax
2. Inclined bets

la Drive at Head Paley

Tmax
Tr + balt slope tension — return sige fiction + Tang
Drive at Tai Paley
Tmax = Te+T
Ti a + Ty + belt slope tension — rotum side friction
3. Deetne belt
la) Regenerative Got — Tail Drive

Tmox = Te + beltslope tension + return side rietion + Tag,

Partially enenerative ~ Head Orie

Tmax = Tet Te
Tmax = Ta + beltslope tension + return side fiction

Partially roenerative ~ Tail Drive
Tmax = Te + Ta

max ~ Belt slope tension + return side friction + Tsay

37. IDLER SPACINGS

RECOMMENDED AVERAGE CARRYING IDLER SPACING (METRES)

GRADUATED IDLER SPACINGS

(On long centre, heavily joa, high tension conveyor system, tis possible to use graduated ide
Spocings. The sg wil wary inverse withthe tension in the bet. Since the tension varies along the
length of the belt the spacing can be graduated, being smallest at the zone of low tension and
increasing ss he bat tension Increase. Saving can thus bo effected on both the carving and return
nuns The spacing at any point can be obtained from the formula

x Ta sg
Let spacing = im (326)
WERT Nig 9.81 x 108) m
Me = Mas of belt ond tive load expressed in klograms per metre.
= Tension at the point bai vestigated (kN
50 = Atpereeotage ofthe ile spacing expressed as decimal and usually 0.02 (2%)

€
ions = ¿(gm 1827
u 5

S Belt speed (wis)
© = Capacity (un)

The figures given in Table 5 of this section wi give a quick check. Men the conveyor is on a uniform
raiemt he gracumted idler spacings in Table B of ths section willbe of aisance in determining a
(recusced system

NOTE: Care should be taken to check belt tensions uncer al possible oad conditions before installing
Idlers ar graduated soacings. les installed at spacings determined by maximum load tension
‘aleulations could cause operating problems through exce elt ag under lightly leaded conditions

38. [BELT TENSIONS (kN) REQUIRED AT LOW TENSION ZONES
‘TO RESTRICT SAG TO 2% OF IDLER SPACING

43

Tre belt tension values given above in kilonewons are calculated from the theoretical sg formula
or a Mat belt, but trey are generally Used for inclined ler roll. These figures re therefore
Conservative vien aoplied 10 a troughes belt because of the added resistance 10 sog vesting from

TABLES
GRADUATED CARRYING IDLER SPACING GUIDE

a L voter
verano | em =

‘Supplementary notes:

(1), Return idee soacing = approximately 20 metres,

(2) Impact idler spcing = approximataly Y 10% carrying der spacing.
() Convex curve idler spacing — at mat % carrying aod return idler spacing.
Ah Sei algning iles — one or two sts forthe return side of bat approaching tal pulley at 6 m 10

8 m imionals from the pulley. Also useful at times on th carrying ice approaching head pulleys
and along the whole carrying and etur runs at approximately 120 m and 60 m respectively

39. FEEDER BELT CALCULATIONS

The following sub section apli to fully std feeder belts.

Belt speeds. For feeder belts supported by ides, belt speeds should not exceed 0.25 m/s with
Abrasive materials and 0.5 m/s with non abrasive materias. For sider bed suppor it is usual not 10
‘xcoes 0.13 ms

Feeder belt capacity. For: width of skirted load = 80% of ett wid
Sopth of skirted oad = 40% of skirted load width (iat be

W2 xMxs

Capacity
1.085

(vn
Wr Bei iat im)

M2 Material density (kg/m)
S 2 Bett speod {mis}

Feeder belt tensions and power. The efectivo height of loadin the hopper supported by the bel can
be assumed ss twice tho loaded bet width for most lumped bulk materials, ths the mass ofthe load
Supportes by and tobe moved by the bel aporoximaraly.

Mos BP Lg x M (kg) 1329)

We = Hopper opening width [ml
Lg = Hopper opening length {m}
Nt Marena density (kal?)

Effective Belt Tension, Ta go x 24? x Lex Mx {9.81 x 109) (KN)

6 = Oval fietion enfin:
10.4 for ie operation)
(0.5 for sider be operation)
(up 10 1.0 for act flow materials}

Maximum bet tension, Tax = (14K) Ta (END

where
"(097 for 190? won, serow take-up, bare tel pulley

90 for 180" wrap, serow taku age Pully}

other values tom Tables 1 and Zof Us section}

Belt power = Tex S (kWh

S = Belt spood {m4}

Note: Height of hooper opening above belt shou les than thre ines maximum lume siz

Feeder belt specification, For carcas design as per Section 4, Page 1. the following considerations
) Carcass: low elongation, high strength carcass refered — such as KN or PN constructions

op covers. usually Irom mn thick for lumps up to 6D me, 10 10 mm thik for lumps up 10.
lc) Bottom covers: 2104 mm thick depending on degro of abrasion nd impac

40. ACCELERATION AND DECELERATION

(a) Accelrating Bot Conveyors

The idea! starting arrangement for a belt conveyor is one which provide a gradual stples increase in
torque, which rises to à value just suficint to put the belt in motion. Once is ls achieved there
Should be a slight pause to alow shock tensions within the system o dampen out. Following this the
Give should continue the sense increase In torque at à Taste rate unt fll speed Is reached

The question of cost must always be considered and generally there is some compromis in choice of
motor and controler The following ‘abl ist most, but rot necessarily ll, methods that can be
‘garded as scceotble, and casts them in respact f idea starting arrangements or the bel

With D.OLL, stating of normal squtrel cage motors, it is often posible to sar a conveyor and not
harm the belt in any way, particularly on snort conte installations, because zh nel ol the driving
Smpanens sin excess 61 the load and thus the traue vransmiitd 19 the Ber quite often below
the customary limit of 180 ~ 160% of the running tra

As necessary, D.O.L, starting characteristics are modified withthe substitution of primary resistance
of auto transiormer starters

TaoLez
‘CONVEYOR STARTING METHODS AND THEIR CLASSIFICATION

CE

Regenerative decline conveyors! an induction motor is driven by its oad in he some direction
generator, taking mognetising current (rom the line and absorbing mechanical power through is shaft
ie Bower I then es bank into the power system, The motor sl restrain she Toad with tle ie
1 sed above synchronous a long s the loud traque does not exceed the maximum torque of the
motor Y maximum torque is exceaded the motor becomes ursable and uns aa
Ice the motor draws magaetising current from the nei follows that no dynamic braking i posible
Wen the conection between the motor starter and tne powerline fs interrupt. A decline corveyor
Y an excelent illustration of this olfoct when the speed of the belt and load are restrained by the
motor. The motor serves asa generator teeding power back into the system without special conto

41. Regenerative braking at speeds below synchranaus is not possible, Retardation must be afecto b
Other braking methods and the Brake elected Tor ropenerative line comayor must have Ine
Following characteristics:

Ai) must always fail sate,

Ail) It must stop the conveyor in a rescate time so that there wil be no damage to the bel, the
ring components orth brake hal

(ii) Wen the brote stops the conveyor o it fal sat, it must have sufficient torque rating to hold
the conveyor motionless under fly loaded conditions of operation

Decline conveyors may tnerofore be stopped by any one of the following means
(0 Dynamic braking

(i) Eady current braking

ie) Frieion baking

Its, of course, possible to use a combination of the above methods ut the only brake that wil fi
sale and hold the load is the fiction type. Asa result, the most common type of broke Used as a
Control on decline conveyors is the gravity or spring actuated shrustor brake

Many factors have o be considered in he selection of brake size of suficien torque to decelerate the
1030 and hols it motonlee. Problems suena gradual deceleration and the heating efect on the drum
shes nave alo tobe consideres. The inertia ofthe driving components wll alo nave a marked efect
and therefore these Brakes must always be designed on a most ieral basis

Horizontal conveyors. Wen power is imarrupted on Iongcenta horizontal conveyors, “if
or “cossting" will te place becouse of the inertia of the system. Normally this condition is not
troublesome unless ne long entre bel is one of multiple system or is feoding oo shorter inclined
Dott win vast different natural decslraton characteristics,

Unless such conveyors aro braked, material may ple up at transfer points with the possibility of

damage to bath bit and machinery. the natural deceleration time 's excessive Yor the system,
Fetardaion may be affected by tho use of dynamic or dy current braking,

(6) Hold Back or Anti-Run Devices

Vian an inclined conveyor is stopped under loas, the force of gravity wil tend o drive the bet in the
reversa direction. A hola back davies is nesesery to prevent the bet backing down the inti. A
reversa of motion would cause sp lag and, in many cases, belt and mechanical damage. The following
Tit deals the most commanly used type

(©) Cuich type holdioeks Thess are among the safest devices and consst of an averrunning

¿lun with its outer ace Del stationary between two lavar arme rgily mounted to the cute
housing. These clutch type hols back are considerably more expeneive than Other devices Dut
‘hey require the lowest maintenance and oporate win 2ero back la on the drive hal

"ome ina wide variety of size, have nigh capacities and cannot be contaminated by dust.

Roller type hold back. These consist of hardened sel roles which lie in wedge she

as long s the hola Back rotor is running in the direction of normal travel. Once te direcion oF
rotation isreversd, ne roller jm in the narrow end ofthe slots holding the rotor against the
Stationary housing

Ratchet and paw holdbacks, These ate the simgles and last expensive type hold back. The
‘umolity of design promotes easy maintenance But unless sevice regulary, dust and lack of
lubrication coulé make the device inefecive. Such units should always be covered i moun
in dusty locations.

42. (iv) Different brake hole backs. This device is also comparatively cheap but ait relies on tition,
À not 98 poste as the other devices listed above. This haldibeck consists of a brake whee,
Drake band and base mounted cam. Movement In normal direction of travel acuate the com
through Icon betwoon the broke wheel and the band in such à manner that she band perimeter
1 incre, allowing fee rotation. Movement in the opposite direction creases the perimeter
Of the band Binding It against the brake whet and preventing movement

Differential band brakes are subject to failure trom over-reasng, wear and cing, If used in dusty
ications, te should lay be covered. Such brakesrequirocaretal adjustment In Ihe fad

Magnetic brake, This fiction brake is normaly actuated by a Ihrustor or solano, and is always
located on the high speed sige of the reducer. I is generally used 10 Supplement te action of

1d), Counterweight Reetion — Accelerating and Braking

Today's long contre, terrain following conveyors quito fruently, during acoserain or deceleration,
Generate forces which Sometimes affect the amount ol counterweight tension required inthe sysem
Wie countenweight is not sufficienty heavy 10 resist such forces, then it wil move inwards and
inevitably cause an accumulation of slack belt at some point of lower tension in the system. Thisin
tun can cause severe spillage, damage 10 bet and/or ilers and in some cases, when the accaeration
Or deceleration phases complete and the belt aves up is energy, the generation of longitudinal
ses in the system producing phenomenon anlagpus fo water hammer, which can severely damage
Terminal equipment sach a pulleys, Dating, structures and even she belt ef

“The accelerating and decelerating oros calculations are based on the simple sssumotion thatthe entire
belt starts or stops at 2 uniform rate of acceleration or deceleration. This assumption is not
Comoletaly accurate because of the elastic qualities ofthe belt it. Textile belts tend to elongate
more with the result that some sections of the belt reach either full spood or standstil much quicker
thon other sections. On the other hang, ste! cord belts, with relatively high modulo elasticity, and
therefore inherently lower sreth eharateritic, tena 10 behave ina manner much closer 10 the single
mes assumption mentioned ear, Depending on Ihe magnitude of acca aration/deceeration forces,
‘a the load condition of she system, the fallowing general conditions il py.

RECOMMENDED DRIVE AND TAKE.UP LOCATIONS WITH COUNTERWEIGHT REACTION

43. Where conditions such as envisaged in 4, 5 and 6 in Table B occur, iti customary to handle such
problem

Ai) Very heavy single counterweight location.
i) Dual counterweight locations.

(ii) Tait end baking

liv) Combinations of haad/ai or head/ntermediat or tiVinta mediat drives

In the cae of fv) itis suggested both the bet supplier and original equipment supoler be consulted
0 ensure that al apoct othe design are covered

(e) Brake or Ant Fol Back Devices

REQUIREMENT FOR BRAKE OR ANTI-ROLL BACK DEVICES

me ==]

Pee = =

(0) Accelerating and Braking Forces

The belt tension during acomlcation or deceleration can be ealulated for any critical pant in the
System leg, vertical eure). This tension is equal o the normal operating tension at that specific
point inthe system plas the additions tension eavsed by the forces of aczaleration or deceleration,
och significantly cifferent condition ol loading shoul be investigate

“The thee base formule use in such calelations areas follows

ma aa
Moss to be accelratd or decelerated (Kg)
Acceleration or deeleration (nf?)

ere time required for acceleration or deceleation has tobe calculated
s

were: $= Belt sooed (m/s)

Average acnlaration or deccertion (n/a?)

44. er coasting is involved and distance is required:

2

Decelertion m/s?)
Deceleratig timo (1

Coasting oF decelerating distance Im}

E
a= & wen

a. F and m ar derived earlier in hi section,

Wen combinations of incline/decline become involved, e. on a terrain following conveyor where
there could be multiple slopes involved, then careful corsideration to accmeraion ana deceleration
Forces shouts be given

APPLICATION OF FORCES

Acceleratng and decelerating forces are distributed around conveyor systems in direct proportion
tothe mass involved, These masses areas follows:
(1) Conveyor Carrying Sido

Bett mass + material mess + mass of carrying idler rotating pars

ett mass = B {kg/m), from Section 8

i o
Materia mass - 35 kom)

os of rough idler pars = (kg

(2) Conveyor Retum Side
ele mass + mass of return idler rotating parts

elt ase g/m), from Section

Mass of retun idler parts = SE kam)

(9) Mass of Terminal Pulloys

(On very long centre bets these are often neglacted but those should be included. Such
weights are readily valle from the origina equipment supplier

From the foregoing, the total mass to be accelerated or decelerated can be calculated for any
particular portion of the comeyor oF loading condition by multiplying the masses per metre ofthe
portion or loading condition being considered by the length 0 that portion,

Note thatthe sum of all mass on the caıyng sido and the sum ofall mass on the return side must
be used in each fore cleulation,

Typical average value for "3", the acceleration of a conveyor for diferent methods of starter contol
are given in Table 10.

45. TABLE10
‘TYPICAL ACCELERATION VALUES "a" (ms?)

NOTE: A check should aiways be mace by comparing the acceleration force calculated, with the
Dermisikle allowable forthe Be, 12. 150% o rated ball tension, Ifthe assumed rate chosen excueds
the latter figure, then te choles of control must be changed or masts.

‘ter calculating the forces involved for each particular lsd condition, he effect of these forces on
belt tension can be determined arithmatically s follows

(a). Calculate the normal running forces in the conveyor forthe loading condition under consider
lation, with tho portion of ose forces which relate to each section of the conveyor on the
Carrying and return ico being calculated

Calculate running tensions for other posible load conditions so that the counterweight for
Fanning conction ean be determined

Calculate the sccelerating and decelerating forces for each section of the conveyor using the
ress” applieableto each of these sections.

hen gravitational aoeleration forces are to be considered or cegenerative belts or gravitational
{deceleration forces for belts requiring power with power switched of hose forces are distributed
Sound the comeyor in proportion tothe masses in each section,

The gravitationalacceleraio or deceleration fora for à particular fous condition is equal tothe
effective tension, Tp for that condition

‘Add andlor subtract all the running and acclerarin/doceleraino forces calculated for the
particular load condition being considered, to the counterweight already determined for the
Eoaveyor in accordance with aa abra sgn rules given below

‘Chock that tere is no case where the minimum tension falls below gag. If this docs occur, more
‘counterweight Is required which wil tact the normal running tendón and possibly the belt

ALGEBRAIC SIGNS OF CONVEYOR FORCES

(1) Emp friction (Formula 9:3, 3.4 and 36) and load fiction (Formula 3.6) are always (+) in
‘he direction of bet travel, and (-) against direction of belt roel

Bei slope tension (Formula 3.8) is always (4) in uphill situations and (in down
Load slo tension (Formula 3.7) iss given for (2 above

‘Acceleration forces (externally applis} are always +] in direction of belt travel and (-
bei rave

46. Gravitational forces to decelerate conveyor ate always (-) in the direction of belt tral and +)
inst direction of bat eave

Gravitationel forces to accelerate conveyor are always (+) inthe direction of belt wave and =)
against direction of bat Wave.

‘COASTING

Unless a conveyor is regenerative, it wil coast 102 gradual halt due o the inertia in the system when
the dive power isshut oft

It may. be necessary to calculate this natural coasting timo (or distance) to determino if xr
retarda in the form of à Drake reguiod

“The thee basic formulae described sarier under “Accelerating and Braking Forces” are again used

Fi

Coasting decsertion (avs?)
Deceleraing gravitational force (N)
Mass tobe decelerated (kg)

Time o cost 0 al (3)

F
S = Normal operating bot speed (m/s)
4 = Distance to cout toa (

In the application of these formulas the terms (Fi) and en) need furtner elaboration

“The decelerating gravitational force (Fi) is composed of two elements:

(a) The effective tension (Ta) for the load condition bang considered (ie. conveyor empty or
fully lame for the whole length or perhaps for any one particular section Of the
conveyor and

‘The Friction Losses of the Drive, As the spoed reducar portion of the drive will have
Sani y greater fisio loss than the motor partion te lttar may be neglected for
Simply, It the efficiency of the reduction unit is not known it may be asumed to b
187 or 98% ie, the fiction loses may be assumed 10 be 2.5%). To convert these losses 10
‘nits of free nawıons) calculate the following expression

edn Unit Power Rating (KW) x 1000 x No. of Rega Units x 1% Loss),

Belt Speed x 100 am

Thus the total decelerating gravitational force (Fi is then the sum of (Te) and the value
obtained from Formula 3.37 above, expressed in newtans

47. “The mas to be deceleratd (m) is also composed of two elements

(a) The total mass of the materia! load, the belt and the rotating ier parts forthe condition
Being considere

CNT (308)
a+ IL ted 3.38)

(0) The Equivalent Mass of the Drive System. To calculate this, the inertia (KE), expresse
inkitogram metre squared, 1 substituted in the following expression

(WK?) x (Reduction Ratol? No. of Drives
(Radius of Drive Pulley in metres)?

is) (339)

Values of WK2 forthe Reduction Unis, Motors and Couplings should be obtain from tho

From the above, values for (Fi) and (ml may now be substituted into the origina basic formulae to
‘termine (1) ime taken on (a distance required fr the conveyor to coast to halt

CHECK LIST FOR LARGE CONVEYOR SYSTEMS

Tensions:
al” Use tension diagram — comparo with ratus tensions
Determine fe of acceleratin and braking forces

Pulleys:
Tal Chock diameters at all Locarons.
(8) Crock focewidtn and lateral clearances at sides of pull
{el Uae of loging
(9) Check use of crown on critical pulleys, e. head pulley.

Vertical cures
(a) Determine adi for concave and convex curves.
(b) Chock Upper design against curve required (empty and loaded).
(e), Determine efect of accloating or braking free on curve rolas

Take up
Ta) Movement requires with respect to belt construction and method of joining — inital
position of take-up governed by typeof erie ete
(o) ect of braking and accelerating orcas on amount of weight — posible use of double
take up.
Check method of maintaining alignment of moving pue.
Protection from sole in vertical take 49S,

Spacing, relative 10 loed and tition factors
‘iting for seltalgeing in un dretiona conveyors
Necesty for transition dlrs o he or tall
Necessity for and location of sit ageing dlrs
Necessity for impact dlrs

Determine percentage o! volumetric capacity
Impact consierations.
‘Check chute and skirt boars design

48. Brakes and anti-roll backs:
fal The necessity of these
(bl Coosting or owe run of conveyors operating in sequence; inertia of motor and of reduction
‘raring shoul be lace,

Motors:
Tai. Type required and starting programme,
Ic} Determine efect of Aia, centtugal o eletrea coupling.

Miscellaneous:

2) Spare bat recommendation.

lb) Number and sizeof als for ene o handing ir fr entry to underground workings
Fila splicing and splice lengths

{G) eon oct

de), Safety devices
fi) Side travel limit sites,
Gi) Counterweight mit travel switches
(ie) Plggod chute and ful bin protection,

(6) Consieration of standardisation programme for belting stocks

66. [
d-D
d

73. 7. Design considerations

MULTIPLE SLOPE AND VERTICAL CURVE CONVEYORS.

Conveyors with grade variations, and particularly decline regenerative systems with concave vertical
‘coves require special consideration, In thai design a thotough any 1 necessary, particular y at
point of low tension, The effect of varying lo conditions as well as acceleration and deceleration
met ba considered corel,

Determination of vertical curves
(1) Concave vertical curves
{a} Selection of radius to prevent belt iting off ils
Ai) Sauirrekeage motor, D OL. star
ne 20028 ig
Bx 981% 10%
(i) Sauirrelcage motor, D.O.L. start with traction type coupling or centrifugal catch
*0710201xT,

em va
Ba (7)

(ii) Squire<age motor, D.O.L. start with 000) type fluid coupling or eddy current clutch;
Ship ina motor electrically controlled start

11.3: 18) xT)

8
Bx 9.87 x 10%

R= Radive of curvature Im)
Maximum operating tencion (total belt width] at he point of tangent
intersection (eN)
Belt mass (g/m,
‘The difference and range in these values apply to the motor and starter chars
triste, and should be varies according 10 the type of contol chosen for the
instalation under consideration

n decline regenerative conveyors even with she best of contol, the very minimum
dus ot the foot ofa steep decline sd always be calculated irom the folowing

st oa
R= aaa |

‘Consideration should then be given to closer ie spacing at locations immediately
following such steep declines,

Section of raius to prevent belt edge tension from dropping below zero and causing

possible buckling

The formula to give radis of curvature which wil result in zero edge tension in the

Sind xWxExN
45 (Te, 0)

a im as

Bert width {m
Elosti modulus (KN/m/ply) from Tabie 3 of this tion
Number of pes.

Maximum operating tension at point of tangent intersection (kN/m).
Carrying ier roughing angle
"For Steel Cord belts, N= 1 and E has units of kllonewtons por mete

74. ion is preferable in the bit edges, the value of tat tension shouldbe substitutes
rorminator of the formula. As à general rue, 44 KN i use as the desired minimum

tension. With that minimum tension value the formula wil read

Sing xWxEXN

45 Tey 44)

R im (759)

Other minimum tension valves coud be substituted o suit particular installations

Note: (In calultions to determino the radius of concave curves to provent the belt ing off
the les design tonnage fares should be used

In calculations to determine the racius of concave curves below which negativo edge
tensions (and hence edge bucking) wi! oocur, actual tonnage rates should be used.
Particularly when design tonnage rates are signcarty above she rates which wil
cur in practica

(21. Convex vertical curves

(a) Selection of radius to kogp belt edge tension within acceptable limits

Sing xWxEXN
45 (Ta Teg)

R (oo us

[bl Selection of radio keep tension at centre of belt above zero and thereby prevent possible

The formula to give zero tension in the centre ofthe bel

Sing WA EXN
am 0 sel

“Troughing angie o caryin ice.
Bete ia Im)
Etc modulas (/m/oly} from Table of this section
Number of ple.
Recommended allonable working tension forthe belt reinforcement used, (kN/m)
fom Table 1 of Section 4

= Maximum operating tension at point of tangent intersection (kN/m)

‘or sel cord belts, N= 1 and E has units of klloncwtons per metre.
As a general rule, postive tension should be provided, and 4.4 KN is usually used asthe
desired minimum tension, in which cae the Formula becomes:
Sind xWxExN

90-44)

A » 0

Ai) In cateultions to determine redius of convex curves to keep edge tension within
‘ootptable limits, design tonnage rates shouldbe used

Gi) In calulations to determine the radius of convex carves below which negativa tension
‘when design tonnige rates are significantly above rates which will occur in practice.

The equipment supplier should always check radial force component caused by the belt on the
idles in the Larson ares. If the Cure is calculated by moans of her la) os (B) above, Ihe
‘general result s that method (a) determine the radius in most cases, For ile load imitans,
‘hack rating ete win te dlr suppl

75. (8) Horizontal curvos

In recent years horizontal curves have been used in long centre oran «folowing conveyors as a
means of elminalng transfer points and 80 reducing Costs and increasing eciney. No attempt is
Made here to dela al ho varables involved in des going such curves. exapt lo say that he largest
BOSS radi shoud always be used and ne minimum allowable radius 5300 x bolt within metres.

Irs in the transitan area shouldbe somewhat wider than usual and not les than 38 cinaton onthe
‘Comying sido and 15 incination on the lu. In some cases normal rough les ae also used on the

In action to forward bling ofthe carry ils In the recon of bat raue, is lo helpful tot the ier
Frames to ronde a reverse camber around the curve That's, lating at the begining ofthe curve,
cg shu be prov ed under the end of ha ler ames at he made ofthe curve. The thickness of
[eS pong shoul be progressive rom say Y mm atthe begianing of he curve 10 about 75 mm atthe
tonite of he come, then progressively decreasing lo 1 mm again a1 Ine end ofthe curve, This reverse
Camber effect assists preventing tha bal cimbing te lars towards the entre ofthe curve,

Inside ond of

Pan of typical horizontal curve

TABLE 4
AVERAGE ELASTIC MODULUS “E*

PLAIN WEAVE FABRICS SPECIAL WEAVE FABRICS

ES 0 EN Crows foot weave

PN200 = 220 Zuoonumpy | PNITS—350 | w00wUm |

Preso momia | Pwoea 00 | zoom,

En sony | rios] coto

Pro = 360 ET Double woave

000 um» [ens m,

76. ‘TERMINAL TROUGHING IDLER ARRANGEMENTS

‘ommended that the fist or last standard toughing idler over which the belt passes under
nigh tension a it leaves or approaches a terminal pulley, mourted on a level which will average
the belt ace stress

(he terminal pulley is set so that a tangent line from is rim is above the top ofthe centre roll
by an amount equal 10 hal! the height of the {roughing Idler. the belt edge stresses are minimised
and the optimum level of Ih as standard roughing ile Is obtained. (See Fi, 2)

Mere the belt is not operating at high tension and very large lumps re card, the best postion
for the terminal plley with respect tothe lost standard troughing flr 6 to Mave the play rim so
9 that the tangent line from Mt willbe tangent 10 the top of the centre rol. (Soo Fig. 3), Ths
position increases belt edge stes Dut lens the chances 0 belt injury due to the impinging effect
ON large lumps against the pull

{At til end oading points with tow to moderate bet tensions. this position is also used, and ensures
that ın bit cannot if at the loading point and interfere with the siting

‘Always locate first the standard roughing idler prior to the loading chute, and incorporate

Intermediate ‘roughing ange her sets Between the terminal pulleys and the steep angle oughing
ide run

TRANSITIONS

‘Suggested minimum belt tr

TRANSITION DISTANCES FOR HEAD PULLEYS — generally high to moderate tension

ee tno ow | van

77. TABLE
TRANSITION DISTANCES FOR TAIL END LOADING POINTS —
generally low to moderate tension
(alo tow tension head drive pulleys and large product lume)

T Auer

‘TAKE-UP ARRANGEMENTS

Gravity takeups — wleanivad spices. The take up travel requirements shown in Table à are
applicable 10 belts operating at between 76% ard 100% of the allowable working tencion, and with
Starting tension limited 10 150% of alanabe working tension

For belts operating at between 50% and 75% of the allowable working tension, the travel distances
snow in Table 4 can be raducad Oy 29%, wns the travel distance for best operating at les than
50% ofthe slowableteasion canbe recuced by 50%

Belts operating at high temperatures or under very wet conditions may require take up trav
distances up 10 50% longer than shown in Table 4

For long to very long conte bots using low elongation Kuralon/Nylon and Polyester/Nyion carcass
constructions, take travel can be progressive) reduced! as necessary to pul avalable space, dawn
10 as lite 25 0.25-0.5% of cen to centre length of conveyor (contact Apex Belting fr recomm
endations). Provided accelerating and braking forces are Kept to reasonable limit, bi stretch afte
‘Some initial elongation Becomes minimal

Screw takeups — vulcnisod splices and all fxtened joints. Travels can generally be reduced 10
approximately halt those shown In Table 4

However, for takeups with vuteanised splices, always provide sufficient travel to permit re spi o
rebel i required without having to insert a new pice

78. GRAVITY TAKE-UP TRAVEL
10) FagRic BELTING

Initial location of tokeups. To etiminate all belt sg on the installation of a new belt, ul! the bit
tends together against the installed counterweight. Take-ups can be initially located as follows

(1) For Nyloa/Nyton area bits, har aginst he inner stop,

(2) For al other synthetic fabric carcase construction, from hard agains the Inner stop to 20%
fof total travel rom inner stop,

(8) With Conon/Cotton carcasses, from 20% up to 50% travel from inner stop for operating

nitions ranging from dry to wel

(8) STEEL CORD BELTING

The high modulus characteristic ofthe soo wire ropes used in he construction of steal cord conveyor
betting resul in exvernely low elongation. This high strength, low stretch characteristic gives tel
ord belting tremandows adventage ove fabric belts on Long single light systems,

With proper tensioning of the beit during the closing slice operation, takeup as low as 0.25% of
Comeyor centre distance is posible. Where the bal s designed 10 operate at tersios up to 100%
tated tension a take up tra of 058 1 notnally recommend.

82. Beltlengih Im)

Belt thickness rm)

95. me J BONDING RUDUER

BOTTOM pulley) COVER