Conveyor Belt Design Manual INDEX INTRODUCTION Dunlop Africa Industrial Products is the leading designer and manufacturer of industrial rubber products in South Africa. In fact our belting systems can be seen on some highly productive plants all around the globe. What more can you expect, when you consider that our belts have been designed and fabricated by some of the best engineers in the industry and from only the finest raw materials. Using the most current technology, many components have taken years of refinement to attain such technological precision. And every belt is guaranteed to provide maximum performance and maximum life. DUNLOP Belting Print Introduction Dunlop Conveyor Belting Range Belting Characteristics Additional Features SABS Specifications Conveyor Belt Design Step By Step Example of Belt Tension Calculation Table 1: Table of Symbols Table 2: Material Characteristics Table 2(a): Typical Flowability Determination of Conveyor Capacities Table 3: Capacities of Troughed Belt Conveyors Table 4: Recommended Maximum Belt Speed for Normal Use Table 5: Recommended Idler Spacing Table 6: Friction Factors Table 7: Sag Factor Table 7(a): Recommended Percentage Sag Table 8: Estimated Belt Mass Table 9: Typical Mass of Rotating Parts of Idlers Table 10: Mass of Moving Parts Table 11: Drive Factor Conveyor Belt Selection Table 12: Maximum Recommended Operating Tensions Table 13: Recommended Minimum Pulley Diameters Table 14: Load Support Table 15: Maximum Number of Plies Recommended for Correct Empty Belt Troughing Table 16: Carcass Thickness Table 17: Mass of Belt Carcass Table 18: Mass of Covers per mm of Thickness Rate of Wear Graph Table 19: Minimum Belt Top Cover Gauge Guide Table 20: Belt Modulus Tabulator Calculations Sheet 1: Empty Belt Sheet 2: Fully Loaded Belt Sheet 3: Non-Declines Loaded Sheet 4: Declines Loaded Tension Tabulator Vertical Curves Maximum Incline Angle Graph for Estimating Belt Length/Rolled Belt Diameter Useful Data Conversion Factors Conveyor Belting Design Manual Page 1 of 33 Dunlop Conveyor Belt Design Manual 24/05/2004 http://www.ckit.co.za/Secure/Conveyor/Troughed/belt_tension/Dunlop/Belting%20B...
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Conveyor Belt Design Manual
INDEX
INTRODUCTION
Dunlop Africa Industrial Products is the leading designer and manufacturer of industrial rubber products in South Africa. In fact our belting
systems can be seen on some highly productive plants all around the globe.
What more can you expect, when you consider that our belts have been designed and fabricated by some of the best engineers in the
industry and from only the finest raw materials.
Using the most current technology, many components have taken years of refinement to attain such technological precision. And every belt
is guaranteed to provide maximum performance and maximum life.
DUNLOP BeltingPrint
Introduction
Dunlop Conveyor Belting Range
Belting Characteristics
Additional Features
SABS Specifications
Conveyor Belt Design
Step By Step Example of Belt Tension Calculation
Table 1: Table of Symbols
Table 2: Material Characteristics
Table 2(a): Typical Flowability
Determination of Conveyor Capacities
Table 3: Capacities of Troughed Belt Conveyors
Table 4: Recommended Maximum Belt Speed for Normal Use
Table 5: Recommended Idler Spacing
Table 6: Friction Factors
Table 7: Sag Factor
Table 7(a): Recommended Percentage Sag
Table 8: Estimated Belt Mass
Table 9: Typical Mass of Rotating Parts of Idlers
Table 10: Mass of Moving Parts
Table 11: Drive Factor
Conveyor Belt Selection
Table 12: Maximum Recommended Operating Tensions
Table 13: Recommended Minimum Pulley Diameters
Table 14: Load Support
Table 15: Maximum Number of Plies Recommended for Correct Empty Belt Troughing
Table 16: Carcass Thickness
Table 17: Mass of Belt Carcass
Table 18: Mass of Covers per mm of Thickness
Rate of Wear Graph
Table 19: Minimum Belt Top Cover Gauge Guide
Table 20: Belt Modulus
Tabulator Calculations
Sheet 1: Empty Belt
Sheet 2: Fully Loaded Belt
Sheet 3: Non-Declines Loaded
Sheet 4: Declines Loaded
Tension Tabulator
Vertical Curves
Maximum Incline Angle
Graph for Estimating Belt Length/Rolled Belt Diameter
And with some 750 000 various specifications available, you can expect to find the right belt for your requirements no matter how
specialised.
This manual contains all the elements, formulae and tables you need to specify the exact belt. It has been compiled for your benefit, as a quick reference book for easy selection. If however you have an application not covered in the following pages, please contact Dunlop Africa
Industrial Products. A team of experienced and helpful engineers will be pleased to assist you.
Our range of excellent products, competitive pricing and impeccable service, has earned Dunlop Africa Industrial Products the reputation of
being the market's first choice.
DUNLOP CONVEYOR BELTING RANGE
Dunlop Africa Industrial Products manufactures the most comprehensive range of conveyor belting in South Africa.
Multi-ply rubber covered conveyor belting
XT textile reinforced conveyor belting with grade N covers
XT textile reinforced conveyor belting with grade M cut resistant covers
Phoenix heat resistant belting
Super Phoenix heat resistant belting
Delta Hete heat resistant belting
Fire resistant belting
Rufftop belting
Riffled concentrator belting
Grey food belting
Salmon pink food belting
Endless belts
Woodmaster
Oil resistant belting
Solid woven PVC belting
Standard solid woven PVC belting
Nitrile covered PVC belting
Steelcord belting
Fire resistant steelcord belting
Steelcord reinforced conveyor belting with cut resistant type M covers
Steelcord reinforced conveyor belting with type N covers
Steelcord reinforced conveyor belting with "Ripstop" protection
Steelcord reinforced conveyor belting with rip detection loops
XT Rubber Conveyor Belting (conforms to SABS 1173-1977)
From the early days of cotton duck plies, progress has been made in the manufacture of all-synthetic plies offering many
advantages.
The range of strengths has been greatly increased, with improvements in the flexible structure. The modern multi-ply belt is
manufactured with a synthetic fibre carcass in a wide slab, then slit to width as required for individual orders.
A wide range of belt specifications is available with current belt constructions having versatile applications.
The standard XT belting (Grade N) incorporates covers suitable for the handling of most abrasive materials, having a blend of
natural and synthetic rubber.
Cut resistant XT Rubber Belting
Grade M Belts have covers with high natural rubber content recommended for belts operating under extremely arduous conditions
where cutting and gouging of covers occurs.
Phoenix Heat Resistant Belting
Phoenix Heat Resistant belting covers are styrene butadiene based and are recommended for belts handling materials with
temperatures up to 1200C.
Super Phoenix Heat Resistant Belting
Super Phoenix Heat Resistant belts have chlorobutyl covers and are recommended for belts handling materials with temperatures
of up to 1700C.
Delta Hete Heat Resistant Belting
Delta Hete heat resistant belting with EPDM synthetic rubber covers in a formulation developed to allow conveying materials of
temperatures up to 2000C.
Fire Resistant Belting (conforms to SABS 971-1980)
Fire Resistant XT belting is manufactured with covers containing neoprene and multi-ply carcass constructions to meet the
stringent standards for safety in all underground mining industries and is therefore particularly suited to shaft applications.
Woodmaster
This belt has been especially developed for the Timber Industry. The rubber has been compounded to provide resistance to oil and
resin, and is non-staining.
Rufftop Belting
This is a range of rough top package belting, of two or three ply all-synthetic carcass belts with deep impression rubber covers. The range is ideal for the packaging and warehousing industries and baggage handling installations such as airports and railway
stations etc.
Riffled Concentrator Belts
Riffled conveyor belting has raised edges, is 1 500 mm wide and available in endless form. These belts are uniquely applied at
gold mine concentrators.
Food Quality Belting
Food quality belting is ideal where foodstuffs come into direct contact with the belt surface. This range of belting is manufactured from non-toxic materials and is resistant to oils, fats and staining, and meets the strict hygiene requirements laid down by the
food processing industry. The two types available are Grey food belting and Salmon pink belting
The complete XT range can be made available as factory spliced endless belts. These belts are recommended for short conveyor
installations. (Suitable for lengths up to 50 in.)
Flinger Belts
Flinger Belts are fitted to flinger conveyors, the primary function of which is to disperse the discharging material over a wide area, thus minimising heap build-up below the main conveyor. The flinging effect is achieved by running the flinger belt at a high speed
in a U configuration. Flinger belts are built and cured on a drum to eliminate a spliced join.
Solid Woven (PVC) Belting (conforms to SABS 971-1980)
Commonly known as 'Vinyplast' solid woven PVC. The construction has inherently high fastener holding qualities. The belting is constructed of polyester and nylon with a cotton armouring, is impregnated with PVC and has PVC covers. These belts have been
specially developed to resist impact, tear, rot and abrasion and to meet the most stringent flame-resistant standards.
Nitrile Covered (PVC) Belting
The nitrile cover on solid woven PVC belts is specially designed to meet the SABS specifications for use in mines, where a fire
hazard exists. In general the nitrile cover has good flame-retardant properties and oil, abrasion and heat resistance.
Steelcord Belting (conforms to SABS 1366-1982)
Steelcord conveyor belting is designed for very long hauls where textile reinforcement would either not achieve the requisite strength or would have too high an elongation at reference load. Resistance to severe shock and exceptional tensile loading is achieved by the wire reinforcement encased between thick top and bottom covers of the highest quality rubber. These belts are
designed to conform to or exceed the requirements of stringent standards and offer a long belt life.
Fire Resistant Steelcord Belting (Conforms to SABS 1366. 1982 type F).
Steelcord belting of fire-resistant quality is made with specially compounded rubbers which render it self extinguishing. Fire-resistant steelcord belting offers great advantages in maintenance-free operation and long belt life for conveyors situated in fiery
mines.
Oil Resistant Belting
Oil resistant belting provides easily cleanable covers of either nitrile or neoprene on all-synthetic fabric plies. Choice of covers gives maximum resistance to mineral and vegetable oils thus permitting the user to convey a wide variety of materials containing
mineral and vegetable oils.
ADDITIONAL FEATURES
1. Rip Protector
As an additional feature rip protection can be incorporated into the belt by means of arranging strong nylon fibres transversely or by inclusion of electronic loops. The textile rip protection can be built into the belt in 2-metre lengths at regular intervals or over
the full length of the belt.
2. Shuron Breaker Ply (XT belting)
For applications where the lump size of the material carried is large and where adverse loading conditions exist, an open weave
breaker ply can be incorporated below the top cover as an extra protection for the carcass.
3. Chevron Breaker (XT belting)
This incorporates steel tyre cord in a 'V shape, as a rip protection, at intervals over the belt length. Particularly recommended for
XT belting where arduous conditions are experienced i.e. slag transportation.
4. Belt Edges
Many conveyor belts track off at some stage of their lives, causing edge damage to a greater or lesser extent. Belts can be supplied with either slit or moulded edges.
Slit edges: All-synthetic constructed carcasses have good resistance to edge chafing, due to modern fibre construction In addition there is minimal penetration of moisture to the carcass and therefore no problem with carrying out hot vulcanised splices or repairs.
The above specifications cover the requirements of the various conveyor belts and are classified according to the minimum full thickness
breaking strength of the finished belting in kilonewtons per metre width.
Further information regarding SABS specifications will be supplied on request.
CONVEYOR BELT DESIGN
Introduction
A conveyor belt comprises two main components:
1. Reinforcement or a carcass which provides the tensile strength of the belt, imparts rigidity for load support and provides a means
of joining the belt. 2. An elastometric cover which protects the carcass against damage from the material being conveyed and provides a satisfactory
surface for transmitting the drive power to the carcass.
In selecting the most suitable belt for a particular application, several factors have to be considered:
1. The tensile strength of the belt carcass must be adequate to transmit the power required in conveying the material over the
distance involved. 2. The belt carcass selected must have the characteristics necessary to:
a. provide load support for the duty. b. conform to the contour of the troughing idlers when empty, and c. flex satisfactorily around the pulleys used on the conveyor installation.
3. The quality and gauge of cover material must be suitable to withstand the physical and chemical effects of the material conveyed.
Belt Tensions
In order to calculate the maximum belt tension and hence the strength of belt that is required, it is first necessary to calculate the effective tension. This is the force required to move the conveyor and the load it is conveying at constant speed. Since the calculation of effective tension is based on a constant speed conveyor, the forces required to move the conveyor and material are only those to overcome frictional
resistance and gravitational force.
Mass of Moving Parts
For the sake of simplicity the conveyor is considered to be made up of interconnected unit length components all of equal mass. The mass of each of these units is called the mass of the moving parts and is calculated by adding the total mass of the belting, the rotating mass of all the carrying and return idlers and the rotating mass of all pulleys. This total is divided by the horizontal length of the conveyor to get the mean mass of all the components. At the outset the belt idlers and pulleys have not been selected and hence no mass for these components
can be determined. Therefore the mass of the moving parts is selected from the tabulated values to be found in Table 10.
Mass of the load per unit length
As is the case with the components the load that is conveyed is considered to be evenly distributed along the length of the conveyor. Given
the peak capacity in ton per hour the mass of the load per unit length is given by:
The effective tension is made up of 4 components
The tension to move the empty belt Tx
The tension to move the load horizontally Ty The tension to raise or lower the load Tz The tension to overcome the resistance of accessories Tu
The effective tension is the sum of these four components
Te = Tx + Ty + Tz +Tu
Tx = 9,8G x fx x Lc
Tz = 9,8Q x H
Various conveyor accessories that add resistance to belt movement are standard on most conveyors. The most common are skirtboards at
the loading point and belt scrapers. Other accessories include movable trippers and belt plows.
Tension required to overcome the resistance of skirtboards Tus
Tension to overcome the resistance of scrapers
Tuc = A x ρ x fc
In the case of a belt plow the additional tension required to overcome the resistance of each plow is
Tup = 1,5W
Moving trippers require additional pulleys in the system and therefore add tension. If the mass of the additional pulleys has been included in the mass of moving parts then no additional tension is added. However, if a separate calculation of the tension to overcome the resistance
of the additional pulleys is required this can be determined for each additional pulley as follows
Corrected length Lc
Short conveyors require relatively more force to overcome frictional resistance than longer conveyors and therefore an adjustment is made to the length of the conveyor used in determining the effective tension. The adjusted length is always greater than the actual horizontal
length.
LC = L + 70
The length correction factor is
All conveyors require an additional tension in the belt to enable the drive pulley to transmit the effective tension into the belt without
slipping. This tension, termed the slack side tension T2, is induced by the take-up system. In the case of a simple horizontal conveyor the
maximum belt tension T1 is the sum of the effective tension Te and the slack side tension T2
ie: T1 = Te + T2
T1 is the tight side tension and 12 is the slack side tension
For a more complex conveyor profile that is inclined, additional tensions are induced due to the mass of the belt on the slope. This tension is
termed the slope tension 'h and increases the total tension.
The slack side tension is determined by consideration of two conditions that must be met in any conveyor. The first condition is that there must be sufficient tension on the slack side to prevent belt slip on the drive. The second condition is that there must be sufficient tension to
prevent excessive sag between the carrying idlers.
Minimum tension to prevent slip Tm
At the point of slipping the relationship between T1 and T2 is
Since T1 = Te + T2
is called the drive factor k. and the value of T2 that will just prevent slip is referred to as the minimum to prevent slip Tm and therefore
Tm = k x Te
Minimum tension to limit belt sag Ts
The tension required to limit sag is dependent on the combined mass of belt and load, the spacing of the carry idlers and the amount of sag
that is permissable.
Ts = 9,8Sf x (B + Q) x ld
The value of the slack side tension must ensure that both conditions are met and therefore T2 must be the larger of Tm or Ts.
Slope tension Th
The slope tension is the product of the belt weight and the vertical lift and has its maximum value at the highest point of the conveyor.
Th = 9,8B x H
Unit tension T
The maximum belt tension T1 has as its reference width the full width of the belt. Usually this is converted to the tension per unit of belt
width as this is the reference dimension for belt strengths.
Absorbed power
The amount of power required by the conveyor is by definition of power equal to the product of the force applied and the speed at which the
conveyor belt travels. The force applied is the effective tension and hence the power required at the shaft of the drive pulley/s is
P = Te x S
STEP BY STEP EXAMPLE OF BELT TENSION CALCULATION
As an example of the application of the formulae the belt tensions for the following conveyor will be determined:
2. Look up the value of the mass of moving parts in Table 10. From the idler roll diameter and the nature of the material conveyed the application is considered as medium duty. For a 900 mm wide belt the mass of moving parts from Table 10 is 55 kg/m
3. Calculate the corrected length and the length correction factor.
LC = L + 70
= 250 + 70
= 320 m
C =LC
L
=320
250
= 1,28
4. Tension to move the empty belt.
TX = 9,8G x fX x LC
= 9,8 x 55 x 0,022 x 320
= 3794 N
5. Tension to move the load horizontally.
TX = 9,8Q x fY x LC
= 9,8 x 79,4 x 0,027 x 320
= 6723 N
6. Tension to lift the load.
TZ = 9,8Q x H
= 9,8 x 79,4 x 20
= 15562 N
7. No accessories are present and therefore the tension to overcome the resistance of accessories is zero.
8. Effective tension.
Te = TX + TY + TZ + TU
= 3794 + 6723 + 15562 + 0
= 26079 N
9. The absorbed power
P = Te x S
= 26079 x 1,4
= 36511W
10. The slack side tension. Slack side tension to prevent slip. The drive factor for 210 degree wrap and lagged pulley with a gravity take-up, as given in Table 11, is 0,38.
Slack side tension to limit sag to 2%. The sag factor for 2% sag is 6,3 and the estimated belt mass for a medium load and 900 mm belt width, as given in Table 8, is 11,1kg/m.
at the load point of the conveyor. To achieve optimum load area the loading chutes must be designed to ensure the most advantageous
initial load shape and this can only be achieved if:
1. The load is placed centrally on the belt. 2. The material is delivered in the direction of belt travel and at a speed approaching that of the belt. 3. The angle of incline at the load area must be less than 1 ~O,
To ensure that the optimum load shape is maintained along the entire belt length:
1. The idler pitch should be such as to limit sag to acceptable levels. 2. The belt must be trained properly. 3. The lump size in relation to belt width must be within the recommended limits. 4. The belt must give adequate support to the load.
Under ideal conditions the cross sectional load area is:
The values given in the table are estimated values for use in the calculation of maximum belt operating tension necessary to make the correct belt selection. When the belt specification has been determined, the mass should be checked more accurately from Table 17. If the actual mass of the specification differs considerably from the approximate value obtained from the table the tension calculation should be
rechecked using the more accurate belt mass.
TABLE 9 TYPICAL MASS OF ROTATING PARTS OF IDLERS (kg/m)
TABLE 10 MASS OF MOVING PARTS G
Belt Width (mm)
Operating Conditions
Light Duty (kg/m)
Medium Duty (kg/m)
Heavy Duty (kg/m)
500 4,1 6,2 10,3
600 5,0 7,4 12,3
750 6,2 9,3 15,5
900 7,4 11,1 18,5
1050 8,6 13,0 21,6
1200 9,8 14,8 24,7
1350 11,0 16,7 27,8
1500 12,3 18,6 30,9
1650 13,5 20,5 33,9
1800 14,7 22,3 37,0
2100 17,2 26,0 43,3
2200 18,0 27,3 45,3
Belt Width
3 Roll Carry Idlers Return Idlers 3 Roll Impact Idlers
1. When calculating the driving tension required for dual drive units, the drive factor selected must correspond to the total angle of driving wrap.
2. The drive factors quoted for gravity or automatic take-up systems are minimum values based on the relationship between angle of wrap and coefficient of friction between belt and drum at the point of slip. In the case of screw take-up units, an adjustment has been made to the drive factor to allow for the extra tension which may be induced in the belt either:
a. to compensate for the effect of belt elongation when the material is loaded.
b. due to the difficulty in measuring the amount of tension applied.
3. In those cases where an electrically or hydraulically loaded winch type take-up is used, where the induced tension can be preset
and controlled, the drive factor should be selected to correspond with a gravity take-up system.
CONVEYOR BELT SELECTION
Belt carcass selection criteria
In selecting the optimum belt construction for a given application it is necessary to consider the following:
Tensile strength
The belt class required is that which has an operating tension greater than or equal to the calculated maximum unit tension T. (Table 12).
Load support Choose the lowest class which meets the tensile strength requirement. Looking at Table 14, determine which load category best describes the load being conveyed i.e. A, B, C, D or E category load. The value obtained at the intersection of the belt specification row and the load
category column gives the maximum width at which that belt specification can be used.
Number of plies for troughability The maximum number of plies allowable, in order to ensure that the empty belt will conform to the contour of the troughing idlers, must be checked referring to Table 15. For a particular belt class the value shown at the intersection of the belt width column and troughing angle
row, is the maximum number of plies that should be used.
Minimum pulley diameters If the size of the pulleys is already determined, the belt construction provisionally selected from the previous considerations can be checked against the relevant pulley diameters for suitability. For a new installation, the pulley diameters should be equal to or larger than those given in Table 13 (It should be noted that, in this context, the diameters quoted refer to the minimum pulleys around which the particular belt construction will flex satisfactorily. The conveyor designer should also take into account the gearbox ratio and required belt speed when
selecting the drive pulley diameter.)
Gauge of covers required The correct gauge of cover necessary to give protection to the belt carcass from material impact and wear must be determined by
consideration of the size and density of the material to be handled. (Table 19).
1. Calculating vertical curves, or 2. Determining belt tension for conveyors of undulating profile.
It is necessary to calculate the belt tensions at various points on the conveyor. Calculating the tension at any point along the conveyor.
The tabulation method described below is a convenient means of calculating the tensions at any point on the conveyor.
Blank copies of the "Conveyor Tabulation Sheets" are available from Dunlop Africa Industrial Products.
The following method is used to determine the tension at any point along the conveyor:
1. Calculate the length correction factor. 2. Look up the mass of moving parts in Table 10. 3. Calculate the mass of the load from the design capacity and the belt speed. 4. Calculate the maximum effective tension under constant speed operation. This will always occur when all the non-declined
sections of the conveyor are fully loaded and the declined sections empty. 5. Determine the minimum value for the slack side tension under maximum load condition. 6. Commencing from immediately behind the drive, label each pulley, intersection point and loading section. Start and end point of
each of the load lengths should also be labelled. 7. Determine the effective tension required to overcome the frictional and gravitational resistances for each of the segments of the
conveyor by using formulae on page 4. The value of 12, determined in 5 above, is used to calculate the
effective tension to overcome pulley friction. 8. The effective tension at any point on the conveyor is the sum of the effective tensions of all preceeding segments. The total
effective tension for the conveyor is the sum of the effective tensions for all segments. 9. The tension at any point 'x' on the conveyor is made up of the effective tension at point 'x' plus the slope tension at point 'x'.
Superimposed on this is the tension applied by the take-up system. The tension applied by the take-up is given by the worst case T2 value i.e. the value of T2 which
a. prevents slip at the highest Te value and, b. limits sag between carry idlers.
It may be found that the value of T2 obtained when the maximum effective tension has been calculated is different to that used in the
calculations. If this is the case the new T2 value is used to calculate tensions at each point.
Steps 7, 8 and 9 should be repeated for four load cases viz empty, fully loaded, non-declined sections loaded and declined sections loaded.