Arpm manual-2-pdf

CONVEYOR AND
ELEVATOR BELT
HANDBOOK
7321 Shadeland Station Way, Suite 285, Indianapolis, IN 46256
Phone: 317-863-4072 Web: www.arpminc.org
© 2011 by the Association for Rubber Products Manufacturers, Inc.
Published in the United States of America
RMA First Edition 1973
RMA Second Edition 1980
RMA Third Edition 1989
ARPM Fourth Edition 2011
ARPM: IP-1
Revised: 2011 • Replaces: RMA 1989 Edition

INTRODUCTION
PREFACE
Conveyor and elevator belts are made to precise specifications and standards to service many useful functions. A better understanding
of the complexities involved in manufacturing belting and the standards that are applied to it will be helpful in selecting the proper belt
for the intended use and in obtaining good service after installation.
Belting covered in this Handbook includes conveyor belting, used to transport bulk or packaged, boxed and bagged materials, and
bucket elevator belting. The belting may be made of natural and synthetic rubbers as well as plastics, such as vinyl, with carcasses of
textile fabrics, which are woven, nonwoven, solid woven, or stitched; fabric cords; or of steel cables.
This handbook is intended for the general guidance and reference of persons interested in the selection and use of conveyor and
elevator belting, but readers are urged to consult individual manufacturers for specific information and recommendations.
ACKNOWLEDGMENT
The Association for Rubber Products Manufacturers is the national trade association of the non-tire rubber manufacturing
industry in the United States. ARPM represents manufacturers of finished rubber products (excluding tires), and their related
suppliers. This publication is provided as a public service, and reference for users of conveyor belt products by U.S.
manufacturers of conveyor belt products, including:
Airboss Compounding Rubber (NC)
Fenner Dunlop Americas (Pittsburgh, PA)
Garlock Rubber Technologies (Paragould, AR)
Price Rubber Corp. (Montgomery, AL)
Veyance Technologies Inc. (Fairlawn, OH)
© 2011 by Association for Rubber Products Manufacturers, Inc.
7321 Shadeland Station Way, Suite 285
Indianapolis, IN 46256
317-863-4072
www.arpminc.org
Published in the United States of America
RMA First Edition 1973
RMA Second Edition 1980
RMA Third Edition 1989
ARPM Fourth Edition 2011
IP:1 2011 Conveyor and Elevator Belt Handbook 2
Association for Rubber Products Manufacturers

TABLE OF CONTENTS
Page
PREFACE..................................................................................................................................................................................................2
ACKNOWLEDGMENT...........................................................................................................................................................................2
CHAPTER 1 - MATERIALS...................................................................................................................................................................4
CHAPTER 2 - ELASTOMER CHARACTERISTICS........................................................................................................................11
CHAPTER 3 - TEXTILE BELT TYPES AND MANUFACTURING METHODS..........................................................................18
CHAPTER 4 - TEXTILE BELT CHARACTERISTICS AND BELT RATINGS.............................................................................23
CHAPTER 5 - TEXTILE BELT TOLERANCES................................................................................................................................35
CHAPTER 6 - TEXTILE BELT TEST METHODS............................................................................................................................36
CHAPTER 7 - SPLICING CONVEYOR AND ELEVATOR BELTS................................................................................................40
CHAPTER 8 - STEEL CORD BELT TYPES AND MANUFACTURING METHODS..................................................................51
CHAPTER 9 - STEEL CORD BELT CHARACTERISTICS & BELT RATINGS..........................................................................53
CHAPTER 10 - STEEL CORD BELT TOLERANCES......................................................................................................................56
CHAPTER 11 - STEEL CORD BELT TEST METHODS..................................................................................................................58
CHAPTER 12 PART A - SPLICING FABRIC CORD CONVEYOR BELTS..................................................................................61
CHAPTER 12 PART B - SPLICING STEEL CORD CONVEYOR BELTS.....................................................................................75
CHAPTER 13 - BELT MONITORING.................................................................................................................................................91
CHAPTER 14 - OPERATION AND MAINTENANCE......................................................................................................................96
CHAPTER 15 - STORAGE OF BELTING........................................................................................................................................112
CHAPTER 16 - GLOSSARY OF CONVEYOR BELTING TERMS...............................................................................................113
CHAPTER 17 - USEFUL TABLES.....................................................................................................................................................130
APPENDIX............................................................................................................................................................................................136

CHAPTER 1 MATERIALS
INTRODUCTION
The purpose of this chapter is to present general descriptions of the construction elements of conveyor belts and the materials which
are presently available to produce belts for the various materials conveyed with suitable strength for the tensions and other conditions
encountered in service. Conveyor belts are sometimes classified as Light and Heavy Weight belts.
Light Weight = RMBT* < 160 PIW
Heavy Weight = RMBT > 160 PIW
*RMBT = Rated Maximum Belt Tension, in pounds per inch width (PIW)
Light weight belting generally is used in very diverse applications such as food and tobacco products, agricultural products, wood
products, baggage and packaging handling, metal stampings, and materials handling in the textile, printing, paper processing, postal,
and electronics industries. Heavy weight belting generally conveys heavy and/or coarse abrasive materials like mineral ore, rock, sand,
gravel, coal, and cement.
In general, most conveyor belts consist of three elements: a top cover or conveying surface; a carcass; and a bottom cover, or pulley
surface. In light weight belting there is a great diversity among the top cover or conveying surfaces used such as smooth or rough
covers and raised patterns; whereas heavy weight belting often has smooth top covers. Custom fabrications with light weight belting
are also more common, including attaching of cleats or V guides or hole punching, for example.
The elements may also be grouped under several general classifications such as: elastomers; fabrics (woven or non-woven); spun;
filament, or monofilament yarn or cord; and steel cords.
A rubber or plastic elastomer is a compounded material that returns rapidly to approximately its initial dimensions and shape after
substantial deformation by a weak stress less than the yield point.
A fiber is a unit of matter having a length at least 100 times its diameter and which can be spun into a yarn.
A steel cord, when used as the tension member, is usually multiple strands of steel wire twisted together.
Yarn is a generic term for continuous strands of textile fibers or filaments.
A fabric is a planar textile structure produced by interlacing yarns, fibers, or filaments. A fabric may be composed of yarns of cotton,
glass, nylon, polyester, steel or other materials. A fabric may be made from one material or a combination of materials.
RUBBER/PLASTIC ELASTOMERS
Polymers are mixed with various chemicals to obtain reinforcement and develop the physical properties of the resulting elastomer
necessary for meeting service conditions. Since it is not the purpose for this Handbook to discuss compounding ingredients or methods
of compounding, discussion of polymers will be restricted to the general properties of the basic polymers.
A wide choice of polymers is available. They can also be blended together to obtain many combinations with intermediate properties.
Elastomeric compounds are used for the top and bottom covers or surfaces of conveyor belting and for bonding together components
of the belt carcass. The elastomeric covering on belts is there to provide protection for the carcass and/or provide a specific property.
The coverings are applied by several processes, depending on the material (rubber vs. thermoplastic) or thickness of the covering.
It is possible to classify elastomers to some extent by the basic polymer used. They are listed in Table 1-1 with a brief description of
their general properties.

Table 1-1.
Rubber/Plastic Polymers Used in Belting
Common Name
ASTM
Designation
D 1418-10
Composition General Properties
Acrylic ABR Acrylate-butadiene
Excellent for high temperature oil and air. Poor
water resistance. Poor cold flow resistance.
Brominated Butyl BIIR
Bromo-isobutene-
isoprene
Similar properties as Butyl except that it can be more
readily adhered to or used in combination with
other polymers.
Butyl IIR Isobutene- isoprene
Excellent resistance to heat. Very good resistance
toozone and aging. Good resistance to abrasion.
Chlorinated Butyl CIIR
Chloro-isobutene-
isoprene
Similar properties BIIR.
EPDM EPDM
Ethylene-propylene-
diene terpolymer
Excellent resistance to heat, ozone, and aging. Very
good resistance to abrasion.
Ethylene Propylene EPR Ethylene-propylene Same properties as EPDM.
Hydrin* CO
Polychloromethyl-
oxirane
Excellent oil and ozone resistance. Good flame
resistance and low permeability to gases. Fair
low-temperature properties.
Hydrin* ECO
Ethylene oxide and-
chloromethyl-oxriane
Excellent oil and ozone resistance. Fair flame resistance
and low permeability to gases. Good lowtemperature
properties.
Hypalon* CSM
Chloro-sulfonyl-poly-
ethylene
Excellent ozone, weathering, and acid resistance.
Good abrasion and heat resistance. Good oilresistance.
Hytrel* PET
Polyethylene
Terephthalate
Thermoplastic with excellent abrasion and cutresistance.
Good chemical resistance. Limited temperature range.
Natural Rubber NR Rubber, Natural
Excellent resistance to cutting, gouging, and abrasion.
Good elasticity and resiliency. Good low temperature
flexibility.
Neoprene* CR Chloroprene
Good ozone and sun-checking resistance.
Goodresistance to petroleum-based oils and to abrasion.
Also good flame resistance.
Nitrile NBR Nitrile-butadiene
Excellent resistance to vegetable, animal and petroleum
oils.
Polybutadiene BR Butadiene
A general purpose synthetic rubber. Generally used
inblends with natural or styrene-butadiene rubber.
Provides excellent abrasion resistance and
high resiliency. Excellent low temperature flexibility.
Polyisoprene IR Isoprene, synthetic Same properties as natural rubber.
SBR SBR Styrene-butadiene
Excellent abrasion resistance and good resistance
to cutting, gouging, and tearing.
Silicone VMQ Modifiedpolysiloxanes
Excellent high and low temperature resistance. Can be
made to give fair oil resistance. Poor physical properties
at room temperatures.

Table 1-1. (continued)
Rubber/Plastic Polymers Used in Belting
TEXTILES
Many types of textiles are used in conveyor and elevator belting. Their use is based on their physical properties, such as strength,
elongation, dynamic fatigue resistance, aging resistance, mildew resistance, heat resistance, and other special properties depending on
service requirements. For special applications, consult the manufacturer.
Yarns used for belt textile reinforcement are classified as either spun or filament depending on whether the base fiber is in staple (3/4
- 2 1/2 in long single fiber) or endless filament form.
A spun yarn is made by twisting relatively short lengths of staple fiber together to form a continuous yarn, called a single’s yarn.
When two or more of these single’s yarns are twisted together, the result is a plied yarn. When two a more plied yarns are twisted
together, the result is cable cord. The tensile strength, elongation, and thickness of a yarn of any fiber type can be changed by varying
twist, size and number of single’s yarns included. Spun yarns may be made from natural or synthetic fibers.
Spun yarn sizes are designated by the number of “hanks” of yarn it takes to weigh one pound. In the cotton system, one hank is 840
yards (770 m) long. One pound of a 12’s cotton yarn is:
12 x 840 yd (770 m) = 10,080 yd (9217 m) long
A filament yarn is produced by extruding synthetic materials through an orifice in a continuous process. A single filament is called a
monofilament. A number of small “filaments” are combined to form a multifilament yarn, which is normally called a filament yarn.
Filament yarns are stronger than the same-size spun yarns of the same synthetic material.
Filament yarns are designated by a denier number which is the weight in grams of 9000 meters of yarn, or a decitex number, which is
the weight in grams of 100 meters of yarn.. Thus a 1650 denier yarn will weigh 1650 grams per 9000 meters.
Table 1-2 provides information on some of the fiber yarns used in belting fabrics or cords.
Common Name ASTM Designation
D 1418-10
Composition General Comments
Urethane AU
Polyester
Urethane
Excellent abrasion, cut and tear resistance.
Good oil resistance.
Urethane EU
Polyether
Urethane
Excellent abrasion, cut, and tear resistance.
Good oil resistance.
Vinyl PVC
Polyvinyl
Chloride
A thermoplastic material which has good
resistance to abrasion. Excellent flame
resistance. Good resistance to animal and
vegetable oils. Limited temperature range.
Viton* FKM
Fluorocarbon Excellent high temperature and chemical
resistance properties.
Teflon* see manufacturer Polymers
*Trade Names
Common Name ASTM Designation
D 1418-10
Composition General Comments

Table 1-2.
Some Materials Used in Belting Reinforcement
TEXTILE REINFORCEMENTS
Textile fabrics are the most commonly used materials for reinforcing plies in conveyor and elevator belting. Textile fabrics are also
used for conveyor belt “breakers” plies. Fabric properties are governed by the yarn material and size and by the fabric construction
and weave.
Fabric is made of warp yarns, which run lengthwise, and filling (weft) yarns, which run crosswise, as the fabric is woven, usually at
right angles to each other.
Non-woven fabric is a mat of fibers bonded together chemically and/or needle-punched, usually to a single-ply of woven scrim.
The most common, and least complicated, fabric pattern used for flat belts is the plain weave, Figure 1-1. In this construction the warp
and filling yarns cross each other alternately. A belt with two or more of these plies of fabric is known as a multi-ply belt. Other
common constructions used to a lesser degree include broken twill, Figure 1-2 and Leno weave, Figure 1-3, which has an open mesh
and is usually used for a breaker fabric.
Solid woven, Figure 1-4, consists of interwoven multiple layers of warp and filling yarns.
Straight warp weave, Figure 1-5, contains basic tension-bearing warp yarns which are essentially straight, that is, without crimp.
Also, binder warp yarns are interwoven with the filling yarns to provide mechanical fastener holding strength. Some of the most
commonly used belting fabrics known by their major fiber content are:
Cotton - A fabric with cotton in both the warp and filling yarns.
Cotton-Synthetic - A fabric with cotton warp yarns and synthetic filling yarns or a fabric with cotton/synthetic blended warp and/or
filling yarns. The synthetics most commonly used are nylon, and polyester.
Polyester - A fabric with polyester fiber warp yarns and filling yarns.
Nylon - A fabric with nylon fiber warp and filling yarns.
Common Name Composition General Comments
Cotton Natural Cellulose
Only natural fiber used to any great extent for belting.
High absorption of moisture. Susceptible to mildew
attack and loss of strength.
Glass Glass High strength. Very low elongation. Used in high
temperature applications.
Kevlar* Aramid Very low elongation and very high strength. Does not
melt but does decompose at high temperature.
Nomex* Aramid Very high strength, low elongation. Excellent high
temperature properties.
Nylon Polyamide
High strength and high elongation, with good resistance
to abrasion, fatigue, and impact. Moderate moisture
absorption. High resistance to mildew.
Polyester Polyester
High strength, low elongation. Good abrasion and
fatigue resistance. Low moisture absorption.
Excellentresistance to mildew.
Steel Cord Steel
Very high strength, very low elongation.
Superiortroughing characteristics. Excellent heat
resistance. Good fatigue and abrasion resistance.
*Trade Name

Polyester-Polyester – A fabric with polyester warp and filling yarns.
Polyester-Nylon - A fabric with polyester warp and nylon filling yarns.
Solid woven fabrics are composed of spun and/or filament yarns. The spun yarns commonly used may be either cotton or synthetic or
combinations thereof. The filament yarns are usually nylon or polyester.
Figure 1-1. Plain Weave Figure 1-2. (Broken) Twill
Figure 1-3. Leno Weave

Figure 1-4. Solid Woven
Figure 1-5. Straight Warp Weave

Figure 1-7. 7 x 19 ConstructionFigure 1-6. 7 x 7 Construction
STEEL REINFORCEMENTS
Steel Cord
Steel cord is used in belting where the properties of steel cord reinforcement are better able to satisfy the requirements of the service
conditions. Steel cord is used to obtain high strength, excellent length stability, low bending stresses and, in some cases, to provide
superior troughing characteristics. The wires, or filaments, used in conveyor belt steel cords are usually made of high carbon steel and
have a surface finish to facilitate adhesion to the surrounding rubber, and provide protection against corrosion. Common constructions
are 7 x 7, Figure 1-6, and 7 x 19, Figure 1-7, although many other constructions are possible.
Steel cords used in conveyor belts are specially manufactured from high carbon steel to meet the high strength requirements demanded
of these belts. The cord is fabricated from strands of wires, or filaments, twisted together. This gives the cord good flexibility and
fatigue resistance when subjected to cyclic loading and bending around pulleys. Two common constructions are illustrated in Figures
1-6 and 1-7.
In order to protect the steel from corrosion, zinc or brass coatings are applied to the wire before drawing it to the final filament size.
Zinc is the most commonly used coating. Typically, the minimum zinc coating expressed in grams per square millimeter is 60 times
the filament size in millimeters.
During belt manufacture, the steel cord is encapsulated in a special core rubber that normally has properties different to the belt
covers. It is important during manufacture that the core rubber penetrates right to the center of the steel cord as this stops adjacent
filaments from contacting one another and fretting during bending and stretching of the cord in service. Once embedded in the core
rubber, the cord strength increases by up to 5% and it becomes less likely to suffer from corrosion caused by water penetrating the
cord. The effectiveness of the rubber penetration can be determined by a special test (AS 1333) which measures if there is any loss in
air pressure along the cord when air is applied to one end of the cord at 14.5 psi (1 bar), and maintained for 1 minute on a 16 in long
belt sample. 5% is the maximum acceptable pressure loss.
Core rubber to cord adhesion should be adequate to maintain the belt and its splices’ integrity during its normal service life.
Due to the very specialized nature of this cord and the difficulties in manufacturing cord to achieve these properties, there are only a
few manufacturers in the world producing steel cord for conveyor belts.
Other Wire Components
Several other forms of wire are used in belting for special purposes, such as rip resistance and transverse stiffness. A variety of wire
structures are used, some of which include: (1) steel filling leno weave breakers, (2) straight warp steel fabrics.

CHAPTER 2 ELASTOMER CHARACTERISTICS
HEAVY WEIGHT CONVEYOR BELT
RUBBER COVER CHARACTERISTICS AND CLASSIFICATIONS
Elastomeric covers for general purpose conveyor belts with textile/cord reinforced carcasses will be defined as either Grade 1 or Grade
2. The properties, test values and minimum requirements described below can serve as a guideline for acceptable performance in most
general purpose applications. It is recognized however that there is no direct correlation between test results and the performance of
the belt in service. The test values as outlined are recognized as obtained from new or factory condition belting.
Reference Documents
ASTM D 378 Standard Test Methods for Rubber (Elastomeric) Belting, Flat Type
ASTM D 412 Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers -- Tension
CONVEYOR BELT RUBBER COVER GRADES
General Purpose Rubber Covers
ARPM Grade 1- Will consist of natural or synthetic rubber or blends which will be characterized by high cut, gouge, and tear
resistance and very good to excellent abrasion resistance. These covers are recommended for service involving sharp and abrasive
materials, and for severe impact loading conditions.
ARPM Grade 2- The elastomeric composition will be similar to that of Grade 1 with good to excellent abrasion resistance in
applications involving the conveying of abrasive materials, but may not provide the degree of cut and gouge resistance of Grade 1
covers.
When covers are tested in accordance with ASTM D 412, the tensile strength, elongation at break shall comply with the requirements
of Table 2-1, for the grade of cover, as appropriate.
The tensile strength and elongation at break values are not always sufficient in themselves to determine the suitability of the belt cover
for a particular service.
The values in Table 2-1 should only be specified for conveyors or materials with a known history of performance, and where it is
known that compliance with the value will not adversely affect other in-service properties.
Covers for Special Applications
Belt covers may be required to perform in various environments e.g. high heat, exposure to fluids, abrasive conditions, high ozone
concentrations, low temperature exposure and noise generation limits.
Cover and Ply Adhesion
When belting is tested in accordance to ASTM D 378, the adhesion for covers and between adjacent plies should not be less than the
values given in Table 2-2. Table 2-2 applies to continuous filament carcass.
ABRASION RESISTANCE
As per RMA’s description and classification for both Grade 1 and 2 belt covers; both of these cover types will provide good to
excellent abrasion resistance. There are several specific tests used by manufacturers to determine the relative abrasion resistance of
different cover formulations. The most common is ISO 4649 (DIN 53516).
While there are no specific U.S. industry limits, maximum or minimum, for test results from abrasion test for General Purpose (ARPM
Grades 1 & 2) Belt Covers; there is enough data to suggest acceptable abrasion values.

A customer preparing to purchase a conveyor belt for abrasion service should, therefore, proceed as follows:
1. Describe as accurately as possible the conditions under which the belt will operate, the nature and composition of the material being
carried, the range of particle size, loading conditions, and tons per hour being handled. In those instances where a replacement belt
is being ordered, indicate in as complete detail as possible the construction of the belt being replaced and describe the nature of its
failure.
2. Point out any condition which might accelerate cover wear, such as excessive heat, moisture, or the presence of oil or other solvents
in the installation.
Table 2-1. Properties of Covers
Table 2-2. General Purpose Rubber Cover and Ply Adhesion
COVER THICKNESS
Top Cover Thickness
The major function of a heavy weight belt cover is to protect the strength-bearing carcass from wear or damage during the life of the
belt.
In a light weight belt, the cover functions also to provide the required degree of sanitation in food contact applications or the desired
friction characteristics, or the required surface characteristics for incline/decline conveying.
The cover thickness required for a speciﬁc belt is a function of the material conveyed and the handling methods used.
Increased cover thickness is required as the conditions become more severe: e.g. material abrasiveness, maximum lump size of
material, material weight, height of material dropped onto the belt, loading angle, belt speed, frequency of loading, etc. The following
table shows the suggested minimum belt cover thicknesses for favorable conditions. Wear rates with identical material under adverse
loading conditions have been observed to be as much as 6 times the wear rate under favorable conditions.
Grade 1 - Top Cover Thickness
Grade 1 covers should be considered for heavy crushed material over 3 in (75 mm) and when large lumps occur if cut or gouge
resistance is the main design criteria. Consult the manufacturer for cover thicknesses.
Grade 2 - Top Cover Thickness (Table 2-3)
Table 2-3. Guide for Minimum Top Cover Thicknesses Under Favorable Conditions for Grade 1 and Grade 2 Belting
Note: Cover thicknesses are nominal values subject to manufacturers’ tolerances.
Grade Minimum Tensile
Strength (p.s.i.)
Minimum Tensile
Strength (MPa)
Minimum Elongation
at Break (%)
Maximum Volume Loss
(mm3) ISO 4649 Part B
1 2500 p.s.i. 17 MPa 400% 125 mm3
2 2000 p.s.i. 14 MPa 400% 175 mm3
Adhesion between adjacent plies Adhesion between cover & ply
30 lbs/in 5 kN/m
1/32 in (0.8 mm) ≤ Cover Thickness
≤ 1/16” (1.6 mm)
Covers greater than 1/16” (1.6 mm)
16 lbs/in 3 kN/m 30 lbs/in 5 kN/m
Class of Material Examples
Minimum Thickness
in mm
Package handling Cartons, food products Friction Surface Friction Surface
Light or ﬁne, non-abrasive Wood chips, pulp, grain, bituminous coal, potash ore 1/16 1.5
Fine and abrasive Sharp sand, clinker 1/8 3
Heavy, crushed to 3 in (75 mm) Sand, gravel, crushed stone 1/8 3
Heavy, crushed to 8 in (200
mm)
ROM coal, rock, ores 3/16 5
Table 2-3

Steel Cord Belt Covers
Cover Carcass Dimensions:
To protect the steel cords from impact, abrasion, and water or any other environmental factors, which could cause a loss of strength,
during the entire service life of the belt, a minimum thickness of rubber must encapsulate the cords. This cover thickness is usually
dictated by the service conditions, but should never be less than 5/32 in (4.0 mm). Failure to respect these limits may lead to uneven,
accelerated cover wear or cord damage which would result in reduced belt life. Table 2-4 indicates the minimum thickness “F” above
and below the cords that is required for this protection.
Figure 2-1.
A = Protective covering for cords during the entire belt life. (A = 2F + D)
B = Amount of top cover used for the service life of the belt.
C = Amount of bottom cover used for the service life of the belt.
D = Diameter of the cord.
E = Rubber encapsulating the steel cords and especially compounded for compatibility with the cover rubber and bonding to the steel
cords.
F = Thickness of rubber to protect the cords during service. This protective rubber is not part of the top or bottom wear covers used
to estimate belt tonnage.
Table 2-4. Guide for Minimum Protective Rubber “F”
* This value has been lowered from the calculated 6.6 mm as a result of favorable ﬁeld experience. For thickness of
covers “B” and “C” consult belt manufacturer.
Note: Minimum thickness of protective rubber “F” should not be less than 3.5 mm or 0.7 times the cord diameter,
whichever is greater.For larger diameter cords contact manufacturer.
Cord Diameter Minimum Thickness “F”
(above & below cords)
mm mm in
4.1
5.6
8.3
9.5
3.5
3.9
5.8
5.8*
0.137
0.157
0.228
0.228

Pulley Cover Thickness
The major function of a pulley cover is the same as that of a top cover: to protect the carcass material. In addition, field studies of
conveyor power have shown that energy is lost by the pulley cover as it passes over each idler roll. This is called rubber indentation
loss and can account for over 60% of the total belt drive power. Special pulley cover rubbers have been developed called “Low
Rolling Resistance (LRR)” covers to reduce the amount of power lost. Further details can be obtained from individual belt
manufacturers.. Since a pulley cover is not subjected to the severe conditions imposed upon a conveyor cover, its thickness does not
need to be equal to top cover. See below section “Cover Thickness Ratio”.
Table 2-5. Suggested Minimum Pulley Cover Thickness for Grades 1 & 2 Belting
* Increased cover thickness helps protect the carcass; however, if impact is severe, the complete system design, including carcass construction, top cover thickness, and
impact rolls in the conveyor, must be considered.
Note: Cover thicknesses are nominal values subject to manufacturers’ tolerances.
Cover Thickness Ratio
The thickness of the cover on conveyor belting must be selected on the basis of the service conditions to which the belting is to be
subjected. The ratio of the thicknesses of the top and bottom covers must also be considered. This factor becomes increasingly
important with conveyor belting where the carcass is thinner than those of comparably rated multi-ply conveyor belts.
A large cover thickness ratio, such as greater than 4:1, where one cover, the top, is much thicker than the other, the bottom - may cause
a conveyor belt to assume a permanent transverse curl or cup, wherein the edges of the belt curl up on the carrying run and down on
the return run. In its more severe state, this curl can adversely affect the training of the belt, especially on the return run. When the curl
has progressed to the point that only the edges of the belt contact the return idlers, training of the belt is virtually impossible.
The transverse belt curl that results from a large cover thickness ratio is a result of the shrinkage that occurs in rubber compounds after
vulcanizing. With a large cover thickness ratio, the shrinkage force of the thicker cover dominates, causing the belt to curl toward the
thicker cover. Multi-ply type belts, with their relatively thick and transversely stiff carcass, tend to resist the curl forces, but thin belt
carcasses offer less resistance.
Although transverse curl may occur in any size of conveyor belt, it is most likely to cause operational problems in narrower belts, up
to 36 in (900 mm) wide. To a lesser degree, it can cause problems with 48 in (1200 mm) widths. With the wider belts, the belt weight
usually forces the center of the belt down into contact with the return idlers, thus allowing normal training action to occur.
Generally, a maximum ratio of 4:1 for multi-ply and 2:1 for single-ply belting is recommended.
Cover thickness ratio specifications vary among manufacturers of conveyor belting. Individual belting manufacturers should be
consulted for their specific recommendations on cover thickness ratios for belting.
POLYVINYL CHLORIDE (PVC) CHARACTERISTICS
PVC is a resin produced from polymerizing vinyl chloride. The term PVC in the belting trade is generally applied to the elastomeric
material that results from the resin having been mixed with various liquids and powders and heat treated to change the mixture into a
usable elastomeric condition.
The mixture of PVC, liquids, and powders may be used in the form of a liquid plastisol for saturating and top coating fabric or as a film
to laminate and top coat fabric.
The PVC elastomer is thermoplastic. It hardens and stiffens with reduced temperature and softens and becomes more flexible with
elevated temperatures.
PVC belting operates well in the range of 20 to 180°F over conventional size pulleys. With special handling, operation down to - 30°F
is possible. General purpose PVC belting becomes hard and cracks when subjected to certain hydro-carbons and oils, which cause a
softening and swelling action on general purpose rubber. PVC can be compounded to prevent the deleterious effect of those
hydrocarbons and oils.
PVC can be compounded to promote good flexibility at -40ºF and to improve flame propagation resistance.
PVC elastomers are resistant to acids, alkalies, strong oxidizing agents and strong chlorinated cleaning agents.
Operating Conditions
Minimum Thickness
in mm
Slider bed package conveyors bareback or friction surface bareback or friction surface
Abrasive materials 1/32 1
*Impact loading 3/32 2.5

SPECIAL SERVICE BELT COVERS AND SPECIFIC CHARACTERISTICS
Belting can be designed to operate in various conditions and environments. No one belt type will handle all conditions well. Specific
environments that require special service belts include: static conductive, flame/fire resistance (MSHA), high (and low) temperature,
oil service, high temperature and oil service, high temperature abrasion, etc.
Specific test protocols are used to determine the elastomer’s response to these conditions and environments. An abbreviated listing of
these tests are offered in Table 2-6 for reference in regards to belt recommendations.
Table 2-6. Test Protocols for Special Service Belt Covers
RECOMMENDATIONS FOR OIL SERVICE BELTING
Various levels of oil service may be required from belt products. These service levels may or may not involve elevated temperatures.
The ARPM classifies belting (or cover formulations) to meet either MOR/VOR (Moderate / Vegetable Oil Resistant). Service
requirements or EOR (Extreme Oil Resistance) service requirements based on the following test criteria.
Table 2-7. %Volume Swell (ASTM D 471) 70 hr @ 100°C
MOR / VOR - Belting is designed to resist swelling and deterioration from vegetable based oils as well as light (napthenic / paraffin /
low aromatic) petroleum oils.
EOR / SOR - Belting is designed for use in extremely oily environments, especially where polar aromatic materials are expected to be
encoutered. Depending on temperature requirements and manufacturers’ recommendations, this class of belt may be suitable in “Hot
Asphalt” applications. Additionally, in coal fired power generation facilities where the fuel is being enriched with petroleum waste oils
or fuel / diesel oils, this may be the belt type required. Consult the manufacturer for recommendations when abnormal conditions are
anticipated.
Most of the cover formulations for belting meeting these classifications will be comprised of, or contain a certain percentage of, one
or more of the following polymers: CR (Polychloroprene / Neoprene), NBR (Nitrile), PVC, Urethane (AU / EU), CPE (Chlorinated
Polyethylene) or other oil resistant types listed in Table 1-1.
Condition Test Method
Friction (Coefficient)
ASTM D 1894 -- Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Filmand
Sheeting
Flame Resistance ASTM D378 13.1 (MSHA -- 30 CFR: part 14) ASTM D378 13.2 Heat Resistance
Heat Resistance
ASTM D 865 -- Standard Test Method for Rubber-Deterioration by Heating in Air (Test Tube
Enclosure)
Heat Resistance
ISO 4195-1 -- Conveyor belts -- Heat resistance -- Part 1: Test method; ISO 4195-2 -- Conveyor belts --
Heat resistance -- Part 2: Specifications
Low Temperature ASTM D 2136 -- Standard Test Method for Coated Fabrics -- Low Temperature Bend Test
Low Temperature
ASTM D 2137 -- Standard Test Methods for Rubber Property -- Brittleness Point of Flexible Polymer-
sand Coated Fabrics
Oil Service / Chemical ASTM D 471 -- Standard Test Method for Rubber Property -- Effect of Liquids
Ozone
ASTM D 1149 -- Standard Test Method for Rubber Deterioration -- Surface Ozone Cracking in a
Chamber
Tear Resistance
ASTM D 624 -- Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and
Thermoplastic Elastomers
Oil Resistance ASTM #1 Oil ASTM #3 or #903 Oil
MOR / VOR
Moderate / Vegetable Oil Resistant
15% Max. 140% Max.
EOR / SOR
Extreme Oil Resistance
5% Max. 30% Max.

HIGH TEMPERATURE SERVICE CLASSIFICATIONS
Belting designed and manufactured to handle elevated temperatures in service will be classified by type depending on the belt cover
characteristics when tested to ASTM D 865 at the specified times and temperatures.
Table 2-8. High Temperature Testing (ASTM D 865)
ISO 4195 is referenced as another testing and classification tool. While the classifications and value limits are similar between these
tests, they differ in both time of exposure (70 hr vs. 168 hr) and method of sample preparation. ISO 4195 calls for the entire belt
sample to be exposed, with test specimens to be cut / prepared from the exposed belt samples. ASTM D 865 allows for test
specimens to be prepared before exposure. The correlation between these methods has not been determined and differences are
expected, since the mass of ASTM sample is small relative to the dimensionally large ISO sample size. Hence the shorter time of
exposure per the ASTM / ARPM protocol.
While these tests and classifications do not validate product usefulness or acceptability in specific environments, they are used as
tools by the industry to more narrowly define criteria for applications involving elevated temperatures. It must be noted that
temperature alone may not be the overriding / determining factor in product suitability. Certain conveyed materials may degrade
various elastomers at test temperatures that the elastomers may be expected to perform based on test conditions. Consult the belt
manufacturer for specific recommendations.
A wide variety of flame tests for conveyor belts exists throughout the world. The standard used in a particular country is usually
dictated by a national or local governing body. For general flame resistant conveyor belting, the selection of the most suitable quality
may be made by the ARPM-FR class designations.
ARPM-FR Class I
Based on the December 31, 2008 U.S. Mine Safety & Health Administration’s (MSHA), CFR Title 30 Section 14, “Requirements for
the Approval of Flame-Resistant Conveyor Belts”, also known as the Belt Evaluation Laboratory Test or “BELT” test, this new
ARPM-FR standard provides a flame resistance quality that is currently mandated by MSHA in the USA for underground coal mines.
This belt quality is appropriate for belts that require flame resistance and which are included in the December 31, 2008 CFR, Title 30,
Mineral Resources, Section 14, which primarily applies to conveyor belts used in underground coal mines.
The test procedure is described in ASTM D 378 Section 13.1 and employs 60 in x 9 in sized belt test samples. Following the original
MSHA guidelines, the acceptance criteria for three belt samples tested to this ARPM-FR Class I standard is each tested sample must
exhibit an undamaged portion across its entire width.
FLAME RESISTANCE SERVICE CLASSIFICATIONS
WARNING: All belting will burn when adequately ignited
Time 70 hr - Test Temperature
Retained Tensile-
from original
Retained Elongation
from original
Hardness pt. change
ARPM-HR Class 1 212°F (100°C) -25% (max.) -50% (max.) +20 (max.)
Belt Designation Sample Size (Qty.) Method (Time) Pass Criteria
ARPM-HR Class 1 60” x 9” (3)
1524 mm x 229mm
ASTM D378 13:1
Burner (5 min)
Some undamage belt in
each sample
ARPM-HR Class 2 6” x 0.5” (4)
152mm x 13mm
ASTM D378 13:2
Bunsen Burner (1 min)
Flame out average < 1 min
No afterglow after 3 min
Table 2-9. Flame Resistance Testing (ASTM D865)

Effective December 31, 2008, the United States changed the minimum standard for flame performance of underground coal mine conveyor testing.
Until December 31, 2009 conveyor belts placed in service in underground coal mines shall be either approved under Part 14; or accepted under Part 18.
Part 18, is an old MSHA standard, “Code of Federal Regulations, Title 30, Mineral Resources, Section 18.65, Flame Testing of Conveyor Belting and
Hose.” Part 18 is commonly known as “2G”. Effective December 31, 2009 conveyor belts placed in service in underground coal mines shall be approved
under Part 14. If MSHA determines that Part 14 approved belt is not available, the Agency will consider an extension of the effective date. Effective
December 31, 2018 all conveyor belts used in underground coal mines shall be approved under Part 14.
Effective December 2, 2005, in Canada, the CAN/CSA M422 M87 “Fire Performance and Antistatic Requirements for Conveyor Belting” standard was
withdrawn. Formerly this standard was the minimum standard for flame performance and electrostatic conductance for underground belting which was
tested in accordance with the CAN/CSA M422 M87 “Fire Performance and Antistatic Requirements for Conveyor Belting” by Energy, Mines and
Resources, Canada, Canadian Explosives Atmospheres Laboratory. They formerly assigned an approval number for each different belt which number,
together with other information in M422, which was branded on the belt at least once every 15m (approx. 50’). Conformance to the M422 specification
about branding was enforced by Provincial Regulatory Agencies.
General
When it is the user’s opinion there is a potential fire hazard, he should consult the belt manufacturer and consider whether belting
manufactured to the above specifications is suitable for the application. In each installation, consideration should also be given to the
following:
a. Fire detection systems
b. Automatic fire suppression systems
c. Slip and sequence interlock systems
d. Sprinklers at transfer points to reduce flammable dust
e. Belt lateral alignment controls
f. Elimination of combustible materials near the conveyor belt
g. Conductive paths to ground for static electricity including conductive grease in bearings
h. Chute probe or level indicators at transfer points
i. Fire retardant, static electricity conducting drum lagging, skirts, scrapers, and chute lining
j. Heat sensors for conveying pulley bearings.
ARPM-FR Class II
Based on the pre - December 31, 2008 U.S. Mine Safety & Health Administration’s (MSHA), CFR Title 30 Section 18.65,
“Requirements for the Approval of Flame-Resistant Conveyor Belts”, also known as the “2G” test, this new ARPM-FR standard
provides a basic flame resistance quality that was formerly mandated by MSHA and was used successfully in the USA for many years.
This belt quality is appropriate for belts, such as above ground belts, that require flame resistance and which are not included in the
December 31, 2008 Code of Federal Regulations, Title 30, Mineral resources, Section 14, which primarily applies to conveyor belts
used in underground coal mines.
The test procedure is described in ASTM D 378 Section 13.2 and employs 6 in x 0.5 in sized belt test samples.Following the original
MSHA guidelines, the acceptance criteria for belt samples tested to this ARPM-FR Grade II standard is defined as the tests of four
specimens cut from any belt sample shall not result in, either duration of flame exceeding an average of 1 minute after removal of the
applied flame, or the continuation of visible glowing of a specimen after flaming has ceased (afterglow) exceeding an average of 3
minutes duration.
ARPM-FR Class Test Responsibility
Each belt manufacturer is responsible to ensure tests are conducted to the appropriate ARPM-FR class specification on each belt order
claiming the ARPM-FR class quality. Tests may be witnessed at any time by the customer or his representative to ensure compliance
to the test standard.
Marking
AARPM-FR class conveyor belt must be permanently and legibly marked with the appropriate ARPM-FR class designation (and/or
MSHA approval number for ARPM-FR Class I) for the service life of the product. The marking must be at least 0.5 in (1.27 cm) high
and placed at intervals not to exceed 60 ft (18.3 m) repeated once every foot (.3 m) across the width of the belt. Records of the initial
sale of each belt order having the ARPM-FR class marking and actual test conditions and test results must be retained for at least 5
years.
POLYURETHANE (PU) CHARACTERISTICS
Polyurethane is generally characterized as a cut and abrasion resistant polymer with excellent mechanical properties in the range of
about -65 to 212°F (-54 to 100°C). There are both thermosetting and thermoplastic grades used in belting, and polymer back bones
that enhance oil resistance or water resistance. The thermoplastic grades are easily spliced in belt constructions, and food contact
polyurethane compounds are available.

CHAPTER 3 TEXTILE BELT TYPES AND MANUFACTURING METHODS
INTRODUCTION
This chapter describes types of textile belting in terms of carcass types and of edge protection. This will be followed by a description
of belt cover designs and textile belt manufacturing methods.
BELT CARCASS TYPES
The belt carcass primarily provides resistance to tension forces that build up in the conveyor system. Also it provides strength to resist
belt tear and loading impact and for load support, troughing, mechanical fastener holding ability, and resistance to wrinkling or edge
cupping.
Textile Fabric Carcass - (See Figure 3-1)
The textile fabric carcass may have one or more plies of fabric bonded by elastomeric compounds to both themselves and to the
belt cover. Belt strength and load support characteristics depend on the fabric construction and the number of plies used. Flexibility/
stiffness are functions of the fabric construction and number of plies of fabric, and skim and cover thicknesses and their elastomeric
properties. The elastomeric compounds in heavy weight belting are often thermosetting.
Light weight belting is reinforced in some constructions by one or more plies of fabric like the heavy weight belting or in other con-
structions by solid woven or interwoven fabric or by non-woven fabric which generally has a woven scrim component. The individual
plies in light weight belting often have monofilaments in the weft to impart transverse stiffness, and the elastomeric materials in the
plied constructions are predominantly thermoplastic.
Textile Fabric -- Multi-Ply Belt Shown with Three Fabric Plies and Cut Edges*
* Refer to Glossary for definition of cut and slit edges..
Solid Woven Carcass
Solid woven belting consists of a single ply carcass made up of multiple layers of warp and filling yarns interwoven. The carcass is
usually impregnated and/or coated with thermoplastic compounds.
BELT EDGE PROTECTION - MOLDED EDGES
Molded (Capped) Edge Belting
Historically all conveyor belting was made with molded (capped) edges (Figure 3-2). Molded edges were necessary to protect the
cotton fiber in the carcass against mildew or chemical action. Thus the carcass, in addition to being covered, was encapsulated around
the edge with the elastomeric compound of the covers, and molded into a square capped edge. It must be recognized this was only a
temporary expedient; since, when the covers were cut, gouged or worn to the fabric and the molded edges were torn or worn off, the
absorption of water and chemicals would occur. With the availability of nylon and polyester fabrics, cut edge belting is now
commonly used.
In light weight belt applications capped edges are used in applications where improved edge protection is required. For example: food
processing to eliminate edge fraying and subsequent absorption of fluids.
Figure 3-1.

Figure 3-2.
Multi-Ply Belt Shown with Four Plies of Reinforcing Fabric, A Breaker Ply, Covers and Rubber-Capped Edges
Cut/Slit Edge Belting
The general use of nylon and polyester yarn for conveyor belt carcasses has eliminated the concern for protecting the belt carcass with
molded edges. The nylon and polyester fibers are resistant to mildew attack and the polyester to most chemicals. Thus most belting is
now supplied with slit edges.
CARCASS PROTECTION
Breaker
Before the use of nylon and polyester carcass fabric, breaker plies of open texture leno weave cotton or nylon yarn were frequently
used between the carrying cover and the belt carcass. It was believed a breaker ply improved the adhesion of the cover. The breaker
ply next to the carcass improved cover cut and gouge resistance and provided material loading impact resistance. Breaker plies are
used where severe impact conditions exist. Sometimes a breaker fabric in a molded edge is wrapped around the fabric edge to provide
edge protection.
BELT COVER DESIGNS
For most applications, conveyor belts have a smooth top and/or bottom cover made of elastomeric compound suitable for the material
to be conveyed. There are, however, some special purpose belt surface finishes described in the following.
Bareback Surface
The outer surface of the top or bottom of the fabric of a bareback belt has neither an elastomeric compound cover nor is it impregnated
with an elastomeric compound. A bare fabric surface provides a low coefficient of friction. A slider bed package conveyor with the
bareback surface down against the slider bed or the bareback surface up in connection with a diverter bar are examples of bareback
surface applications.
Friction Surface
The outer top and/or bottom surface of the fabric of a friction surface belt has a light impregnation of elastomeric compound.
Brushback Surface
Certain friction compounds may be buffed to further reduce the coefficient of friction while retaining the elastomeric compound in the
interstices of the fabric.
Bareback, brushback and friction surface belts can be provided with a cover on one side of the belt.
Impression (Rough Top) Surface
Impression belts have an embossed profile in a cover made by curing the elastomeric cover against a mold, fabric, or stamped metal or
by embossing a thermoplastic cover. Impression belts are often used to convey material on inclines and declines where slippage may
occur.
Cleated, Flanged (Sidewall) or Ribbed Top Surface
Cleats, flanges or ribs in transverse, longitudinal, continuous or intermittent, and of angular, straight or curved design may be molded
onto or affixed to the cover. They improve the ability to carry coarse material on incline and decline applications. The height and
spacing of the cleats, flanges or ribs depend on the size of the material to be conveyed.

BELT MANUFACTURING METHODS
SINGLE AND MULTI-PLY BELTS
Drying
Cotton and spun synthetic yarn fabrics must be heated before they are frictioned so the friction rubber can be properly impregnated
into
the interstices of the fabric. Also the cotton, rayon, and nylon spun yarn fabrics must be thoroughly dried to remove moisture which in
the belt curing operation could cause blisters between the plies of fabric or under the covers.
Textile Fabric Treatment
Generally, most multi-filament textiles (nylon, polyester, etc.) require an RFL treatment to ensure adequate adhesion in service. RFL
is an industry term designating a treatment mixture of resorcinol formaldehyde latex (RFL), whereby the woven textile is dipped in
the emulsion and dried under specific temperature and tension conditions. This process is used for most rubber based belting (Natural,
SBR, NBR, CR, EPDM, etc.). For thermoplastic type belt, the treatment can involve acylics, polyurethane, PVC or other treatment for
the respective textile reinforcements.
Rubberizing (Skimming, Bank Coating, and Frictioning)
The fabric is impregnated with a suitable elastomer by “frictioning” and/or “skim coating” on 3-roll or 4-roll calenders.
Frictioning forces the pre-softened rubber compound into the interstices of the fabric by the wiping action of two calender rolls
running at different surface speeds.
In skim coating the calender roll speeds are essentially the same, and a thin layer of rubber compound is laid on the fabric.
During the calendering operations, uniform tensions are maintained on the fabric to prevent undesirable distortion.
Carcass Building
Calendered plies of fabric are laminated and consolidated by squeezing between two rolls of a building unit. Depending on equipment
design, from two to five plies can be laminated in a single pass through the unit. Uniform tension is maintained on each ply to ensure
maximum efficiency during service.
Longitudinal seams (ply splices) result when it is necessary to use more than one strip of fabric to make the full ply width. The seam
is made by bringing the two edges together and, if necessary, placing a rubber cord over the joint so that a void does not occur when
vulcanizing the finished belt. Longitudinal seams are generally made during the laminating pass through the building unit. Seams shall
be at least 4 in from the edge, separated by 12 in within the ply and be removed from the idler junction area. Number of seams are
limited by belt width.
Tranverse seams (ply splices) result when the fabric length is less than the full length of the finished belt. The ends of the two or more
pieces are prepared by cutting on a 20° to 45° bias angle. The ends are then butted against each other and if necessary, a strip of
rubber compound is placed over the joint to prevent a void from forming during subsequent manufacturing operations. The preparation
of the bias cut ends is done during the actual laminating operation at the carcass building machine, which results in a good matching of
the two ends being joined. Transverse seams shall be at an angle between 26.5° and 70°, shall be separated by at least 50 ft, and be at
least 50 ft from the end of the belt. No transverse seams are allowed in the outer plies.
Belt Covers
The elastomeric covering on belts is there to provide protection for the carcass, and/or provide a specific property. These coverings are
applied by several processes, depending on the material (rubber vs. thermoplastic) or thickness of the covering.
For rubber belting covers are either extruded or calendered. Extruded rubber sheets of specific widths and thickness are then laminated
or press plied onto the carcass. similarly, thermoplastic covers can also be extruded and laminated.
For most thin belt covers (i.e. pulley “side” covers), less than 1/8 in (3.2 mm), application is performed at a calender unit where the
elastomeric compound is “skimmed” onto the textile. This process can accommodate some thermoplastic materials as well as rubber.
PVC covers are also applied with roll or knife coating processes.

Release Coating
After applying the last cover, a light coat of release agent, is applied to one or both surfaces of the belt. This is done to prevent the
unvulcanized belt from sticking in the roll before cure and to help in stripping the belt from the press surface after cure.
After release coating and before curing, the cover is usually perforated with fine pricker needles to help release gases that may be
present withing the body of the belt. These holes are completely sealed during the vulcanization operation.
Curing
The belt is vulcanized in either a flat platen press (index cure) or a rotary press (continuous cure). In either case, curing is done at a
temperature in the range of 280-320°F (140-160°C) while under pressure. Edge irons or rings are set at the desired belt width to retain
and/or mold the rubber covered edges.
Since it is essential that a small excess of material be present to create proper pressure during cure, a small overflow of cover occurs
at the side retaining irons. This is removed by trimming or buffing as the cured belt comes from the press. Slab belts which are slit to
width have the entire edge cut away during a subsequent operation.
Tension is generally applied to the belt during cure so that the elongation of the finished product is within acceptable limits.
Branding of the belt with the manufacturer’s name, grade or type of belt, and date of manufacture is generally accomplished by
placing a metal stencil on the uncured belt at regular intervals. This produces an embossed label cured onto the surface.
Slitting
Slab belting is slit to the final width after it is cured. Full-width rubberized fabric is used to build the carcass.
SOLID-WOVEN RUBBER BELTS
Carcass
The woven fabric is generally treated with a special bonding adhesive which is applied by passing the fabric through a bath containing
the adhesive. (See “Dipping.” under Single and Multi-ply Belts above.)
Rubberizing
The dried carcass is then impregnated by frictioning and/or coating on a calender. (See “Rubberizing” under Single and Multi-ply
Belts above.)
Covering, Dusting, and Curing
These steps are essentially the same as for Single and Multi-ply Belts above.
SOLID-WOVEN PVC BELTS
Textile Fabric Treatment
The single- and multi-ply fabric is impregnated with PVC plastisol during and/or following weaving.
Covering and Fusing
The carcass is first passed through a plastisol dip tank for impregnation and cover application and then into a heated oven where
plastisols are fused to the consistency required to meet service conditions. The PVC compound can alternatively be calendered into
a film or sheet which can then be applied to the carcass. If smooth cover surfaces are required, fusing may be accomplished in flat or
rotary presses. If rough top, cleated or ribbed top cover surfaces are required, embossing of the cover may be done immediately
following the fusion process.

SINGLE AND MULTI-PLY THERMOPLASTIC BELTS
Single and multi-ply PVC belts may be produced by dipping and/or top coating the carcass fabric with PVC plastisols, which provide
the elastomeric binding layer between plies and the top cover surface. Fusion of the PVC compounds is done by heating to
temperatures of approximately 350-380°F (177-193°C), and the surfaces of the belting are smoothed or embossed to provide the
required textures and finish.
Single and multi-ply polyurethane belts may be produced by coating the carcass with a film or sheet of compound from a hot melt
coater or extruder or spraying operation and then cooling or by building a laminated construction using films or sheets of compound
that are later heated in a flat or rotary press. Pre-treating the carcass is done to enhance adhesion of compounds.
There are some extruded single-ply thermoplastic belts made with Hytrel or polyurethane, with no textile reinforcement.

INTRODUCTION
The tension rating for a belt is the recommended maximum safe working stress that can be applied to the belt.
Belt tension is commonly referred to as the force applied to the belt per unit of belt width, such as Pounds per Inch width (PIW), or
Kilo Newtons per Meter width (kN/m). Textile fabrics are frequently rated for their maximum safe working stress which is expressed
as the force applied per ply of fabric per unit width of the belt.
There is variation among manufacturers about the following information that relates to number of plies of fabric, belt carcass
thickness, minimum pulley diameter, troughability, etc., to the belt maximum safe working stress because of differences in materials
and manufacturing methods.
Some key differences which exist are:
1.The fiber, polyester and/or nylon, used for the fabric.
2.Recommended safe working strength for the fabric used.
3.Ratio of belt breaking strength to belt maximum safe working stress (safety factor).
These factors also affect the belt carcass thickness, belt weight, minimum pulley diameter, troughability, load support with different
angle idlers, transition distance, impact resistance, etc. Thus, it is essential to confer with the belt manufacturer about the belt proposed
for each application.
CONVEYOR BELT AND SYSTEM TENSION CALCULATIONS
Conveyor systems will take on a variety of configurations relative to drive location, elevation or descent of the load, idler and pulley
type and condition, and other factors too numerous to detail in this handbook. Belt manufacturers or conveyor engineering
companies should be consulted for belt (system) recommendations. The Conveyor Equipment Manufacturers Association (CEMA)
provides a Handbook for in-depth system analysis and tension calculations. International Standard ISO 5048 and the German standard
DIN 22101 also provide detailed methods for system tension calculations.
The tables below provide an example of the basic information on multi- and single-ply fabric belt tension ratings. This information is
for illustrative purposes only. Information on a specific belt construction can be provided by the belt manufacturer.
The data in the following tables apply if the following service conditions occur:
Mechanical Fastener Splice
1.Pulley diamters recommended by the belt manufacturer and fastener manufacturer are used.
2.No abnormal conditions, such as heat or chemicals, are exposed to the belt that will reduce the belt fabric strength or change the
flexibility of the belt fabric.
3.Recommended fasteners are properly applied.
4.Across the line starting tension is limited to not greater than 150% of the splice rating. Step phase or soft starting is preferred.
Vulcanized Splice
1.Pulley diameters recommended by the belt manufacturer are used.
2.Automatic take-up with adequate take-up travel.
3.Splices are made strictly in accordance with the belt manufacturer’s specifications.
Where an adverse environmental condition or some special belt application exists, it is critical that the belt fabric ply tension rating be
reduced by some factor recommended by the belt manufacturer. Some of the special conditions are:
1.Continuous excessive ambient temperature.
2.Exposure to deleterious chemicals.
3.Holes punched in the belt.
CHAPTER 4 TEXTILE BELT CHARACTERISTICS & BELT RATINGS

Elevator Belt Tension Recommendations
Elevator tension ratings may require modification under certain adverse environmental conditions. In such cases the rating in the
following tables should be multiplied by an environmental factor of 0.75.
Adverse environmental factors for elevator belts include:
1.Elevated temperatures in the belt reinforcing fabric due either to high ambient temperatures or to conveying hot materials.
2.Abrasion of surface plies which are not protected by an elastomeric cover, such as friction surface belting in abrasive service.
3.Chemical service detrimental to the carcass fiber.
Safety Factors
Conveyor belt operating tensions are chosen as a small percentage of the belt’s breaking strength. This provides spare strength for (1)
temporary higher transient loads such as during starting and stopping, (2) handling unusual system loads such as misalignments or
frozen idlers, and (3) loss of strength due to materials’ aging and other degradation factors. The ratio of original belt strength to
operating tension is called the belt’s Safety Factor. Traditionally, the conveyor industry has used safety factors around 10:1 for fabric
belts and around 6.7:1 for steel cord belts, however, higher and lower factors are common. It is recommended to contact the belt
manufacturer for a safety factor recommendation for a specific application.
In recent years, studies have linked a belt’s safety factor to its dynamic splice strength and tests have been developed to measure the
dynamic strength of the splice. There are now international standards, such as DIN 22110, that define how the dynamic splice strength
can be measured. There are also standards, such as DIN 22101, that provide a method to calculate the safety factor for a belt. A general
guideline is that fabric belt splices have a dynamic splice efficiency of 35% of the belt’s breaking strength and steel cord belt have
45%. In practice, many conveyor belts deteriorate due to abuse or accidental damage and historical data should always be considered
when selecting a safety factor. Other factors that should be considered when selecting a belt’s safety factor include the effects of a
catastrophic belt break. For example, personnel safety, loss of production, clean up cost, repair time, accessibility of the belt for repair,
and availability of repair labor and materials. There are examples where a critical conveyor belt has broken due to loss of strength
from accidental damage combined with a high peak transient load. Such events can cost millions of dollars of lost production. The
recent availability of cord monitoring systems for conveyor belts offers improved capability of accidental damage surveillance in steel
cord belts. When used correctly, such systems offer additional safeguards for the operation of belts with lower safety factors.

Table 4-1. Typical Ratings
Note 1: These are typical values only, please consult your belt manufacturer for speciﬁc product values.
Note 2: Table 4.1 includes expanded product ratings.
CONVEYOR
Working Strength (PIW) 220 250 330 375 400 440 500 600 750 800 1000 1000 1200
Number of Plies 2 2 3 3 2 4 4 3 3 4 4 5 6
Approximate Carcass Thickness
(in)
.12 .146 .16 .20 .182 .220 .254 .258 .27 .265 .28 .335 .38
Approximate Carcass Weight
(lb/sq. ft)
.70 .81 .94 1.12 1.02 1.3 1.39 1.42 .135 .125 .141 .165 .188
Minimum Pulley Diameter (in) (% of rated max. belt tension)
81-100% 16 16 18 18 16 24 24 24 22 30 30 36 42
61-80% 14 14 16 16 14 20 20 20 24 20 24 24 30
41-60% 10 10 12 14 12 18 18 18 20 16 20 20 24
To 40% 10 10 12 12 10 16 16 16 18 14 18 18 20
TROUGHABILITY
Idler Troughing Minimum Belt Width (in) for Empty Troughing
Angle˚
20˚ 14 18 18 24 18 24 30 24 36 36 42 48 NR
35˚ 18 24 24 30 24 30 36 30 36 30 36 42 42
45˚ 24 30 30 36 30 36 42 36 42 36 42 48 48
Maximum Belt Width (in) for Empty Troughing
Material Weight (lb/cu. ft)
20˚ 0-40 48 54 60 72 60 72 84 84 84 72 84 84 84
41-80 48 48 60 60 54 66 72 72 72 72 72 84 84
81-120 42 42 54 54 48 60 72 72 72 72 72 84 84
Over 120 36 36 48 48 42 54 60 60 60 60 60 72 84
35˚ 0-40 42 48 54 60 54 60 72 72 84 72 72 84 84
41-80 36 42 48 60 48 60 60 60 72 60 66 72 84
81-120 36 42 48 54 48 54 60 60 72 60 60 72 84
Over 120 30 30 42 42 36 48 54 54 60 54 54 60 72
45˚ 0-40 36 48 48 60 54 54 72 72 72 72 72 84 84
41-80 36 36 42 48 42 48 54 54 60 54 72 72 84
81-120 30 30 42 48 42 48 54 54 60 54 72 72 84
Over 120 NR NR 36 36 30 42 48 48 54 48 54 54 72
ELEVATOR
Minimum Pulley Diameter
81-100% tension 18 18 20 20 18 30 30 30 36 22 30 36 42
61-80% 16 16 18 18 16 24 24 24 30 20 24 30 36
Up to 60% 12 12 14 14 14 20 20 20 18 20 24 30 36
Maximum Pulley Projection
Spaced Industrial 100 lb/cu. ft 6 7 7 8 9 10 11 10 11 9 10 11 12
Spaced Continuous 5 6 7 8 9 10 11 12 14 9 12 14 16

Table 4-2. Typical Ratings - Straight Warp Conveyor or Elevator Rubber Belting
Note 1:These are typical values only, please consult your belt manufacturer for speciﬁc product values.
Note 2: Table 4.2 includes expanded product ratings.
CONVEYOR
Single-Ply Straight Warp Fabric Double-Ply Straight Warp Fabric
Working Strength (PIW) 190 220 275 390 385 440 440 550 660 800 1000 1250 1500
Approx. Carcass Gauge (in) .078 .103 .125 .131 .157 .165 .195 .234 .250 .281 .320 .328 .359
Approx. Carcass Weight
(PIW) Factor (lb) .038 .049 .056 .064 .067 .072 .105 .114 .120 .134 .148 .165 .172
Minimum Pulley Diameter (in) Depending on Fastner Splice Selected
Working Tension
81-100% 16 16 18 20 24 24 24 30 30 36 42 42 42
61-80% 14 14 16 18 20 20 20 24 24 30 36 36 36
Up to 60% 12 12 14 16 18 18 18 20 20 24 30 30 30
TROUGHABILITY
Troughing Angle Minimum Belt Width (in) for Empty Troughing
20˚ 12 14 14 18 18 18 24 24 24 30 30 30 30
35˚ 14 20 20 24 24 24 30 30 30 36 36 36 36
45˚ 16 24 24 24 24 24 36 36 36 42 42 42 42
Maximum Belt Width (in) for Load Support
Material Weight (lb/cu. ft)
20˚ 41-80 lb/cu. ft 36 42 54 60 60 66 84 84 84 84 84 84 84
81-120 lb/cu. ft 30 36 42 48 48 54 84 84 84 84 84 84 84
Over 120 lb/cu. ft 30 36 42 48 48 54 60 66 84 84 84 84 84
35˚ 41-80 lb/cu. ft 30 36 42 54 54 60 84 84 84 84 84 84 84
81-120 lb/cu. ft 24 30 36 42 48 48 84 84 84 84 84 84 84
Over 120 lb/cu. ft 24 30 36 42 42 48 54 60 66 84 84 84 84
45˚ 41-80 lb/cu. ft 30 36 42 48 48 54 60 66 84 84 84 84 84
81-120 lb/cu. ft 24 30 36 42 42 48 54 60 84 84 84 84 84
Over 120 lb/cu. ft 18 24 30 36 36 42 48 54 60 66 84 84 84
ELEVATOR
Minimum Pulley Diameter
Working Tension
81-100% 16 16 18 20 24 24 30 30 30 36 42 42 42
61-80% 14 14 16 18 20 20 24 24 24 30 36 36 36
Up to 60% 12 12 14 16 18 18 20 20 20 24 30 30 30
Maximum Bucket Protection
Space Industrial 6 7 8 9 9 9 11 11 13 13 14 15 16
Continuous Industrial 6 7 8 9 9 9 11 11 13 13 14 15 16

Belt operating tension is not the only belt characteristic to be considered when selecting belt design for an application. Other important
items exist that effect how the belt will perform on a given system. The importance of these characteristics is presented below.
ELONGATION
Most new conveyor belts will exhibit some permanent stretch very early in their service life, as a result of the normal cyclic tensile
forces exerted by the conveyor system on the belt. This length change will vary among belt constructions, but it is generally much less
than one percent of the original relaxed length of the belt. The conveyor take-up system must compensate for this length change as
well as the normal belt elongations which are proportional to belt tensions in the elastic region of the stress strain curve.
Table 3-3. Recommended Minimum Take-Up Travel
(percentage of the distance between centers of the convenor*)
*For belts installed at average empty running, take-up position 90% of the travel, and drive location at or near the high tension end of
the conveyor.
**Only short endless feeder belts and the like would normally be vulcanized on conveyors with a manual take-up.
TROUGHABILITY AND LOAD SUPPORT
In order to achieve the desired carrying capacities of bulk materials without spillage over the edges, most conveyor belts are operated
in a troughed configuration where the trough is usually formed by a 3-roll idler system as indicated by Figure 4-1 below. The angle of
the troughing rolls will usually range from 20° to 45°.
Figure 4-1. Belt Troughing In-Line Idler
When the belt is running empty, it must have sufficient lateral flexibility to retain contact with the center roll. Failure to do so will
usually cause the belt to wander from side to side, and considerable edge damage may result.
Conversely, when the belt is running fully loaded, it must have sufficient lateral stiffness to support the load and bridge the gap
between the center and troughing rolls. If the belt is too flexible in this regard, it will tend to crease into the idler gap and fail
prematurely at that point. This potential problem can be reduced by using offset troughing idlers. With offset idler systems the load
support may be liberalized (consult belt manufacturer).
Type of Take-Up and
Carcass Material (warp)
Percent of Rated Tension
100% 75% 50% or less
Manual Take-Up**
Nylon 4.00% 3.00% 2.00%
Polyester 2.50% 2.00% 1.50%
Automatic Take-Up
Nylon 3.00% 2.50% 1.50%
Polyester 0.00% 1.00% 1.00%

LIMIT OF IDLER GAP BETWEEN CARRYING IDLERS FOR TROUGHED BELT CONVEYORS
The Association for Rubber Products Manufacturers has established the following limit for gap between carrying idlers for troughed
conveyors.(ARPM IP-1-2) The limits provided serve as a guideline for acceptable performance of conveyor belts in the idler junction
area, preventing junction failure.
Reference Document: ISO 1537 -- Continuous mechanical handling equipment for loose bulk materials -- Troughed belt conveyors
(other than portable conveyors) -- Idlers
Limit for gap between in-line positioned troughed carrying idlers:
The maximum gap between the carrying idlers will be 3/8 in (10 mm).
Figure 4-2.
Overlap and Offset Dimension for staggered (or off-set) troughed carrying idlers:
A minimum overlap between the carrying idlers will be 3/8 in (10 mm).
Figure 4-3. End View
A maximum offset dimension of the idler in the running direction will be: Idler diameter plus 3/16 in (5 mm).
Figure 4-4. Top View

From the foregoing it is apparent that there are two extremes of lateral belt flexibility to be considered in making a belt selection, and
these are generally referred to as minimum and maximum ply design. Reference to manufacturers’ published tables is recommended,
especially when the belt selection will be at or near either the minimum or maximum ply extreme, because of belt design variations
and the fact that there are often two or more fabrics available with differing trough characteristics.
The ability of the belt to trough may be measured by using a standard test method (ASTM D 378). In this test, the troughability of the
belt is defined as the ratio F/L where F is the natural drop height at the center of a 6 ft (1.8 m) long belt sample freely suspended at its
edges and L is the belt sample width. Table 4-4 provides a guideline for the minimum values of F/L required to ensure that a belt will
trough correctly in the listed troughing idlers.
Table 4-4*. Three Identical Idler Rollers -- Minimum Required Values of the Ratio of Deflection (F) to the Belt Width (L)
Several belt constructions made from two or more plies of synthetic fabrics are widely used and are generally referred to as
multi-ply constructions. Because of the wide variety of fabric strengths, constructions, and other factors offered in these types of belt,
it is necessary to consult the various manufacturers for specific data. Tables showing typical belt selection data are in Chapter 5.
TRANSITION DISTANCE ON THREE EQUAL LENGTH IDLER ROLLS FOR TEXTILE BELTS
A. General
In changing the troughed belt to a flat section at the head pulley or the flat belt to a troughed section at the tail pulley, edge tension is
increased as the edges are stretched between the last idler and the pulley. This tension mal-distribution can be kept within safe limits
by maintaining a proper transition distance between the last trough idler and the pulley to minimize the stretch induced into the belt
edges. At the head (high tension end), the purpose is to avoid excessively high edge tensions. At the tail (low tension end), excessive
edge tensions rarely will be encountered. If the transition is too short, however, an excessive difference between edge and center
tensions can overcome lateral belt stiffness, pull the belt down into the trough, and buckle it longitudinally along the bottom roller.
B. Recommended Terminal Pulley Location
The vertical position of the terminal pulley with respect to the troughing idlers is of great importance in determining the minimum
transition distance since this position determines the vertical drop of the belt edge. The higher the pulley location with respect to
the idlers the shorter will be the minimum required transition distance.
Figures 4-5 and 4-6 illustrate two terminal positions commonly used. Figure 4-5 usually is recommended from a belt standpoint;
it places the pulley so that the belt edge will be lowered (or raised) approximately one-half the trough depth and requires much
less transition distance than Figure 4-6 while still maintaining a troughed section across the belt width. Figure 4-6 is used
occasionally where belt tension is low, lumps are large, and belt speed is high to minimize impact forces at the discharge pulley.
Inclination of side idler rollers
20° 0.08
25° 0.10
30° 0.12
35° 0.14
40° 0.16
45° 0.18
50° 0.20
55° 0.23
60° 0.26
* referenced from ISO 703

Figure 4-5. Half-Trough Transition
Figure 4-6. Full-Trough Transition
C. Minimum Recommended Transition Distances
The transition distances required to maintain proper edge and center tension relationships are a function of the elastic modulus or
stretched characteristic of the belt carcass, the rated belt tension, and the vertical drop or rise of the belt edge through the transition.
Using the elastic modulus of various belt fabrics from 1500 to 10,000 pounds per ply inch it is possible to develop a transition distance
suitable for all fabric belts (Tables 4-5 and 4-6) since the maximum and minimum requirements do not vary too widely.
Table 4-5. Minimum Transition Distance with Terminal Pulley at Approximately One-Half Trough Depth
Idler (deg) Percent ofrated
tension
Fabric belts Steel cord belts
20°
35°
45°
More than 90
60 to 90
Less than 60
More than 90
60 to 90
Less than 60
More than 90
60 to 90
Less than 90
0.9w
0.8w
0.6w
1.6w
1.3w
1.0w
2.0w
1.6w
1.3w
2.0w
1.6w
1.0w
3.4w
2.6w
1.8w
4.0w
3.2w
2.3w

Table 4-6. Minimum Transition Distance with Terminal Pulley at Full Trough Depth
Note 1: The above transition distances are conservative and have been used in service for years. Contact the belt manufacturer if
shorter distances are desired.
Note 2: Steel cord belts with their very low stretch characteristics require much greater transition distances than fabric belts. These
distances at times seem unreasonably great, but a small amount of stretch in steel cord can induce an enormous stress. In one
actual case, an 18 ft (5.5 m) steel cord belt transition was lengthened approximately eight more feet when it was shown that
the theoretically induced edge stress caused by edge stress in the 18 ft (5.5 m) distance amounted to approximately an
additional one-half of the rated belt tension.
VERTICAL CURVES
General
Vertical curves in conveyor belt systems are used to join two tangent sections with different slopes.Two different types of vertical
curves exist; a concave curve resulting from a negative change in grade; and a convex curve, resulting from a positive change in grade.
Each application needs to be evaluated to determine the correct curve radius in order to avoid problems during operation.
Figure 4-7. Vertical Curves
Concave Vertical Curves
A concave vertical curve should be designed with sufﬁcient radius to allow the belt to follow the path of the troughing idlers under all
conditions. The lack of a correct concave curve is immediately apparent, as the belt will lift off the idlers. Especially during startup,
if the belt tensions are too high, the belt will lift off the idlers in the curve area. On the other hand, very low tension could result in
excessive edge sagging and possible load spillage. In rare cases, it might also be necessary to verify that the tension at the center of the
belt does not exceed the tension rating of the belt. This center tension should be limited to 115% of the rated belt tension.
Convex Vertical Curves
Unlike concave curves,convex vertical curves can be improperly designed and still permit belt operation at the expense of belt life.
Three main items need to be investigated when designing convex curves; edge tension, center tension, and idler pressure. In a convex
curve, the belt edges have a greater tension than the center of the belt. It is important to limit this tension to 115% of the rated belt
tension. If the tension at the center of the belt becomes too low, the belt can buckle. To avoid this condition, a minimum of 5% of the
rated belt tension should be maintained in the center of the belt.
Idler (deg) Percent ofrated
tension
Fabric belts Steel cord belts
20°
35°
45°
More than 90
60 to 90
Less than 60
More than 90
60 to 90
Less than 60
More than 90
60 to 90
Less than 90
1.8w
1.6w
1.2w
3.2w
2.4w
1.8w
4.0w
3.2w
2.4w
4.0w
3.2w
2.8w
6.8w
5.2w
3.6w
8.0w
6.4w
4.4w

Convex curves can also be restricted by the idler pressure. When going through a convex curve, the belting is forced downward onto
the idlers.Convex curve limitations from the idler pressure standpoint are not created by the belt but by idler requirements. As a result,
the idler manufacturer should be consulted if this appears to be the limiting factor. If the manufacturer permits a greater loading, then
the radius can be reduced accordingly. Otherwise, the only other solution is to reduce idler spacing to live with the desired radius.
Short convex curves can cause idler junction failure as the belt will be forced in the idler gaps. Idler junction failure will be dependent
on the idler gaps, fabric type, belt rigidity, curve radius and edge / center belt tension.
PULLEY DIAMETERS
Pulley diameters are important to belt performance. Pulley diameters which are too small for a given belt construction, could result in
damage to the belt carcass or premature splice failure.As a belt travels around a pulley, a bending stress is induced as the outer fabric
plies must elongate and inner plies must shrink. This extra stress is dependent on the diameter of the pulley, the thickness of the belt,
and the elastic constant of the material. It is important to the integrity of the belt that this stress is kept within safe limits. Minimum
recommended pulley diameters can be obtained from the belt manufacturer for a given belt application based on the belt construction
and system tension.
IMPACT RESISTANCE
Loading bulk material on a conveyor belt creates some impacting force on the belt. This occurs since the material is dropped from
some height above the belt surface and the forward speed of the belt may be different than that of the material when it contacts the
belt.
Fine materials, regardless of weight per unit volume, do not present a problem on impacting the belt because the force is spread over a
relatively large surface area. Cover damage due to gouging is minimal and carcass bruising is normally very low in operations
involving ﬁne materials.
Lumpy materials can cause appreciable impact on the belt. The heavier the lump, the greater height of fall, and the greater its angular
velocity when it contacts the belt, the greater will be the energy tending to rupture the belt. When the material strikes the belt directly
over a support such as an idler, damage to the carcass can result from the crushing action of the lump against the idler-supported belt.
Lumpy material having sharp corners and edges can cause cover nicks, cuts, and gouges. The heavier the lump, the greater height of
fall, and the greater its angular velocity at the time of contacting the belt, the more extensive will be the damage to the cover. Sharp,
pointed lumps can even penetrate the cover into the carcass and in rare instances completely penetrate through the belt.
To minimize impact damage, every effort should be made to provide good loading conditions for the material handled. (See Chapter
14 on loading and discharge).
Given full information regarding the material conveyed and the loading conditions, the belt manufacturer can provide a belt that will
embody the necessary elements to resist the damaging effects of impact. The selection of a cover grade and thickness, the type of
textile ﬁber, fabric design, and number of plies can be varied depending upon the severity of the impact conditions.
The maximum fabric ratings shown in this chapter are based on the use of impact idlers and good design of loading and transfer areas.
The impact energy equals the lump weight factor (Tables 4-7 and 4-8) times the equivalent free fall.

Equivalent Free Fall Calculation
Equivalent free fall is: H
Where: Hf
f + Hr (sin2 Δ)
= total free fall, ft (m)
Hr = vertical height on loading chute slope, ft (m)
Δ = angle in degrees that chute slope makes with the horizontal
Figure 4-8. Equivalent Free Fall and Location of Values H f and Hr
Lump Weight Factor
The following tables are a close approximation of the weight of a lump based on cubic lump and slab breakage characteristics:
Table 4-7. Lump Weight Factor in Pounds
Table 4-8. Lump Weight Factor in Newtons*
* Newtons, rather than kilograms, have been used to simplify calculations.
Density-
lb/ft3
Lump Size (in)
2 3 4 5 6 7 8 9 10 12 14 16 18
50
75
100
125
150
175
0.4
0.6
0.7
0.9
1.1
1.3
1.3
1.9
2.6
3.2
3.8
4.5
3.0
4.5
5.9
7.4
9.0
10.4
5.8
8.6
12.0
14.0
17.0
20.2
10
15
20
25
30
35
14
21
28
35
42
49
21
31
41
52
62
73
30
44
59
74
89
104
40
61
81
101
121
142
70
105
140
175
210
245
100
149
199
248
298
348
148
222
296
371
444
518
211
316
421
527
632
737
Densi-
tykg/m3
Lump Size (mm)
50 75 100 125 150 175 200 225 250 300 350 400 450
800
1200
1600
2000
2400
2800
6812
15
17
21
14
21
27
33
40
46
26
38
53
62
76
90
45
68
90
111
133
156
62
93
124
156
186
218
93
137
182
231
274
323
133
196
263
329
396
461
178
271
360
449
539
631
312
466
622
777
931
1088
445
613
882
1102
1323
1548
657
990
1313
1646
1980
2303
931
1401
1872
2372
2813
3273

COEFFICIENT OF FRICTION
A coefficient of friction is the ratio of the force required to slide a belt over its supporting structure to the normal force holding the belt
to the supporting structure. The static coefficient of friction uses the force needed to start the belt into motion from rest, and the kinetic
coefficient of friction uses the force to keep the belt in motion. Where reference is made to a coefficient of friction of belting, generally
the kinetic coefficient is meant, unless specified otherwise.
This important belt characteristic affects the suitability of belting in specific applications. Generally, very low coefficients of
friction are required on the bottom surface for slider bed conveyors to minimize power requirements, and low coefficients of friction
are desired on the top surface of belting in applications involving plowing off conveyed objects toward the belt edges. A higher
coefficient of friction on the top surface is generally desired when the top surface is used to drive carrying rollers.
Very low coefficients of friction are in the range of 0.15 to 0.25 typically. Untreated textile products have a coefficient of friction
against steel of approximately 0.20. Friction surfaces of belting have coefficients of friction against steel of about 0.40 to 0.50, and
belt covers have quite high coefficients of friction, from about 0.8 to values even greater than 1.0 depending on the formulation.
STATIC CHARGE DISSIPATION
In some belting applications the generation of static electrical charges can be very detrimental to safety. This is especially true where
static electrical discharges can ignite explosive mixtures of flammable materials such as dust from coal, grain, or wood. The ability of
the belt to help dissipate these static charges is a very important characteristic in these applications. The establishment of a properly
bonded grounding path from the belt through the conveyor to an earthing point is an important consideration.
ASTM D 257 -- Standard Test Methods for DC Resistance or Conductance of Insulating Materials and ISO 284 -- Conveyor belts --
Electrical conductivity -- Specification and test method, currently establishes 300 megohms (3 x 10 8 ohms) as the maximum electrical
resistance for belting. It is recommended that belting used in underground mines and in grain elevators meet this specification.
There are belting applications in the electronics industry and in ammunition plants that require an even higher level of electrical
conductivity, perhaps in the 10 4 to 106 ohms range. Although no national or international standard currently exists for this level of
performance, there are belting products that can be specifically designed to meet these requirements.

CHAPTER 5 TEXTILE BELT TOLERANCES
The width tolerances listed in Table 5-1 are the commercially accepted standards of the conveyor belt manufacturing industry. Tighter
tolerances may be specified by agreement between the individual manufacturer and his customer.
Table 5-1. Belt Width Tolerances
Zero Plus or Zero Minus Tolerances
If a customer specifies a zero plus or a zero minus tolerance, the full tolerance still applies to the belt. For instance, if a customer
requests a 26 in slit edge belt with a minus zero tolerance, the tolerance will read 26 in + 3/8, 0, but if molded edge + 3/4, 0. This
method of tolerancing is being used for clarity and simplicity and takes no stand on pricing of belt based on plus tolerances.
Tolerances on Lengths
The permissible tolerances for the lengths of conveyor belts, measured loose, are given in Tables 6-2 and 6-3 and as specified in ISO
251.
a) For endless belts, so delivered and mounted:
Table 5-2. Endless Belts
b) For open belts:
Table 5-3. Open Belts
Note: The lengths of conveyor belts are not standardized.
Belt Widths
Molded Edge Width Tolerance Slit Edge Width Tolerance
in mm in mm
Up to 24 in (600 mm) ± 1/4 ± 6 ± 3/16 ± 5
24 in (600 mm) up to 36 in (900 mm) ± 3/8 ± 10 ± 3/16 ± 5
36 in (900 mm) or greater ± 1% ± 1% ± 1% ± 1%
Length ft (m)
Tolerance in (mm)
over up to (inclusive)
-- 49 (15) ± 2 (± 50)
49 (15) 66 (20) ± 3 (± 75)
66 (20) -- ± 0.5% of the size in meters
Belt Delivery Condition
Tolerance (maximum permissible difference between the delivered length and the
ordered length)
As one length + 2.5%, - 0.0%
In several lengths for each single length ± 5%
for the sum of all lengths
+ 2.5%, - 0.0%

CHAPTER 6 TEXTILE BELT TEST METHODS
TEST METHODS
Below are the list of the tests against various standards.
ASTM International
ASTM D 378 Standard Test Methods for Rubber Elastomeric Belting, Flat Type
Included are tests for:
Measurements of Dimensions
Physical Properties of Elastomeric Covers
Immersion Tests
Adhesion Tests
Breaking Strength and Modulus Testing
Flame Test for Belting
Carcass Tear Test
Troughability Test
Breaking Strength of Mechanical Fastenings (Static Test Method)
Elevator Belt Bolt Holding Strength Test
ASTM D 2228 Standard Test Method for Rubber Property - Relative Abrasion by Pico Abrader Method
ASTM International standards can be obtained at www.astm.org.
Canadian Standards Association
CAN/CSA-M422-M87 -- Fire Performance and Antistatic Requirements for Conveyor Belting
CSA standards can be obtained at www.csa.ca.
International Organization for Standardization (ISO)
ISO 251 Conveyor belts with textile carcass -- Widths and lengths
ISO 252 Conveyor belts -- Adhesion between constitutive elements -- Test methods
ISO 282 Conveyor belts -- Sampling
ISO 283 Textile conveyor belts -- Full thickness tensile strength, elongation at break and elongation at the reference load --
Test method
ISO 284 Conveyor belts -- Electrical conductivity -- Specification and test method
ISO 340 Conveyor belts -- Laboratory scale flammability characteristics -- Requirements and test method
ISO 433 Conveyor belts -- Marking
ISO 433 Conveyor belts -- Marking (Amd 1)
ISO 505 Conveyor belts -- Method for the determination of the tear propagation resistance of textile conveyor belts
ISO 583 Conveyor belts with a textile carcass -- Total belt thickness and thickness of constitutive elements -- Test methods
ISO 703 Conveyor belts -- Transverse flexibility (troughability) -- Test method
ISO 1120 Conveyor belts -- Determination of strength of mechanical fastenings -- Static test method
ISO 1537 Continuous mechanical handling equipment for loose bulk materials -- Troughed belt conveyors (other than portable
conveyors) -- Idlers
ISO 3684 Conveyor belts -- Determination of minimum pulley diameters
ISO 3684 Conveyor belts -- Determination of minimum pulley diameters (Amd 1)

ISO 3870 Conveyor belts (fabric carcass), with length between pulley centres up to 300 m, for loose bulk materials --
Adjustment of take-up device
ISO 4195 Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods
ISO 4195 Conveyor belts with heat-resistant rubber covers -- Heat resistance of covers -- Requirements and test methods (Cor
1)
ISO 5284 Conveyor belts -- List of equivalent terms
ISO 5284 Conveyor belts -- List of equivalent terms (Cor 1)
ISO 5285 Conveyor belts -- Guidelines for storage and handling
ISO 5293 Conveyor belts -- Determination of minimum transition distance on three idler rollers
ISO 5293 Conveyor belts -- Determination of minimum transition distance on three idler rollers (Cor 1)
ISO 9856 Conveyor belts -- Determination of elastic and permanent elongation and calculation of elastic modulus
ISO 10247 Conveyor belts -- Characteristics of covers -- Classification
ISO 10247 Conveyor belts -- Characteristics of covers -- Classification (Amd 1)
ISO/TR 10357 Conveyor belts -- Formula for transition distance on three equal length idler rollers (new method)
ISO 14890 Conveyor belts -- Specification for rubber or plastics covered conveyor belts of textile construction for general use
ISO 14890 Conveyor belts -- Specification for rubber or plastics covered conveyor belts of textile construction for general use
(Cor 1)
ISO 15147 Light conveyor belts -- Tolerances on widths and lengths of cut light conveyor belts
ISO 16851 Textile conveyor belts -- Determination of the net length of an endless (spliced) conveyor belt
ISO 18573 Conveyor belts -- Test atmospheres and conditioning periods
ISO 21178 Light conveyor belts -- Determination of electrical resistances
ISO 21179 Light conveyor belts -- Determination of the electrostatic field generated by a running light conveyor belt
ISO 21180 Light conveyor belts -- Determination of the maximum tensile strength
ISO 21181 Light conveyor belts -- Determination of the relaxed elastic modulus
ISO 21182 Light conveyor belts -- Determination of the coefficient of friction
ISO 21183-1 Light conveyor belts -- Part 1: Principal characteristics and applications
ISO 21183-2 Light conveyor belts -- Part 2: List of equivalent terms
ISO 22721 Conveyor belts -- Specification for rubber- or plastics-covered conveyor belts of textile construction for underground
mining
ISO Standards can be obtained at www.ansi.org.
German DIN Specifications
Many DIN specifications are used internationally and most are available in English.
22101 Continuous conveyors - Belt conveyors for loose bulk materials - Basis for calculation and dimensioning
22102-1 Conveyor belts with textile plies for bulk goods; dimensions, specifications, marking
22102-2 Conveyor belts with textile plies for bulk goods; testing
22102-3 Conveyor belts with textile plies for bulk goods; permanent joints
22109-1 Conveyor belts with textile plies for coal mining - Part 1: Mono-ply belts for underground applications; dimensions,
requirements

1/2 “ D
1 1/16 “ D
4 1/2 “
22109-2 Conveyor belts with textile plies for coal mining - Part 2: Rubber - belts with two plies underground applications;
dimensions, requirements
22109-4 Conveyor belts with textile plies for coal mining - Part 4: Rubber - belts with two plies for above applications;
dimensions, requirements
22109-5 Conveyor belts with textile plies for coal mining; branding
22109-6 Conveyor belts with textile plies for coal mining - Part 6: Testing
22118 Conveyor belts with textile plies for use in coal mining; fire testing
22121 Conveyor belts with textile plies for coal mining - Permanent joints for belts with one or two plies; dimensions,
requirements, marking
DIN standards can be obtained at www.din.ne, or through ANSI at www.ansi.org.
BOW OF CONVEYOR BELTS
Bow is the concave deviation of the edge of the belt from a straight line between two points along the belt edge. (Camber is the
convex phenomenon, on the other edge of the belt.)
Bow is measured by unrolling at least 50 ft (15 m) and more preferably 100 ft (30 m) of the belting from a shaft-supported roll onto a
flat surface, so there is no tension on the belt. Place a tape or string between two points along the belt edge. Measure the belt length
between these two points, and also the distance at the mid-point of the length between the belt edge and the tape or string.
The amount of bow is the ratio of the distance, midway between the above two points, between the belt edge and the tape or string,
and the tape length between the two points. To express it in percent, calculate the ratio in hundredths and multiply by 100. For
example the point-to-point length of 100 ft (30 m) has a bowed width of 18 in (450 mm) or 1.5 ft so 1.5/100 x 100 = 1.5% bow. Bow
may not be troublesome. It may “pull out” when the belt is tensioned and operate satisfactorily.
The main causes of bow are:
a. Bowed filling yarns transversely across the fabric of the carcass;
b. Crooked slitting of the belt into a narrower belt, and;
c. Storage of a belt on its edge when the floor is damp or water and/or other liquids reach the belt edge on the floor.
RIP TEST SPECIFICATION
1. Purpose
a. Test the ability of a given fabric carcass to resist
ripping/tearing in the longitudinal direction once an
object has become logged both in the belt and the
system at the same time.
2. Sample Size
a. Sample Base - Length X Width - 12 in x 10 in
b. Punch 3 - 5/8 in holes in the upper half of the sample
with each hole being 2 in from the edges of the sample.
c. Punch one 1 1/16 in hole in the center of the sample
approximately 4 1/2 in from the end of the sample.
(opposite of the 3 - 5/8 in holes)
d. This is a carcass test, to eliminate variable effects of
covers the covers must be removed or a line must be cut
in the direction of the rip. Using a special blade that is
dulled on on the end cut a vertical line through the
Figure 6-1.

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Arpm manual-2-pdf