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CEMA Bucket Elevator Book-Section 7June 11, 2015 D-5

CEMA Bucket Elevator Book, Best Practices in Design1st Edition-SECTION 7, BeltsBucket Elevator CommitteeChair: Warren Knapp, SCC

Vice-Chair: Kris Gililland, KWS

ATTENTION: EDITORS / REVIEWERS, you must add your name and Draft number below if you are providing suggested edits and/or reviewing.

Contacts and ReferencesName Company Email AddressRaul Morales, Chapter Owner Rexnord [email protected] Tarver Maxi-Lift [email protected] Hannigan CEMA [email protected]

DRAFT / REVIEW* HISTORY

DRAFT 's # (i.e. D-1, D-2, etc.) Submittal Name DateDraft 1 Raul Morales 2/12/2013

Draft 2 Chris Tarver 2/14/2013Draft 3 Phil Hannigan 2/17/2013Draft 4 Raul Morales 5/28/2015Draft 5 Raul Morales 6/01/2015

REVIEWER's # (i.e. R-1, R-2, etc.) Name DateREVIEW 1REVIEW 2

FINAL


Chapter 7

BELTS


INTRODUCTIONBelts have been used in conveying since the 19th century, their first inceptions were quite primitive. In 1892, Thomas Robins began a series of inventions which led to the development of a conveyor belt used for carrying coal, ores and other products. The first steel conveyor belts produced were invented and introduced to the market in at the beginning of the 20 th century, allowing the transport of heavier loads at longer distances. In 1905 the first conveyor belts for use in coal mines were put in operation, which revolutionized the mining industry. These concepts were simultaneously being considered for use in higher incline conveyors and vertical conveyance i.e. bucket elevators.

As new materials are developed and quality materials become more readily available, changes in design have been made to adapt to these materials. New technology has improved both structural and mechanical design as well as manufacturing procedures. In recent times computer technology has helped reduce design time, lessen rework and increase understanding of the behavior of materials under different loadings. Likewise new technologies in manufacture have reduced production time, costs, weight and improved tolerances. These changes have allowed increased discharge height and greater capacities to be obtained. Clearly, this combination can only be achieved if the belts and chains used to elevate the material via buckets can be built for the increased tension, cycling and temperature requirements.

Early designs used multi-layered cotton belts which were constructed by rubberized cotton fabric layers plied one over another without adding eternal covers, or plied rubber belts, in which the high workloads were reached by means of accumulating fabrics with layers of rubber in between. This approach requires the use of larger pulley diameters to avoid the layers from delaminating as the belt flexes over the pulleys. Canvass-rubber belts are still in use although they are not adequate for handling abrasive materials. They also elongate considerably more and have less tension capacity than other types of belt construction.

Figure 7.01 - Examples of Canvass-Rubber


In a later evolution solid woven PVC types are also used, as shown in the example below.

Today there are multiple types of conveyor and elevator belts available that have been created for conveying different kinds of materials and to withstand more extreme temperatures. An additional consideration is the requirement for lower energy consumption. Cover is often one of various rubber or plastic compounds specified by use of the belt; two most common materials being PVC and rubber, but can be made from more specialized materials such as silicone for unusual applications.

The belt consists of one or more layers of material. Many belts used in light duty general material handling have two layers. An under layer of material to provide linear strength and shape called a carcass and an over layer called the cover. The carcass is often a woven fabric having a warp & weft. The most common textile carcass materials are polyester, nylon and cotton. Alternatively for higher capacity requirements the carcass will be made out of steel cables or a combination of fabric and steel. Polyester fabrics offer improved mechanical performance and better resistance to difficult operation conditions such as temperature, humidity and shock loads than historically conventional fabrics made from cotton.

Because of the nature of bucket elevators where the material is conveyed vertically, belts used in elevators are often exposed to extremely demanding and technically challenging environments. The consequences of an elevator belt or chain failing can be catastrophic, which is why safety must be the single most important consideration when selecting, applying, installing and operating them in a bucket elevator.

Fabric Carcass BeltsFabric (textile) carcass or core belts are the most common used in general light to medium duty industry and in the agricultural products handling segment. There is a large variety of styles in the market suited for an array of requirements.A very important consideration in belt selection is the overall center distance between foot and head pulleys because some belt styles are more prone to elongation. As the belt elongates it is necessary to adjust the take-up to maintain the constant required tension on the belt. Belts tend to elongate most during the first hours of operation but will continue to elongate progressively during their life, thus requiring periodic tensioning. Textile core belts present elongation that is proportional to the center distance between shafts and is exacerbated under high operating capacities or the weight of heavy gauge buckets required for abrasive materials. It is not unusual for total elongation of a synthetic textile core belt in a bucket elevator to be in the 1.5-2.0% range, and cotton fabric belts exceeding 3%. For an elevator with 200 ft (61 meter) centers the synthetic fabric core belt elongation will be approximately 6-8 ft (1.8-2.4 m), thus requiring 3-4 feet (0.9-1.2 m) of take-up travel. Since this exceeds the normal range of the take-

Figure 7.02 - Solid Woven PVC Belt Cross Section

Figure 7.03 - Belts with one layer of fabric braid will elongate more than multiple layer braid and steel core belts.

Figure 7.04 - Multi-layer fabric braids will elongate less than single layer braid fabric. Steel core belts will experience the lowest elongation. Picture shows examples of white material covers use in food

and fertilizer industries.


up travel it will require at least one instance of shortening and re-splicing the belt and removal of one or more buckets.

Multi-plied fabric construction distributes the load evenly, reducing elongation.

GRAIN HANDLING/AGRICULTURAL/INDUSTRIAL ELEVATOR & CONVEYOR BELTINGStandard Specifications for Common Rubber & PVC Belts

PVC/Solid Woven Single Ply ConstructionIdeal for service in bucket elevators conveying grain, feed & seed or applications requiring a low stretch, good cut, gouge & tear resistant all polyester carcass which is moderately oil resistant. PVC has excellent ozone and weather resistance and can wrap smaller pulleys than rubber belting. Not recommended in subzero temperatures although low temp PVC belts are available on the market. PVC does not have a high abrasion resistance and the thinner covers will wear away in abrasive industrial application however due to the impregnating of PVC in the solid woven fabric, during the manufacturing process, the belts will greatly resist further wear even after covers are worn away which can make PVC a lower cost option in industrial elevators.


Heavy PVC belts, greater than 200#, made domestically in the U.S. are typically formulated for grain elevator service meeting OSHA standards for static conductivity and MSHA standards for flame resistance. Covers are typically listed as CBS, cover both side, also the same CXC, cover x cover, and COS, cover one side.

Interwoven PVC Styles PVC 200 PVC 250 PVC 350 PVC 450 PVC 600Working Tension (PIW) 200 250 350 450 600Elevator Rating (PIW) 180 220 310 400 530Max Bucket Projection 5" 6" 8" 9" 11"Min Pulley Diameter 4" 6" 8" 10" 12"Thickness .240" .260" .300" .360" .375"Belt Weight (#PIW) 0.133 0.146 0.167 0.200 0.208

Temp Range (°F) Min/Max 0/180 0/180 0/180 0/180 0/180*CBS - Cover Both Sides

SBR Rubber/Plied Construction (RMA Grade 1 & 2)Mainly used for bucket elevators or conveyors handling aggregates, sand, gravel, ores, cullet, coal, salt and potash where impact and abrasion are a concern. Styrene-butadiene rubber, commonly known as SBR is a general purpose rubber that is lesser expensive and is typically more abrasion resistant than other rubber compounds found in elevator and above ground conveyor belting making it the primary belt for most industrial application. It is not recommended in applications where oil is present and would not be recommended in application greater than 200° F (93° C). Heavy covers, ¼” (6.4 mm) and greater, are recommended when impact from loading is a concern which is mainly in conveyor applications. Heavy covers are not all that necessary in elevator application although due to the availability of these specs they are typically more common on plied rubber belts greater than 330 lbs.

Table 7.05 - Ratings for PVC BeltsPVC BELTS, MODERATELY OIL RESISTANT, STATIC CONDUCTIVE, FLAME RESISTANT


Plied Rubber Styles 2-220 3-330 3-330 4-440 3-600

International Designation EP400/2 EP600/3 EP600/3 EP800/4EP1050/

3No. of Plies 2 ply 3 ply 3 ply 4 ply 3 plyWorking Tension (PIW) 220 330 330 440 600

Standard Covers3/16x1/1

63/16x1/1

61/4x1/1

61/4x1/1

6 1/4x1/16Elevator Rating (PIW) 190 290 290 380 520Max Bucket Projection 6" 7" 7" 10" 10"Min Pulley Diameter 12" 14" 14" 18" 18"Thickness 0.370 0.410 0.475 0.530 0.550

Belt Weight (#PIW) 0.185 0.210 0.255 0.270 0.275Temp Range (°F) Min/Max -30/200 -30/200 -30/200 -30/200 -30/200

Nitrile Rubber/Plied Construction (Types SOR, SC & FR)Best for service in bucket elevators or conveyors handling oil-treated grains, crushed soybeans and other materials where animal or vegetable fats are a deteriorating factor and where combustion properties area concern. All of the belts in these groups contain Nitrile rubber, also known as Buna-N, Perbunan, acrylonitrile butadiene rubber, and NBR, which is a synthetic rubber copolymer of acrylonitrile (ACN) and butadiene. (SOR) Superior or Super Oil resistant is regarded as having a high amount of Nitrile rubber, 70% or higher. (OR) Oil resistant will typically have around 50% Nitrile rubber and (MOR) compounds are typically 30% or greater Nitrile with some woodchip MOR belts having down to 10% Nitrile rubber. (SC) Static Conductive to meet OSHA Standards and (FR) to meet MSHA standards. Covers are usually balanced covers 1/16 x 1/16.

Plied Rubber Styles 2-220 3-330 3-330 4-440 3-600

International Designation EP400/2 EP600/3 EP600/3 EP800/4EP1050/

3No. of Plies 2 ply 3 ply 3 ply 4 ply 3 plyWorking Tension (PIW) 220 330 330 440 600


63/16x1/1

61/4x1/1

61/4x1/1

6 1/4x1/16Elevator Rating (PIW) 190 290 290 380 520Max Bucket Projection 6" 7" 7" 10" 10"Min Pulley Diameter 12" 14" 14" 18" 18"Thickness 0.370 0.410 0.475 0.530 0.550

Belt Weight (#PIW) 0.185 0.210 0.255 0.270 0.275Temp Range (°F) Min/Max -30/200 -30/200 -30/200 -30/200 -30/200

Table 7.06 - Ratings for SBR Belts

Table 7.07 - Ratings for Nitrile Belts Belts

SBR RUBBER BELTS (RMA GRADE 1 & 2 INDUSTRIAL APPLICATIONS

SBR RUBBER BELTS (RMA GRADE 1 & 2 INDUSTRIAL APPLICATIONS


High Temperature Nitrile/Plied Construction (HOR) & (HAR)Same as Nitrile rubber above this belt would be ideal in applications where oil is a deteriorating factor but an operating temperature up 400°F is also needed. This belt can be called either (HOR) heat & oil resistant or (HAR) Hot Asphalt Rubber, and in some cases may be available in a grain compound that would be (SC) static conductive and (FR) flame resistant.

EPDM/Plied Rubber Construction (High Temp)Main use is bucket elevators or conveyors requiring peak operating temperatures up to 350°F, for fines, and 400°F for lumps. EPDM (ethylene propylene diene monomer), also known as Nordel™ has excellent resistance to heat, ozone, weather and steam. It also has superior resistance to hardening and cracking within its recommended service temperature range. EPDM is not recommended if oils are present.

Newly developed rubber compounds based on (EPDM) allow operational ranges up to a material temperature of 300 °F (150 °C) for some belt bucket elevators. Even peak temperatures up to 338 °F (170 °C) may be reached during brief periods. Load tests under industrial daily routines have shown that EPDM-belts are much more resistant to aging than belts made of SBR.

Plied Rubber StylesEPDM

220EPDM

330 HOR 220 HOR 330International Designation EP400/2 EP600/3 EP400/2 EP600/3No. of Plies 2 ply 3 ply 2 ply 3 plyWorking Tension (PIW) 220 330 220 330


61/4x1/1

63/16x1/1

63/16x1/1

6Elevator Rating (PIW) 190 290 190 290Max Bucket Projection 6" 7" 6" 7"Min Pulley Diameter 12" 14" 12" 14"Thickness 0.370 0.475 0.370 0.410Belt Weight (#PIW) 0.175 0.245 0.185 0.210Temp Range (°F) Min/Max -30/400 -30/400 -10/300 -10/300

Table 7.08 - Ratings for EPDM Belts BeltsHIGH TEMP BELTS, (EPDM) (HEAT & OIL RES)


The table below can be used as a summarized reference for belt cover material selection. It does not include all variations as manufacturers can create a large variety of polymer blends for specific application requirements.

In both fabric and steel core belts the cover materials available are available in various materials but because steel core belts are considered a premium product for more severe and/or critical applications it is most common to find them in EPDM type materials.

STEEL CORE BELTS

Steel core belts for bucket elevators were developed in response to the market demands for greater elevator heights and/or larger volumetric material handling capacities, exceeding the limitations of chain and textile core belts for very tall bucket elevators. These are for use only by reputable bucket elevator manufacturers due to the liability consequences.

For example, in the cement industry the requirement for greater energy efficiency has resulted in new plant designs. Multiple stage preheaters and pre-calciners make use of the waste heat from the kiln and clinker cooler to pre-heat and pre-process the kiln feed, and thereby allow for considerable energy savings. Whenever economically feasible a wet process kiln can be converted to a state-of-the art dry process production facility that includes either a multi-stage preheater, or a multi-stage pre-heater and a pre-calciner. Such transformations are usually feasible for new plants and major upgrades. Kiln systems with five cyclone preheater stages and precalciner are considered standard technology for ordinary new plants. Typical efficiency values that can be obtained with the use of multi-stage preheaters and pre-calcination is provided in the table below*:

Table 7.09 - Reference Table of Commercially Available Belt Cover Materials


Heat Consumption of Different Cement Kiln Technologies (IEA, 2007. p.145))

Process Fuel Consumption (GJ/t-clinker)

Wet processes 5.9 – 6.7

Long dry processes 4.6

1 stage cyclone preheater 4.2




5 stage cyclone preheater 3.0 – 3.1


*Source: Industrial Efficiency Technology Database; a project of the Institute for Industrial Productivity

Higher efficiency requirements are creating an increased need for multistage preheater towers that have six cyclone stages. Since preheaters operate in a downward flow each additional stage requires a taller structure and, thus taller bucket elevator to transport the raw kiln feed. These bucket elevators are amongst the tallest in the world, commonly achieving inlet to discharge lifts in excess of 360 ft (120 m).

Table 7.10 - Heat Consumption

Figure 7.11 - Dry Kiln with Five-Stage Pre-heaters & In-line Calciner


The center distances of bucket elevators required for preheater towers and many large grain storage facility silos exceed the maximum height and/or capacity of chain and textile core belt bucket elevators, which are constrained by several factors:

Chain elevator heights are limited by the added weight of the chain supported below, which is additional to the weight of the buckets and material being elevated. The added chain weight reduces the amount of material that can be elevated before exceeding the chain’s working load limits and requires the use of an oversized head shaft. Even though chain elevators have been successfully built and operated reliably for discharge heights exceeding 200 ft (61 m) these might not be sufficiently tall for some of the industry requirements. As chain technology evolves the height limitation will progressively be set at taller elevator designs.

Steel core belt bucket elevators can operate at higher speeds than chain elevators, achieving speeds in excess of 500 fpm (2.5 m/s) which allow for increased capacity.

Since, as noted previously in this chapter, textile core belts present elongation that makes their use in very tall-high capacity elevators impractical because of the added maintenance requirements, plants operating critical equipment where downtime is very costly opt for premium steel carcass belts.

Proper belt tracking is sometimes difficult to achieve in tall textile cord belt elevators due to the inherent elasticity of the belt.

Higher lifts are possible due to the strength-to-weight ratio of the steel cord belt, which can achieve ratings of tensile ratings of 4000 N/mm, which at a safety factor of 10 could roughly be equivalent to 2,280 PIW rated working load. Textile core belts normally rate at a maximum of 1,000 PIW. It is important to note that steel cord belts are not rated using the PIW rating system customary in the USA; they are rated based on N/mm breaking strength.

Construction of Steel Core BeltsThere are four main concepts utilized in steel cable configuration within the belts:

a) Evenly spaced longitudinal cables: Steel cables running only in longitudinal manner and evenly spaced throughout the belt width.

b) Longitudinal cables with cable free zones: Steel cables running only in longitudinal manner having cable free zones along the locations of the bucket attachment bolts.

Table 7.12 - Common Ratings for Steel Core Belts and Equivalencies**Between PIW and N/mm when applying the industry accepted safety factor of ultimate strength rating at 10 times greater than operating calculated rating.


c) Weft-mesh construction, which combines steel cables evenly spaced throughout the belt width with a transversal weft arrangement.

d) Weft-mesh construction with longitudinal cable frees zones, similar to weft-mesh construction but has longitudinal cable-free zones for bucket attachments, while retaining most lateral integrity.

Weft Mesh (steel-fabric) constructionFigure 7.14 - Typical Cross Section of a Steel Cable used in Conveyor Belts and Bucket Elevators.

Picture shows a belt lacking warp cables.

Figure 7.04 - Steel Cable Belts Running Only in Longitudinal Configuration

Steel cable belts

running only in

longitudinal configuratio

n.

Steel cable belts running

only in longitudinal

configuration.

Figure 7.13-Steel Core Belts


This belt for bucket elevators is a steel carcass rubber covered elevator belt constructed with special quality, low elongation yet high elasticity steel cords in the length and cross rigid cables in the width.

Their construction and characteristics differ from those of traditional steel cable belts. They are destined for heavy duty industrial applications with long centre distances, requiring stable running and reliable belts with high safety factor.

Elevator Belts consist of a steel carcass in a solid rubber mass that cannot delaminate. The built-in elasticity allows running over slightly crowned pulleys while the cross rigid weft construction results in excellent straight tracking characteristics.

The structure of weft mesh style elevator belts is a steel carcass composed by a strong warp of steel cords with suitable elastic modulus, longitudinally aligned, such to reach the best compromise between low elongation and good flexibility. This characteristic makes the belt easier to be aligned than traditional steel cord elevator belt which only uses longitudinal cables.

The minimum cover used for this type of belt is 3 + 3 mm.

The most important characteristics of the metallic meshes used are:

Maximum elongation of 0.5% (0.3% for the best quality belts) at full working load, even for the longest belts.

Possibility of constructing the mesh with “free areas” (the standard construction of the mesh does not include areas free of warp cables).

The cables used in the warp direction (length of the belt) along with the weft direction cables (transverse to the belt) form a compact mesh with a structure which is resistant to deformation and offers enhanced resistance to potential damage.

The open construction of the cables allows the belt rubber to penetrate the structure, thus avoiding the potential corrosion of the cables in the case of accidental cover damage.

.Furthermore, the cable elasticity allows the use of smaller diameter pulleys with, depending on the requirements of belt splice (clamp) and buckets.

Two regular steel wefts placed on top and bottom cover give to the belt high transversal stiffness, necessary to assure the best stability during its operation; at the same time, it helps to significantly maintain belt integrity in the area of bucket bolts, highly increasing cutting and tear resistance and reducing the risk of bucket dislodgment.

Due to the high quality of steel cords required for the carcass construction, it is possible to design weft mesh style belts with lower safety factors than Figure 7.14 - Steel weft mesh construction showing warp (longitudinal) cables, which have a larger diameter, and weft (transversal) cables. Mesh is secured in desired configuration by the zigzag brown nylon cords.


the ones required in traditional cable-only construction without cable free zones. It is critical to note that, since some cords are broken during the punching process, it is always recommended to use a minimum safety factor of 10 calculated considering the useful belt width. However, if very low elongations are required the safety factor should be doubled.

IMPORTANT: Always consult the belt manufacturer for specific recommendations regarding safety factors. The number of bucket attachment holes punched, size of these and separation between them will affect the belt strength, thus it is always best to contact the belt manufacturer for guidance on selection and ratings.


Belts with cable-free zonesSome elevator manufacturers prefer to utilize steel core belts with sections that are free of longitudinal (warp) cables. These cable free zones are located in the same positions as the bucket attachment bolt holes, with the intention of making the belt hole punching process easier, since it does not require cutting through the steel cables. Some manufacturers’ strength ratings of the belt are based on this construction, thus the safety factors required are usually lower than when the holes are punched through cable sections as in the standard weft construction where the minimum safety factor of 10 is used to partially offset the decreased belt ratings caused by hole-punching.

Figure 7.16 - Steel weft construction with warp cable-free zones. The transversal weft cables are maintained for integrity and uniformity.

Figure 7.17 - Steel cord construction with cable-free zones. This design does not include weft (transversal) cables.

Table 7.15 - Belt classes*

*Table above is representative of high capacity steel core elevator belts. Note that the construction for 3000 and 3500 N/mm rated belts uses dual weft (transversal) cord sizes to better maintain belt integrity


One drawback of cable free zones that do not include weft (transversal) cables is the potential of the bucket attachment bolts ripping the belt longitudinally along the cable free zones, as shown in the image below.

BELT SPLICING

Belt Splices and SplicingBelt splices are used to connect two ends of belt and therefore allow the belt to make a continuous loop around the head and tail pulleys. The belt splicing system is a very critical element in the belt elevator system; proper selection and application are best left to the suppliers of this very important component to ensure reliability and safety of the belt bucket elevator. Because of the high fatigue cycles they endure (>1 million cycles in many cases) proper selection is critical to the reliability, long life and safety of the bucket elevator. Likewise, due to the critically of belt splices, when servicing the elevator never re-use hardware: Always use new bolts, nuts & washers. In all instances this guide should never be used for man-lift applications. Use on wing pulleys is not recommended under the ratings listed here – consult the manufacturer.

Method of textile belt splicing is determined by the number of plies and the severity of service required. For most elevators, plate type fasteners can be used.

Fabric Belt Splicing Without Use of Mechanical ClampsBelt splicing can be achieved without the use of mechanical clamps but it is not the preferred method for high capacity or very tall elevators as the overlapped belts are subject to higher stresses which could shorten the belt life and increase the risk of failure. Since the bolts securing the splice are also holding buckets and their load there is more potential for failure than if the bolts are only securing the clamp.

Lap Splice: For belt thickness up through six ply, the belt ends are lapped for a minimum of three buckets. These buckets are bolted though both thicknesses of the belt lap. To avoid damage to belt end when coming in contact with the pulleys it is important to cut it at a bevel, as shown in Figure 7.xx

Figure 7.18 - Picture shows the consequences on a belt from bucket bolts tearing a steel core belt without transversal weft steel cables. Nylon cables (ripped in picture) are in many instances insufficient to retain the bucket load.


Butt & Strap Splice: For belt thicknesses of seven ply or more, a butt and strap joint (also known only as butt splice) is more satisfactory than the lap type splice because severe stresses are set up in the outer plies as the belt passes around the head and boot pulleys. These stresses are decreased when the two ends of the belt are butted together and a layer of strong and flexible nylon fabric belting is placed over the joint, extending under a minimum of two buckets in each direction, although for a safe splice it is preferable to have a minimum of three buckets in each direction. The buckets are bolted though both layers of belting.

Usually the Butt & Strap method can be used instead of Lap Splice but not vice versa.

Fabric Belt Splicing Using Mechanical ClampsFollowing are various types of mechanical belt splices commonly applied:

1. Light Duty Aluminum Fastener

The light duty style aluminum fastener is used for fabric belts requiring a maximum rating of 220 PIW. The two ends of the belt are gripped between extruded serrated plates, clamped together by zinc plated high tensile bolts, secured by plated self locking nuts to give a reliable light duty rustproof fastener.

This fastener forms a butt joint, the belt runs smoothly over the pulley with minimum stress to the joint and no relative movement can take place between the two belt ends, as is the case when an overlapping joint passes over the pulleys.

Figure 7.19 - Lap Splicing Method Figure 7.20 - Butt and Strap Splicing Method


Light duty bar style aluminum fasteners should never be used on man-lifts or wing pulleys.

For belts up to 220 PIW and up to 3/8" (10.0 mm) thick

Vise grip between serrated jaws Must be secured by high tensile bolts and self

locking nuts The bars should have radius rounded edges to

reduce joint wear Commercial range of standard lengths from 2 to 12

inches

2. Medium Capacity Grooved Mechanical Belt Splice

The mechanical belt splice is a mechanical clamping device with a simple three-piece construction used on textile belts. Two are identical outside plates, and the third is a center plate with an elongated center hole. The outside plates and the center plate are “mating” parts with peaks and valleys opposite of each other for firm gripping. The splice functions by using the tension supplied by the belting. This tension on the belt ends pulls the outer plates apart and forces gripping pressure towards the teeth on the splice unit. The greater the belt tension, the more pressure is exerted on the gripping teeth at the forward end of the splice. The splice is held together by a ½” diameter, grade 5 bolt. The length of the bolt varies depending on belt thickness. Use 4” long bolts for belts up to ¼” thick. Use 4-1/2” long bolts for belts between ¼” and ½” thick, and use 5” long bolts for belts between ½” and ¾” thick.

Grooved sectional mechanical belt splices are manufactured out of two different materials, a bronze alloy (AB) and hot-dipped galvanized cast iron (CI). AB splices are typically used in agricultural and heavy duty industrial applications as they are non-sparking, non-corroding, and non-rusting and are usable on belts of up to 800 PIW tensile. CI splices are typically used in industrial applications as they can spark and can corrode and are usable on belts of up to 600 PIW tensile. Each splice is good for 2” of belt width (Ex: A 10” or 11” wide belt would use 5 splices.). Template tape that will peel and stick directly onto the belting is typically provided and shows the location of all the holes and splices to simplify installation.

NON-FERROUS

Usable on belts of up to 800 PIW tensile strength Non-sparking, non-corroding & non-rusting Bronze color Average commercial weight 2.9 lbs. each

FERROUS Usable on belts of up to 600 PIW Tensile Strength Silver Color Average commercial weight 2.6 lbs. each

Figure 7.21 - Light Duty Aluminum Belt Fastener


FEATURES For Belts 600 to 800 PIW Tensile Strength Use on PVC and Rubber Belting For Belts 600 to 800 PIW Tensile Strength Non-Sparking (Non-Ferrous Version) Max. Temperatures: CI Ferrous 600°F (315°C), BA Non-Ferrous 500°F (260°C) Each Splice Accommodates 2" of Belt Width

3. High Capacity Grooved Mechanical Splice

For use with elevator belts rated at 800 - 1200 PIW. The design is similar to the three piece construction of the medium duty mechanical splice clamp, and clamps together using two grade 5 bolts per section. The high capacity clamp is constructed using a central vise-grip section bracketed by two exterior solid clamps. Utilizes clamping force and friction to secure the load. The addition of the NBR rubber wedge protects belts for long life. Rubberized wedge section shall be oil resistant, suitable for use up to 176° F / 80° C (Use aluminum wedge for higher temperatures).

Typical commercial size: Each splice accommodates 3” of belt width.

4. Heavy Duty Clamp Splice

Figure 7.22 - Hot-dipped galvanized cast iron (CI) medium capacity clamp

splice

Figure 7.23 - Bronze alloy (BA) medium capacity clamp

splice

Figure 7.24 - Construction of CI and BA style medium capacity

mechanical clamps

Figure 7.25 - ?????????????????????


For belt of capacity exceeding 800 PIW, sometimes encountered at river and export facilities and 24 hour processing plants, even more substantial mechanical belt splices are utilized (i.e. Heavy Duty Splice). This three piece splice is constructed out of aluminum and is non-sparking / corrosion resistant. It is constructed of a central aluminum vise-grip section which is bracketed by two exterior solid aluminum clamps. Utilizing clamping force and friction to secure its load, the belt ends are bent through a 75 mm radius to a 90° angle. The central wedge is equipped with a rubber backing on the pulley side to prevent belt wear due to pressure and friction generated in operation. This type of splice is currently being used on up to 1400 PIW belting.

Steel Core belt Splicing - Only Mechanical ClampingThe belt splice is one of the most critical components in the belt elevator system. Due to the very high tension which steel cord belts are built to sustain, the belt splice must be designed and selected with the following key features in mind:

strength resistance to fatigue ease of installation

Figure 7.26 - High capacity splice (Aluminum) with rubberized wedge section suitable for use up to 266 °F/130 °C. For temperatures exceeding 266 °F/130 °C the rubber segment should be replaced by an all

aluminum wedge.


The strength of the splice comes from the clamping force that is exerted on the belt ends from the two outer splice plates and the center plate. Standard splice fasteners use locknuts to reduce the risk of bolts loosening. Because the belt will compress after initial installation and potentially will creep during operation, this requires other standard bolt designs using flat washers to be re-tightened periodically. The mechanical cord clamp at the end of the splice joins the bare ends of the steel cords to provide an added safety factor to the belt splice.

The belt rating will determine the required style of cord clamp to be utilized. In the image below the splice for the belt section is the same but the rating is determined by the length or number of sections in the cord clamp(s).

Figure 7.27 - Steel core belt elevator belt splice design widely industry-accepted. Aluminum portion (light color) clamps the full belt width. Steel clamp is designed to securely hold the steel core cables;

number of linear bots is proportional to the PIW or N/mm belt rating.


A premium design splice design is available in which the splice fasteners use disc springs to maintain bolt tension so that the fasteners do not suffer fatigue. The disc springs are designed to compensate for the inevitable creep of the rubber belting which requires other splice designs to be re-tightened periodically.

Other belt splice designs utilize molten metal or epoxy for cord end entrapment. These processes require following detailed installation procedures which must be carefully performed due to the inherent danger of handling hot molten metal or risk improper mixing of epoxy which would result in a weak bond.

Figure 7.28 Premium style splice with disc springs to ensure proper bolt

tightening is maintained as belt covers compress during operation

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