Mechanical fasteners offer an economical, reliable and long lasting belt splice method. They are the most common belt splicing method in use today, for both light and heavy-duty conveyor belt applications. Mechanical belt fasteners are easily installed with only a modest amount of mechanical skills and tools. The purpose of this section of the reference section is intended to acquaint the reader with some of the mechanical fasteners available today. The information contained herein is intentionally general in nature. It is recommended that the fastener manufacturers be consulted for specific product and application information and recommendations.

The majority of belts being manufactured today are made of synthetic materials, which lend themselves to mechanical attachment, and most modern conveyor belts are designed for use with mechanical fasteners. This, coupled with constantly improving designs and materials in mechanical belt fasteners provide belt operators with a reliable, long-lasting and quite inexpensive way to splice belts. The combination of belts designed for mechanical fastener splices and improved fastener designs has extended the use of mechanical fastener splices to service at higher tensions, and this trend will continue with further fastener and belt developments.

Mechanical fastener splices today offer permanence once considered not available with them. This is due to the combination of fasteners designed and made with improved materials and modern belts that are designed for fastener splices. It also is due to other features designed for fastener splices such as countersinking which permits maintaining the belt profiles. All belt fastener processes, fastener installation, countersinking, etc. are designed for short notice rather than waiting for outside contractors. This translates into significant cost savings as downtime is minimized and production may continue without substantial interruption.

In summary, some of the benefits of using mechanical fasteners are:

1. Cost - Typically, mechanical fasteners offer the lowest cost approach to belt splicing. This is due to lower splice material cost for the mechanical fastener splice components and the fact that the work can be done in-house.
2. SPEED OF INSTALLATION - Typical splices can be installed in minutes, reducing downtime.
3. EASE OF INSTALLATION - Splicing requires relatively simple and inexpensive tooling which is readily available and can usually be kept on site. While some mechanical skill is needed, it is relatively simple to splice with mechanical fasteners.
4. SAFE TO USE - There is little or no exposure to chemicals, sharp instruments or heat when installing mechanical fasteners.
5. EASE OF INSPECTION - Splices are visible and give signs of impending failure.
6. LITTLE EXTRA BELT LENGTH REQUIRED - The only belting cut off and discarded is that generated in squaring the belt ends when making mechanical fastener belt splices. The extra length of belt required for mechanical fastener splices is measured in inches.
7. NO SHELF LIFE LIMITATION - Mechanical fastener splice materials do not deteriorate while in storage.

Mechanical conveyor belt fasteners are manufactured in two styles, solid plate and hinged. Each has its particular advantages and the selection of fasteners should begin with this basic understanding. Solid plate fasteners span opposing belt ends that have been butted together, forming a tight, sift-free splice. Hinged belt fasteners are applied as individual segments to each belt end and then brought together and connected by means of a connecting hinge pin.

Solid plate fasteners are generally employed where a sift-free splice is required, such as bulk conveying applications. The two belt ends, having been brought firmly together, prevent fines from sifting through the splice area. Generally, solid plate fasteners are considered as a permanent attachment and are seldom used where the belt or the conveyor must be frequently taken apart. For the most part, solid plate fasteners require larger minimum pulley diameters than hinged fasteners.

Hinged fasteners, as implied above, can be operated on systems employing smaller pulley diameters. This inherent design feature allows for a broader range of applications than is available with corresponding solid plate fastener styles. Hinged fastener splices can be separated for belt removal or maintenance by removing the hinge pins. Some hinged fasteners have a sift preventing component and thus can be used on belts conveying fines, but they are more frequently applied in other applications.

As the "working" part of a hinged fastener splice, the hinge pin should be selected as carefully as the fastener itself. Quite often it makes sense to select a pin of the same material as the fastener. For example, a stainless steel pin would be chosen for a stainless steel fastener. Solid (single) wire pins are the easiest to insert and are most often used on non-troughing applications. Stranded cable wire pins are recommended for troughing conveyors given their greater flexibility.

Both solid wire pins and stranded cable pins are offered either with or without an external polymer covering. This polymer "jacket" serves as a lubricant when positioned between the loops of the hinged fasteners. As such, this pin style is less likely to wear or corrode. However, they are not the preferred choice where fine abrasive materials are being conveyed, wherein a solid wire or unjacketed cable pin is a better selection.

Other hinge pin choices include nonmetallic pins for smooth running at lower belt operating tensions as well as notched or corrugated pins, which reduce the likelihood of pin migration.

Hinge pin selection is as important as proper hinged fastener selection. Properly selected and installed, they contribute to maximum splice life and performance. As with selecting hinged fasteners, the fastener manufacturers should be consulted for hinge pin recommendations.

The market for conveyor belt fasteners generally breaks down into two major segments, light duty and heavy duty. NIBA designates light duty belts as those having a tension rating of 160 PIW or less, and heavy duty belts as those with tension ratings over 160 PIW. Light duty conveyor belt fasteners include wire hooks, common bar lacing, stapled plate fasteners, plastic hinged plate fasteners and plastic spiral loop fasteners. Heavy-duty conveyor belt fasteners include bolted and riveted plate fasteners and stapled, bolted and riveted hinge fasteners. Heavy-duty fasteners are available for operating tensions up to 1500 PIW. While it is suggested that the individual manufacturer fastener catalogs be consulted for application information, a representative sampling of fastener types is illustrated in the following pages for reference.

Wire Hook

1.  A hinged fastener comprised of high strength formed wire hooks utilizing a connecting pin.

Generally provides a strong belt splice, which is flexible in both axis of the belt.

Common Bar Wire Hook

2.  The same as above except the welded cross wire decreases the chance of hooks becoming dislodged from the balance of the belt splice.

Common Bar Lacing

3.  A hinged fastener made by stamping and forming teeth from a continuous ribbon of steel. Generally, only a hammer is needed for installation, making it more practical for some applications.

Stapled Plate

4.  A light to medium duty hinged plate fastener that derives its strength by the compressive clamping action of either rivets or staples. Provides stronger splices in most types of belts.

Plastic Spiral Loop

5.  A light duty non-metallic fastener, supplied in a webbing that is vulcanized or cemented to the conveyor belt. Provides a low profile splice that can be used with metal detectors.

Plastic Hinged Plate

6.  A non-metallic hinged fastener for light duty belts. Available in multiple styles. Can be used with metal detectors. Available in FDA approved materials. Also available in weather resistant materials.

Bolted Hinge

7.  A heavy duty bolt hinge fastener for bulk haulage applications. Commonly used in low to medium tension industrial belts requiring a hinged splice. The fastener plates are compressed into the belt by special bolts and nuts. Only simple hand tools needed for installation.

Riveted Hinge Plate

8.  A heavy duty riveted hinge fastener for medium to high-tension bulk haulage applications. Available in several types of rivets and fasteners. Special rivets are driven through the belts, without prepunching holes, to compress the fastener plates into the belt.

Heavy Stapled Plate

9.  A heavy duty stapled hinged fastener for medium to high-tension bulk haulage applications. High strength staples are driven through the belts without prepunching holes, to compress the fastener plates into the belt. Provides a very flexible splice.

Bolted Solid Plate

10.  A solid plate butt joint compression belt splice. Like the bolt hinge, special bolts and nuts are used to compress the plates into the belt surfaces. These fasteners are generally used for the heavier bulk haulage applications where a sift-free, more permanent belt installation is needed. Only simple hand tools needed for installation.

Riveted Solid Plate

Mechanical fasteners for belting are to be selected in much the same process as belting. To properly select a mechanical belt fastener both the physical and environmental factors must be considered, but not to be forgotten are the experience factors. Many belting manufacturers provide a recommended belt fastener style based on working tension, pulley size and construction of the belting. Mechanical belt fastener manufacturers provide tables, which are to be used as a guideline based on belt thickness and pulley diameters.

While the user/installer should refer to the belting and fastener selection guides, the decision process must then include product based on type of service desired (Hinged - Solid Plate), type of material (Carbon Steel - Stainless Steel - Plastic - Other), installation techniques (Hand or Power Tools, or Specialized Machines).

MILD CARBON STEEL

General service where corrosion, sparking or magnetic attraction is not a consideration, sometimes plated to prevent rusting.

HIGH CARBON STEEL

Same as above, except for improved tensile strength and abrasion resistance.

HARDENED ALLOY STEEL

Highly abrasion resistant, providing several times service life of regular steel in highly abrasive situations. Not recommended for corrosive environments.

CAST MALLEABLE STEEL

Severe abrasion in corrosive environments, i.e., coke and sinter operations.

400 Series

Provides some corrosion and chemical resistance when compared with carbon steel; is magnetic and can be used with magnetic tramp removal devices.

300 Series

Non-rusting and provides extra resistance to corrosion from acids and chemicals; excellent where sanitation requirements are high; basically non-magnetic.

Nickel and copper alloy (Monel)

Exceptional corrosive resistance in environments that quickly deteriorate carbon and stainless steel, such as brine, hydrogen fluoride or dry chlorine. Work hardens good abrasion resistance.

Hastelloy and Inconel

Superior corrosion and chemical resistance at elevated temperatures, including sulphur and chloride ions.

BRONZE ALLOY (EVERDUR), SILICON AND PHOSPHOR BRONZE ALLOY

Fully non-magnetic and non-sparking.

OTHERS

Having carefully selected the best fastener style suited to the application, properly installing these fasteners will greatly improve the splice service life. The first step towards ensuring that the fasteners and belt will work effectively in tandem with each other, and the supporting framework, is to install the fasteners square to the belt centerline. With any mechanical splice, the most common installation error is not applying the splice straight.

Although there are many suggested methods of accomplishing this, placing a carpenter's square along an average centerline of the belt (taken at several points along its length) is the simplest. Using the belt edge as a squaring guide is not generally recommended. Preparation of the belt ends is important and operators should be sure they have the right tools for doing the job properly. These include cutters, pull-up clamps and any special equipment for recessing fasteners in the belt cover. This procedure is generally helpful to extend fastener life and avoid operating problems. Splice life may also be prolonged through a good program of preventive maintenance, including periodic inspection and, where necessary, replacement of worn splice sections or entire splices.

(Refer to Tech Note #14 Establishing Centerlines and Squaring Belt Ends For Splicing.)

COUNTERSINKING / SKIVING

While mechanical conveyor belt fasteners can be readily applied directly to the belt covers, there are some instances where it is advantageous to lower the fasteners into the belt. Countersinking the fasteners lowers the overall profile of the splice and is most frequently done on the carrying side of the belt. Depending on the belt construction, fasteners may also be countersunk into the bottom covers.

When fasteners have been countersunk, less material is left exposed to contact with the contents being conveyed, scrapers, plows, idlers and other related conveyor hardware. Wear through abrasion is greatly minimized thereby extending splice service life. Under running conditions there is also less abusive impact wear to both the splice and the belt.

Countersinking is equally suited to light or heavy-duty belts, although generally there are subtly different reasons for choosing to install belt fasteners in this fashion. In the greater number of instances, light-duty belts are more apt to be suspended on slider beds. In these cases, countersinking will reduce abrasive wear of both the fastener and the slider bed.

"Hidden" splices are a form of countersunk fastener. After the belt ends have been prepared and the fasteners installed, replacement cover stock is laid over the fasteners and cured. This replacement cover stock may be from such materials as two component systems or uncured rubber stock. The replacement top cover that hides the splice also serves to protect the fasteners from impact and abrasive wear.

Preparing a belt for countersinking is readily accomplished using only some additional portable tooling. The options range from small hand held tools to larger, more mechanical, devices. All are designed for field use by company personnel. The fastener manufacturers offer these tools, and should be consulted for information relating to them.

BELT NOTCHING

PROBLEM,
SOLUTION CODE

Fastener "comb-out" through end of belt without opening
6,2,3,4,5

Fasteners open up and release from belt
2,1,3,7

Belt breaks behind fastener
2,4,6

Splice failing at edges
3,1,5

Fastener parts fracture and fail
5,3,2,4,7

Belt fails under splice
6,3,1

Fastener wears out prematurely
7,8

1=Improper fastener installation, including splice not in squarely.

2=Improper fastener selection, particularly in the choice of too large a fastener.

3=Tension excessive and/or counterweight excessive.

4=Pulley problems, worn lagging, dual pulley speed differential, too small pulleys, material buildup on pulleys.

5=Splice "hang-up" on worn idlers or other parts of the conveyor.

6=Conveyor drive under belted.

7=Improper metal selection.

ELEVATOR BELTS

In most cases, the same types of mechanical fastener splices are used in elevator belts as are used in conveyor belts. However, there are alternate types of mechanical fastener splices sometimes used in elevator belts. The overlap splice and the butt strap splice are illustrated below. Bolt plate fasteners are used in both types. The fastener manufacturers or their authorized agents should be contacted for instructions on fastener selection and recommended arrangements for such supplies.

Another kind of fastener that is used only on elevator belts is a "clamp type" fastener and is illustrated below. This fastener can be used on PVC and rubber belting. It is available in ferrous and non-ferrous metals and accommodates practically any belt thickness and pulleys of 8" (200mm) diameter or greater. (Note: It is not recommended for use with wing type pulleys.)

Contact the manufacturer for maximum tension ratings and further information.

Click here for the Fastener Selection Chart