CONVEYOR BELT JOINTING PROCESS

Three Ways to Join,
One Way to Do It Right.

The joint is the weakest point of any conveyor belt. A good belt with a poor joint will fail early, and most “belt failures” we are called for turn out to be joint failures. There are three ways to join a fabric belt. Each has its place – the trick is to pick the right one and then not cut corners.

Which Joint Should You Use?

Before Any Joint – Getting the Ends Ready

1. Clamp both belt ends and set the belt tension with the take-up close to its shortest position.
2. Mark the belt centre line on both ends over the full joint length plus a margin.
3. Cut both ends square to the centre line – a joint cut at a slight angle is the most common cause of a belt that will not track.
4. Decide the joint length. It depends on the number of plies and the ply strength; stronger belts need longer steps. Our team can give you the step lengths for your belt.
5. Mark the steps on both ends so they match each other exactly, like two halves of a staircase.

Hot Vulcanised Step Splice

1. Strip the steps. Cut through one ply at each step line and peel it back carefully. Do not cut into the ply below – a nicked ply is a weak ply.
2. Buff. Lightly buff all the stepped surfaces and the cover bevels to a rough, clean finish. Remove all dust.
3. Clean. Wipe with the recommended solvent and let it flash off completely. From here on, nobody touches the surfaces with bare hands.
4. Apply solution. Brush on the vulcanising solution in thin, even coats and let each coat dry as specified.
5. Lay the tie gum and ply fillers. Place the uncured tie rubber between the steps and fit the two ends together along the centre line.
6. Build the covers. Fill the top and bottom cover areas with uncured cover rubber of the same grade as the belt, slightly proud of the surface.
7. Cure in the press. Close the press with edge bars in place and cure at the temperature, pressure and time set for that belt thickness and compound.
8. Cool before release. Let the joint cool under pressure before opening the press. Opening hot causes blisters.
9. Inspect. Check for blisters, soft spots, gaps at the edges and straightness before running.

Site tip: Heat resistant, fire resistant and oil resistant belts need matching jointing compounds. Using general purpose rubber in the joint of a UHR belt will make the joint the first thing to crack.

Cold Bonded Joint

A cold joint uses the same stepped preparation, but the bond comes from a two-part adhesive that cures at site temperature instead of heat and pressure. We supply cold vulcanising cement and hardener – details on our belt jointing solution page.

1. Prepare, step, buff and clean the ends exactly as for a hot joint.
2. Mix the adhesive with the hardener in the ratio given on the pack, and use it within its pot life.
3. Apply a first thin coat to both surfaces and let it dry fully.
4. Apply a second thin coat and wait until it is touch-dry (it should feel tacky but not wet).
5. Bring the two ends together from the centre outwards, pressing out air. Hammer or roll firmly across the full joint.
6. Support the joint on a flat board or plate and allow the recommended curing time before loading.

Site tip: Humidity and dust are the enemies of a cold joint. In the monsoon, make a small tent over the work area and keep the surfaces dry.

Mechanical Fastener Joint

• Choose the fastener size to match the belt thickness and the smallest pulley diameter.
• Cut the belt end square and, on thick belts, skive the top cover so the fastener sits flush.
• Fix the fasteners with the correct tool, evenly across the width.
• Check the pulleys and scrapers – scrapers must be suitable for running over a fastener.
• Treat it as temporary on high-tension belts and replace with a vulcanised joint at the next shutdown.

After the Joint

Run the belt empty, watch the joint pass over each pulley, and check tracking. Record the date, joint type and team on the belt history. For the full start-up routine see our installation guide, and if a joint keeps failing, see the troubleshooting guide.

Talk to Our Team

Tell us what you are conveying, the temperature, the belt width and the running length. We usually reply the same working day with a price and a delivery date. Phone: +91 98275 92612 / +91 90395 92612 · Email: info@shrirambeltings.com.