Every belt fails at its weakest point, and on most conveyors that point is the splice. The joint carries the full tension through a discontinuity in the material, and every splice type trades strength against installation time, pulley clearance and cleanability.
Three splice types, three different compromises
Vulcanised (hot or cold) splice. The belt ends are stripped, joined with uncured rubber and pressed under heat. Strength reaches 70 to 90 percent of the belt's own tensile strength, the joint runs flat over small pulleys and there is no metal to trap product. Installation takes two to six hours and needs a press, a power supply and a trained technician.
Mechanical fastener. A metal comb or plate joins the two ends and is closed with a hammer or a press. Strength is 40 to 60 percent, installation takes 20 to 40 minutes and any maintenance fitter can do it. The fastener leaves a hinge that catches product, and the metal is a foreign-body risk in food areas.
Finger splice. The belt ends are cut into interlocking fingers and bonded, usually cold. Strength is 50 to 70 percent. It is flatter than a mechanical joint and cheaper than a full vulcanised splice, which makes it the usual choice for PVC and PU belts on small pulleys.
What decides the choice
Pulley diameter
A mechanical fastener adds 3 to 6 mm of thickness and will not run over a pulley smaller than roughly 50 times the belt thickness. On a small nose bar or a 50 mm pulley, only a vulcanised or finger splice will track.
Hygiene level
In food production, a mechanical fastener is a documented foreign-body risk: the combs corrode, fragments enter the product and the hinge provides a harbourage point that no amount of cleaning reaches. Most food safety schemes accept a vulcanised splice and question a mechanical one.
Downtime
A vulcanised splice needs a window of half a shift and a technician who may not be on site. Plants that cannot accept that window keep a spare belt with a pre-fitted splice, or use a mechanical joint as a temporary repair and schedule the permanent splice at the next shutdown.
| Method | Joint strength | Install time | Hygiene | Best for |
|---|---|---|---|---|
| Hot vulcanised | 80 to 90% | 3 to 6 h | Excellent | Food, heavy duty, small pulleys |
| Cold vulcanised | 60 to 75% | 2 to 4 h | Very good | PVC and PU belts, medium duty |
| Finger splice | 50 to 70% | 1 to 2 h | Good | Small pulleys, light belts |
| Mechanical | 40 to 60% | 20 to 40 min | Poor | Temporary repair, non-food bulk |
Making any splice last
Square the cut. A belt cut at 1 degree off square will track to one side and wear the edge within weeks. Use a squaring jig, not a chalk line.
Respect the step length. The splice length is normally 200 to 300 mm for a two-ply belt and 300 to 450 mm for three plies; shortening it to save time reduces strength faster than most people expect.
Check the belt tension after the splice. A new splice shortens the belt slightly, and the take-up that was correct before will be too loose.
Inspection interval
Inspect the splice at every belt inspection, and at least monthly. Look for edge separation, exposed fabric, a step at the joint, and belt dust under the splice. A splice that has started to open will usually show a fine crack at the trailing edge before it fails.
