VULCANIZED BELT SPLICE

A vulcanized belt splice is the permanent, heat-cured joint formed when two ends of a conveyor belt are merged using uncured rubber, fresh skim sheets and a portable hot press. For fabric belts the join is stepped — each ply is bevelled by one ply length and overlapped with the corresponding ply on the other belt end. For steel cord belts the cords are stripped, cleaned, interleaved in a precise diamond or rhombus pattern, and re-vulcanized inside a new hard core rubber bed. Both methods reconstitute the carcass into something close to a continuous belt.

Strength retention is the key metric. A properly executed vulcanized splice on a fabric belt retains 70–80 % of nominal belt strength, and on a steel cord belt 90 % or more — values that govern the safety factor used in tension calculation (DIN 22101 recommends a steady-state safety factor of S₀ ≈ 8 for fabric and 6.7 for steel cord, with reductions allowed when splice quality is verified). Mechanical splices (clip-type, bolt-solid-plate, hinge) typically retain only 35–50 % and concentrate stress on the fastener line, which is why they are confined to short belts, low tensions or emergency repairs.

A high-quality splice requires a clean environment, accurate cord spacing, controlled cure temperature (typically 145–155 °C) and dwell time, and a press long enough to cure the full step pattern in one shot. Splice failures account for a large share of belt downtime; X-ray inspection at commissioning and periodically thereafter is standard practice on overland steel cord belts.