Full definition
The count of textile reinforcement layers (plies) in a conveyor belt carcass, a primary factor determining the belt total breaking strength and transverse stiffness (troughability). Common configurations: 2 plies (light duty, short conveyors), 3-4 plies (standard general purpose), 5-6 plies (heavy duty, long conveyors, large lump material). Total belt strength = number of plies × strength per ply (e.g., EP200/4 = 4 plies × 200 N/mm per ply = 800 N/mm total). More plies increase: tensile strength (linear), transverse rigidity (belt holds trough shape), impact resistance, and puncture resistance. However, more plies also increase: belt weight, minimum pulley diameter (thicker belt requires larger bend radius), and cost. Trough ability: the belt must be flexible enough to form the desired trough angle on the idler stations — too many plies on a narrow belt creates a stiff belt that won't trough. Per ISO 14890 and DIN 22102. Steel cord belts have a single layer of cables instead of plies.