PLY RATING (EP200, NN200, ETC.)

Ply rating is the standard notation for designating fabric conveyor belts. The format combines a fabric-type prefix with two numbers: EP200/4 means an EP (polyester warp, nylon weft) carcass with a nominal per-ply strength of 200 N/mm, built in 4 plies, giving a total nominal breaking strength of 4 × 200 = 800 N/mm. Common fabric prefixes are EP (polyester-nylon, by far the most common today), NN (all-nylon, more elastic and used where shock absorption matters), and EE (all-polyester, lowest elongation and used where length stability is critical).

Per-ply ratings run 100, 125, 150, 200, 250, 315, 400 and 500 N/mm; ply counts run 2, 3, 4, 5 and 6. The combination gives total belt strengths from EP125/2 (250 N/mm, used for packaging and light unit loads) up to EP500/6 (3000 N/mm, heavy mineral haulage). For the same total strength, fewer plies of higher per-ply rating give a thinner, more flexible carcass (smaller minimum drum diameter, easier to trough deeply), while more plies of lower per-ply rating give a thicker carcass with better impact and tear resistance.

Selection between ply counts is largely a question of duty. Quarry conveyors with heavy lump impact prefer more plies (EP200/4 over EP400/2); long overland and high-trough-angle belts prefer fewer plies (EP630/3 or EP800/3). The carcass choice also feeds back into [breaking strength](/glossary/breaking-strength-belt), minimum pulley diameter, splice procedure and bend radius, all of which the [pulley diameter calculator](/tools/pulley-diameter-calculator) helps verify.