BREAKING STRENGTH (KN/M)

Breaking strength is the published minimum longitudinal tensile force at which a new conveyor belt's carcass fractures, expressed per unit of belt width and measured per the standard test procedures of ISO 14890 (textile belts) or ISO 15236 (steel cord). The value is normalized to N/mm of belt width, which is dimensionally identical to kN/m. A belt designated EP500 has a nominal breaking strength of 500 N/mm = 500 kN/m: a 1.0 m wide EP500 belt fails at 500 kN longitudinal pull.

Belt designations directly encode breaking strength. EP200 = 200 N/mm; EP500/4 = a 4-ply EP belt with 500 N/mm total nominal strength; ST 2000 = a steel cord belt rated 2000 N/mm. Fabric belts typically run from EP 200 to EP 2500; steel cord belts from ST 500 to ST 5400. Breaking strength is the certificate value — actual breaking force on a tested sample is usually 10–20 % higher, but design must use the published minimum.

Working tension is not breaking strength. Designers divide breaking strength by the [safety factor](/glossary/safety-factor-belt) — typically 8–10 for fabric belts and 6.7 for steel cord per DIN 22101 — to obtain allowable working tension. T1 must remain below this allowable tension at every operating case, including transient start-up and stop. The same breaking strength × width capacity must also cover any expected capacity expansion over the belt's 5–15 year service life; many engineers oversize by one rating step (e.g. specify EP630 where EP500 is theoretically sufficient) to leave room for future cargo or speed upgrades.