Conveyor Belt Calculator — Capacity, Drive Power & Belt Tensions (ISO 5048)

The volumetric capacity of a troughed belt conveyor is the product of the load cross-section area A (m²) and the belt speed v (m/s), scaled to t/h by the material bulk density. The cross-section is the sum of the trough trapezoid A₂ (below the chord between wing-roll tips) and the surcharge cap A₁ above the chord at the dynamic surcharge angle φ — taken as a parabolic cap (tan φ · b₁²/6) for the capacity, and as the full triangle (0.25 · tan φ · b₁²) for the belt load that feeds the resistances and tensions, an upper bound. On a slope the capacity is reduced by an incline factor k — our estimate (a typical rule of thumb, rough and conservative), k = 1 − (A₁/A)·(1 − √((cos²δ − cos²β)/(1 − cos²β))), the surcharge being lost entirely once the incline reaches the surcharge angle β; the forces and tensions keep the full load. The usable belt width b = 0.9B − 0.05 m allows for edge spillage; the three equal-length rolls each contact b/3 of that width.

Mass capacity then follows directly from the volumetric rate, and the material belt-load per metre q_G (kg/m) is used in all resistance calculations downstream.

ISO 5048 splits the total effective pull F_U into the primary (main) resistance F_H — arising from idler rolling friction, belt bending and material flexure over the full length L — and a secondary resistance F_N that accounts for loading-zone acceleration and skirt friction, belt wrap and pulley-bearing friction on short to medium belts. The ratio C = (F_H + F_N) / F_H is the length factor tabulated in ISO 5048 Table 2; it approaches 1.0 for very long belts and rises to ~3.6 for conveyors shorter than 20 m. Belt cleaners, skirtboards beyond the loading zone and tilted idlers are special resistances F_S1 + F_S2 that C does not cover — the calculator assumes two belt cleaners at 900 N per metre of belt width each (an estimate) until you enter your own cleaners, skirtboard length and any other special resistance. The incline lift resistance F_St is material-only (the belt's weight on the carry run is offset by its weight on the return run in the closed loop). Shaft power and motor input power follow directly.

The tight-side tension T₁ and slack-side tension T₂ are related by the Euler belt-friction equation for the drive pulley wrap angle α and the rubber-to-steel friction coefficient μ. The minimum slack-side tension is set by the sag limit: the DIN 22101 / CEMA criterion requires that the carry-run belt sag ratio (droop/span) stays below 1.5 % to prevent material spillage and excessive idler impact loading. The calculator checks the sag at the slack side — the lowest tension point on a head-driven conveyor — where under-tension is most likely. Take-up travel is derived from the belt elongation at average tension using the ISO 9856 per-unit-width elastic modulus; the recommended take-up range adds a 50 % installation and wear allowance.