Conveyor pulley failure: when to refurbish and when to replace

Equipment

A conveyor pulley is a drum shell welded to two end discs, carried on a shaft through locking elements or a keyed hub, running in bearings in plummer blocks. Head and drive pulleys transmit power and carry the highest belt tension; take-up pulleys tension the belt; snub and bend pulleys increase wrap or change direction. Drive and head pulleys are lagged with rubber or ceramic to increase friction and protect the shell.

Failure modes

Lagging wears through or delaminates, letting the belt slip and the shell wear. Shells crack at the end-disc weld under cyclic bending. Locking elements lose clamp force, letting the shaft fret and the hub bore wear. Bearings overheat from contamination, lubrication failure or misalignment until they seize.

Common causes

Belt tension above design; mistracking that loads one end disc; material build-up on the shell; water and fines entering bearings through failed seals; lagging bonded to a poorly prepared shell; and pulleys re-used beyond the fatigue life of the end-disc weld.

Inspection

Walk the conveyor with the belt running and stopped. Look for lagging loss, exposed shell and grooves; measure lagging thickness at several points around the drum. Listen and use a temperature gun on plummer blocks. Check locking-element bolt torque and look for rust bleed at the hub, which indicates fretting. On a stopped conveyor, dye-penetrant or magnetic-particle test the end-disc welds where cracking is suspected.

Maintenance

Keep belt tension and tracking within the design; maintain scrapers so material does not build up on the drum; grease bearings to the schedule with the correct grade and quantity; replace seals when the first contamination appears; record lagging thickness and bearing temperatures at each inspection.

Repair and refurbishment

A pulley with a sound shell and end discs can be re-lagged, fitted with a new shaft or new locking elements, and re-machined at the bearing seats. Refurbishment is worth doing when the shell wall is within tolerance and the end-disc welds test clean; it is a false economy when the shell is thin or cracked because the repair cost approaches a new pulley without the fatigue life.

Replacement

Replace when the shell wall is below the minimum, when end-disc welds show cracks, or when the pulley is undersized for the belt tension it now carries. A new pulley should be manufactured to the OEM or client drawing with a quality control plan, material certificates for shell, discs and shaft, and dimensional inspection before lagging.

Umbusso capability

Umbusso manufactures new pulleys and refurbishes existing ones to drawing under a quality control plan and inspection and test plan. The reference order is eighteen pulleys for Eskom Holdings SOC Ltd in 2025, executed under a plan counter-signed by Eskom Quality Assurance and delivered with matching bearings, plummer blocks and couplings.

This article is general technical guidance. Intervals, standards and methods must be confirmed against the current regulation, the manufacturer’s documentation and the site standard before they are applied.