Screw Conveyor Wear in EPB TBMs: Managing Shaft, Flight and Liner Life

On an EPB TBM the screw conveyor is the only continuous path between the pressurised excavation chamber and the belt, so it absorbs everything the ground throws at it. In desert metro and utility tunnels, fine sand with high quartz content grinds the flights and casing liners; where sand meets rock, blocky cobbles add impact loading on the shaft and blade edges. Each element — screw shaft, flights, wear-resistant liners — wears at a different rate, so a single "screw conveyor life" figure is misleading.

Practical wear management starts with routine measurement: casing wall thickness, flight outer-edge profile, liner thickness at the discharge end, and hardfacing condition along the shaft. Sacrificial liners and replaceable flight edge bars convert major wear into scheduled consumable changes, while build-up welding restores profiles between campaigns. The real cost driver is not the part but the stoppage — an unplanned screw failure means lost rings, muck handling risk and a difficult intervention in a confined, pressurised area.

That is why buyers in Middle East mixed-ground projects increasingly stock critical screw conveyor items before drive start. OUSUN, based in Deyang, Sichuan — China's largest TBM industrial cluster — manufactures screw shafts, flights, liners and other EPB spares to interchangeable drawings, with typical spares lead times of two to four weeks. Matching wear rates to a planned replacement window keeps the machine boring instead of waiting. Contact [email protected] or visit tunnel-boring.com.