Drum Outlet Chute

Function

The outlet chute must discharge mix cleanly and continuously, without bridging, build-up, or forced cooling. Any ledge, rough weld bead, or poorly angled surface inside the chute causes hot mix to adhere and accumulate, eventually bridging and stopping production — a stoppage that requires manual clearing under hot conditions. The chute also maintains the pressurised separation between the rotating drum and the fixed conveyor or elevator, and its seal performance prevents hot gas from escaping at the discharge interface, which is both an energy and an occupational hygiene concern.

Construction & quality

Fabricated from 8–12 mm mild steel structural plate for the outer shell. Internal surfaces are lined with HARDOX 400 plates 8–12 mm thick, installed flush using countersunk fasteners so no bolt head protrudes into the mix flow path. All welds on the mix-contact surface are ground smooth and free of cavities. Chute geometry is designed at 55–65° slope to guarantee free flow of dense-graded mix at 155–175 °C. The seal to the rotating drum end plate uses multiple-layer ceramic-fibre rope or spring-loaded graphite seal rings. A hinged inspection door allows visual observation of the discharge stream. External surfaces are insulated with 50–75 mm mineral-wool blanket clad in aluminium sheet to limit heat loss and reduce touch-face temperature for maintenance access.

When to replace

• Hot-mix build-up and bridging inside the chute causing recurring flow stoppages
• Bitumen seepage or staining at the drum-to-chute seal joint
• Liner plates worn with visible grooving or thinning below 50% of original thickness
• Overheating of the external cladding or burning smell indicating insulation failure
• Cracking or distortion of the outer shell around the seal seating from thermal fatigue cycling