Bitumen Heated Gear Pump

Function

The meshing gear-pair creates a sealed cavity at the pump inlet, traps a fixed volume of bitumen per revolution, and displaces it to the outlet port under positive pressure. This action is independent of downstream head, so the flow rate is directly proportional to shaft speed — allowing variable-frequency drive control to precisely trim bitumen delivery to match batch-cycle timing and recipe weight. Accurate, pulse-free bitumen supply at the correct temperature directly determines binder-content uniformity in each batch, governing mix quality and road performance. A failed or worn pump manifests as under-weight bitumen batches, extended fill times, and ultimately mixer shutdowns that halt the entire plant.

Construction & quality

Pump casing and front and rear end-plates are precision-machined from high-grade cast iron (EN-GJL-250 equivalent), stress-relieved before machining to minimise distortion under cyclic thermal loading. The gear set — both drive and idler — is manufactured from 20CrMnTi or equivalent case-hardened alloy steel, carburised and ground to DIN 3962 Grade 7 or better, delivering a surface hardness of 58–62 HRC on tooth flanks. The shaft is EN24T (709M40) alloy steel, ground to h6 tolerance on bearing seats. Front and rear bearings are sleeve-type in leaded bronze, self-lubricating by the bitumen film. The mechanical shaft seal is a carbon-graphite and tungsten-carbide face pair rated for continuous 200 °C service with bitumen. Jacketing covers the full pump body and end-plates; thermal-oil connections are 1/2″ BSP female ports. External surfaces are shot-blasted and high-temperature epoxy-primed before assembly.

When to replace

• Audible whine or knocking from the pump head indicating gear-flank wear or cavitation onset
• Bitumen delivery weight consistently below recipe setpoint despite correct tank level and pump speed
• Visible bitumen seepage at the mechanical seal face or end-plate joints
• Rising pump motor current without a change in speed setpoint, indicating internal leakage across worn gear-to-casing clearances
• Casing temperature exceeding thermal-oil supply temperature, signalling bearing seizure onset