Analysis of a Butane Pump Failure

Abstract

A refinery fire at a liquid butane pump engulfed the pump, mechanical pump seals, bearing and motor shaft. The principal question to be answered was if the bearing or mechanical seals failed first. Seal failure would likely have resulted in a fume explosion, causing fracture of the shaft. Bearing failure/seizure could have caused the shaft to fracture, damaging the seals in the process, releasing liquid butane that then ignited without a forceful explosion as it contacted hot metal surfaces. The observed distortion and microstructural changes in the bearing and shaft components showed that bearing failure by possible lubrication starvation was the cause of the fire. The bearing lubrication level had been checked 30 min prior to the event, and the plastic lug removed to check the level was never found.