Analysis of causes of burst failure of a buffer tank

Abstract

An explosion failure occurred in a buffer tank at an oil transfer station. The explosion fragments flew out, causing 2 deaths and 1 injury. To analyze the root cause of the failure, visual inspection, thickness measurement, mechanical test, chemical composition test, corrosion product analysis, fracture analysis, pressure-bearing capacity check, explosion analysis, and operational condition investigation were conducted. The results showed that the chemical composition and mechanical properties of the buffer tank meet the standard requirements; the metallographic structure of the steel is ferrite, pearlite, and a small amount of Widmanstatite, and the structure has not deteriorated after a long time of service; the buffer tank has local corrosion, and the pressure-bearing capacity still meets the design requirements; operational condition investigation revealed that when the buffer tank burst, the operating personnel were conducting pressure test on the newly-built pipeline outside the station. The pressure test medium used was air. The buffer tank was isolated from the pressure test equipment, and the valve connecting the pressure test pipeline and the buffer tank had internal leakage. Gas entered the buffer tank, causing an overpressure explosion of the tank, and the overpressure wave leads to the collapse of the wall and casualties. Explosion energy analysis showed that the location of casualties was within the range of overpressure wave casualties. In order to avoid such incidents, the use of gaseous media for pressure testing should be avoided.