A Severe Pump Explosion Surprises Employees

Some employees reported that it sounded like two railroad cars running into each other. Witnesses reported that windows rattled in a building located about 200 feet from the small pump that fractured into pieces. There were no injuries. 

Part of the chemical manufacturing complex in Tennessee had been shut down, was idle, and there was no immediate intent to restart it. Some equipment had not yet been drained and washed. The system included a 50% sodium hydroxide (caustic soda) tank and the associated centrifugal pump. The pump was an ordinary 1750-rpm pump, driven by a 10-hp electrical motor. Both the suction and discharge manual block valves on this caustic pump were closed. However, the breaker box was still energized. [12] 

Investigators learned that one afternoon, a contractor entered the area to start a local ventilation fan in preparation for an unrelated nearby maintenance job. The electrical switch used to start the pump was identical to the type of switch used to start the ventilation fan. Although the switch was labeled, the tag was hard to read. These switches were over 50 feet from the outdoor caustic soda pump installation, well outside of the diked area. The pump continued to run, unnoticed by anyone. There was no instrument in an occupied location indicating that the pump was running. [12] 

Without warning, a loud boom rattled windows. In a spectacular manner, the pump bowl and piping were knocked backwards. The impeller, shaft, and bearing housing were 

The culprit was determined to be a remote start button that allowed the liquid-filled pump to start and run undetected and isolated for a significant length of time. The trapped liquid continued to heat, expand, and boil, creating pressures sufficient to allow a catastrophic rupture of the pump. 

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