A 75 HP centrifugal pump was operated with both suction and discharge valves closed for about 45 minutes. It was believed to be completely full of liquid. As mechanical
A 75 HP centrifugal pump was operated with both suction and discharge valves closed for about 45 minutes. It was believed to be completely full of liquid. As mechanical energy from the motor was transferred to heat, the liquid in the pump slowly increased in temperature and pressure until finally – the pump failed catastrophically. One fragment weighing 5 pounds was found over 400 feet away. Luckily, no one was in the area so there were no injuries.
Why would events such as this happen?
• This situation is different than operating a pump “deadheaded” – where the suction valve is open but there is no flow through the pump. Here, pressure relief occurs back through the pump suction line.
• In the past, this event likely would have ended with a seal failure – seal leakage would have been sufficient to relieve the pressure. New seal designs are significantly improved. This older “relief system” can no longer be counted upon.
• As processes have become more automated it is now much easier to accidentally start a pump or operate the wrong valve.
• Spare pump arrangements can also be a problem if the “incorrect” pump is started. For example, the “north pump” has valves aligned for operation but the “south pump” is started.