Alert 10 – 23 Repairing Centrifugal Pump Results in a Near-Miss
A welder was in the process of removing a seized threaded impellor from the 2-1/2” shaft of a centrifugal mud pump. To loosen the impeller from the shaft the welder used a welding torch to heat it. The impeller is screwed onto the shaft with right-hand threads and the threads are sealed inside the back of the impeller with an “O”-ring. When the shaft/impeller was installed previously, the threads were greased and cavity was filled with grease. As the impeller was being heated, the heat from the torch caused the grease to expand inside the impeller thread cavity. The expanding grease caused the cast center of the impeller to explode outward (see photo), striking a nearby welding machine.