This case study summarizes the problem of repeat thrust bearing failures encountered during the commissioning of the primary heat transport (PHT) pressurization pumps and the resolution of the issue.

The PHT pressurizing pumps is an Ingersoll Rand – HMTA, 10 stage pump designed with impeller suction facing the same direction creating a resultant thrust which is absorbed by the balance drum and thrust bearings. The pumps were initially commissioned in the 1970’s.

The PHT system is a closed loop that removes heat from the reactor fuel and transports to the boilers, the PHT pressurizing pumps is used to maintain the system pressure of the system.

U2 was in laid up state and had undergone a major refurbishment. During the pump start up of 2-33310-P2, the thrust bearing failed within 20 seconds.

Resolution of repeat failures required the understanding of the cause, revising the maintenance procedures to resolve the problem.

Keyword: Precision Maintenance