Solutions To Abrasive Wear-Related Rotordynamic Instability Problems On Prudhoe Bay Injection Pumps

Abstract

Prudhoe Bay produced water injection pumps suffered serious vibration problems and high balance piston leakage a few months after initial startup. Even though initial pump orientation at low water rates was satisfactory, time between overhauls deteriorated to as little as 700 hours as rates increased. This resulted in oil production cutbacks and significant operating problems. A high priority investigation was initiated, and with the manufacturer’s assistance, the cause of the vibration was identified as rotor instability due to abrasive wear in the pump’s wear rings and balance piston assemblies. Various solutions were evaluated. It was decided to • Reduce the abrasives in the produced water as much as practical • Increase in the hardness of the pump’s wearing parts. • Add a “swirl brake” to the balance piston sleeve to increase rotor stability The changes were implemented during the fall of 1986 with encouraging results. As of fall 1987, two of the pumps had approximately 5500 hours on them and two others had about 4000 hours. Even though it is believed some wear has occurred, no additional problems with wear related vibration has been encountered since the improvements. A minimum service life of three years is desired. The pumps are being closely monitored. Additional improvements, such as alternate coatings, further improvements in water quality, etc., will be evaluated if the life target is not achieved.