Vibration Behavior Of Heber Hydrocarbon Booster Pumps

Abstract

The Heber Project is a demonstration power plant which operates on a binary cycle using a geothermal heat source. It has four booster pumps in the hydrocarbon working fluid circuit. These pumps have had a long history of high vibration leading to a number of outages from seal and bearing failures. A particular baffling problem was a sharp increase in vibration whenever pump load was rapidly increased. In an effort to understand the cause of the vibration, a rotordynamic analysis of the pump was carried out. Particular attention was given to the fluid film stiffness and damping of the water ring seals. The results of the study showed the cause of the vibration sensitivity was a first critical frequency very close to running speed. It was also shown that an unusual coupling existed between pump load and the seal stiffness and damping available to support the rotor and control its motions. A redesigned thrust balancing device was shown to provide a solution to both vibration problems.