Summary
The following report explains what pump lift is, how it is accomplished, and the theoretical underpinnings of why it is needed, especially as it relates to the vertical, mixed flow Service Water Pumps at Cooper Nuclear Station. An example is then provided which demonstrates the significance of lift adjustments on Service Water Pumps. A pump which was on the verge of being declared inoperative on July 13, 2000, because of low pressure output, "bounced" back on July 22, 2000, to midrange performance values by a simple lift adjustment.
The report then identifies a problem with Service Water Pumps in the timeliness that lift adjustments are currently being done. Because not enough lift adjustments are done per operating year, Service Water Pump impellers and bowls are periodically grinding into each other. This causes accelerated wear, approximately 42 mils per year, and 84 mils between turn-arounds. The problem is solvable, however, by simply performing lift adjustments on a quarterly basis. When this is done, the wear will not occur.
In assessing work practices associated with the Service Water Pumps, it is recommended that lift adjustments to the Service Water Pumps be regularly scheduled to occur in tandem with quarterly Service Water Pump surveillances. This is because a performance surveillance is required after each lift adjustment, and surveillances are required to be done quarterly.
The report further assesses the link between lift adjustments and the current turn-around periods of Service Water Pumps. The current turn-around time is two years. By scheduling lift adjustments to occur on a quarterly basis, the amount of wear that occurs in the pumps is significantly reduced. This reduction in pump wear allows the turn-around time of the Service Water Pumps to be safely increased from 2 years to 4 years. This is a significant savings in internal labor resources and cash outlays for the company. Over a ten year period, this will save the company about 2.5 million dollars
.