Wear in an operating pump is inevitable. As a pump wears, it is normal that the flow rate will decrease. Not all pumps wear at the same rate, pumps that are the same but used even slightly differently will wear at different rates. However, pump manuals typically specify the period between maintenance with no reference to the wear. Economic justification is becoming increasingly relevant, and maintenance can at times be viewed as an unnecessary expense. This paper is a desktop case study that reviews the ongoing energy cost for a pumping system that has worn. Two different scenarios that commonly cause reduced flow are examined, each for two different intensities that result in 10% and 20% reduction in flow. The results show that for the pump and scenarios reviewed, the ongoing excess energy consumption may be ½ to 1 ½ times the flow reduction. Another finding is that the pump duty point has moved further from the Best Efficiency Point, indicating that the rate of wear will increase if operation is continued. The case study demonstrates a process that can be utilised and allows the wear for a specific pump to be evaluated.
Author
Troy Leyden, Operations Engineer, Variable Efficiency