Quantifying the cost of pump efficiency decay on the Department of Water and Sanitation

Abstract

By analysing the usage of water in South Africa, together with the energy consumption from pumps in the industry, it is easy to identify a problem. A need exists in determining what influence the decay in efficiency of bulk water pumps has on energy costs. Of all the water supplied to consumer units during 2013, 44.7% of this water was supplied free of charge, making the need to supply water as efficiently as possible a great concern. The average energy component of the life cycle cost of a pump accounts for about 60% of the cost. The literature study in this dissertation focuses on the operation, maintenance and monitoring of centrifugal pump systems. A detailed investigation on symptoms that cause efficiency decay of a centrifugal pump system was done. This investigation was used to determine the average efficiency loss and possible efficiency gain that could be realised given that the correct monitoring and maintenance procedures are implemented on the pump system. This study was used to simulate the operation of well monitored and maintained centrifugal pumps. The operational simulation of the centrifugal pumps was done where maintenance was simulated by reinstating the pumps' original efficiency after a certain maintenance period. The maintenance period was determined by making use of a Pump Energy Indicator. The cumulative additional operational costs (energy costs) were calculated using a simulated maintained pump and a simulated unmaintained pump. The potential savings for maintaining a high pump system efficiency was determined. The simulation was done on a total of fourteen centrifugal pump systems. The results showed that, if possible, the correct operation, maintenance and monitoring of centrifugal pump systems could spare a substantial amount of energy costs. From the fourteen cases, the average energy cost savings calculated to 0.29 R/kW/h