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Good design is key to efficiency

17 March 2019

Gary Wilde offers advice on how to minimise pump system costs throughout their lifecycle. 

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Maintenance and energy consumption represent the two most significant costs throughout the life of a pump. These costs can be minimised by ensuring a well-designed pumping system – where the pump is specified as correctly as possible to the demands of the application. The energy consumption and efficiency of a pump is closely linked to the way that a pumping system is designed and operated. 

Key factors which need to be considered when specifying and operating a pump, to help deliver optimum performance and economy throughout its service life include a good understanding of the different type of pumps available, each of which is suited to use in specific applications. The two most popular types are centrifugal pumps and positive displacement pumps. Centrifugal pumps are generally suited to fast flowing or low viscosity liquid applications where the pressure is relatively constant. They perform most efficiently and cost-effectively when operating at or near their Best Efficiency Point (BEP).  

Positive displacement pumps are best suited to use in high viscosity applications as they are better able to maintain a constant rate of flow. 

It may also be necessary to consider what type of material the pump is manufactured from. Hygienic processes in the food and beverage industries, for example, are subject to the strict requirements of the Food and Drug Administration (FDA), EHEDG or 3A which call for equipment to be manufactured from 316L stainless steel but can also have specific alloys depending on the application.  

Other questions which need to be asked before specifying a pump include:

Is there enough pressure for the pump to work effectively? The efficiency and operation of centrifugal pumps can be affected by the Net Positive Suction Head (NPSH) available. This is the amount of pressure required to prevent the liquid being pumped from vaporising inside the pump.  If the liquid vaporises, bubbles can be formed which will be carried into the pump. When these bubbles encounter zones of higher pressure in the pump, they will collapse violently, resulting in cavitation which can severely damage the pump. So it is essential to ensure that the available pressure on the pump inlet is greater than the pressure required within the pump to avoid the occurrence of cavitation. 
Is the pump positioned in the correct place? The positioning of a pump within a pipeline can also affect its performance. As well as determining the amount of pressure available, the positioning of a pump can also affect the quality of the product being pumped. This, in turn, can lead to friction losses which can affect the flow rate of the substance being pumped. This, in turn, can affect the efficiency of the pump.  The presence of pipe fittings, such as elbow joints, filters or other in-line equipment, can also affect the flow rate of a substance to the pump. 

Your pump supplier or manufacturer should be able to offer advice and guidance to ensure that users get the best performance from their pump systems. Digital technology advances which now offers capabilities such as the Internet of Things (IoT) allows users to gain detailed information, by analysing pump system data and it is important to look at these capabilities when specifying new pump systems or system upgrades. Data taken from internal or external sensors fitted to the system can be turned into information which can help ensure optimum system performance and efficiency and can help in the development of planned maintenance strategies. 

The British Pump Manufacturers Association (BPMA) website includes a Pump Search facility which offers further pump selection guidance. Go to:

Gary Wilde is technical services officer at the BPMA.

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