The energy crisis has been a hot topic for the past few months. Businesses are really starting to feel the pinch from their increasing energy bills, and while some support is being given, there is uncertainty about how long this will last. To help users of pumping systems reduce their energy usage, Castle Pumps explores seven ways the energy efficiency of a pumping system can be improved.
Around 16% of a typical industrial facility’s electricity costs are generated by its pumping systems. With energy prices at a high, inefficient pumps are becoming even more expensive to run. The good news is that there are usually savings to be made. Let’s look at seven ways to optimise your pumping systems’ energy consumption.
Avoid oversizing the pump
In the design process, oversizing a pump is common to cater for any uncertainties of the duty required. However, as a higher performance in terms of flow and pressure requires the motor to run at a higher power, an oversized pump uses more energy than necessary. For that reason, a pump should be selected to run as close to its Best Efficiency Point (BEP) as possible.
Impeller trimming
If a pump has been oversized, a throttling valve is sometimes used to achieve a lower duty. This, however, is less energy efficient than trimming the impeller, which is a relatively cost-effective way of reducing the pressure and flow produced. In turn, variable frequency drives are more energy efficient than impeller trimming, as the casing clearance gets larger when an impeller is shaved.
Variable frequency drives
The purpose of a variable frequency drive is to vary the speed of the motor to achieve the application’s actual performance requirements as opposed to the maximum that the pump can provide, therefore reducing energy waste. Firstly, it can slow the motor on an oversized pump and secondly, it can control a pump in situations where there are differing duty requirements at different times, i.e. sometimes it needs to operate at full speed and others it doesn’t. An example is a cooling pump, where the temperature of the component needing to be cooled may vary considerably.
Parallel pumping systems
Another energy-efficient solution for an installation with differing performance requirements is the use of parallel pumping systems. When the occasional duty requirements are significantly higher than the standard operating conditions, a single pump could operate far from its BEP for much of the time. By installing a second smaller pump to meet the average system requirements, the larger, higher energy consuming pump would only need to be used when it warrants it.
Limit pipework pressure loss
The pump’s power needs to account for pressure loss in the system, which is affected by the length, diameter, layout and internals of pipework. Bends and changes in the size of the pipework should be kept to a minimum, and the diameter should be carefully selected, as smaller pipework results in more friction. Corrosion and rust can increase resistance resulting in pressure loss, which means cleaning and maintaining pipework is important too.
Eliminate unnecessary use
It might surprise you how often pumps are in operation when they aren’t doing anything, just due to lack of control. Control systems can be implemented to shut down pumps not in use, and using pressure switches, the number of pumps in service can be automatically adjusted as duty requirements vary.
Carry out maintenance
Like any equipment, wear can reduce efficiency. A pump’s energy efficiency can degrade as much as 10-25% before it’s replaced, making routine maintenance vital. It is vital to replace wearing parts such as wear rings, as leakages mean the power requirements to produce the same flow increase.
