The sweet spot: How to keep your pump operating near its Best Efficiency Point (BEP)
Each pump has what is called a ‘best efficiency point’ (BEP) or sweet-spot – a combination of head and flow rate where it will deliver its best performance in terms of both energy efficiency and service life.
A key to getting the best overall system performance is to make sure that each pump in the system is operating as close as possible to its BEP. Not only does this give you the best return on your energy dollar, but doing so will reduce your maintenance costs as well. Pumps run most smoothly and have the longest service lives when operated near their BEP.
How can you determine if your pump is operating close enough to its Best Efficiency Point? First identify your operating point by finding where your pump performance curve and system curve intersect. The pump manufacturer will supply you with the pump curve, but determining your system curve is up to you. You’ll need to calculate this using a number of variables such as pressure, metering units, volume and resistance.
Once you have your pump curve and system curve, you can see your operating point which is where the two curves intersect. The pump manufacturer will identify where BEP is on the pump curve. The relationship between your operating point and your BEP can tell you a lot about what you can expect from your pump and its surrounding system. The graph below shows if you are operating to the left of your BEP you can expect all sorts of system symptoms from cavitation and overheating to recirculation depending on how far from BEP you are. If you fall to the right of BEP your pump is likely requiring more maintenance and replacement parts than it should be or experiencing cavitation in more extreme examples. As the graph below shows, best practice is to be somewhere between 10% to the left of BEP and 5% to the right.
Of course selecting the right pump for your system is of the utmost importance, but that doesn’t guarantee that your pump is still operating near BEP. In real life, systems change over time. There are increases or decreases in system demand, and corrosion or sediment build-up in pipes can increase friction and demand different pressure. Additional fittings such as valves, elbows, or flanges either upstream or downstream of the pump can also change your system curve.
If your system is experiencing some of the symptoms mentioned above and you expect your pump isn’t running near BEP, or if you know your system has changed significantly since pump selection, we can help get your system back on track! Our SES (System Efficiency Services) can provide a deep understanding of what is going on in your system and our experienced engineers can interpret this information into actionable suggestions which not only decrease maintenance needs but also increase the energy efficiency of your system. Another option which can actually shift your pump curve and BEP closer to your operating point without replacing the entire pump is impeller trimming.
If you’d like to look into increasing your system’s efficiency or have additional questions, don’t hesitate to contact us. We’ve built our business on helping customers just like you to get the most from their systems.