What is the Best Efficiency Point (BEP)?
The best efficiency point (BEP) is the point along a pump curve where efficiency is the highest.
When a pump manufacturer draws a pump curve, the point at which pump efficiency peaks is called the best efficiency point or BEP. For pumps that are subject to a pump performance test, the BEP determined by the pump test may be slightly different than the BEP indicated on the catalogued pump performance curve. In these instances, the difference may be due to slight variations in pump and impeller castings as well as the wear of pattern equipment over time.
Certain other pump values are derived from BEP. For example:
- The preferred operating range or POR is defined as 70% to 120% of flow at BEP for most centrifugal pumps.
- Specific speed (Ns) is an index of impeller design based on the relationship between head, flow, and rotation, and is based on the pump’s performance at BEP.
- Suction specific speed (Nss) is an index of impeller design based on the relationship between head, NPSHr, and rotation, and is based on the pump’s performance at BEP.
Pumps should be selected to operate as close to BEP as possible. When a pump operates at BEP it is at it’s most efficient, meaning it is using input power as efficiently as possible and reducing energy costs. When a pump operates at BEP it also produces the lowest vibration readings, meaning that pump longevity is increased and maintenance costs are decreased.