What is the Preferred Operating Range (POR)?
The preferred operating range, or POR, is a region of the pump curve defined in relation to the best efficiency point (BEP), and represents the portion of the curve in which continuous operating conditions should be located if possible.
The preferred operating range (POR) is defined by centrifugal pump standards such as the Hydraulic Institute Standards (HI) or American Petroleum Institute Standard 610 (API 610). This is in contrast to the AOR which is a manufacturer-defined region of the curve.
The POR, as defined by HI or API 610, varies depending on the type of impeller, but in most cases extends from 70% to 120% of flow at the best efficiency point (BEP). In some high-energy pumps the POR is smaller, and may only extend from 80% to 115% of flow at BEP.
To understand how the POR is determined, consider this example for a standard centrifugal end-suction pump.
- For a fictional end-suction pump, BEP falls at a flow of 1000 gallons per minute (GPM).
- The left side of the POR falls at 70% of BEP: 700 GPM in this example.
- The right side of the POR falls at 120% of BEP: 1200 GPM in this example.
- The POR in this example extends from 700 GPM to 1200 GPM. Any operating condition within those outer bounds falls within the POR.