What do the AOR and POR terminology for centrifugal pumps mean?

　　What is the meaning of the AOR and POR terminology for centrifugal pumps?

　　AOR: Allowable Operating Region

　　Allowable operating region (allowable operating region, AOR), API610 11th edition of the standard interpretation of this term: in this area of the flow rate of operation, the pump vibration is higher, but is still “acceptable” level.

　　The AOR is the part of the pump curve determined by the pump manufacturer within which the pump can be operated continuously without affecting the performance or service life of the pump.

　　The AOR of a centrifugal pump is the area between the minimum continuous steady flow and the maximum allowable operating flow.

　　The AOR is determined by the pump manufacturer through engineering analysis, performance testing and experience. It is the range of operating conditions deemed acceptable by the manufacturer. While the pump may be operated outside the AOR for short intermittent periods, it is required that the vast majority of the operation should remain within the AOR.

　　POR: priority work area

　　Priority operating region (preferred operating region, POR), API610 11th edition of the standard interpretation of this term: in the region, the pump vibration is within the basic limits of this standard. The standard also states that the pump should be given a preferred operating region, which is located in the provided impeller's optimum efficiency point flow rate of 70 % to 120 % of the interval. The rated flow point should be in the range of 80 % to 110 % of the optimum efficiency point flow of the impeller supplied. ...... It is well recognized that for pumps with low suction ratio speeds it may not be possible to achieve flows in excess of 105 % to 110 % of the BEP.

　　The optimal choice would be for the rated flow point of the pump to be to the right of the BEP and the normal operating point to be to the left of the BEP, but this is hardly a very satisfactory choice in practice. As a guideline, however, the pump should be operated at or near the preferred operating condition.

　　Summarizing

　　Contrary to the POR, the AOR is defined by the pump manufacturer and not by the HI standard or API 610 standard specification.

　　There are a number of factors that affect the allowable operating zone of centrifugal pumps, including the following: vibration, noise, bearing and mechanical seal life, temperature rise, NPSH margin, power limitations, inlet return, specific speed, internal mechanical contact and pump size.