Nomal Flow vs Rated Flow (Related to BEP)

Not very clear about the question.

Preferred operatiing region = normal flow ie the flow at which the pump will be usually operating.

Rated flow = designed flow (what has been used by the designer) and will be almost the worst condition where the pump will operate,

As per 5.1.15 the BEP must preferably lie somewhere between those two (and that is common sense too). The other two % are the guide lines but this is the principle.

Based on the basic data you calculate the designed Op Point. Then try to calculate the normal operating point (which may not be very accurate and may vary over time due to wear outs etc). Select the pump such that the BEP is falling between the two

UD15

I suspect the two sentences of the API spec apply to two different people. The full rating of a pump would include its curve, but the mfr is allowed to state a single gpm/head rating within 80-110% of BEP. The end user is given more latitude, 70-120%, partly because it may be difficult to estimate actual operating conditions any closer than that.

Ok guys thanks for your response.. I have got quotation from vendor, it tells us that ratio of normal flow and BEP is 72%. And i think it is within the range that API stated (70-120%)

Any additional information will be appreciated to be heard.. Thanks..