I received the pump test bed data (flow rate, head and RPM Q-H curve). The test was conducted on cold conditions (i.e. at 28°C and 2,982 rpm). The vendor has converted the flow rate and head base on site conditions (i.e 135°C and 2,975 rpm) as follows. The flow rate was converted as 100.6 m3/hr x 2975/2982 = 100.4 m3/hr * 0.93 (i.e. specific gravity @ 135°C) = 93.3 tph and head was converted as 597.56 m x 2975/2982 = 594.76 m. Based on such converted flow rates and heads measured at different points during the test, the capacity Vs Head curve was prepared and declared to represent the conversion of head and flow rate to 135°C without taking any impact due to difference in density. Will this performance curve represent the flow and head at 135°C? If not, how should we can convert these parameters to 135°C for getting confirm that pump will able to perform according to site conditions?
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Ross Mackay Forum Moderator 93 Posts
Re: Flow rate test data10 May 2007 at 1:29pmI was a little confused by the conversion factors you showed. The characteristic performance curve of a pump shows the relationship of the flow rates against the respective differential heads. The reason we use the differential head and not pressure is so that the curve will be applicable to all liquids of different densities. When a pump is tested, the pressures are normally identified in pressure readings, which are, in turn, converted to head using the density (or specific gravity) of the tested liquid. Flow rates do not require correction. Nor does the minimal difference in rotational speed. I am unsure of how the heads you identify were converted, but it will require the use of the density at the higher temperature to convert from the pressure reading on the test bed to the resultant Head to be used to draw the performance curve.