PUMPS CURVE

Could someone help me to understand how the pump curve was established for the two pararrel pumps curve shown in this problem. This sheet is basically the solution to the problem. The problem asked: If a scond pump was connected in parallel with the first pump, at what maximum elevation could the pumps be set to in order to operate and prevent cavitation. The Pump curve (one pump) and the system curve were given in the original problem and graph. The operating point and pump curve(two pumps were later found and graphed). I just cannot figure out how the pump curve(two parallel pumps) were determined, even though it is explained here.

http://i536.photobucket.com/albums/ff330/T...UMPS_Page_2.jpg

By putting pumps in parallel, you get twice the flow for the same TDH. In your example, @ 68ft TDH, one pump would deliver 200 gpm, two pumps (in parallel) would deliver twice that (2Q) or 400 gpm. They just doubled the flow amounts for each of the TDH points on the pump curve.

Spyderman said:

Could someone help me to understand how the pump curve was established for the two pararrel pumps curve shown in this problem. This sheet is basically the solution to the problem. The problem asked: If a scond pump was connected in parallel with the first pump, at what maximum elevation could the pumps be set to in order to operate and prevent cavitation. The Pump curve (one pump) and the system curve were given in the original problem and graph. The operating point and pump curve(two pumps were later found and graphed). I just cannot figure out how the pump curve(two parallel pumps) were determined, even though it is explained here.
http://i536.photobucket.com/albums/ff330/T...UMPS_Page_2.jpg

Click to expand...

The curve is gone. Be careful some of the problems are just common sense and can throw you off. Without seeing the curve, I'd say look for the NPSH required. Pump curves are ALWAYS provided by pump suppliers. Tests start at shutoff head (0 gpm) and using a variable orifice on the piping at the lab head and flow are measured (together with Voltage, Amps and KW). Like the prior post says, parallel pump flows are additive...