This gives extra flexibility for maintenance and in case the process flow varies. Buying pumps for a new system is fairly straightforward. The first step is to determine the desired flow, the required head, the desired pipe diameter and length, and the valves and fittings included in the system. Next, plot a system curve. Let s say a particular application requires 900 gpm at a constant head of 82 feet.
Suction is flooded.
This constant head may be the pressure of a pipeline from which the liquid is to be pumped, or the elevation of a reservoir, tank or pressure vessel. The last step is to plot the friction losses against flow. Two pumps in parallel Figure 3 shows a straight line parallel to the y-axis drawn at 900 gpm and intersecting the system curve at 82 ft. This particular system requires a pump that delivers 900 gpm with a discharge head of 82 ft. Two pumps each delivering 450 gpm, or three pumps each delivering 300 gpm, will achieve the same result.