Us Gallons Per Minue

FIGURE 13 Performance coverage for multistage, axially split pumps

Pumping Stations The typical piping of a main line pump station in which the units are arranged in series is shown in Figure 14. As pipeline capacities have increased, one of the major problems has been the pressure loss at each station. For the station shown, three discharge valves (one 16 in (406 mm) ball valve manifolded in parallel with two 24 in (610 mm) control valves) were used. This arrangement limited the calculated pressure drop to that of a length of 36 in (914mm) pipe equal to the distance across the manifold and still allowed the use of control valves of proven size. When line conditions require throttling, the 16 in (406 mm) ball valve is first completely closed. If additional throttling is needed, the two 24 in (610 mm) control valves are closed to produce the required pressure drop. In order to move scrapers or batch separators through each station without interrupting flow through the pumps, signals (PIG SIG), hydraulically operated 24 in (610 mm) valves, and sequence control wiring are used. The distance between PIG SIG 1 and PIG SIG 2 represents the volume of station loop to be displaced. The tripping of PIG SIG 3 and PIG SIG 4 controls the valve opening and closing required to divert flow from the station discharge piping to behind the scraper or batch separator, thus forcing it to leave the station in the same relative position as it entered. Elbows at pump suction are arranged to avoid uneven flow distribution in the inlet of the double suction impeller.

Pipeline pumps are tested in accordance with Hydraulic Institute Standards. Reduced speed tests may be required because of the power limitations of manufacturing plants and available drivers, and such tests have proven to be extremely accurate indicators of full speed performance.

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