There are many ways to design multiple-pump hook-ups. This section discusses several configurations that satisfy various conditions. The primary and standby pump arrangement illustrated shown below indicates two ways in which the pumps may be tied together.
Although the preferred hookup is directly across and over headroom, the operating temperature of many pumps requires the addition of a flexibility loop to reduce stresses on the pump nozzles.
The loop need not take the routing as shown, but it should be configured so that the piping receives optimum support. Another concern is the elevation of the block valve hand wheel in the discharge line, which must he within the reach of plant operations personnel—the preferred arrangement and an alternative layout are shown below.
In larger line sizes with higher pressure ratings, the valves place the horizontal piping too high, especially if they are beneath the pipe rack. Therefore, the alternative arrangement shown in the exhibit solves the layout problem.
Following figure illustrates how a common standby pump is used for two primary pumps; this is the ideal layout, with flexibility loops added as required.
Following drawing shows how the suction line for service B is tied into the suction line for service A below or down-stream from the block valve and upstream from the strainer. The discharge line for service B is tied in downstream from the check valve.