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valve is open or closed. The microprocessor also uses this signal to find which tank should be
monitored for low-level conditions. The outlet lines from the tanks feed the pump suction
manifold in the pumphouse.
6.4. Pumphouse. This paragraph covers the pumphouse components, and will trace the flow of fuel
through the system during a refueling operation.
6.4.1. Fueling Pumps. Refueling pumps are 2271 liters per minute (600 gallons per minute), single-
stage centrifugal, horizontally mounted, vertical or radial split case, enclosed impeller, with end
suction and top vertical discharge conforming to API Std 610. They are statically and dynamically
balanced for all flow rates, from no flow to 120% of the designed rate.
6.4.2. Flow Switches. Typically, open flow switches are installed downstream of each pump
discharge. When there is flow, a vane in the pipeline is raised, rotating the attached shaft and closing
the double-pole double-throw snap-action switch, allowing the pump to continue to run. If flow is not
established within a preset time, the microprocessor calls off the unresponsive pump and calls on the
next pump in the start-up sequence.
6.4.3. Rate-of-Flow, Nonsurge Check Valve (41AF-1A).
126.96.36.199. This valve (Figure 6.3) is very similar to the nonsurge check valve used in Type I and II
systems, except it also provides flow control by using an orifice plate and DP controller. The flow
control is typically set for 2460 liters per minute (650 gallons per minute) to keep the pump from
operating outside its pump curve when one pump discharges into multiple F/Ss.
Figure 6.3. Rate-of-Flow Nonsurge Check Valve (41AF-1A).
188.8.131.52. Valve Setting. Set the CDHS-2B rate-of-flow control by turning the adjusting stem
clockwise to increase the fuel rate of flow and counterclockwise to decrease it. The valve should
be set for about 2460 liters per minute (650 gallons per minute). The valve-opening rate is set by
adjusting the CV flow control. Turn the CV flow-control adjusting stem clockwise to make the
main valve open slower and counterclockwise to make the valve open faster. Set the valve to open