Taylor-Wharton High Capacity GST Storage Tanks - Manual (Page 23)

23
CONTROL VALVES
These tanks have two automatic valves that control operating pressures.
The PRESSURE BUILDING REGULATOR opens on falling tank pressure and closes on rising
pressure. This valve is factory set at 150 psig (10.34 bar/1034 kPa).
The BACK PRESSURE REGULATOR is a backpressure device that opens on rising tank pressure
and closes on falling pressure. This valve is factory set at 165 psig (11.37 bar/1137 kPa).
The factory setting of the control valves may be field adjusted. The BACK PRESSURE
REGULATOR should be set to open at a pressure above the shut-off pressure of the pressure
building circuit.
Before attempting repair of either of the control valves, isolate and depressurize the valves by
closing the PRESSURE BUILDING ISOLATION VALVES, ECONOMIZER ISOLATION
VALVE. Turn the BACK PRESSURE REGULATOR set screw counterclockwise to the end of its
adjustment. Open TOP AND BOTTOM FILL VALVES. Vent pressure by opening FILL DRAIN
VALVE. Close TOP AND BOTTOM FILL VALVES and FILL DRAIN VALVE. Carefully
loosen the THERMAL EXPANSION RELIEF VALVE to release any pressure in the line. When
repairs are complete, purge lines and retighten the THERMAL EXPANSION RELIEF VALVE and
pressure test all joints that were disassembled.
Order replacement parts from the valve manufacturer. Be sure to give all information on the valve
nameplate, including the factory Part Number, as well as Taylor-Wharton part number listed in the
"Replacement Parts" provided in this manual to ensure receiving the correct parts for these special
valves.
RESETTING CONTROL VALVES
Use the following procedures to change control valve settings or to readjust the valves after
completing repairs of the valves.
The PRESSURE BUILDING REGULATOR should be set so that tank pressure is held about 5
psig (0.34 bar / 34 kPa) above the desired delivery pressure. The BACK PRESSURE
REGULATOR should be set at least 10 psig (0.7 bar / 70 kPa) above the setting of the PRESSURE
BUILDING REGULATOR. If both controls are to be reset, set the PRESSURE BUILDING
REGULATOR before setting the BACK PRESSURE REGULATOR.
NOTE: The tank must contain liquid for setting control valves. The BACK
PRESSURE REGULATOR must be adjusted while product is being
withdrawn through the product withdrawal line.