AXIAL FLOW VALVES

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ApplicationsUnderpressure shutoff. As long as thedownstream pressure is above the setpoint, thepilot is held open causing a drop across therestrictor and allowing the valve to remain open.If downstream pressure decreases below thesetpoint, the pilot is forced closed and inletpressure is applied to the control port of theAFV, equalizing the pressure across the sleeveand closing the valve. The needle valve is usedto start up and reset the system. With Valve Aopen, there is a pressure drop across therestrictor, allowing the AFV to open. Once thedownstream system is pressurized, close valveA.Pressure regulation with instrumentcontroller. To overcome the limitations ofspring-loaded regulators, the AFV can be usedas the final control element with a pressurecontroller and a small diaphragm motor valve.Among the advantages are overcoming springdroop, responding to the rate of change indownstream demand and the ability to regulatepressures above 600 psig (up to 1440 psig).
Regulation with check valve in alternatefeed line. In this application, gas is suppliedto a process line at 550 psi. Two AFV’s inparallel are used to reduce the supplypressure and combine it with the output of anLNG plant for other uses within the facility.During normal operation, AFV #2 is heldclosed since the control pressure (550 psi) ishigher than the normal outlet pressure (300psi).If there is a disruption in the normal gassupply, valves #1 and #3 are closed whileAFV #2 goes full open. Under theseconditions, the facility can continue to operatethe process line, at a reduced rate, using thelower pressure LNG supply.
Page 1 and 2: SB9509.3AXIAL FLOWVALVES
Page 3 and 4: Basic valve operationBecause there
Page 5 and 6: ApplicationsSingle-stage pressure r
Page 7: Pressure relief valve. With the ZSC
Page 11 and 12: Sizing the American AFVfor pressure

AXIAL FLOW VALVES

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