AXIAL FLOW VALVES

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Pressure reduction with monitor. Duringnormal operation, a single AVF, the worker,performs the pressure cut. The monitoring pilot isset at an output pressure slightly higher than theworking pilot. Since the monitoring pilot is alwaysopen, the monitor AFV is held in the full openposition. If a malfunction occurs on the workerside, the output pressure rises to the monitorsetpoint and it assumes control. The roles ofworker and monitor can be reversed by simplyresetting the pilots.Two-stage regulators with monitor override.Under normal conditions, both AFV’s areperforming pressure cuts. However, they aresized so either one can handle the entire cut in theevent of a malfunction. If a problem occurs in the1st stage, P2 increases and the 2nd stage makesa correspondingly larger cut. If the 2nd stagemalfunctions, P3 increases and the override pilotassumes control of the 1st stage AFV, causing itto take a larger single stage pressure cut. Themaximum interstage pressure, P2, is limited to themaximum spring adjustment of the 1st stage pilot–325 psi for the SZC or 600 psi for the ZSC-320.
Pressure relief valve. With the ZSC-150 pilot,the AFV is closed as long as upstream pressureis below the setpoint. Because the exhaust portis normally at atmosphere, once the regulatoropens, a large drop occurs across the restrictor,causing the AFV to open quickly.On/off control of flow in a pipeline. When theelectrically operated valve is open, the inputpressure is bled downstream causing a dropacross the restrictor. Since the control pressureis less than the input pressure, the AFV opensto allow flow in the pipeline. Closing theelectrically operated valve causes the controlpressure to build up to the input pressure,closing the AFV.
Page 1 and 2: SB9509.3AXIAL FLOWVALVES
Page 3 and 4: Basic valve operationBecause there
Page 5: ApplicationsSingle-stage pressure r
Page 9 and 10: Regulation with check valve in alte
Page 11 and 12: Sizing the American AFVfor pressure

AXIAL FLOW VALVES

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