Fluid handling – Processes
Patent
1993-05-04
1994-09-20
Schwadron, Martin P.
Fluid handling
Processes
1374895, 137488, 137489, F16K 31365
Patent
active
053480368
ABSTRACT:
An automatic control valve has a main valve member moveable between open and closed positions thereof in response to pressure applied to a first piston or diaphragm in a first control chamber. The valve member moves to modulate flow through the valve to maintain desired flow conditions. Pilot pressure signals are generated to reflect the flow conditions, usually upstream and downstream from the valve, which signals are processed to generate a control signal which is fed to the first control chamber to control pressure therein. Normal movement of the valve produces wear which causes leakage of the diaphragm or seals oft he piston causing loss of primary control of the valve member which tends to fail "open". This causes an initial rise in flow through the valve which is detected by the pilot pressure signal but because of the leakage, is unable to correct. This prior art problem is avoided by providing a back-up piston or diaphragm which is maintained in an inactive position during normal operation of the valve by the first piston or diaphragm, and thus does not wear. When pilot pressure signals reflect primary control failure, the back-up piston or diaphragm moves to an active position and selectively cooperates with the main valve member to control flow conditions through the valve independently of the first control chamber.
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patent: 4944249 (1990-07-01), Takeuchi et al.
LaBar Grant V.
Oksanen Kari J.
Lee Kevin L.
Schwadron Martin P.
Singer Valve Inc.
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