Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1982-01-29
1984-08-07
Cohan, Alan
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
137488, F16K 1710, F22B 3744
Patent
active
044637764
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an actuator for a fluid pressure relief system.
As is well known, fluid pressure relief valves or "safety valves" are provided to relieve automatically any excessive pressure build-up which may occur in a pressure vessel (or chamber). When a pre-determined pressure level is exceeded in the pressure vessel, a valve element of the relief valve lifts-off its seating against spring biasing in order to allow the escape, through the valve, of the fluid medium which is at an excessive pressure level, until such time as the pressure level falls back to a valve below the predetermined level when the spring biasing re-seats the valve element.
It is known to provide an actuator which is coupled via a linkage with the valve element, and which is operable, when fluid under pressure is supplied to the actuator, to raise the valve element from its seat against the spring biasing.
The operation of the actuator is controlled by a control valve which, in turn, is controlled by a pilot pressure instrument which responds to the pressure in the pressure vessel with which the relief valve is used. The pilot pressure instrument has a separate pressure connection with the vessel, and is able to control the pressure therein, at selected levels which are lower than the predetermined maximum safe pressure as determined by the valve element and its spring biasing, by effecting controlled opening of the relief valve via the control valve and the actuator.
It is also known to provide, in the linkage between the valve element and the actuator, a lost-motion connection which allows the actuator to operate the valve element, but which also allows the valve element to lift-off its seating (when the safe pressure is exceeded) without imparting action on the actuator via the linkage.
In the known arrangement the seating of the valve element is provided solely by means of its spring biasing and, inevitably, over a period of time, the performance of the relief valve deteriorates so that unintentional leakage of pressure medium occurs from the pressure vessel. This may arise due to improper seating of the valve element, e.g. caused by uneven wear and/or the build-up of deposits on the seating or valve element, or by a reduction in the effectiveness of the spring biasing due to temperature relaxation or creep.
Having regard to the enormous increases in energy costs during recent years, the unintentional loss of pressure medium e.g. steam represents a significant waste of energy, so there exists therefore a need to provide means for applying a controllable supplementary loading on the valve element in order to counter such losses.
The present invention in one of its aspects, seeks to provide such means in simple manner for a fluid pressure relief system.
According to one aspect of the invention there is provided an actuator head adapted for mounting in a fluid pressure relief system comprising a relief valve having a valve element spring biased to a closed position and arranged to be movable under the action of a fluid pressure medium in order to allow the escape of the fluid pressure medium through the valve for pressure relief purposes, said actuator head comprising:
an actuator adapted for coupling with said valve element and having a member displaceable in response to fluid pressure applied to said member;
a linkage for coupling together the valve element and the actuator and having a lost-motion connection which allows the valve element to move against its spring biasing for pressure relief purposes without imparting movement to the displaceable member of the actuator;
biasing means arranged to oppose displacement of said member of the actuator, upon the application of fluid pressure to the member;
and control means for controlling the supply of fluid pressure to said member;
in which said member is arranged to be displaceable upon the application of fluid pressure to the member by said control means, so as to apply a supplementary valve-closing load to said valve element via said linkage.
According to a second aspe
REFERENCES:
patent: 2162779 (1939-06-01), Leutwiler
patent: 2528440 (1950-10-01), Kmiecik
Cohan Alan
Crosby Valve and Engineering Company, Limited
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