Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1986-07-18
1987-11-17
Cohan, Alan
Fluid handling
Line condition change responsive valves
Direct response valves
137527, 251 82, 251175, 251284, 277168, F16K 1503, F16K 1518, F16K 2500
Patent
active
047067063
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to check valves.
A check valve comprises a housing which forms a through passage which is to be connected into a fluid pipeline when the valve is in use. There is an annular valve seat which extends around the passage, and an obturating member which is cooperable with the valve seat to close the through passage and which is displaceable from the valve seat to allow fluid flow through the through passage.
U.S. Pat. No. 4,410,007 discloses a check valve comprising a housing which forms a through passage which is to be connected into a fluid pipeline when the valve is in use, the housing including an annular valve seat which extends around the passage and tapers towards the upstream end of the passage in the context of the normal direction of flow through the passage, and an obturating member cooperable with the valve seat to close the through passage and displaceable from the valve seat to allow fluid flow through the through passage, the obturating member carrying an annular seal which effects a metal to metal seal between the obturating member and the valve seat when the through passage is closed by the obturating member. In the context that it is difficult to make such metal to metal seals leak proof, a soft seal backup to the main metal to metal seal is provided and provision is made for reverse fluid flow to be conducted through the obturating member and applied to the soft seal so as to expand it into engagement with the valve seat to form a secondary seal so that flow through the check valve is prevented.
One aspect of this invention arises from our appreciation that the sealing forces that act between the annular seal and the valve seat would be increased if the angle of taper of the valve seat is reduced as compared with that of the tapered valve seat that is incorporated in the check valve disclosed in U.S. Pat. No. 4,410,007, and that the risk of jamming of the obturating member in the resultant tapered orifice could be avoided by arranging for the obturating member to make direct face to face contact with an abutment surface separate from the tapered surface of the valve seat so that the hydrostatic forces applied to the obturating member by the reverse fluid flow would be reacted by the abutment surface and not be the tapered surface of the valve seat.
Known forms of sub-sea check valve are either provided with a remotely-controllable actuator having an actuating element which is permanently coupled to the obturating member, the actuator being operable to positively seat the obturating member and to unseat it as required, or are arranged with the obturating member mounted for free pivotal movement within the housing such that it floats in normal fluid flow through the through passage in one direction and is thereby displaced from the valve seat, but is caused to seat on the valve seat by a tendency for fluid to flow through the through passage in the opposite direction whereby to close the through passage and inhibit such flow in that opposite direction. The former variety of sub-sea check valve has the advantage that the obturating member can be displaced from the through passage into an alcove in the housing by operation of the actuator so as to leave the through passage clear for passage through it of a device known as a pig which is for effecting any one of a number of functions such as cleaning the walls of the passage, removal of debris or measuring the inside diameter of the passage, but it does not close automatically in response to certain conditions, say any tendency for the direction of flow to reverse such as would occur in the event of a failure in the pipeline upstream of the check valve. The latter variety will close automatically but suffers from the disadvantages that at least part of the obturating member obstructs the path of a pig since it either floats in fluid flow through the pipe or seats on the valve seat due to the action of gravity.
Another object of this invention is to provide an improved from of check valve which is suitable for u
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Milton John S.
Page Robert G.
Cohan Alan
Corrotex Limited
Rivell John
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