GB2206912A - Blow-out preventing valve - Google Patents

Abstract

A blow-out preventing valve (10) has upper and lower housing halves (13A, 13B) through which extends an unrestricted axially-extending clearway 15. Clearway (15) passes through an upper frusto-conical chamber (16) the lower end being diametrically greater than the upper end. A piston (18) is mounted below chamber (16) having its lower end face (18A) exposed to fluid pressure in clearway (15) and is held against upward movement by fluid under controlled pressure passing through a port (20). A pair of half frusto-conical sealing rams (24A, 24B) are mounted within chamber (16) on the upper end of the piston (18), the curved surfaces of the rams (24A, 24B) sliding against the curved surfaces of the chamber (16). Upward movement of the piston (18) drives rams (24A, 24B) from the lower end of the upper chamber (16) in which the clearway (15) is open to a location at the upper end of the chamber (16) in which the clearway (15) is sealingly closed with the planar surfaces of the rams (24A, 24B) in mutual abutment. <IMAGE>

Description

BLOh'-OUT PREVENTING VALVE This invention relates to a blow-out preventing valve.

Blow-out preventing valves are of particular use in the oil drilling industry being located adjacent the well head between the christmas tree and the lubricator for the purpose of containing well fluids in the event of a blow-out and for isolating the lubricator from the well.

Known forms of blow-out preventing valves comprise a housing defining an unrestricted clearway through the valve and a plurality of valve members movable transversely of the clearway by hydraulic or mechanical means in order to seal off the clearway. Movement of such valve members requires manu l intervention to drive the valve members to their closed position so that the blow-out preventing valve is not fail-safe. Such valves are also of relatively complicated construction and require to be pressure tested independently of the lubricator.

It is an object of the present invention to provide a new and iproed blow-out preventing valve in which the foregoing disadvantages are obviated or mitigated.

According to the present invention there is provided a blow-out preventing valve comprising a housing defining an unrestricted clearway through the valve, the clearway extending axially through an upper frusto-conical chamber the lower end of which is diametrically greater than the upper end, and a lower cylindrical chamber, an annular piston slidably mounted in the lower chamber and having a lower end surface exposed to fluid pressure in the clearway and an upper end surface extending into the upper chamber and of lesser area than said lower end surface, means for effecting a predetermined force on the piston to hold the piston against expected levels of fluid pressure in the clearway, a pair of half-frusto-conical sealing rams located in the upper chamber and mounted on the upper end surface of the annular piston by transversely extending guides whereby upward movement of the piston drives the rams from a location at the lower end of the upper chamber in which the clearway is open to a location at the upper end of the upper chamber in which the clearway is sealingly closed with the curved surfaces of the rams in engagement with the curved surfaces of the upper chamber and the planar surfaces of the rams in mutual abutment, and inclined cam means in the upper chamber in engagement with the rams for returning the rams to said location at the lower end of the upper chamber on downward movement of the piston.

It is preferred that the sealing rams are of layered construction, at least one layer being made of an elastomeric material and at least the top and bottom layers being made of rigid material (such as steel).

The means for effecting the predetermined force on the piston to hold the piston against expected levels of fluid levels in the clearway is preferably a hand pumped hydraulic supply provided to a recess in the outer surface of the annular piston, the predetermined force being controlled by a pre-set non-return check valve mounted in the housing of the valve.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing in which: Fig. 1 is a part sectional elevational view of a valve according to the present invention; and Fig. 2 is an exploded perspective view of the principal components of the Fig. 1 valve.

In the drawing the valve 10 shown in Fig. 1 is symmetric about its longitudinal axis 12, the right hand half of Fig. 1 being a sectional view on the plane containing axis 12 and the line A in Fig. 2 whilst the upper and lower portion of the left hand half are sectioned on two different planes each containing axis 12 and which are approximately 600 inclined to the plane containing the line A.

The valve 10 comprises a housing having an upper housing half 13A connected by Acme screw threads 14 (which in the left hand half of Fig. 1 are visible in elevation due to the different planes of section) to a lower housing half 13B and defines an unrestricted clearway 15 of essentially constant diameter throughout the length of the valve, the clearway 15 extending axially through an upper frusto-conical chamber 16 the lower end of which is diametrically greater than the upper end, and a lower cylindrical chamber 17. An annular piston 18 is slidably mounted in chamber 17 and has a lower end face 18h exposed to fluid pressure in the clearway 15 and an upper end face 18B extending into the upper chamber 16.Face 18B is of lesser area than face 18 so that piston 18 tends to move upwardly due to the pressure differential and is held against such movement by provision of a hand pump (not shown) connected to port 20 in upper housing half 13A which is in fluid communication with an annular void 21 formed at the outer surface of the piston 18 due to the reduced size of face 18B, the level of such hydraulic force on the piston 18 being set by an adjustable non-return check valve 22 connected to port 20 and to a dump port 22A.

Located within the upper chamber 16 is a pair of half frusto-conical sealing rams 24A, 24B, which are mounted on the upper end surface 18B of the piston 18 by transversely extending tenon guides 25A, 25B, which mate with tenons 26A, 26B, formed at diametrically opposed locations on piston end surface 18B. The curved surfaces of the rams 24A, 24B, each slide against the curved surfaces of the upper chamber 16 and upward movement of the piston 18 drives the rams 24A, 24B, from their location shown on Fig. 1 at the lower end of the upper chamber in which the clearway 15 is open to a location at the upper end of the chamber 16 in which the the clearway 15 is sealingly closed with the planar surfaces of the rams 24A, 24B, in mutual abutment.

Within chamber 16 and mounted on the floor thereof, which is formed b a collar 30, are a pair of inclined cam members 28A, 28B, which are also diametrically opposed with respect to the clearway 15 and orthogonally with respect to the tenons 26A, 26B, the cams 28A, 28B, engaging respective guide slots 29A, 29B, in each of the rams 24A, 24B, so that on downward movement of the piston 18 the rams 24A, 24B, are returned to the illustrated Fig. 1 location at the lower end of the chamber 16 and thereby re-open the clearway 15.

The rams 24A, 24B, are each formed of a five-layer laminate or sandwich of alternating steel and elastomeric material, the upper and lower layers of the laminate being steel, and the sandwich is held together by axially extending shoulder screws which preferably are sufficiently tightened to cause the elastomeric material to bulge in relation to the steel layers to provide for good sealing of the clearway 15.

When the rams 24A, 24B seal the clearway 15 pressure is contained beneath the rams and enhances the sealing action due to the large surface area of the rams exposed to the pressure. To enable the rams to open the pressure differential across the rams requires to be reduced and this is effected by a manually operable normally-closed valve 31 and associated porting 32 which bypasses the rams 24A, 24B, in their sealing location.Also since in the standard use of the valve 10 a wire line extends through the valve for actuation of tools etc. at a location beneath the valve 10 the planar faces of rams 24A, 24B, are provided with half grooves 33A, 33B, which mate to form a cylindrical cavity within which the wire line (not shown) runs and sealing of this cavity against egress of pressurised fluid when the rams are in their sealing location is provided by a grease port 35 in the upper housing half 13A which registers with a passageway through ram 24A leading to the cylindrical wire line cavity.

The rams 24A, 24B, can be manually pumped to their sealing position by hydraulic fluid applied to lower cylindrical chamber 17 via port 36.

It will be appreciated that valve 10 is free of external protruding components which might be damaged inadvertently and is fail-safe to the sealing condition such that the greater the well head pressure the tighter is the seal. The valve has very few dynamic seals and in the particular embodiment there are only three associated with the piston 18, these being of Tconfiguration. External pressure is required to hold valve 1O in its open condition and each time the lubricator is pressure tested the valve 10 cycles to its closed condition which effectively tests operability of the salve 10. The rams 24A, 24B, are easily removed from the valve 10 for repair and/or replacement and are capable of accomrocating wire line operations with stranded line, or slick line or coiled tubing.

Claims (5)

1. A blow-out preventing valve comprising the combination of a housing defining an unrestricted clearway through the valve, the clearway extending axially through an upper frusto-conical chamber, the lower end of which is diametrically greater than the upper end, and a lower cylindrical chamber, an annular piston slidably mounted in the lower chamber and having a lower end surface exposed to fluid pressure in the clearway and an upper end surface extending into the upper chamber and of lesser area than said lower end surface, means for effecting a predetermined force on the piston to hold the piston against expected levels of fluid pressure in the clearway, a pair of half-frusto-conical sealing rams located in the upper chamber and mounted on the upper end surface of the annular piston by transversely extending guides whereby upward movement of the piston drives the rams from a location at the lower end of the upper chamber in which the clearway is open to a location at the upper end of the upper chamber in which the clearway is sealingly closed with the curved surfaces of the rams in engagement with the curved surfaces of the upper chamber and the planar surfaces of the rams in mutual abutment, and inclined cam means in the upper chamber in engagement with the rams for returning the rams to said location at the lower end of the upper chamber on downward movement of the piston.

2. A blow-out preventing valve as claimed in claim 1 wherein said sealing rams are of layered construction, at least one layer being made of an elastomeric material and at least the top and bottom layers being made of rigid material.

3. A blow-out preventing valve as claimed in either preceding claim wherein said means for effecting the predetermined force on the piston to hold the piston against expected levels of fluid pressure in the clearway comprises a controlled hydraulic supply provided to a recess in the outer surface of the annular piston, the predetermined force being controlled by a pre-set nonreturn check valve mounted in the housing of the valve.

4. A blow-out preventing valve as claimed in any preceding claim wherein to open the rams a normally-closed manually-operated valve is provided in porting extending through the housing and which bypasses the rams in their sealing location.

5. A blow-out preventing valve as claimed in any preceding claim wherein the planar faces of the rams are provided with half grooves which mate to form a cylindrical cavity for accommodating a wire line.