GB2121090A - Well safety valve - Google Patents

Abstract

Hydraulic actuating means for actuating a subsurface safety valve 10 includes a metal piston 40 movable in a cylinder 48 in which the cylinder is connected to one side of the piston to a hydraulic control fluid passageway 32 and on the second side of the piston to pressure in the safety valve. The cylinder 48 includes a valve seat 50, 52 on each side of the piston and valve elements 54, 56 are connected to each side of the piston for seating on the valve seats for providing positive seals. A universal connection 58, 60 may be provided between the first and second sides of the pistons and the respective valve elements. <IMAGE>

Description

SPECIFICATION Well safety valve It is well known to utilize an elastomer seal in a hydraulic piston and cylinder assembly in a safety valve such as shown in U.S. Patent Nos.

4,1 61,21 9 and 4,049,052. However, elastomer seals are limited as to the temperatures in which they can operate, the pressures which they can withstand, the corrosive environment in which they can operate, and the length of time before they must be replaced. GB-2 109 895A discloses a metal-to-metal seal used in a piston and cylinder actuating assembly in a subsurface safety valve. However, it is difficult to manufacture metal-to-metal seals which will seal under all pressure conditions and which will seal against gases.

The present invention is directed to a hydraulic actuating means for actuating a subsurface well safety valve which avoids the use of elastomer seals and can be used in both high and low pressure and high and low temperature applications and in the presence of corrosive fluids and gases.

The present invention is directed to a well safety valve for controlling fluid flow through a well conduit which includes a housing and a valve closure member moving between open and closed positions by providing an improved hydraulic actuating means for actuating the valve closure member; at least one cylinder is provided in the housing with a piston movable in each cylinder; the cylinder on one side of the piston is in communication with a hydraulic control fluid passageway and the cylinder on the second side of the piston is in communication with fluid pressure in the valve housing; the cylinder includes a first valve seat on one side of the piston and a second valve seat on the second side of the piston; a first valve element is connected to one side of the piston and adapted to seat on the first valve seat when the piston moves away from the first valve seat, and a second valve element is connected to the second side of the piston and adapted to seat on the second valve seat when the piston moves away from the second valve seat.

The valve elements provide a positive seal for sealing off the hydraulic actuating means even if fluid leaks by the piston.

The piston may include a metal seal for sealing against the cylinder and the valve seats and valve elements are metal to provide metal-to-metal seals.

A universal connection may be provided between the first and second sides of the piston and said valve elements for allowing the piston to align itself properly with the cylinder.

An embodiment of the present invention provides a well safety valve for controlling the fluid flow through a well tubing and including a housing and a valve closure member moving in the housing between open and closed positions. A longitudinally tubular member is telescopically movable in the housing for controlling the movement of the valve closure member by providing an improved hydraulic actuating means for actuating the tubular member. A metal double acting piston having a metal seal is movable in a cylinder in the housing and the cylinder includes a first metal valve seat on one side of the piston through which hydraulic control fluid can flow to the piston and includes a second metal valve seat on the second side of the piston through which fluid pressure in the safety valve can flow to the piston.First and second metal valve elements are connected to opposite sides of the piston and are adapted to seat on the first and second valve seats for providing positive seals.

A presently preferred embodiment of the invention will now be described by example, reference being made to the accompanying drawings in which: Figure 1 is an elevational view, in quarter section, of a well safety valve utilizing hydraulic actuating means, embodying the present invention and shown in the open position, Figure 2 is an enlarged cross-sectional view of the hydraulic actuating means of Figure 1 with the hydraulic piston being in its full upward position, Figure 3 is an exploded perspective view of the hydraulic actuating means, and Figure 3A shows a modified type of piston.

While the present invention will be described in connection with a subsurface tubing safety valve having a flapper type valve closure member, it is understood that the present invention may be used with other types of safety valves and other valve closure members.

Referring now to Figure 1, a subsurface tubing safety valve 10 includes a body or housing 12 which is adapted to be connected in a well tubing to permit well production therethrough under normal operating conditions, but in which the safety valve 10 may close or be closed in response to abnormal conditions.

The valve 10 includes a bore 14, an annular valve seat 1 6 positioned about the bore 14, and a valve closure element such as a flapper valve 1 8 connected to the body 12 by pivot pin 20. Thus, when the flapper valve 18 is in the upward position and seated on the valve seat 16, the safety valve 10 is closed blocking flow upwardly through the bore 14 and well tubing.

A sliding longitudinal tubular member 22 is telescopically movable in the body 12 and through the valve seat 1 6. As best seen in Figure 1, when the tubular member 22 is moved to a downward position, the tube 22 pushes the flapper 1 8 away from the valve seat 1 6. Thus, the valve 10 is held in the open position so long as the tube 22 is in the downward position. When the tube is moved upwardly, the flapper 1 8 is allowed to move upwardly onto the seat 1 6 by the action of a spring 24 and also by the action of fluid flow moving upwardly through the bore 1 4 and behind the flapper 1 8.

The tubular member 22 is biased in an upward direction by a suitable means which may include a spring 26 for yieldably urging the member 22 in an upward direction to release the flapper 1 8 for closing the valve 10. The safety valve 10 is controlled by the application or removal of a pressurized fluid, such as hydraulic fluid, through a control path or line, such as one or more control lines 32 extending to the well surface or the casing annulus, which supplies pressurized fluid to the top of one or more pistons 40 which in turn act on the tubular member 22 to move the tubular member 22 downwardly forcing the flapper 18 off the seat 1 6 and into the full open position.The piston 40 may be an annular piston or may be a plurality, e.g. two, of circular pistons 40 positioned in the housing 12 and connected to the tubular member 22 by a connection 42. The safety valve 10 is controlled by the application or removal of pressurized fluid through the control lines 32 and a fluid passageway 46 to supply hydraulic control pressurized fluid to the cylinder 48 and the top of the piston 40. The bottom of the piston 40 is exposed to fluid pressure in the bore 14 which acts against the bottom of the piston 40 for biasing the tubular member 22 to the closed position when fluid control pressure is removed from the control line 32.

The above description is generally as disclosed in GB-2 109 895A mentioned above. However, the prior art, which has utilized a metal piston 40, such as in the form of cup seals, is difficult to manufacture to obtain desirable sealing under all pressure conditions and particularly in sealing gases. Furthermore, in some applications, the metal piston 40 is subject to wear and tear in its hostile environment and may leak. The present invention is directed to providing positive valve element seals connected to the piston 40 which will provide a positive seal in both directions for the double acting piston 40, and will provide a working hydraulic actuator even in the event that the piston 40 deteriorates to a condition which allows a considerable fluid bypass between the piston 40 and cylinder 48.

Referring now to Figures 1 and 2, the cylinder 48 includes a first metal valve seat 50 on one side of the piston 40 and in communication with the fluid control passageway 46 whereby hydraulic control fluid can flow to and actuate the top of the piston 40 through the valve seat 50. A second metal valve seat 52 is provided on the cylinder 48 on the second side of the piston 40 through which fluid pressure in the safety valve and tubing can flow to the bottom side of and actuate the piston 40. Afirst metal valve element 54 is provided connected to the first side of the piston 40 and is adapted to seat on the first valve seat 50 to provide a positive seal when the piston 40 moves away from the first valve seat 50 (Figure 1).A second metal valve element 56 is connected to the second side of the piston 40 and is adapted to seat on the second valve seat 52 and provide a positive seal when the piston 40 moves away from the second valve seat 52 (Figure 2).

Preferably, the valve elements 54 and 56 are connected to the piston 40 by ball and socket universal connections 58 and 60 respectively, for allowing the piston 40 to align itself properly in the cylinder 48 without binding. The piston 40 merely provides a dynamic seal in the cylinder 48 sufficient to cause movement of the piston 40 in the cylinder 48 to actuate the sliding tube 22. The valve elements 54 and 56 provide a static and positive seal when they are seated on their respective valve seats 50 and 52. Therefore, with the use of the positive valve elements 54 and 56 leakage of fluids past the piston 40 will not cause the hydraulic actuating system to become inoperative so long as the piston 40 seals sufficiently in the cylinder 48 to move the valve elements 54 and 56 to their seated positions.

Once the valve elements 54 and 56 are in the seated position, fluid pressure acting on the back side of the elements 54 and 56 will positively seat and keep the valve elements 54 and 56 seated.

The piston 40 may be in the form 41 shown in Figure 3A which is a conventional turbulent seal which has a minimum of sealing action. In fact the piston 40 could be merely a smooth elongated rod with a sufficiently close fit in the cylinder 48 whereby the pressure drop acting across the piston would move the valve elements 54 and 56 into their seated position.

Figure 3 is an exploded perspective view of two hydraulic piston and cylinder actuators which are identical and wherein the numbers of the second actuating means utilize the suffix "a" to correspond to like parts. Thus, the cylinders 48 and 48a are threadably secured at their upper ends to a housing member 13 and are enclosed by semi-circular housing members 15, which are secured to member 13 by suitable bolts 1 7.

In operation, when hydraulic control fluid is supplied through the line 32 fluid will flow into the passageway 46 and into the cylinder 48 above the piston 40 moving the piston 40 downwardly which in turn carries the sliding tube 22 downwardly to open the flapper 18. Downward movement of the piston 40 carries the valve element 54 downwardly until it contacts and seats on valve seat 50 (Figure 1) to provide a positive seal and further fluid pressure in the fluid passageway 46 acts on the back of the valve element 54 to hold it in the sealed position. When it is desired to close the valve, the pressure in the hydraulic control line 32 is reduced thereby reducing the pressure in the hydraulic passageway 46 and on the top of the valve element 54. The fluid pressure in the bore 14 of the safety valve 10 is in communication with the cylinder 48 and the bottom of the piston 40 and along with the spring 26 biases the piston 40 in an upward direction until, as best seen in Figure 2, the valve element 56 is seated on the valve seat 52 to provide a positive seal in the upward direction. Thereafter, the fluid pressure in the well tubing and bore 1 4 acts on the back of the valve element 56 to maintain it in a sealed position on the valve seat 52.

Claims (6)

1. A well safety valve for controlling the fluid flow through a well conduit including a housing and a valve closure member moving between open and closed positions, and hydraulic actuating means for actuating the valve closure member, comprising a cylinder in the housing; a piston movable in the cylinder, said cylinder on one side of the piston in communication with a hydraulic control fluid passageway, and said cylinder on the second side of the piston in communication with pressure in the safety valve, said cylinder including a first valve seat on said one side of the piston and including a second valve seat on the second side of the piston; a first valve element connected to the one side of the piston and adapted to seat on the first valve seat when the piston moves away from the first valve seat; and a second valve element connected to the second side of the piston and adapted to seat on the second valve seat when the piston moves away from the second valve seat.

2. A well safety valve according to Claim 1, including a universal connection between the respective first and second sides of the piston and said valve elements.

3. A well safety valve according to Claim 1, wherein the valve seats and the valve elements are metal.

4. A well safety valve according to Claim 3, wherein the piston includes a metal seal for sealing against the cylinder.

5. A well safety valve for controlling the fluid flow through a well tubing and including a housing and a valve closure member moving in the housing between open and closed positions, a longitudinally tubular member telescopically movable in the housing for controlling the movement of the valve closure member, and hydraulic actuating means for actuating the tubular member comprising a cylinder in the housing, a metal piston having a metal seal and movable in the cylinder, said cylinder on one side of the piston being in communication with a hydraulic control fluid passageway, and said cylinder on the second side of the piston being in communication to fluid pressure in the safety valve, said cylinder including a first metal valve seat on said one side of the piston through which hydraulic control fluid can flow to the piston and including a second metal valve seat on the second side of the piston through which fluid pressure in the safety valve can flow to the piston, a first metal valve element connected to the one side of the piston, and adapted to seat on the first valve seat when the piston moves away from the first valve seat, and a second metal valve element connected to the second side of the piston and to the tubular member and adapted to seat on the second valve seat when the piston moves away from the second valve seat.

6. A well safety valve substantially as hereinbefore described with reference to the accompanying drawings.