GB2526765A

GB2526765A - Sealing Seat Arrangement

Info

Publication number: GB2526765A
Application number: GB1400780.1A
Authority: GB
Inventors: Paul Shillito
Original assignee: OLIVER VALVETEK Ltd
Current assignee: OLIVER VALVETEK Ltd
Priority date: 2014-01-17
Filing date: 2014-01-17
Publication date: 2015-12-09
Anticipated expiration: 2034-01-17
Also published as: GB2526765B; GB201400780D0

Abstract

A sealing seat arrangement 16a suitable for use as an upstream sealing seat arrangement of an isolation valve assembly such as a rotary gate valve comprises an annular seat 34 extending along an axis B and comprises a first portion 36, a second portion 38, and a shoulder portion 40 linking the first and second portions. The first portion 36 has a diameter greater than that of the second portion 38. A generally frustoconical seal ring 44 and a first seal arrangement 42 are received on the second portion 38 of the seat 34 such that the seal ring 44 is received between the shoulder portion 40 of the seat and the first seal arrangement 42.

Description

Sealing Seat Arrangement The present invention relates to a sealing seat arrangement. In particular, the present invention relates to a sealing seat arrangement suitable for use as a sealing seat arrangement of an isolation valve assembly. The present invention also relates to an isolation valve assembly including a sealing seat arrangement, and a method of assembly of an isolation valve assembly including a sealing seat arrangement.

Various types of fluid isolation valve assembly are known. Some examples of known fluid isolation valve assembly may be incorporated into subsea production equipment.

One type of known isolation valve assembly is a rotary gate valve assembly.

Some known isolation valves include a valve body which supports an obturator. The obturator is located in a fluid flow path within the isolation valve assembly. The obturator is movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly via the fluid flow path, and a closed position in which fluid flow through the valve assembly via the fluid flow path is substantially prevented.

In such arrangements it is known for the isolation valve assembly to include a sealing seat arrangement located generally adjacent the obturator. The sealing seat arrangement is used to seal the valve body with respect to the obturator and thereby prevent fluid from leaking past the obturator.

The sealing seat is usually a separate component to the valve body and is usually received within a sealing seat receiving bore of the valve body. It is common for known isolation valves to utilize plastic ring seals between the sealing seat and valve body in order to attempt the seal the sealing seat and valve body, and thereby prevent fluid passing through the fluid flow path of the isolation valve from passing between the seat and the valve body.

It has been found that although the plastic seal initially provides adequate sealing between the sealing seat and valve body, over time, and in certain environments, the plastic can degrade. Degradation of the plastic of the seal between the sealing seat and valve body can result in the seal losing effectiveness such that fluid which enters the isolation valve assembly can pass between the sealing seat and valve body, and then a past the obturator, such that fluid can leak through the isolation valve. It will be appreciated that leakage through an isolation valve is generally undesirable.

It is an object of the present invention to provide a sealing seat arrangement which obviates or mitigates the above described disadvantage or at least one disadvantage present in the prior art. It is a further object of the present invention to provide an alternative sealing seat arrangement. It is a further object of the invention to provide an isolation valve assembly and method of assembling an isolation valve assembly which also obviates or mitigates the problem discussed above, or at least one problem present

in the prior art.

According to a first aspect of the invention there is provided a sealing seat arrangement suitable for use as an upstream sealing seat arrangement of an isolation valve assembly, the sealing seat arrangement comprising an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions, the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a generally frustoconical seal ring; wherein the seal ring and first seal arrangement are received on the second portion of the seat such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement.

The seal ring of this configuration of sealing seat arrangement may enable a more effective and/or more durable seal between the seat and a valve body of the isolation valve assembly.

The seal ring may be formed of a metal material.

The scaling scat arrangement may be configured such that a base portion of the seal ring may contact the first seal arrangement and a head portion of the seal ring may contact the shoulder portion of the seat.

The base portion of the seal ring may be located radially outboard of the head portion of the seal ring.

The first seal arrangement may comprise a first seal member and a second seal member intermediate the first seal member and the seal ring.

The first seal member may be formed of a plastic material and the second seal member may be formed of a metal material.

The slant height of the generally frustoconical seal ring may be greater than the difference between the radius of the first portion and the radius of the second portion.

The seat may be formed of a metal material.

The first portion of the seat may include a face portion, the face portion being configured to co-operate with an obturator of an isolation valve assembly in order to form a seal between the sealing seat arrangement and obturator of the isolation valve assembly.

The sealing seat arrangement may be configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of the seal ring in the relaxed state.

The seal ring may be formed of a resilient material and wherein the sealing seat arrangement may be configured such that if the first seal arrangement ceases to be urged axially towards the first portion of the seat, the seal ring substantially returns to the relaxed state.

In the relaxed state a minimum internal diameter of the seal ring may be greater than the diameter of the second portion of the seat such that there is a clearance fit between the seal ring and the second portion of the scat.

According to a second aspect of the invention there is provided an isolation valve assembly including a valve body, obturator and a sealing seat arrangement according to any proceeding claim; wherein the obturator is movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly via a fluid passage, and a closed position in which fluid flow through the valve assembly via the fluid passage is substantially prevented; and wherein the seal ring is configured to form a seal between the sealing seat arrangement and the valve body.

The sealing seat arrangement may be located upstream, with respect to a fluid flow direction through the valve assembly in use, of the obturator.

The valve body may be formed of metal material.

The isolation valve assembly may be configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of seal ring in the relaxed state such that it contacts the valve body.

The valve body may comprise a sealing seat receiving bore, the sealing seat arrangement being received by the sealing seat receiving bore.

The base portion of the seal ring in the deformed state may contact a wall of the sealing seat receiving bore.

The isolation valve assembly may be configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the head portion of the seal ring in the deformed state being radially inboard of the head portion of the seal ring in the relaxed state such that it contacts the seat.

The sealing seat arrangement may define a fluid flow path between a portion of the fluid passage upstream of the obturator and the first seal arrangement.

The isolation valve assembly may be configured such that pressurized fluid located in the portion of the fluid passage upstream of the obturator may contact the first seal arrangement via the fluid flow path and thereby urge the first seal arrangement axially towards the first portion of the seat.

In a relaxed state, a maximum external diameter of the seal ring may be less than an internal diameter of the sealing seat receiving bore such that there is a clearance fit between the seal ring and the sealing seat receiving bore.

The obturator may be one of a ball, a gate or a rotor, such that the isolation valve assembly comprises a ball valve, a gate valve or a rotary valve respectively.

According to a third aspect of the invention there is provided a method of assembling an isolation valve assembly, the isolation valve assembly comprising valve body comprising a sealing seat receiving bore, an obturator movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly and a closed position in which fluid flow through the valve assembly is substantially prevented, and a sealing seat arrangement, the sealing seat arrangement including an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions! the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a generally frustoconical seal ring having a base portion and a head portion; and the method comprising: the second portion of the seat receiving the seal ring and first seal arrangement such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement; the sealing seat receiving bore receiving the sealing seat arrangement; allowing pressurized fluid into the sealing seat receiving bore; allowing pressurized fluid in the sealing seat receiving bore to contact the first seal arrangement via a fluid flow path defined between the seat and the sealing seat receiving bore; and the pressurized fluid urging the first seal arrangement axially towards the first portion of the seat such that the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforniing the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of seal ring in the relaxed state such that it contacts the valve body, and the head portion of the seal ring in the deformed state being radially inboard of the head portion of the seal ring in the relaxed state such that it contacts the seat, thereby forming a seal between the seat and the valve body.

According to a fourth aspect of the invention there is provided a sealing seat arrangement suitable for use as an upstream sealing seat arrangement of an isolation valve assembly, the sealing seat arrangement comprising: an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions, the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a seal ring; wherein the seal ring and first seal arrangement are received on the second portion of the seat such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement; and wherein the seal ring is configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, and wherein the radial thickness of the seal ring in the deformed state is greater than the radial thickness of the seal ring in the relaxed state.

Features relating to any particular aspect of the invention above may be applied to any other aspect of the invention.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-sectional view of a known rotary isolation valve assembly; Figure 2 shows a schematic part cross-sectional view of an isolation valve assembly including a sealing seat arrangement according to an embodiment of the present invention; Figure 3 shows a perspective view of a cross-section taken through the sealing seat arrangement shown in Figure 2; Figure 4 shows an enlargement of a portion of the cross-section in Figure 2; Figure 5 shows a schematic cross-section through a further isolation valve assembly including two sealing seat arrangements according to an embodiment of the present invention; and Figures 6a and 6b show schematic cross sections through portions of two possible alternative sealing seat arrangements including alternative seal rings.

Figure 1 shows a schematic cross-sectional view through a known isolation valve assembly 10. The isolation valve assembly 10 includes a valve body 12, an obturator 14 and a sealing seat arrangement 16.

The valve body 12 includes a fluid flow passage which has a first portion 17a and a second portion 17b. In use the isolation valve assembly 10 is configured such that fluid flows through the isolation valve assembly in the direction indicated by the arrows F. Consequently, it can be said that the first portion 17a of the fluid flow passageway is upstream of the obturator and the second portion 17b of the fluid flow passageway is located downstream of the obturator 14.

The obturator of the isolation valve assembly 10 as shown in Figure 1 includes a rotor 18 such that the isolation valve assembly comprises a rotary valve. The rotor 18 is located within a valve cavity defined by the valve body and is generally disk-shaped and includes a rotor flow passage 20 which passes through the rotor 18 and which forms part of the fluid flow passage of the isolation valve assembly 10.

The obturator 14 (and hence rotor 18) is movable relative to the valve body 12 between an open position as shown in Figure 1 in which fluid is permitted to flow through the fluid flow passage of the valve assembly (i.e. from the first portion of the flow passage 17a to the second portion of the flow passage 1 7b via the rotor passage 20 of the rotor 18), and a closed position in which fluid flow through the fluid flow passage of the valve assembly is substantially prevented.

In the isolation valve assembly shown in Figure 1 the obturator 14 is supported by the valve body 12 such that, in order for the obturator to move between the open and closed positions, the obturator 14 rotates about an axis A (i.e. such that the rotor 18 rotates about the axis A relative to the valve body 12 and within the valve body 12).

The obturator is provided with a handle 22 which is linked to the rotor 18 by a shaft 24 such that a user can rotate the handle 22 in order to rotate the obturator 14, including the rotor 18.

The closed position of the isolation valve assembly 10 is any position of the obturator 14 relative to the valve body 12 in which fluid is substantially prevented from flowing from the first portion 1 7a of the flow passage to the second portion 1 7b of the flow passage via the rotor passage 20. It will be appreciated the fluid will not flow from the first portion of the fluid passageway 1 7a to the second portion of fluid passageway 1 7b via the rotor passage 20 when the rotor passage 20 is no longer aligned with either one or both of the flow passage portions 1 7a, 1 7b.

For example, if the obturator 14 is rotated about the axis A by approximately 90° the rotor passage 20 will be aligned in a direction such that the rotor passage 20 extends perpendicular to the plane of the Figure. Consequently, the rotor passage 20 will not be aligned with the first and second portions of the fluid flow passageway 17a, 17b. As such, it will not be possible for fluid to flow between the first and second portions 17a, 17b of the fluid flow passage with the obturator in this position, and hence the obturator 14 is in a closed position. It will be appreciated that, depending on the shape of the first and second portions 1 7a, 1 7b of the fluid flow passage adjacent the obturator 14, and of either end of the rotor passage 20 at the edge of the rotor 18, the amount of rotation required to move the obturator relative to the valve body from a fully open position to a closed position may vary.

As previously discussed, the isolation valve assembly 10 includes a sealing seat arrangement 16. The sealing seat arrangement 16 is located upstream, with respect to fluid flow direction F, of the obturator 14. The sealing seat arrangement includes a generally annular seat 26. A seat flow passage 28 passes through the seat 26 and enables fluid to flow from the first portion 1 7a of the fluid flow passage to the obturator 14.

The sealing seat arrangement also includes a plastic seal ring 30 which surrounds the seat 26. The sealing seat arrangement 16 is received by a sealing seat receiving bore formed in the valve body 12. The sealing seat arrangement is received by the sealing seat receiving bore 32 such that the seal ring 30 both locates the sealing ring arrangement 16 within the sealing seat receiving bore 32 and forms a seal between the sealing seat 26 and valve body 12 (in particular the wall of the sealing seat receiving bore 32 of the valve body 12).

Within Figure 1, the clearance between the wall of the sealing seat receiving bore 32 and the sealing seat 26 is exaggerated so as to aid clarity.

If pressurized fluid is supplied to the first portion 17a of the fluid flow passage then, because the sealing seat arrangement 16 is located upstream of the obturator 14, when the obturator 14 is in a closed position, the pressurized fluid will exert a force on the sealing seat 26 which urges the sealing seat 26 against the obturator 14, thereby improving the sealing between the seal seat 26 and obturator 14. This will in turn help to ensure that when the obturator 14 is in the closed position there is substantially no leakage through the isolation valve assembly from the first portion 17a of the fluid flow passage to the second portion 1 7b of the fluid flow passage.

It has been found that over time and in certain environments the plastic seal ring 30 within this known type of isolation valve will degrade. If the seal ring 30 degrades then fluid passing through the valve may leak between the sealing seat and valve body. In this case, fluid may flow around the obturator to the second portion 1 7b of the fluid flow passage, thereby allowing leakage of fluid through the valve (usually from the first portion 1 7a of the fluid flow passage to the second portion 1 7b of the fluid flow passage).

The embodiments of the invention described below overcome the above described problem.

Figure 2 shows an isolation valve assembly which includes a sealing seat arrangement according to an embodiment of the present invention. Features of the isolation valve assembly 1 Oa which correspond to those of the known isolation valve assembly 10 shown in Figure 1 have been given the same numbering within the other Figures. It can be seen that the isolation valve assembly shown in Figure 2 is the same as that shown in Figure 1 except that it comprises a different sealing seat arrangement 1 6a. That is to say, the isolation valve assembly 1 Oa shown in Figure 2 includes a valve body 12, obturator and sealing seat arrangement 1 6a. As before the obturator is movable relative to the valve body 12 between an open position in which fluid is permitted to flow through the valve assembly ba via the fluid flow passage and a closed position in which fluid flow through the valve assembly 1 Oa via the fluid flow passage is substantially prevented.

In particular, the obturator in this embodiment comprises a rotor 18 including a rotor fluid passage 20 and the rotor 18 is rotatable relative to the valve body 12 about an axis to enable said movement between the open position and the closed position.

The sealing seat arrangement 16a is located upstream, with respect to a fluid flow direction F through the valve assembly 1 Oa in use, of the obturator.

In this embodiment the valve body 12 is formed of a metal material such as steel.

However, in other embodiments, the valve body may be formed of any appropriate metal material.

The valve body 12 comprises a sealing seat receiving bore 32, the sealing seat arrangement 16a being received by the sealing seat receiving bore. The sealing seat arrangement 1 6a of the isolation valve assembly 1 Oa shown in Figure 2 is now described in more detail with reference to Figures 3 and 4.

Figure 3 shows a perspective cross-section through the sealing seat arrangement 16a and Figure 4 shows an enlargement of a portion of the cross-section shown in Figure 2.

Referring first to Figure 3, the sealing seat arrangement 1 6a comprises an annular seat 34. The seat 34 extends along an axis B such that the annulus surrounds the axis B. The seat 34 comprises a first portion 36 and a second portion 38. A shoulder portion 40 links the first and second portions 36, 38. The first portion 36 has a diameter (relative to the axis B) which is greater than that of the second portion 38.

The sealing seat arrangement 1 6a also includes a first seal arrangement 42 and a generally frustoconical seal ring 44. The seal ring 44 and first seal arrangement, which is generally annular, are received on the second portion 38 of the seat 34 such that the seal ring 44 is received between the shoulder portion 40 of the seat 34 and the first seal arrangement 42.

In this embodiment the seal ring is formed of a metal material.

The sealing seat arrangement is configured such that a base portion 44a of the seal ring make contact the first seal arrangement 42, and a head portion 44b of the seal ring may contact the shoulder portion 40 of the seat 34. Because of the generally frustoconical shape of the seal ring 44, the base portion 44a of the seal ring 44 is located radially outboard (with respect to axis B) of the head portion 44b of the seal ring 44. This follows from the fact that a frustoconical article (i.e. something that has a generally truncated cone shape) has a base with a greater diameter than its head.

It will be appreciated that when the sealing seat arrangement forms part of an isolation valve assembly, the head portion of the seal ring will be located closer to the obturator than the base portion of the seal ring.

As can be seen best in Figure 4, the slant height H of the seal ring 44 is greater than the difference between the radius (relative to the axis B) of the first portion 36 of the seat 34 and the radius (relative to the axis B) of the second portion 38 of the seat 34. In other words, the slant height H of the seal ring 40 is greater than the radial thickness of the shoulder portion 40 of the seat 34. A further way of defining the slant height of the sealing ring is that the slant height H is greater than the difference between the radius (relative to axis B) of the wall of the sealing seat receiving bore 32 of the valve body 12 and the radius (relative to axis B) of the second portion 38 of the seat 34.

In this embodiment the seat 34 is formed of a metal material, such as, for example, steel.

In other embodiments the seat may be formed of any appropriate metal.

The sealing seat arrangement 1 6a is such that the first portion 36 of the seat 34 includes a face portion 46. The face portion 46 is configured to cooperate with the obturator (in this example rotor 18) of the isolation valve assembly 1 Oa so as to form a seal between the sealing seat arrangement 16a and obturator of the isolation valve assembly. The seal formed between the sealing seat arrangement and obturator is such that it substantially prevents fluid which flows through the sealing seat flow passage 28 from passing between the face portion 46 of the seat 34 and the obturator 14 (in the embodiment shown, rotor 18). The exact manner in which the face portion 46 cooperates with the obturator 14 of an isolation valve assembly 1 Oa so as to form a seal between the sealing seat arrangement and obturator is discussed in more detail further below.

As previously discussed, and as seen best in Figures 3 and 4, the sealing seat arrangement 1 6a includes a first seal arrangement 42. The first seal arrangement 42 comprises a first seal member 48 and a second seal member 50. The second seal member 50 is located intermediate the first seal member 48 and the seal ring 44. In particular, the sealing seat arrangement 1 6a is configured such that the base portion 44a of the seal ring 44 may contact the second seal member 50 of the first seal arrangement 42.

In the embodiment shown, the first seal member 48 is formed of a plastic material and the second seal member 50 is formed of a netal material. The second seal member 50 has a generally planar ring shape. The first seal member 48 has a generally U-shaped cross-section such that the first seal member 48 includes first and second side portions 48a, 48b which depend from a central base portion 48c.

The seal ring 44 is configured to form a seal between the sealing seat arrangement 16a and the valve body 12. The way in which this is achieved is discussed in more detail with reference to Figure 4.

The sealing seat arrangement 16a is configured such that if the first seal arrangement 42 is urged axially towards the first portion 36 of the seat (i.e. such that it is urged in the direction indicated by arrow C) the seal ring 44 is pressed between the first seal arrangement 42 and shoulder portion 40 of the seat 36. This causes the seal ring 44 to deform from a relaxed state (as shown in Figure 3) to a deformed state (as shown in Figure 4). In the deformed state of the seal ring 44 the base portion 44a of the seal ring 44 is radially outboard of the base portion 44a of the seal ring 44 in the relaxed state. In other words, the outer radius (relative to axis B) of the seal ring 44 in the deformed state is greater than that of the base portion 44a of the seal ring 44 in the relaxed state.

Because the base portion 44a of the seal ring 44 in the deformed state (shown in Figure 4) is radially outboard of the base portion 44a of the seal ring 44 in the relaxed state (as shown in Figure 3), in the deformed state the base portion of the seal ring 44a contacts the valve body 12. In particular, when the seal ring 44 is in the deformed state, the base portion 44a of the seal ring 44 contacts the wall of the sealing seat receiving bore 32.

In addition, the sealing seat arrangement is configured such that in the deformed state the head portion 44b of the seal ring 44 is radially inboard of the head portion 44b of the seal ring 44 in the relaxed state. In other words, the inner radius (relative to the axis B) of the head portion 44b of the seal ring 44 is less than that of the head portion 44b of the seal ring 44 in the relaxed state. Because the head portion 44b of the seal ring 44 in the deformed state (shown in Figure 4) is radially inboard of the head portion 44b of the seal ring 44 in the relaxed state (as shown in Figure 3), the head portion 44b of the seal ring 44 contacts the seat 34 in the deformed state.

It follows from the description above that if the first seal arrangement 42 is urged axially in the direction C then this causes the seal ring 44 to be deformed such that it contacts both the valve body 12 and the seat 34. The contact between seal ring 44 and both the valve body 12 and the seat 34 results in the seal ring 44 forming a seal between the sealing seat arrangement (and in particular the seat) and the valve body 10. The seal formed between the sealing seat arrangement and the valve body ensures that fluid flowing through the valve assembly is substantially prevented from passing between the valve body and seat 34 at the location of the sealing ring 44. If the valve body 12, seat 34 and seal ring 44 are all formed of a metal material, then in the deformed state of the seal ring 44 there will be a metal-to-metal seal formed between the sealing seat arrangement (and in particular the seat) and the valve body 10. Such a seal is much less likely to degrade over a given time in a given environment compared to the plastic

seals of the prior art.

The metal-to-metal nature of the seal which is possible using a sealing seat arrangement according to the present invention is less likely to degrade compared to known plastic sealing arrangements and, as such, the sealing efficiency of any isolation valve assembly of which such a sealing seat arrangement according to the present invention forms part will be improved as compared to that of known isolation valve assemblies.

In order to urge the first seal arrangement 42 in the axial direction towards the first portion 36 of the seat 34 (as indicated by direction C), any appropriate method may be used. In the embodiment of isolation valve assembly shown in Figures 2 and 4, it is achieved as follows.

The sealing seat arrangement 16a defines a fluid flow path between a portion of the fluid flow passage through the isolation valve assembly which is upstream of the obturator, and the first seal arrangement 42. In the present embodiment the sealing seat arrangement defines a fluid flow path (indicated generally by 52) between a portion of the fluid flow passage through the isolation valve assembly which is upstream of the sealing seat arrangement, and the first seal arrangement.

The isolation valve assembly is configured such that pressurized fluid located in the portion of the fluid passage upstream of the obturator may contact the first seal arrangement 42 via the fluid flow path 52 in order to urge the first seal arrangement 42 axially towards the first portion 36 of the seat 34 (i.e. in direction C). This is achieved as follows.

The first seal member 48 of the first seal arrangement 42 is configured such that it is sandwiched between the seat 34 (in particular the second portion 38 of the seat 34) and the valve body 12. Pressurized fluid supplied by the fluid flow passage 52 acts on the legs 48a and 48b of the seal 48 so as to improve sealing by the first seal member 48 and the valve body and seat 34. The pressurized fluid acts on the first seal member 48 to impart a generally axial force on the first seal member 48 in a direction which is generally indicated by C. This force is applied by the first seal member 48 to the second seal member 50 and then to the seal ring 44.

In some embodiments the seal ring 44 of the sealing seat arrangement 1 6a is formed of a resilient material such that the seal ring of the sealing seat arrangement is configured such that if the first seal arrangement ceases to be urged axially towards the first portion 36 of the seat 34 (or is urged to a lesser extent axially towards the first portion of the seat), the seal ring 44 substantially returns to its relaxed state (as shown in Figure 3).

That is to say, if the first seal arrangement is no longer urged axially in the direction C, the seal ring will no longer be pressed between the first seal arrangement 42 and shoulder portion 40 of the seat and consequently the force which deforms the seal ring into the deformed state is no longer applied to the seal ring, thereby allowing the seal ring to return to its relaxed (undeformed) state.

As previously discussed, in the deformed state of the seal ring 44, the base portion 44a of the seal ring 44 is located radially outboard of the base portion 44a of the seal ring 44 in the relaxed state. Likewise, the head portion 44b of the seal ring when the seal ring is in the deformed state is located radially inboard of the head portion 44b of the seal ring 44 when the seal ring is in the relaxed state. Furthermore, when the seal ring 44 is in the relaxed state, a minimum internal diameter of the seal ring 44 (which will be defined by the head portion 44b of the seal ring 44) is greater than the external diameter of the second portion 38 of the seat 34. In this manner there is a clearance fit between the seal ring 44 and the second portion 38 of the seat 34 when the seal ring 44 is in the relaxed state. The clearance fit between the seal ring 44 and second portion of the seat 34 has several advantages. First, when the sealing seat arrangement is being assembled, it is possible to readily slide the seal ring 44 on to the seat 34. Secondly, the clearance between the seal ring and second portion of the seat will enable easy disassembly, if required, of the sealing seat arrangement from the isolation valve assembly (i.e. without the use of significant force).

In addition, when in the relaxed state, the seal ring 44 has a maximum external diameter which is less that the internal diameter of the sealing seat receiving bore 32. In other words, when in a relaxed state, the maximum external diameter of the base portion 44a of the seal ring 44 is less than the internal diameter of the wall of the sealing seat receiving bore 32. It follows from the above that in the relaxed state of the sealing ring 34 there is a clearance fit between the seal ring 44 and the sealing seat receiving bore 32. Again, in some embodiments, this is advantageous because it will allow easy assembly (insertion) and disassembly (removal) of the sealing seat arrangement within the sealing seat receiving bore of the isolation valve assembly when the sealing seat 44 is in a relaxed state.

As previously discussed, the resilient nature of the seal ring 44 means that when it is in the deformed state the deformed seal ring tries to return to the relaxed state. The force responsible for this may be elastic stress within the deformed seal ring 44. Another advantage of the seal ring being resilient and wanting to return from its deformed state in which a seal is formed between the seat 34 and valve body 12 by the seal ring 44) to its relaxed slate (in which the sealing ring does not form a seal between the valve body 12 and seat 34) is as follows.

Some embodiments of isolation valve assembly require what is known as cavity relief.

Cavity relief is where, if pressure increases within a trapped fluid within the valve cavity, the fluid is allowed to pass the seal between the sealing seat and valve body from the valve cavity to a portion of the valve fluid flow passage located upstream of the sealing seat arrangemenl. It follows that if pressure increases within a trapped fluid within the valve cavity, the force exerted by the trapped fluid on the seat 34 and seal ring 44 in the direction substantially opposite to the direction C will increase. If this increased force is sufficient, it will overcome lhe force of the pressurized fluid on the first seal arrangement 42 in the direction C. In this situation the first seal arrangemenl 42 may move in an axial direction away from the first portion 36 of the seat 34 such that the seal ring 44 can enter its relaxed state, thereby breaking the seal between the seat 34 and valve body 12. and consequently enabling the fluid within the valve cavity to pass between the seat 34 and valve body 12 back to a portion of the valve fluid flow passage upstream of the sealing seat arrangement.

In some embodiments the face portion 46 of the seal 34 may have either a hard coating or a soft seal insert to improve the sealing between the seat and the obturator.

As previously discussed, in an isolation valve assembly according to the present invention, the obturator is movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly via the fluid flow passage, and a closed position in which fluid flow through the valve assembly via the fluid flow passage is substantially prevented. The closed position of the obturator relative to the valve body substantially prevents fluid flow through the valve assembly via the fluid passage as follows. When the obturator is placed in the closed position, the obturator creates an initial seal with the seat 34 by a portion of the obturator engaging the face 46 of the obturator and blocking the fluid flow passage 28 which passes through the seat 34. This causes an increase in the fluid pressure upstream of the obturator. The fluid is prevented from passing between the valve body 12 and seat 34 by a primary seal formed between the valve body 12 and seat 34 by the first seal member 48 of the first seal arrangement 42. The pressurized fluid upstream of the obturator exerts a force on both the seat 34 and first seal member 48 which urges each of these components in a generally axial direction towards the obturator (i.e. in a direction indicated by arrow C).

Urging of the seal seat 34 towards the obturator increases the force with which the face 46 of the seat 34 contacts the obturator. This results in an increased sealing effectiveness between the seat 34 and the obturator. As previously discussed, urging the first seal member 48 of the first seal arrangement 42 in a generally axial direction towards the obturator results in a sealing ring 44 forming a seal (which may in some embodiments be a metal-to-metal seal) between the seat 34 and the valve body 12.

It follows from the above that the sealing seat arrangement of the present invention enables axial movement of the seat 34 relative to the valve body 12 as well as the forming of a seal between the seat 34 and valve body 12.

Figure 5 shows a schematic cross-section through a further isolation valve assembly 1 Ob which includes two sealing seat arrangements 16a in accordance with an embodiment of the present invention. The isolation valve assembly lOb includes a valve body 12a and an obturator 14a which includes a rotor 18a including a rotor fluid passage 20a. The rotor 18a is mounted for rotation relative to the valve body 12a about an axis D. The rotor 18a is connected to a shaft 24a and linkage 22a. In use, rotation of the linkage 22a results in rotation of the shaft 24a and hence the connected rotor 1 8a. The isolation valve assembly includes a fluid flow passage 17c which includes a first portion 17d, a second portion 1 7e and a rotor portion 20a which links the first and second portions 1 7d, 1 7e when the obturator is in the open position (as shown in Figure 5).

The isolation valve assembly shown Figure 5 differs from those previously discussed in that it is a bi-directional isolation valve assembly. In order to facilitate this, the isolation valve assembly 1 Ob includes two sealing seat arrangements 1 6a according to an embodiment of the present invention. A first sealing seat arrangement is located such that it forms part of the first portion 17d of the valve fluid flow passage 17c. A second sealing seat arrangement is located such that it forms part of the second portion 17e of the valve flow passage 17c. Consequently, when the obturator is in the open position relative to the valve body 12a (as shown in Figure 5), one sealing seat arrangement 16a is located at each end of the rotor fluid flow passage 20a.

The isolation valve assembly lOb is bi-directional because it includes two sealing seat arrangements. The reason for this is as follows. In order for each sealing seat arrangement 16a to be effective, it must be located upstream (relative to the flow direction of fluid through the valve assembly) of the obturator 14a (in this case, the rotor 18a). In a first fluid flow direction through the valve assembly, when fluid flows through the fluid passage 17c of the isolation valve assembly lOb such that it is inlet in the direction E, the first sealing seat arrangement 16a located within the first portion 17d of the fluid passage 17c (i.e. the upper sealing seat arrangement 16a shown within Figure 5) is upstream of the obturator with respect to the fluid flow direction. As such, in this situation the first sealing seat arrangement 16a will seal the fluid flow passage 17c when the obturator is in a closed position such that substantially no fluid can pass the obturator (for example, between the obturator and the seat of the sealing seat arrangement, and between the valve body and seat). Likewise, in a second fluid flow direction through the valve assembly, in which fluid flows through the fluid passage 17c of the isolation valve assembly such that fluid is input into the valve assembly in the direction indicated by arrow G, the second sealing seat arrangement 16a located in the second portion lie of the fluid passage 7c (i.e. the lower of the two sealing seat arrangements 16a shown in Figure 5) is upstream of the obturator with respect to the fluid flow direction. As such, in this situation the second sealing seat arrangement 16a will seal the fluid flow passage 17c when the obturator is in a closed position such that substantially no fluid can pass the obturator. Because the valve assembly can be sealed (such that substantially no fluid can pass the obturator) when fluid is flowing in either direction, the valve assembly is said to be bi-directional.

Other possible modifications and applications of the invention will be readily apparent to the appropriately skilled person.

For example, the seal ring, second seal member, seat, and valve body of the embodiments of isolation valve assembly discussed above are metal. In other embodiments, they may be formed of any appropriate material. Furthermore, within the above described embodiments the first seal member is formed of a plastic material.

Again, in other embodiments, the first seal member may be formed of any other appropriate material.

The valves in the embodiments described above are rotary isolation valves. It will be appreciated that in other embodiments of the present invention, the sealing seat arrangement according to the present invention may form part of any other appropriate type of valve.

Whilst in the embodiments described above the sealing seat arrangement is located upstream with respect to the direction of fluid flow through the valve assembly of the obturator. In other embodiments, the sealing seat arrangement may have any appropriate location within a valve assembly. For example, in some embodiments, the sealing seat arrangement may be located downstream of the obturator.

The previously described valve assemblies all have an obturator which includes a rotor such that the isolation valve is a rotary valve. It will be appreciated that in other embodiments the obturator may take any appropriate form. For example, the obturator may be a ball or a gate such that the isolation valve is a ball valve or a gate valve.

In some embodiments the seal ring may be coated with a material which enables the seal ring to provide enhanced sealing between the seat and the valve body.

The sealing areas of the seal ring may be machined in such a way so as to provide multiple sealing points.

Within the described embodiments the isolation valve assembly is referred to as being suitable for having a fluid flow through it. The fluid may be any appropriate liquid or gas at any appropriate temperature or pressure. That is to say, the isolation valve assembly and sealing seat arrangement may be configured such that they are suitable for creating a seal between the seat and the obturator and/or a seal between the seat and the valve body which is suitable for any desired liquid and/or gas at any desired temperature or pressure.

Within the described embodiments the first seal arrangement is formed of two separate parts of a particular configuration. It will be appreciated that in other embodiments the first seal arrangement may be formed of any appropriate number of parts, for example a single part or three or more separate parts. Any part or part forming the first seal arrangement may have any appropriate configuration providing that it can make an initial seal between the seat and the valve body and provided that it is capable of exerting an axial force on the sealing ring as discussed.

Within the above described embodiments of sealing seat arrangement and isolation valve assembly, the seal ring is generally frustoconical. This need not be the case. The seal ring may have any appropriate form provided that the seal ring is configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, and wherein the radial thickness of the seal ring in the deformed state is greater than the radial thickness of the seal ring in the relaxed state. Radial thickness may be defined as difference between the maximum (outer) radius of the seal ring and the minimum (inner) radius of the seal ring. The radii may be measured relative to the axis B. The increase in radial thickness of the seal ring in the deformed state allows the seal ring to contact both the seat and the valve body when it is in the deformed state to thereby seal the seat with respect to the valve body. In one example the seal ring may have a generally v-shaped cross-section. By generally v-shaped, it is meant that two arms are joined at a point, there being an angle of less than 1800 (preferably less than 900) subtended between the two arms.

As shown in Figure 6a, the seal ring 44a with a generally v-shaped cross-section may be received on the second portion 38 of the seat 34 and between the first seal arrangement 42 and shoulder portion 40 such that the end 44aa of each arm 44ab of the v-shaped seal ring which is remote from the point 44ac at which the arms are joined is radially spaced from an outer surface 38a of the second portion of the seat by less than the radial spacing between the outer surface 38a of the second portion of the seat and the point 44ac at which the arms are joined.

As shown in Figure 6b, the seal ring 44b with a generally v-shaped cross-section may be received on the second portion 38 of the seat 34 and between the first seal arrangement 42 and shoulder portion 40 such that the end 44ba of each arm 44bb of the v-shaped seal ring which is remote from the point 44ac is located adjacent the first seal arrangement 42 such that it may contact by the first seal arrangement 42. The point 44ac at which the arms are joined is located adjacent the shoulder portion 40 such that it may contact the shoulder portion. In another embodiment the end of each arm of the v-shaped seal ring which is remote from the point may be located adjacent the shoulder portion 40 such that it may contact the shoulder portion and the point 44ac at which the arms are joined may be located adjacent the first seal arrangement 42 such that it may contact by the first seal arrangement 42.

Claims

Claims 1. A sealing seat arrangement suitable for use as an upstream sealing seat arrangement of an isolation valve assembly, the sealing seat arrangement comprising: an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions, the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a generally frustoconical seal ring; wherein the seal ring and first seal arrangement are received on the second portion of the seat such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement.
2. A sealing seat arrangement according to claim 1, wherein the seal ring is formed of a metal material.
3. A sealing seat arrangement according to claim 1 or claim 2. wherein the sealing seat arrangement is configured such that a base portion of the seal ring may contact the first seal arrangement and a head portion of the seal ring may contact the shoulder portion of the seat.
4. A sealing seat arrangement according to claim 3. wherein the base portion of the seal ring is located radially outboard of the head portion of the seal ring.
5. A sealing seat member according to any preceding claim, wherein the first seal arrangement comprises a first seal member and a second seal member intermediate the first seal member and the seal ring.
6. A sealing seat arrangement according to claim 5, wherein the first seal member is formed of a plastic material and the second seal member is formed of a metal material.
7. A sealing seat arrangement according to any preceding claim, wherein the slant height of the generally frustoconical seal ring is greater than the difference between the radius of the first portion and the radius of the second portion.
8. A sealing seat arrangement according to any preceding claim, wherein the seat is formed of a metal material.
9. A sealing seat arrangement according to any preceding claim, wherein the first portion of the seat includes a face portion, the face portion being configured to co-operate with an obturator of an isolation valve assembly in order to form a seal between the sealing seat arrangement and obturator of the isolation valve assembly.
10. A sealing seat arrangement according to claim 3 or any claim dependent on claim 3, the sealing seat arrangement being configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of the seal ring in the relaxed state.
11. A sealing seat arrangement according to claim 10, wherein the seal ring is formed of a resilient material and wherein the sealing seat arrangement is configured such that if the first seal arrangement ceases to be urged axially towards the first portion of the seat, the seal ring substantially returns to the relaxed state.
12. A sealing seat arrangement according to either claim 10 or claim ii, wherein, in the relaxed state, a minimum internal diameter of the seal ring is greater than the diameter of the second portion of the seat such that there is a clearance fit between the seal ring and the second portion of the seat.
13. An isolation valve assembly including a valve body, obturator and a sealing seat arrangement according to any proceeding claim; wherein the obturator is movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly via a fluid passage, and a closed position in which fluid flow through the valve assembly via the fluid passage is substantially prevented; and wherein the seal ring is configured to form a seal between the sealing seat arrangement and the valve body.
14. An isolation valve assembly according to claim 13, wherein the sealing seat arrangement is located upstream, with respect to a fluid flow direction through the valve assembly in use, of the obturator.
15. An isolation valve assembly according to either claim 13 or claim 14, wherein the valve body is formed of metal material.
16. An isolation valve assembly to any of claims 13 to 15 when dependent on claim 3 or any claim dependent on claim 3, the isolation valve assembly being configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of seal ring in the relaxed state such that it contacts the valve body.
17. An isolation valve assembly according to any of claims 13 to 16, wherein the valve body comprises a sealing seat receiving bore, the sealing seat arrangement being received by the sealing seat receiving bore.
18. An isolation valve assembly according to claim 17 when dependent on claim 16, wherein the base portion of the seal ring in the deformed state contacts a wall of the sealing seat receiving bore.
19. An isolation valve assembly according to any of claims 16 to 18, the isolation valve assembly being configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the head portion of the seal ring in the deformed state being radially inboard of the head portion of the seal ring in the relaxed state such that it contacts the seat.
20. An isolation valve assembly according to claim 17 or any claim dependent on claim 17. wherein the sealing seat arrangement defines a fluid flow path between a portion of the fluid passage upstream of the obturator and the first seal arrangement.
21. An isolation valve assembly according to claim 20, wherein the isolation valve assembly is configured such that pressurized fluid located in the portion of the fluid passage upstream of the obturator may contact the first seal arrangement via the fluid flow path and thereby urge the first seal arrangement axially towards the first portion of the seat.
22. An isolation valve assembly according to claim 17 or any claim dependent on claim 17, when further dependent on claim 3 or any claim dependent on claim 3, wherein, in a relaxed state, a maximum external diameter of the seal ring is less than an internal diameter of the sealing seat receiving bore such that there is a clearance fit between the seal ring and the sealing seat receiving bore.
23. An isolation valve assembly according to any of claims 13 to 23 wherein the obturator is one of a ball, a gate or a rotor, such that the isolation valve assembly comprises a ball valve, a gate valve or a rotary valve respectively.
24. A method of assembling an isolation valve assembly, the isolation valve assembly comprising valve body comprising a sealing seat receiving bore, an obturator movable relative to the valve body between an open position in which fluid is permitted to flow through the valve assembly and a closed position in which fluid flow through the valve assembly is substantially prevented, and a sealing seat arrangement, the sealing seat arrangement including an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions, the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a generally frustoconical seal ring having a base portion and a head portion; and the method comprising: the second portion of the seat receiving the seal ring and first seal arrangement such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement; the sealing seat receiving bore receiving the sealing seat arrangement; allowing pressurized fluid into the sealing seat receiving bore; allowing pressurized fluid in the sealing seat receiving bore to contact the first seal arrangement via a fluid flow path defined between the seat and the sealing seat receiving bore; and the pressurized fluid urging the first seal arrangement axially towards the first portion of the seat such that the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, the base portion of the seal ring in the deformed state being radially outboard of the base portion of seal ring in the relaxed state such that it contacts the valve body, and the head portion of the seal ring in the deformed state being radially inboard of the head portion of the seal ring in the relaxed state such that it contacts the seat, thereby forming a seal between the seat and the valve body.
25. A sealing seat arrangement suitable for use as an upstream sealing seat arrangement of an isolation valve assembly, the sealing seat arrangement comprising: an annular seat extending along an axis comprising a first portion, a second portion, and a shoulder portion linking the first and second portions, the first portion having a diameter which is greater than that of the second portion; a first seal arrangement; and a seal ring; wherein the seal ring and first seal arrangement are received on the second portion of the seat such that the seal ring is received between the shoulder portion of the seat and the first seal arrangement; and wherein the seal ring is configured such that if the first seal arrangement is urged axially towards the first portion of the seat, the seal ring is pressed between the first seal arrangement and shoulder portion of the seat thereby deforming the seal ring from a relaxed state to a deformed state, and wherein the radial thickness of the seal ring in the deformed state is greater than the radial thickness of the seal ring in the relaxed state.