GB2285673A

GB2285673A - Choke valve assembly

Info

Publication number: GB2285673A
Application number: GB9400652A
Authority: GB
Inventors: David Bernard Martin; Eric Gates
Original assignee: Kent Introl Ltd
Current assignee: Kent Introl Ltd
Priority date: 1994-01-14
Filing date: 1994-01-14
Publication date: 1995-07-19
Also published as: GB9400652D0

Abstract

A valve assembly comprises a choke valve having a flow control element (13) in the form of an apertured sleeve which is slidable within a fixed apertured sleeve (4). A further sleeve (12) is movable with the sleeve (13) and carries a valve seating surface (16) which seats against a shoulder (8) on the sleeve (4) in the closed position of the valve assembly to define a shut-off valve. The choke valve is operable to allow fluid to pass therethrough only when the shut-off sleeve (12) is in an open position. The valve seating surface (16) is protected from fluid flow by an annular lip (15) and is arranged to be withdrawn from the main flow path before the choke valve opens. <IMAGE>

Description

A VALVE ASSEMBL', The present invention relates to a valve assembly, particularly, but not exclusively, a valve assembly for incorporation in a so called christmas tree of the type used in oil or gas production.

Fluid flow through known christmas trees is generally controlled by a combination of a stop valve, for instance a wing valve, and a choke valve. A known type of choke valve used in such applications comprises two concentric sleeves, the inner of which is slidable within the outer sleeve by suitable operation of an actuation means. Each sleeve is provided with an array of apertures in axially spaced circumferential rows. The valve is operated by moving the inner sleeve within the outer sleeve thereby bringing the two sets of apertures into and out of register to permit and prevent fluid flow respectively. The overall flow rate through the valve can be controlled by bringing more or less apertures into register.

A disadvantage of such choke valves is that even without any apertures in the inner and outer sleeves in register, the valve will not be fluid tight due to the necessary running clearances between the two sleeves. It is for this reason that a separate shut-off valve must be provided upstream of the choke valve.

It is an object of the present invention to obviate or mitigate the above disadvantage.

According to the present invention there is provided a valve assembly comprising a fluid flow control arrangement which has an inlet and an outlet and is operable to permit and prevent fluid flow therethrough, and a flow shut-off member associated with the control arrangement, said shut-off member being movable between a closed position so that a seating surface thereof locates on a seat to prevent fluid flow to the control arrangement and an open position in which said member permits fluid flow to the control arrangement, and said control arrangement being operable to allow fluid to pass therethrough only when the shut-off member is in an open position.

Thus the present invention provides a single valve assembly which provides a combination of a stop valve and a fluid flow control valve. Moreover, the assembly is arranged such that the control arrangement cannot be opened to allow fluid to flow therethrough unless the shut off member has first been moved into an open position.

The fluid flow control arrangement may be, for example, a choke valve assembly.

The shut off member and the control arrangement are preferably operated by a single actuation means.

In a preferred embodiment of the invention the fluid flow control arrangement is a choke valve assembly comprising two concentric and relatively moveable sleeves each of which has an apertured portion, the arrangement being such that fluid flow through the choke valve assembly may be established by relative axial movement of the sleeves to bring the apertured portions into register, and vice versa.

In the above preferred embodiment, the shut off member preferably comprises a cylindrical shroud which is disposed concentrically around the outer of said sleeves any 1 relatively moveable with respect thereto to cover and uncover the apertured portion of said outer sleeve.

Preferably the control arrangement, e.g. choke valve etc., is selectivelv operable to varv the fluid flow therethrotlgr Preferably the seating surface of the shut o.~. mer-ber is protected by a flange or lip so as no: to ive directly e.; sec to the main flow stream through the valve assembly when ; *.e shut off member is in an open position.The seating surface oF tne shut off member is thus substantially protected from any erosion that might otherwise occur as a result of abrasive particulate debris. e.g. sand.

present in the flow stream. Such erosion would have a detrimental effect on the integrity of the seal iormed between the shut off member seating surface and the valve seat when the shut off member is in the closed position.

Preferably the control arrangement may be operable to allow fluid to flow therethrough only when the shut off member is in an open position in which said seating surface is outside the main flow stream through the assembly. Ey removing the shut off member seating surface from the main flow stream before the fluid flow is established, the seating surface is further protected from the potential erosive effect of particulate debris in the flow stream.

Preferably the control arrangement is operable to permit fluid to flow therethrough only when said shut off member is in an open position in which said seating surface is clear of the whole of the control arrangement inlet.

A specific embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of one embodiment of a valve assembly in accordance with the present invention, the valve assembly being shown in a closed position; Fig. 2 shows the valve assembly of Fig. 1 in an intermediate position; and Fig. 3 shows the valve assembly of Fig. 1 in a fully open position.

Referring to the drawings, the illustrated valve assembly is shown in situ in an L-junction of a Fipe:ine, the L-junction comprising an inlet passageway 1 which opens into a cylindrical inlet chamber 2, and an outlet passageway 3. The top cf the inlet chamber 2 is closed with an end cap (not shown).

The valve assembly comprises a sylindrical sleeve 4, and a slidable valve member 5 mounted on tize end of an actuating rod 6 which extends through the end cap. The lower end of the sleeve 4 is mounted in the outlet passageway 3 and its upper end extends into the inlet chamber 2 past the opening oi the inlet passageway i. The sleeve 4 is provided with an array of apertures 7, arranged in axially spaced circumferential rows, which open into the inlet chamber 2. An abutment shoulder 8 extends around the circumference of the sleeve 4 adjacent the base of the inlet chamber 2. The abutment shoulder 8 has an upper surface defining an annular valve seat 9.

The slidable valve member 5 comprises a cylindrical plug 10 located concentrically and slidably within the sleeve 4. The upper end of the plug 10 defines a radially outwardly extending flange 11 from which depends a cylindrical shroud 12 which locates around the outer surface of the sleeve 4 in slidable engagement therewith. The axial length of the shroud is slightly greater than the axial length of that portion of the sleeve 4 which extends into the inlet chamber 2.

The lower end of the plug 10 is provided with an integral tubular extension 13, hereinafter referred to as the inner sleeve 13 which is provided with an array of apertures 14 arranged in axially spaced circumferential rows. The openings of the apertures 14 in the outer surface of the inner sleeve 13 are widened to a diameter greater than the diameter of the apertures 7. The axial and circumferential spacing of the apertures 14 is the same as that of the apertures 7 provided in the sleeve 4.

The lower circumferential edge of the shroud 12 is radially stepped so as to define an outer annular lip 15 and an inner annular recess provided with a soft faced seat 16.

Operation of the valve assembly will now be described with reference to Figs. 1, 2 and 3 which, in turn show the valve in closed, intermediate and fully open positions.

Fig. 1 shows the slidable valve member 5 in its lowermost position in which the shroud 12 covers all of the apertures 7 in the outer sleeve 4. In this position the soft faced annular seat 16 of the shroud locates on the annular valve seat 9 provided by the abutment shoulder, thereby forming a good fluid tight seal preventing fluid from flowing through the valve assemb'. This is therefore the closed position of the valve assembly.

It can be seen from Fig. l that with the valve member in the closed position the uppermost aper.;.,es 14 in the inner sleeve and the lowermost apertures 7 in the outer sleeve are axially separated by a distance FD. The valve is opened bv lftin the slidable valve member 5, by suitable operation of the actuating rod 6, to raise the shroud 12 to bring at least some of the apertures 14 into register with the apertures 7 in the sleeve 4.However, lifting the valve member D through the distance FD on. urirgs the valve member into the intermediate position shown in Fig. 3. in this position it will be seen that the shroud has uncovered all of the apertures 7 but none of the apertures 14 in the inner sleeve 13 register with the apertures 7.

Thus there will be no fluid flow through the valve (disregarding the small amount of fluid which may flow between the sleeve 4 and the valve member 5 as a result of the running clearance between the two) as the valve member is moved through the distance FD. The distance FD hence constitutes a flow deadbano.

Fluid flow through the valve assembly will only commence once the valve member 5 is raised beyond the intermediate position shown in Fig. 2, thereby to bring at least some of the apertures 14 into register with apertures 7 in the sleeve 4. It will be appreciated that by virtue of the widened openings of the apertures 14, absolutely accurate alignment of the apertures 14 and 7 is not necessary to being the apertures into register. The fully open position, shown in Fig.

3, is achieved when all of the apertures 14 in the inner sleeve 13 are aligned with apertures 7 in the sleeve 4 so that fluid flow through the valve assembly is at a maximum. It will be apparent that the rate of fluid flow through the valve assembly may be controlled by suitable adjustment of the position of the valve member 5 such that more or less apertures 7 and 14 are in register.

From the above it will be evident that, in the described embodiment, the invention provides a combined choke and stop valve assembly. The shroud 12 provides means for shutting off fluid flow through the valve assembly completely i.e. by stopping fluid from flowing to the sleeve 4 from where it might otherwise leak through the valve assembly between the sleeve e . and the valve member 1.

Once the shroud 12 has been lifted from ;iie valve seat fluid may flow to the sleeve 4 but no appreciabie flow : rough the valve assembly will occur until the shroud has moved through the flow deadband FD and apertures 14 in the inner sleeve 1 are brought into a:.gn:nent with apertures 7 in the sleeve. This is a further advantage of the described embodiment of the present invention. as the soit seating face 16 of the shroud 12 will be moved out of the main flow stream before an appreciable fluid flow is established.The soft seating face 16 is thereby protected from erosion which might otherwise occur as a result of the abrasive action of particulate debris, e.g. sand. in the flow stream.

In the described embodiment of the invention, the soft seating face 16 is further protected from the abrasive action of debris in the flow stream by the annular lip 15. The lip 15 may itself suffer from erosion but this will not affect the integrity of the seal formed between the seating face 16 and the valve seat 9.

It will be appreciated that many alterations and modifications may be made to the valve assembly described above. For instance, whilst it may often be preferable to have a flow deadband sufficiently large to ensure the shroud is moved clear of the apertures in the sleeve 4 before flow begins, this is not absolutely necessary. For example, an advantageous effect, i.e. some protection of the shroud's soft seating face, could be achieved with a much smaller flow deadband. Moreover, the flow deadband might be omitted altogether in applications where, for instance, the erosion of the shrouds seating face is expected to be negligible or may be disregarded for any other reason. Similarly, the protective lip 15 is desirable but not essential and therefore could be omitted.

In addition, it will be appreciated that the shroud seating surface need not necessarily be soft faced but could be hard faced.

In this case it may, however, be necessary to apply greater force to the shroud when in the closed position to obtain a good fluid tight seal.

It will be understood that wreas in the above described embodiment of the invention the valve assembly includes a fluid flow control means in the form of a choc. valve, this could be replaced with other, for instance much sImper, fluid flow control means.

Similarly, it will be appreciated that a valve assembly in accordance with the present invention could rear: he be configured to operate in line with parallel inlet and outlet passageways.

Claims

1. A valve assembly comprising a fluid flow control arrangement which has an inlet and an outlet and is operable - to permit and prevent fluid flow therethrough, and a flow shut-off member associated with the control arrangement, said shut-off member being movable between a closed position so that a seating surface thereof locates on a seat to prevent fluid flow to the control arrangement and an open position in which said member permits fluid flow to the control arrangement, and said control arrangement being operable to allow fluid to pass therethrough only when the shut-off member is in an open position.

2. A valve according to claim 1, wherein the shut off member and the control arrangement are operated by a single actuation means.

3. A valve assembly according to claim 1 or claim 2, wherein the control arrangement is a choke valve assembly.

4. A valve assembly according to claim 3, wherein the choke valve assembly comprises two concentric and relatively moveable sleeves each of which has an apertured portion, the arrangement being such that fluid flow through the choke valve assembly may be established by relative axial movement of the sleeves to bring the apertured portions into register, and vice versa.

5. A valve assembly according to claim 4. wherein the apertured portion of one or both of said sleeves comprises a plurality of apertures.

6. A valve assembly according to claim 4 or claim 5, wherein the shut off member comprises a cylindrical shroud which is disposed concentrically around the outer of said sleeves and is relatively moveable with respect thereto to cover and uncover the apertured portion of said outer sleeve.

7. A valve assembly according to any one of claims 4 to 6, wherein the outer sleeve is fixed in position.

8. A valve assembly according to any preceding claim, wherein the control arrangement is selectively operable to vary the fluid flow therethrough.

9. A valve assembly according to any preceding claim, wherein the seating surface of the shut off member is protected by a flange or lip so as not to be directly exposed to the main flow stream through the valve assembly when the shut off member is in an open position.

10. A valve assembly according to claim 8, wherein the control arrangement is operable to allow fluid to flow therethrough only when the shut off member is in an open position in which said seating surface is outside the main flow stream through the assembly.

11. A valve assembly according to claim 10, wherein when in the closed position the shut off member covers the inlet to the control means, and the control means is operable to permit fluid to flow therethrough only when the shut off member is in an open position in which said seating surface is clear of at least that portion of the control arrangement inlet which is open to fluid flow.

12. A valve assembly according to claim 11, wherein the control arrangement is operable to permit fluid to flow therethrough only when said shut off member is in an open position in which said seating surface is clear of the whole of the control arrangement inlet.

13. A valve assembly, substantially as hereinbefore described, with reference to the accompanying drawings.