Valve Assembly

Abstract

The invention relates to a valve assembly that can be provided of a length to meet conventional fitting dimensions and requirements. The valve assembly includes a valve body housing, at least first and second valve balls. Between the first and second valve balls are provided first and second valve seats. The valve seats are biased towards their respective valve balls by common biasing means. The valve seats, that lie between the valve balls, are typically provided as part of a common valve seat assembly that includes the biasing means.

Description

The invention to which this application relates is to a valve assembly. Particularly, although not necessarily exclusively the invention relates to an improvement to the type of valve known as a double block and bleed valve in which typically three independent valve units are provided within a valve body.

The provision of double block and bleed valves is well known in the industry and the applicant has several granted patents in this field. One common problem, which is experienced with this form of valve, is the requirement to fit the valve assembly into the space, which is available between adjacent pipe flanges. For larger diameter pipelines in particular the length of the conventional double block and bleed valve assembly can be greater than the ANSI B16.10 specified space. This means that if, for example, the conventional double block and bleed valve is being used to replace a single valve in an existing pipeline, the space available is too small. This therefore means that additional works are required to be performed on the pipeline, which can lead to additional time and expense being incurred.

A further problem is that the conventional double block and bleed valve assembly includes a significant number of components, which add to the complexity of the assembly process and the time for assembly.

The aim of the present invention is therefore to provide a valve assembly which can more readily be provided of a length to meet conventional fitting requirements. A further aim is to provide a valve assembly, which can be more easily assembled whilst at the same time providing the required operating performance.

In a first aspect of the invention there is provided a valve assembly, said valve assembly including a valve body housing, first and second valve balls and between said first and second valve balls are provided first and second valve seats wherein said valve seats are biased towards their respective valve balls by common biasing means.

Typically said biasing means are springs and more typically coil springs. Typically said biasing means are positioned to lie between said first and second seats with a first end of said biasing means acting on the first seat and the opposing end of said biasing means acting on the second seat. In one embodiment, when the fluid flows through the valve in a first direction, the biasing means acts on one of the first or second seats to move the same towards the first or second valve ball respectively, and when the fluid flows through the valve in the opposing direction the same biasing means act on the other of the first or second seats to move the seat towards the other of the first or second valve balls.

In one embodiment the first and second seats and the biasing means are provided as a seat assembly which is located within the valve assembly.

The valve seats are typically provided to seal against the valve ball and typically the strength of the biasing means, and/or the number of the same which are provided are selected with respect to the fluid passing through the valve, the size of the valve passage along which the fluid flows and/or the pressure of the fluid. When a number of biasing means are provided the same are typically spaced around the circumference of the passage of the valve.

Typically the fluid acts in conjunction with the biasing means to exert the movement force on said first or second seat depending on the direction of flow of the fluid.

In one embodiment the valve body is formed from two parts, the interface of which is located at, or close to, the location of the seats and biasing means. Alternatively, the valve body is formed of one part and the seats and biasing means are introduced into position from an end of the valve body.

Typically the valve assembly includes a passage from a first end to a second end and the first and second valve units are provided spaced along the passage, each valve unit provided to allow the selective closing and opening of the passage.

In one embodiment there is provided a vent located intermediate the first and second valve units. In one embodiment the vent passage is formed around the circumference of the seat assemblies.

By providing biasing means which act on both seats so the overall length of the valve assembly can be significantly reduced and, importantly, can be reduced sufficiently so that the same is at or less than the required ANSI B16:10 length for the particular pipe diameter. Also, as the length of the valve body can be reduced so material savings can be made which can lead to significant savings in weight and material costs incurred.

In a further aspect of the invention there is provided a double block and bleed valve assembly, said assembly including a first ball valve unit and a second ball valve unit spaced apart in a fluid passage through the valve assembly and wherein intermediate said first and second valve balls there is provided a seat assembly including a first seat and a second seat and biasing means to exert a biasing force on the first and second seats in opposing directions.

Typically the same biasing means exerts the biasing force on both the first and second seats and is retained in position between the same.

Typically the biasing force is used to move each seat to seal on the valve ball of the respective first or second valve unit.

In one embodiment the biasing means are spaced around the circumference of the seats so as to exert a constant movement force around the seat.

Specific embodiments of the invention will now be described; wherein;

FIGS. 1 illustrates a conventional double block and bleed valve arrangement in section along the longitudinal centre axis;

FIGS. 2-3 illustrate a valve assembly in accordance with two embodiments of the invention in section along the longitudinal centre axis; and

FIG. 4 illustrates a detailed view of the seat arrangement in accordance with the invention.

Referring firstly to FIG. 1 there is illustrated a conventional form of a double block and bleed valve assembly 2. Said assembly comprises a body 4, which has a passage running between ends 8, 10. The housing contains two ball valve units 12, 14 each of which include a valve ball 16 with respective seats 18, 20, 18′, 20′ on either side. The seats 18, 20 are biased onto the respective ball 16 by biasing means in the form of springs 22 which are mounted on the valve body at one end and the other end acts on the seat to force the same towards the ball. Typically the springs are provided in sufficient number and of a size to suit the size of valve assembly to ensure that sufficient force is applied to the seat onto the ball so as to allow a seal to be created.

The seats 18′20′ lie intermediate the valve balls 16 and conventionally, as shown, in order to allow the seats and springs to operate correctly a land portion 24 is provided in the valve body. The provision of the land portion causes the length of the valve assembly, at least for certain sizes, to be greater than the ANSI B16:10 standard length which causes problems in terms of expense and time of installation.

FIGS. 2-4 illustrate two embodiments of a valve assembly 102 in accordance with the invention. The parts of the valve assembly that are common with those of FIG. 1 are provided with the same reference numbers as FIG. 1 and are not described again. The main feature of the valve assembly 102 in accordance with the invention is that the central seats 18′ 20′ and land 24 of FIG. 1 have been withdrawn and replaced by a valve seat assembly in another manner so as to provide significant benefits in terms of reducing the length of the valve assembly.

In accordance with the invention, the seats 104, 106 are no longer separated by a land and are positioned adjacent to each other as shown in detail in FIG. 4. In addition, the seats are now acted upon by biasing means in the form of springs 108 which are common to both seats inasmuch that the ends 110 of the springs are positioned act on the seat 104 to apply force to move the seat towards the ball 16 of valve unit 12 and the ends 114 of the springs act on the seat 106 to move the same towards the ball 16 of valve unit 14.

It will be appreciated that the springs can be spaced around the seats so as to allow a uniform force to be exerted thereon. Also the pressure of the fluid acts in conjunction with the springs to move the seat towards the ball and typically, dependent on the direction of fluid through the passage 6 of the valve assembly, at any given time the springs will be exerting a greater force in one direction on one seat than on the other seat. Typically the biasing means will be exerting a greater force on the valve seat 104 or 106 which is positioned downstream with respect to the direction of flow of fluid along the valve passage.

The valve body can be formed of two parts joined together at an interface which is located intermediate the valves 12,14 as shown in FIG. 3, or alternatively can be a single part in which the components are introduced from one end and a bolt on end flange is provided to complete the assembly as shown in FIG. 2. Alternatively a single threaded insert can be used.

The present invention therefore allows the characteristics of operation of the valve assembly of this type to be maintained and also allows the length of the valve assembly to be reduced, which has considerable benefit.

Claims

1. A valve assembly, said valve assembly including a valve body housing, first and second valve balls, and between said first and second valve balls are provided first and second valve seats wherein common biasing means are provided which are capable of biasing said valve seats towards their respective valve balls.

2. An assembly according to claim 1 wherein the biasing means is a spring.

3. An assembly according to claim 2 wherein the spring is a coil spring, wave spring and/or disc spring.

4. An assembly according to claim 1 wherein the biasing means are positioned to lie between the said first and second seats, with a first end of the biasing means acting on the first valve seat and the opposing end of the said biasing means acting on the second valve seat.

5. An assembly according to claim 1 wherein when the fluid flows through the valve in a first direction, the biasing means acts on one of the first or second seats to move the same towards the first or second valve ball respectively and, when the fluid flows through the valve in the opposing direction, the same biasing means acts on the other of the first or second seats to move that seat towards the other of the first or second balls.

6. An assembly according to claim 5 wherein the valve seat acted on by the biasing means is that which is located downstream with respect to the direction of the flow of fluid through the valve passage.

7. An assembly according to claim 1 wherein the first and second seats and biasing means are provided as a seat assembly located within a valve assembly.

8. An assembly according to claim 1 wherein the valve seats are provided to seal against the valve ball.

9. An assembly according to claim 1 wherein a single biasing means is provided.

10. An assembly according to claim 1 wherein a plurality of biasing means are provided, each capable of acting on the said first and second seats.

11. An assembly according to claim 1 wherein the fluid acts in conjunction with biasing means to exert a movement force on said first or second seat depending on the direction of flow of the fluid.

12. An assembly wherein the valve body is formed from two parts and the interface between which is located at or adjacent to the location of the first and second valve seats and biasing means therefore.

13. An assembly according to claim 1 wherein the valve body is formed as one part and the seats and biasing means are introduced into position from an end of the valve body.

14. An assembly according to claim 1 wherein the valve body is provided in two parts which are joined together intermediate the ends of the valve body.

15. An assembly according to claim 14 wherein the join is located substantially centrally with respect to the length of the valve body.

16. An assembly according to claim 1 wherein the valve includes a passage which passes from a first end to a second end of the valve body, said valves balls provided spaced along the passage and each valve ball is provided to allow the selective closing and opening of the passage.

17. An assembly according to claim 16 wherein a vent is located intermediate the first and second valve balls.

18. An assembly according to claim 17 wherein the vent is formed around the circumference of the seat assembly.

19. An assembly according to any of the preceding claims 1 wherein the overall length of the valve assembly is at or less than the required ANSI B16:10 length for the particular pipe diameter to which the valve is to be fitted.

20. A double block and bleed valve assembly, said assembly including a first ball valve unit and a second ball valve unit spaced apart in a fluid passage through the valve assembly and wherein, intermediate said first and second ball valves there is provided a seat assembly including a first seat and a second seat and biasing means capable of exerting a biasing force on the first and second seats in opposing directions.

21. An assembly according to claim 20 wherein the same biasing means exert a biasing force on both the first and second seats and are retained in position between the same.

22. An assembly according to claim 20 wherein the biasing force is used to move the seats to seal on the ball of the respective first and second valves.

23. An assembly according to claim 20 wherein the biasing means are spaced around the circumference of the seats so as to exert a uniform movement force around each of the seats.

24. An assembly according to claim 20 wherein at any given time, the biasing means exert a biasing force to move one of the seats onto the adjacent wall with the particular seat in question being that which lies downstream of the biasing means with respect to the flow of fluid through the valve assembly at that time.