GB1567170A

GB1567170A - Valve assemblies

Info

Publication number: GB1567170A
Application number: GB687676A
Authority: GB
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1976-02-20
Filing date: 1976-02-20
Publication date: 1980-05-14
Also published as: JPS52112822A; DE2707436A1

Description

(54) VALVE ASSEMBLIES (71) We, NORTHBRN ENGINBERING INDUSTRIES LIMITED, of NEI House, Regent Centre, Newcastle upon Tyne NE3 3SB., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it Is to be perfonned, to be particularly described in and by the following statement:- This invention relates to valve assemblies.

According to the present invention there is provided a pressure control valve assembly comprising a main body; a first valve within said main body for controlling a flow of fluid along a first path between opposite faces of said main body, this valve comprisin a valve member and a seat therefor, the valve member being mounted for movement towards or away from one or other of said opposite faces to seat on or lift off the valve seat; a housing mounted on said main body externally thereof; a second valve within said housing; and means for applying a control pressure to control the second valve; the second valve controlling flow of fluid along a second path which is open at both its ends to said first path and which includes a first pressure chamber on one side of the second valve and in which pressure acts in use of the valve assembly in the sense to close the first valve, and a second pressure chamber on the other side of the second valve and in which pressure acts in use of the valve assembly in the sense to oppose the effect of the control pressure on the second valve.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectional side view of a valve assembly, Figure 2 is a view similar to Figure 1 of a modified form of valve assembly, Figures 3 and 4 are views similar to Figure 1 and 2 but illustrating modifications of the assemblies of Figures 1 and 2 respectively, and Figures 5 and 6 are section side views of two further forms of valve assembly.

The valve assembly shown in Figure 1 has a thin main body 1 that can be elamped (as illustrated) between pipe flanges 2A, 2B. Within the body 1 there is a first, main valve 3. A housing 4 screwed into the side of the body 1 contains a second, control valve 5. By providing this housing 4 outside the main body 1, the size of the body is minimized.

Main fluid flow ducts 6 in the body 1 extend from one side face 1A of the body to terminate at a common orifice 7 in the opposite side face 1B of the body 1 whereby there is provided a first path for fluid between the opposed faces 1A, 1B of the assembly. A head 8A of the valve member 8 of the main valve 3 co-operates with a seat 9 around the rim of the orifice 7, the valve member being biased away from the seat 9 by a spring 10. The face of the base 8B of the valve member 8 remote from the seat 9 and which is of greater effective surface area than the face of the head 8A that co-operates with the seat 9 forms one wall af a first pressure chamber 11 into which open a bleed passage 11 A extending from the main body face 1A, and a flow duct 12 extending from a duct 13 in the housing 4.An annular recessed portion 14 of the body 1, openling through the face 1 B, is also connected to a flow duct 15 in the housing 4, this connection being via a duct 16 in the body 1.

The duct 13 extends to a chamber 17 housing a spring 18 that acts on the valve member 19 of the control valve 5 in the sense to close this valve. The chamber 17 is connected to one side of the orifice 20 of the valve 5. On the other side of this orifice 20 there is a second pressure chamber 21 into which the duct 15 opens. A part of the wall of the chamber 21 opposite the orifice 20 is formed by a face 22A of a piston 22, the opposite face 22B of which co-operates with a diaphragm 23 that divides into two parts 24A, 24B a chamber 24 housing the piston 22. A fluid supply duct 25 opens into the chamber part 24B.

The valve member 19 carries a rod 26 for co-operation with the piston 22.

If the valve assembly of Figure 1 is mounted, as illlustrated, between flanges 2A, 2B of two pipes A and B fluid flow can take place as indicated by chain-dot arrows and provided the main valve 3 is open, from pipe A via the main flow ducts 6 and through the orifice 7 into pipe B, that is through the body 1 (via the first path mentioned above) from the face 1A to the face lB via the main valve 3. This flow is metered by its passage between the head 8A of the valve member 8 and the seat 9 so that there is a pressure drop through the main valve 3.An effect of this pressure drop is that, with suitable dimensioning of the valve member 8 and suitable characteristic of the spring 10, if the control valve 5 is closed, pressure build-up in the first pressure chamber 11 (brought about by feed of fluid from pipe A via the bleed passage 11A into the chamber 11) acts eventually to overcome the spring 10 and close the main valve 3.

By applying a fluid control pressure to the chamber part 24B via the duct 25, the piston 22 can be used to move to open the control valve 5, whereupon the pressure in chamber 11 drops (vented to pipe B via flow path 12/13/17/21/15/16/14 by-passing the main valve 3) and the spring 10 asserts itself to open the main valve 3. The path llA/11/12/13/17/21/15/16/14 constitutes a second path for fluid which is between the opposed faces 1A, 1B of the assembly and hence is open at both its ends to the first such path.The pressure in the chamber 21 which is included in the path that by-passes the main valve 3, and which pressure opposes the control pressure applied via the ducts 25, is that in pipe B and if this pressure rises sufficiently to overcome the control pressure (the relative dimensions of the orifice of the control valve 5 and the bleed passage 1 lA being appropriately selected to permit pressure to build-up in the chamber 21) the piston 22 is moved to permit spring 18 to assert itself to close the control valve 5. With the control valve 5 closed, pressure can again build up in the first pressure chamber 11 for closing the main valve.Thus the pressure that can be reached in the downstream pipe B is determined by the control pressure applied to the control valve 5 and hence, if a suitable value is selected for this control pressure, the valve assembly as a whole functions as a pressure reducing valve between pipes AandB.

Instead of utilizing a fluid control pressure as described, the diaphragm 23 or the piston 22 can be spring-loaded to obtain a control pressure.

The valve assembly of Figure 2 is similar to that of Figure 1, with the following exceptions. The spring 10 is replaced by a spring 10' positioned so as to act to close the valve 3; the bleed passage 11A is replaced by a bleed passage 11A' extending through the valve member 8 to open through the face co-operating with the seat 9; and the duct 16 is replaced by a duct 16' opening through the valve face 1A.

With pressure in pipes A and B, and control pressure applied to the piston 22 to open the control valve 5, the main valve 3 is held closed for as long as the pressure in the first pressure chamber 11 applied from pipe A via flow path 16'/15/21/17/ 13/12 and controlled by the bleed passage 11A' is sufficiently high, coupled with the force exerted by the spring 10', to overcome the effect of pressure in pipe B. If the pressure in pipe A drops sufficiently the main valve 3 opens so that both valves 3 and 5 are now open. Fluid flow can take place from pipe B to pipe A via the ducts 6, as indicated by chain-dot arrows. If, instead of dropping, the pressure in pipe A increases sufficiently to overcome the control pressure, valve 5 closes and valve 3 opens, provided that the pressure in pipe B is sufficiently high.The open orifice of the control valve 5 is larger than the orifice of the bleed passage 11A' so that pressure can build up in the chamber 11, and eventually the main valve 3 closes again. It will be noted that in this form the second flow path for fluid between the faces 1A, 1B is the path 16'/15/21/17/13/12/llA'.

In the modifications of the assemblies of Figures 1 and 2 respectively illustrated in Figures 3 and 4 the valve member 8 is in each case supported intermediate its head 8A and its base 8B in a bearing 27 carried by a web 28. The chamber 29 which is thus formed between the base 8B of the valve member 8 and the web 28 is, in each case, vented to one of the flow ducts 6 via a restricted orifice 30, which, however, does not offer as great a resistance to fluid flow as do the bleed passages 11A (Figure 3) or 11A' (Figure 4). In each case a spring 10" is conveniently located in a recess 31 in the valve base 8B and opening into, and hence forming part of, the pressure chamber 11, although the spring 10" could be located at a position similar to that illustrated for the spring 10' in Figure 2.Thus in each of these forms the action of the spring 10" is to close the main valve 3. It is here to be noted that in Figure 2 the spring 10' could be located in the pressure chamber 11.

As in the case of Figure 1, in use of the form of Figure 3 fluid flow is from pipe A to pipe B. From the main valve closed condition and with the control valve 5 also closed, fluid pressure builds up more quickly in the chamber 29 than in the chamber 11 (as the orifice 30 offers less resistance to fluid flow than the bleed passage 11A) to reach that prevailing in pipe A and if this pressure becomes sufficiently high to overcome the action of the spring 10" the main valve 3 will open.Thereafter movement of the valve member 8 with pressure in the chamber 29 is damped by the resistance offered by the orifice 30 to the flow of fluid via this orifice 30 out of, or into, the chamber 29, which flow is caused by the change of volume of the chamber 29 that occurs as the valve member 8 moves, the valve assembly otherwise operating as described for the valve assembly of Figure 1, the characteristic of the spring 10" and the area subjected to fluid pressure being selected taking into account the direction of action of the spring 10". In particular in this form the valve member head 8A has to have a smaller pressure surface area than the base 8B.

In the case of Figure 4 flow is from pipe B to pipe A and initial opening of the main valve 3 occurs when the pressure in pipe B is sufficiently high, whereafter the pressure in chamber 29 builds-up to that prevailing in pipes B and A and operation is as described for the valve assembly of Figure 2 with the addition of the damping effect of fluid pressure in the chamber 29.

In the valve assemblies of Figures 5 and 6 parts corresponding to those already described are indicated by the same reference numerals. These assemblies operate as back pressure controllers or relief valves with flow taking place from pipe A to pipe B in Figure 5 and from pipe B to pipe A in Figure 6. In each case the valve member 19 of the second valve 5 is carried by the piston 22 so that control pressure in the chamber part 24B acts in the sense to close the valve 5, whilst pressure in the chamber 21 acts in the sense to open the valve 5. A light spring 18' biases the valve member 19 to the open position.In the case of Figure 5 the chamber 21 is connected via the duct 15 to a duct 16' that opens through the valve face 1 A. In the case of Figure 6 the chamber 21 is connected via the duct 15 and the duct 16 to the annular recessed portion 14 of the body 1 that opens through the valve face 1B. In both cases the spring 10 of the main valve 3 acts to open the main valve and in each case the second path for fluid is open at both its ends to the first path for fluid, in these cases solely on the upstream side of the first valve.

As already mentioned, the main body 1 of each of the valve assembles described is of minimum thickness, and yet the control valve 5 utilizes fluid pressure within the assembly for controlling the main valve 3 and there is no mechanical linkage for actuating the main valve under the control of the control valve. In those forms where the chamber 29 and its related orifice 30 are provided, damping of the movement of the member of the main valve is obtained utilizing high pressure fluid and in all cases the downstream side of the main valve is free of all encumbrances permitting convenient addition of further devices such as a silencing device.

WHAT WE CLAIM IS: 1. A pressure control valve assembly comprising a main body; a first valve within said main body for controlling a flow of fluid along a first path between opposite faces of said main body, this valve comprising a valve member and a seat therefor, the valve member being mounted for movement towards or away from one or other of said opposite faces to seat on or lift off the valve seat; a housing mounted on said main body externally thereof; a second valve within said housing; and means for applying a control pressure to control the second valve; the second valve controlling flow of fluid along a second path which is open at both its ends to said first path and which includes a first pressure chamber on one side of the second valve and in which pressure acts in use of the valve assembly in the sense to close the first valve, and a second pressure chamber on the other side of the second valve and in which pressure acts in use of the valve assembly in the sense to oppose the effect of the control pressure on the second valve.

2. A valve assembly as claimed in claim 1, wherein said second path extends between said faces and by-passes the first valve; and wherein the action of said control pressure is to open the second valve so that pressure in the second chamber acts in the sense to permit closure of the second valve.

3. A valve assembly as claimed in claim 1, wherein said second path communicates with said first path on one side only of the first valve; and wherein the action of said control pressure is to close the second valve so that pressure in the second chamber acts in the sense to open the second valve.

4. A valve assembly as claimed in any one of claims 1 to 3, wherein the second valve is disposed to cut off communication via the second path between the first and second pressure chambers.

5. A valve assembly as claimed in any

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Claims

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spring 10" is to close the main valve 3. It is here to be noted that in Figure 2 the spring 10' could be located in the pressure chamber 11.

As in the case of Figure 1, in use of the form of Figure 3 fluid flow is from pipe A to pipe B. From the main valve closed condition and with the control valve 5 also closed, fluid pressure builds up more quickly in the chamber 29 than in the chamber 11 (as the orifice 30 offers less resistance to fluid flow than the bleed passage 11A) to reach that prevailing in pipe A and if this pressure becomes sufficiently high to overcome the action of the spring 10" the main valve 3 will open.Thereafter movement of the valve member 8 with pressure in the chamber 29 is damped by the resistance offered by the orifice 30 to the flow of fluid via this orifice 30 out of, or into, the chamber 29, which flow is caused by the change of volume of the chamber 29 that occurs as the valve member 8 moves, the valve assembly otherwise operating as described for the valve assembly of Figure 1, the characteristic of the spring 10" and the area subjected to fluid pressure being selected taking into account the direction of action of the spring 10". In particular in this form the valve member head 8A has to have a smaller pressure surface area than the base 8B.

In the case of Figure 4 flow is from pipe B to pipe A and initial opening of the main valve 3 occurs when the pressure in pipe B is sufficiently high, whereafter the pressure in chamber 29 builds-up to that prevailing in pipes B and A and operation is as described for the valve assembly of Figure 2 with the addition of the damping effect of fluid pressure in the chamber 29.

In the valve assemblies of Figures 5 and 6 parts corresponding to those already described are indicated by the same reference numerals. These assemblies operate as back pressure controllers or relief valves with flow taking place from pipe A to pipe B in Figure 5 and from pipe B to pipe A in Figure 6. In each case the valve member 19 of the second valve 5 is carried by the piston 22 so that control pressure in the chamber part 24B acts in the sense to close the valve 5, whilst pressure in the chamber 21 acts in the sense to open the valve 5. A light spring 18' biases the valve member 19 to the open position.In the case of Figure 5 the chamber 21 is connected via the duct 15 to a duct 16' that opens through the valve face 1 A. In the case of Figure 6 the chamber 21 is connected via the duct

15 and the duct 16 to the annular recessed portion 14 of the body 1 that opens through the valve face 1B. In both cases the spring

10 of the main valve 3 acts to open the main valve and in each case the second path for fluid is open at both its ends to the first path for fluid, in these cases solely on the upstream side of the first valve.

As already mentioned, the main body 1 of each of the valve assembles described is of minimum thickness, and yet the control valve 5 utilizes fluid pressure within the assembly for controlling the main valve 3 and there is no mechanical linkage for actuating the main valve under the control of the control valve. In those forms where the chamber 29 and its related orifice 30 are provided, damping of the movement of the member of the main valve is obtained utilizing high pressure fluid and in all cases the downstream side of the main valve is free of all encumbrances permitting convenient addition of further devices such as a silencing device.

WHAT WE CLAIM IS: 1. A pressure control valve assembly comprising a main body; a first valve within said main body for controlling a flow of fluid along a first path between opposite faces of said main body, this valve comprising a valve member and a seat therefor, the valve member being mounted for movement towards or away from one or other of said opposite faces to seat on or lift off the valve seat; a housing mounted on said main body externally thereof; a second valve within said housing; and means for applying a control pressure to control the second valve; the second valve controlling flow of fluid along a second path which is open at both its ends to said first path and which includes a first pressure chamber on one side of the second valve and in which pressure acts in use of the valve assembly in the sense to close the first valve, and a second pressure chamber on the other side of the second valve and in which pressure acts in use of the valve assembly in the sense to oppose the effect of the control pressure on the second valve.
2. A valve assembly as claimed in claim 1, wherein said second path extends between said faces and by-passes the first valve; and wherein the action of said control pressure is to open the second valve so that pressure in the second chamber acts in the sense to permit closure of the second valve.
3. A valve assembly as claimed in claim 1, wherein said second path communicates with said first path on one side only of the first valve; and wherein the action of said control pressure is to close the second valve so that pressure in the second chamber acts in the sense to open the second valve.
4. A valve assembly as claimed in any one of claims 1 to 3, wherein the second valve is disposed to cut off communication via the second path between the first and second pressure chambers.
5. A valve assembly as claimed in any

one of claims 1 to 4, wherein an end wall of the valve member of the first valve that is remote from the valve seat of this valve is a wall part of the first pressure chamber.
6. A valve assembly as claimed in any one of claims 1 to 5, wherein the valve member of the first valve is slidably supported by a bearing intermediate the end of this valve member that co-operates with the valve seat of the first valve and the opposite end wall of this valve member.
7. A valve assembly as claimed in claim 6, wherein said bearing is carried by a wall part of a further chamber. a further wall part of which is defined by a part of the valve member of the first valve, this further chamber being in fluid communication via a restricted orifice with the first fluid path such that, in use, valve-opening or closing movement of this valve member is damped by the resistance offered by this orifice to the flow of fluid via this orifice out of, or into, this further chamber, which flow is caused by the change in volume of the further chamber that occurs as the valve member of the first valve moves.
8. A valve assembly as claimed in claim

2 or any one of claims 4 to 7 as appendant directly or indirectly to claim 2, wherein the first pressure chamber is in communication with the upstream side of the first valve via a bleed passage included in the first path.
9. A valve assembly as claimed in claim

8 as directly appendant to claim 5, wherein a valve head of the valve member of the first valve co-operates with the valve seat of this valve such that there is a pressure drop through the first valve when, in use, fluid flows through the first path, the valve member of the first valve being spring urged into its valve-open position and the arrangement being such that in use with the second valve closed pressure build-up in the first pressure chamber brought about by feed of fluid from the upstream side of the first valve via the bleed passage into the first chamber acts eventually to overcome the spring opposition and close the first valve.
10. A valve assembly as claimed in claim 8, wherein the valve member of the first valve is spring-urged into its valve-closed position, the arrangement being such that in use with the second valve open and after opening of the first valve has been brought about by a sufficiently high fluid pressure acting in the first path in the sense to overcome the spring action and open the first valve, with fluid pressure in the first path thereafter prevailing on both sides of the first valve and with the second valve remaining- open, the first valve remains open so long as the spring-action and the pressure in the first pressure chamber is insufficient to overcome the effect of the fluid pressure acting in the first path in the sense to open the first valve.
11. A valve assembly as claimed in claim

8 as appendant to claim 7, wherein the valve member of the first valve is spring-urged into its valve-closed position in opposition to the action of any fluid pressure prevailing in said further chamber, the arrangement being such that in use with the first and second valves closed fluid pressure in the first path on the side of the valve member of the first valve that is in communication with said further chamber can act, in this further chamber, to overcome the spring action to open the first valve, whereafter, with the second valve remaining closed, pres sure build-up in said first pressure cham ber brought about by feed of fluid from the upstream side of the first valve via said bleed passage into said first chamber acts eventually, with said spring action, to over come the fluid pressure in said further cham ber and close the first valve.
12. A valve assembly as claimed in claim

3 or any one of claims 4 to 8 as appendant directly or indirectly to claim 3, wherein it is solely on the upstream side of the first valve that the second path is in communi cation at both its ends with the first path, the first pressure chamber being in communi cation with the upstream side of the first valve via a bleed passage included in the first path; and wherein the value member of the first valve is spring-urged into its valve-open position.
13. A valve assembly as claimed in claim

10 or 12 each as appendant to claim 5, wherein said bleed passage extends through the valve member of the first valve from the pressure chamber forming end wall of this valve member to the end wall of this valve member that co-operates with the valve seat of the first valve.
14. A valve assembly as claimed in claim

10 or 11 each as appendant to claim 7, wherein the valve member of the first valve is spring-urged into the valve-closed position by spring means disposed in said first pressure chamber.
15. A valve assembly as claimed in any one of the preceding claims, wherein a wall part of the second pressure chamber is formed by a piston adapted to be subjected to said control pressure in use, the piston cooperating with the valve member of the second valve for effecting opening and closing movement of this valve member.
16. A valve assembly substantially as hereinbefore described with reference to any one of the Figures of the accompanying drawings.