GB2091389A - Improvements in or relating to soft seating valves - Google Patents

Abstract

A diaphragm valve has a compressor 14 which is asymmetric to an operating spindle 15 for moving the diaphragm between open and closed positions. The asymmetric compressor is movable carried by the operating spindle so that if, for any reason, the diaphragm is destroyed, the asymmetric compressor makes emergency sealing with the valve body, preferably downstream of the valve body in the direction of fluid flow through the valve. An emergency "indestructible" sealing member 20 is preferably mounted in the downstream part of the compressor which is movably mounted on the spindle by spring discs 18. <IMAGE>

Description

SPECIFICATION Improvements in or relating to soft seating valves This invention relates to soft seating valves commonly referred to as diaphragm valves or pinch valves. The characteristic feature of these valves in the use of an elastomer to close the valve and provide the primary seal to atmosphere for the fluid contained in and passing through the valve.

It is an object of the present invention to provide a soft seating valve having an improved emergency shut-off characteristic than is presently available with such valves upon destruction of the sealing elastomer (diaphragm or tube) caused, for example, by fire or severe chemical attack.

According to the present invention there is provided a soft seating valve a body defining a through-flow passage, an elastomeric sealing or closure member associated with the body, and a compressor means mounted on the body and operatively connected with the elastomeric sealing or closure member to move the latter between positions in which the through-flow passage is fully open or fully closed, the valve being characterised in that the compressor means is of asymmetric construction and is adapted, upon destruction of the elastomeric sealing member, to make emergency sealing engagement with the valve body to close the through-flow passage.The valve is a diaphragm valve and preferably has a normally-ineffective emergency sealing member associated with the diaphragm and/or compressor means and/or valve body which is adapted, upon destruction of the elastomeric sealing member, to be urged into a position sealing off the through-flow passage of the valve.

Preferably, the valve is a diaphragm valve having an elastomeric diaphragm connected to and movable by a compressor which has incorporated therein, or otherwise associated therewith, an emergency sealing member, preferably indestructible, adapted to be resiliently or otherwise urged into a position relative to the valve body whereby the downstream side of the valve is sealed to atmosphere.

In one embodiment, the compressor is, as usual, secured to the valve operating spindle but is split into an upstream part fixed relative to the spindle, and a downstream part forcibly movable relative to the spindle, upon diaphragm destruction, to urge the emergency indestructible sealing member carried thereby into sealing engagement with the valve body.

The downstream compressor part is preferably spring-loaded to valve-closed position.

The split compressor is preferably constructed with the downstream part the larger of the two parts.

In a second embodiment, the compressor is of unitary construction and is forcibly and bodily movable relative to the spindle, upon diaphragm destruction, to urge the emergency indestructible sealing member, which is on the downstream side of the valve, into sealing engagement with the valve body.

Here again, the compressor is spring-loaded to valve-closed position.

The asymmetric nature of the compressor in both embodiments is such as to permit, upon diaphragm destruction, upstream fluid pressure to communicate with the rear of the compressor and so assist, or, indeed, if the spring loading is omitted to effect emergency closure.

In a third embodiment, the compressor at its downstream side incorporates a spring-loaded piston adapted to engage a valve seat on the valve body to seal the downstream side of the valve (from atmosphere) upon diaphragm construction.

This construction may be reversed, i.e. springloaded piston in body, seat on compressor.

Here again, the compressor is movable relative to the valve spindle, and fluid pressure may assist emergency closure.

In all of these embodiments, one or more burst holes can be formed in the upstream side or part of the compressor to encourage early destruction of the diaphragm under emergency conditions and also to assist communication of line pressure to the compressor rear.

An alternative method of encouraging early diaphragm destruction is to make the upstream flexing side of the diaphragm thinner than the downstream side.

It is also envisaged that diaphragm-puncturing means may be employed to obtain early application of line pressure to the compressor rear.

Such means may be manually, remotely or automatically, e.g. fusible capsule, operated.

The present invention is illustrated by way of diaphragm valves which have a number of conventional features, well known to those skilled in the art, which, for convenience, are not illustrated in the present invention nor described in detail herein. Briefly, such features include, inter alia:- 1. The provision of secondary seating to atmosphere between the valve bonnet and body and the spindle operating mechanism. The techniques used are well established and involve the mating of accurately manufactured surfaces and the use of an indestructible material such as asbestos.

2. Clamping means between the valve body and bonnet to secure same together.

3. Operating mechanism -- this is illustrated in the present specification as a simple spindle but any rotary or axial means of manual or remote operation can be used.

4. Attachment of the diaphragm to the compressor-when required this will be by means of a stud or studs remote from the emergency seat seating line. In the event of only the edges and normal seat seating part of the diaphragm being destroyed it is important to prevent large parts of the diaphragm being carried downstream.

5. Guides to prevent rotation of the compressor assembly during opening and closing of the valve.

Additionally when a split compressor is used one half must be able to move axially independently of the other.

6. Housing and captivation of springs to prevent their ejection.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal sectional view of a diaphragm valve according to the present invention in the normal valve-closed position; Fig. 2 is a corresponding part-sectional plan view on the line I1--II of Fig. 1; Fig. 3 is a view corresponding to Fig. 1 with the valve in the emergency closed position; Fig. 4 is a view similar to Fig. 3 of an alternative valve construction; Fig. 5 is a part-sectional plan view on the line V-Vof Fig. 4; Fig. 6 again is a view similar to Fig. 3 of yet another valve construction; Fig. 7 is a plan view of one diaphragm construction for use in a valve according to the invention; and, Fig. 8 is a sectional view on the line VIll-Vill of Fig. 7.

Reference is made to Figs. 1 to 3 which show a diaphragm valve comprising a valve body 10 and valve bonnet or cover 11 between which are clamped a valve-closing diaphragm 12, the latter being secured between the bonnet 11 and seating flanges 13 of the valve body 10.

The diaphragm 12 is secured to a compressor 14 which is, in turn, secured to a valve-operating spindle 15.

The compressor 14 is asymmetric (see Fig. 2) to the spindle centre line 16 and is split along line 17 into a small upstream part 1 4A and a large downstream part 1 4B. Upstream compressor part 1 4A is fixed relative to the spindle 1 5, while downstream compressor part 1 4B is capable of movement relative to the spindle 1 5 under the influence of spring discs 18 surrounding a guide pin 19 secured to the downstream compressor part 148 and traversing a hole in the spindle 15.

An emergency indestructible sealing member 20 formed, for example, of asbestos is incorporated in the downstream compressor part 148 or the downstream side of the diaphragm 12.

The spring effort axis is indicated at 21.

Upon destruction of the diaphragm 12, for whatever reason, when the diaphragm 12 is in the normal closed position the downstream compresor part 14B is immediately spring urged to bring the emergency sealing member 20 into contact with the valve body 10 and seating flanges 13, to seal off the downstream side of the valve and prevent continuing flow through the valve.

This emergency closure is powerfully assisted by line pressure acting on the rear or back face of the compressor 14, access thereto being facilitated by the asymmetric nature of the split compressor (see Figs. 2 and 3).

It is to be noted that improved emergency closure is obtained by reducing the length of the emergency seating line between the compressor 14, valve body 10 and valve seating flanges 13 by suitably shaping the contour of the emergency sealing member which cooperates with the valve body 10. In this regard see Figs. 5 and 7.

It should be noted that the spring effort axis need not be parallel with the spindle axis. It may be inclined if this would make better use of the spring seating force. The seating force can be applied by means other than mechanical springs, e.g. it may be applied manually or by means of a fusible plug.

There may, of course, be multiple seating force units (spring or otherwise) and the seating force instead of being applied through the compressor may be applied through the spindle or indeed through a separate mechanical system associated with the compressor and/or spindle.

The position of the emergency seal line need not coincide with the normal seating position of the flexible diaphragm.

Under normal opening and closing conditions the relatively-movable compressor parts are not harmful to the diaphragm. On opening the spring 18 does cause relative movement between the two compressor parts 1 4A, 1 4B but suitable designing ensures no adverse effects on the diaphragm.

It is to be noted that if the diaphragm is destroyed with the valve fully open or in an intermediate position then the valve is operated in the usual way to effect closure.

Reference is now made to Figs. 4 and 5 and for convenience only the differences compared to Figs. 1 to 3 will be described.

In this embodiment the compressor 22 is again of asymmetric construction but is of unitary construction with the emergency indestructible sealing member 23 at its downstream side.

The spindle 24 has a cross-pin 25 which extends through elongate slots 26 in the sides of a cap 27 and registering elongate slots 28 in the compressor 22. The cap 27 fits into a recess 29 in the compressor 22 for movement therewith.

Within the cap 27 and compressed between same and the end of the spindle 24 are spring discs 29.

It will be manifest that when the valve is operating normally, the cross-pin 25 will lie towards the bottom of slots 26 and 28 but, upon diaphragm destruction, the spring discs 29 urge the cap 27 and compressor 22 down to seat the emergency sealing member 23 as shown and thereby seal the downstream side of the valve.

The emergency sealing line 30 can be seen in Fig. 5. If desired, this can be offset to the spindle centre line.

Otherwise, the features and functioning aspects described with reference to Figs. 1 to 3 apply equally well to this embodiment.

Referring now to Fig. 6, it can be seen that the compressor 31 is of asymmetric and unitary construction and can move axially relative to the spindle 32 due to the cross-pin 33 in the spindle 32 and elongate slots 34 in the compressor 31.

In this instance, the compressor 31 at its downstream side houses a spring-loaded sealing piston 35 which, when, as shown, the diaphragm is destroyed, seals against a valve seat 36 in the downstream side of the valve.

In this instance also, a bursting hole 37 (more than one may be provided) is formed in the upstream side of the compressor 31 to encourage early diaphragm destruction under emergency conditions and also to assist communication of line pressure to the rear or back face of the compressor 31.

Such early destruction may be effected by making the diaphragm of reduced thickness on its upstream side or by providing means for intentionally bursting the diaphragm under emergency conditions.

These early destruction facilities are applicable to the other embodiments of diaphragm valve disclosed herein.

In this embodiment the components effecting the emergency sealing are easier to machine.

In a modification of this embodiment, the spring-loaded piston may be mounted in the valve body and the valve seat on the compressor. When, in this case, the valve is opened the piston partially moves into the flow passage sufficiently slightly to impair the fluid flow but not sufficiently to close the flow passage. The sealing member may be conical or spherical and several such seals may be provided in the compressor and/or valve body.

Reference is finally made to Figs. 7 and 8 which shows a diaphragm 38 into which indestructible material 39 has been introduced during manufacture. This material 39 provides the emergency sealing member when the remainder of the diaphragm 38 has been destroyed. With a suitable emergency sealing effort this will seal on a valve seat to close the valve.

The emergency shut-off line can be along the conventional diaphragm sealing line or positioned over a port in the valve body.

The stud 40 (or studs) securing the diaphragm 38 to the compressor can be used to assist in locating the indestructible material 39 during manufacture.

The indestructible seal 39 may be stabilised with metal rings 41 to improve its performance during emergency operation. This is shown in the peripheral seal (Fig. 8) which has vertical sided metal rings of diameters "x" and "y".

It is conceivable that the separate emergency sealing member be omitted in the embodiments of Figs. 1 to 5 and that emergency sealing be obtained by metal-to-metal contact between the compressor and valve body.

It is also considered possible to reverse the upstream and downstream sides of the valve by the use of suitable emergency closing forces (e.g.

suitable spring forces).

Finally, it is envisaged that no separate closing forces be provided in the valves, the emergency closing forces being obtained purely from line pressure.

In a pinch valve, as is well known to those skilled in the art, the flexible tube is closed or "pinched" by a compressor similar to that employed in diaphragm valves and it will accordingly be manifest that the present invention is equally applicable to pinch valves.

In the case of a diaphragm valve opening and closing of the valve is effected by movement of an elastomeric diaphragm across the flow passage, whereas in the case of a pinch valve the flow passage is through an elastomeric tube which is compressed to restrict or stop flow and released to permit flow.

References hereinbefore and in the claims to "elastomeric sealing member" are to be interpreted as including both a diaphragm and a flexible tube.

It is envisaged that the same emergency closure functioning can be obtained with a symmetric compressor if one side, usually the upstream side, of the compressor is ported (one or more ports), or alternatively if both sides, upstream and downstream, are provided with porting of different areas.

It will be manifest that, upon diaphragm destruction fluid pressure will act upon the back side of the compressor through the port or ports to move the compressor into a closed position.

The compressor assembly construction may be in accord with any of the embodiments described above save that it is symmetric.

Claims (27)

1. A soft seating valve comprising a body defining a through-flow passage, an elastomeric sealing or closure member associated with the body, and a compressor means mounted on the body and operatively connected with the elastomeric sealing or closure member to move the latter between positions in which the throughflow passage is fully open or fully closed, the valve being characterised in that the compressor means if of asymmetric construction and is adapted, upon destruction of the elastomeric sealing member, to make emergency sealing engagement with the valve body to close the through-flow passage.

2. A soft seating valve as claimed in claim 1, in which the asymmetric compressor means is of two-part construction, one part being movable to effect the emergency sealing.

3. A soft seating valve as claimed in claim 2, in which the movable part is disposed downstream of the through-flow passage.

4. A soft seating valve as claimed in claim 2 or 3, in which the asymmetric compressor means is carried by an operating spindle, there being associated with the compressor means and/or spindle resilient means operable to move the compressor means part into emergency sealing engagement with the valve body.

5. A soft seating valve as claimed in any one of claims 2 to 4 in which the movable compressor means part is larger than the other part.

6. A soft seating valve as claimed in claim 1 in which the asymmetric compressor means is carried by an operating spindle and is movable relative to the operating spindle to effect said emergency sealing.

7. A soft seating valve as claimed in claim 5, in which the asymmetric compressor means is connected to the operating spindle by a slot connection, there being resilient means between the operating spindle and compressor means to cause movement of the latter to effect said emergency sealing.

8. A soft seating valve as claimed in claim 1 in which the asymmetric compressor means incorporates a piston adapted to close a port in the valve body to effect said emergency sealing.

9. A soft seating valve as claimed in claim 8 in which the piston is spring loaded and is normally retained in ineffective position by the elastomeric sealing member.

10. A soft seating valve as claimed in claim 8 or 9, in which the asymmetric compressor means is carried by and is relatively movable to an operating spindle.

11. A soft seating valve as claimed in any one of claims 1 to 10 in which the asymmetric construction of the compressor means is such as to permit, upon destruction of the elastomeric sealing member, fluid pressure in the through-flow passage to assist or effect said emergency closure of the latter

12. A soft seating valve as claimed in any one of claims 1 to 11 in which emergency sealing of the valve is effected by a means external of the valve body with or without the assistance of internal resilient means and/or fluid pressure.

13. A soft seating valve as claimed in any one of claims 1 to 12 comprising a normallyineffective emergency sealing member associated with the compressor means and/or elastomeric sealing member and/or valve body.

14. A soft seating valve as claimed in claim 13 in which the emergency sealing member is "indestructible" and is mounted in the downstream side of the compressor means.

15. A soft seating valve as claimed in claim 14, in which the emergency sealing member is formed of asbestos.

1 6. A soft seating valve as claimed in any one of claims 13 or 15 in which the emergency sealing member is embedded in the elastomeric sealing member.

17. A soft seating valve as claimed in any one of claims 1 to 1 6 in which the asymmetric compressor means has one or more bursting holes.

1 8. A soft seating valve as claimed in any one of claims 1 to 17 in the form of a diaphragm valve with the diaphragm of the latter constituting the elastomeric sealing member.

19. A diaphragm valve as claimed in claim 18, in which the seating line of the emergency sealing member is different from that of the diaphragm.

20. A diaphragm valve as claimed in claim 1 8 or 19, comprising means for intentionally bursting the diaphragm.

21. A diaphragm valve as claimed in any one of claims 1 8 to 20 in which the diaphragm is of reduced thickness on its upstream side.

22. A soft seating valve as claimed in any one of claims 1 to 17 in the form of a pinch valve with the flexible tube of the latter constituting the elastomeric sealing member.

23. A soft seating valve comprising a body defining a through-flow passage, an elastomeric sealing or closure member associated with the body, and a compressor means connected with the elastomeric sealing or closure member to move the latter between positions in which the through-flow passage is fully open or fully closed, the valve being characterised in that the compressor means is adapted so that upon destruction of the elastomeric sealing member, the through-flow passage communicates with the back side of the compressor means which makes emergency sealing engagement with the valve body to close the through-flow passage.

24. A soft seating valve as claimed in claim 23 in which the compressor means is asymmetric.

25. A soft seating valve as claimed in claim 23 in which the compressor means is symmetric and is ported at its upstream and/or downstream sides.

26. A soft seating valve as claimed in claim 25 in which, where the compressor means is ported at both its upstream and downstream sides, the porting areas are different.

27. A diaphragm valve, substantially as hereinbefore described with reference to Figs. 1 to 3,7 and 8, or Figs. 4,5,7 and 8 or Fig. 6 ofthe accompanying drawings.