GB2152143A

GB2152143A - Pressure release device

Info

Publication number: GB2152143A
Application number: GB08334433A
Authority: GB
Inventors: Rodney Gomersall; Arthur Guy Thomas
Original assignee: STARDAM Ltd
Current assignee: STARDAM Ltd
Priority date: 1983-12-23
Filing date: 1983-12-23
Publication date: 1985-07-31
Also published as: GB8334433D0

Abstract

A pressure release device 1 comprises a housing 2 which is secured to the wall 4 of a pressure vessel. A pin 17 is secured firmly within the housing 2 by a nut 22 which is tightened to bring a head 18 of the pin firmly against the O-ring 19, the pin being held in tension. Pressure fluid in the vessel is free to flow through the aperture 5 and the bores 6 and 9 into the bore 10 where the pressure fluid exerts a force on the pin to urge the head 18 of the pin to the left (as seen in Fig. 1). When the pressure within the vessel exceeds a predetermined value, the forces acting on the pin become sufficient to cause the reduced diameter portion thereof to rupture and to expel the head 18 into the chamber 13. This releases the sealing effect of the O-ring and allows pressure fluid to vent to atmosphere through radial passageways 14. The ruptured pin 17 may conveniently be replaced by a new pin to enable the device to be used again as a pressure release device. <IMAGE>

Description

SPECIFICATION Pressure release device This invention relates to pressure release devices.

According to one aspect of the present invention, there is provided a pressure release device comprising a housing adapted to receive pressure fluid and a valve element mounted in the housing, the valve element comprising a first part which provides a seal to pressure fluid in the housing and a second part which is adapted to rupture upon application of a predetermined force thereto, the arrangement being such that, upon a pressure greater than a predetermined value prevailing in the housing, said second part is caused to rupture and thereby release pressure in the housing. Upon rupturing, said second part preferably releases said first part at least to the extent of releasing the said seal to release pressure in the housing.

The first part of the valve element may cooperate with a resilient sealing member in the device to provide said seal. Such a resilient member may comprise an O-ring.

Said second part preferably comprises a reduced diameter portion of the valve element. The valve element may be in the form of a pin, and may be secured under tension in the housing. The valve element may be provided with a screw-threaded portion with which a screw-threaded fastener engages to secure the valve element in the housing.

The valve element may be secured directly to a part of the housing. Alternatively, it may be secured to a part of the device which part is itself mounted in the housing.

The pressure release device may also be arranged as an outlet valve for a pressure vessel. To this end, the valve element may be secured to a valve piston which is slidably mounted within said housing and is operative to control normal outlet of pressure fluid through the housing. The valve piston may be arranged to be urged under pressure within the housing into a closed position, and be provided with an external projection by which the valve piston may be urged away from its closed position.

Means may be provided for removably securing said housing to a pressure vessel.

The pressure release device may include a member for limiting movement of said first part when said second part of the valve element ruptures. Such a member may comprise a cap which is removable from the device.

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 diagrammatic drawings, in which: Figure 1 illustrates in longitudinal section a pressure release device mounted on the wall of a pressure vessel; and Figure 2 is a view similar to Figure 1, but showing a pressure release device which is arranged also as an outlet valve for a pressure vessel.

In the figures, like reference numerals denote like or corresponding parts.

As shown in Figure 1, a pressure release device 1 commprises a housing 2 which is of substantially circular cross-section and is provided with an annular flange 3 by which it is secured to the wall 4 of a pressure vessel. The annular flange 3 is secured to the wall 4 by any suitable means. For example, it may conveniently be so secured by means of removable screw-threaded fastening members, such that the device 1 may readily be removed from and replaced on the wall 4. A fluid tight seal is provided between the flange 3 and the wall 4.

An aperture 5 is formed in the wall 4 of the pressure vessel, and communicates directly with a bore 6 formed within the housing 2. A central portion 7 of the housing 2 affords a central bore 8 and a plurality of outer bores 9.

The outer bores 9 provide a passageway for pressure fluid between the bore 6 and an inner bore 10, of the same diameter as the bore 6.

Further bores 11 and 1 2 lead to a chamber 13, which communicates with atmosphere by way of radial passageways 1 4. The housing 2 is recessed at its free end to provide a seat 1 5 for a removable end cap 1 6.

A pin 1 7 is disposed within the housing 2, and is mounted for sliding movement within the bores 8, 11 and 1 2. At one end, the pin 1 7 is formed with a head 1 8 which is arranged to bear against a resilient O-ring 1 9.

At its other end, the pin 1 7 is formed with an externally screw-threaded portion 20, which engages with a nut 22.

The pin 1 7 is formed with a reduced diameter portion 21, which is located in the bore 10.

The pressure release device 1 operates as follows.

The device 1 is firstly assembled as illustrated in Figure 1. In this condition, the pin 1 7 is secured firmly within the housing 2, the nut 22 being sufficiently tightened to bring the head 1 8 of the pin to bear firmly against the O-ring 19, which provides a seal between the bore 10 and the chamber 1 3. It will be appreciated that the pin 1 7 is thus secured in tension within the housing 2.

Pressure fluid in the vessel is free to flow through the aperture 5 and bores 6 and 9 into the bore 1 0. There, forces are exerted on the pin 17, by the pressure fluid. It will be appreciated that, due to the pressure differential between the bore 10 and the chamber 13, there is a resultant force on the pin 1 7 which urges the head 1 8 to the left (as seen in Figure 1). When the pressure within the vessel exceeds a predetermined value, the forces acting on the pin 1 7 become sufficient to cause the reduced diameter portion 21 thereof to rupture.Thus, the head 1 8 is expelled into the chamber 13, releasing the sealing effect of the O-ring 19, and allowing the pressure fluid to vent to atmosphere (or to whatever ambient conditions are provided) through the radiai passageways 1 4.

When the cause of the excessively high pressure has been rectified, the device 1 may be removed from the wall 4 of the pressure vessel, the pin 1 7 replaced with a new pin, and the device 1 then replaced for use on the wail 4.

It will be appreciated that the cap 1 6 serves to prevent the head 1 8 from being ejected out the device 1 at dangerously high velocity, upon rupturing of the pin 1 7. Subsequently, the cap 1 6 may be removed for replacement of the pin 17.

The nut 22 may be freely mounted, which necessitates the removal of the device 1 for replacement of the pin 1 7. Alternatively, it may be welded to or provided as a part of the central portion 7 of the housing 2. In such a case, it may be possible to remove a ruptured pin 1 7 from the device 1 solely by access through the chamber 1 3, with the provision of suitable tools. Then, the new pin 1 7 may be replaced similarly by access only through the chamber 13, in which case if would be appropriate to form the head 1 8 for engagement with a suitable tool.

The device 30 which is shown in Figure 2 operates in a manner similar to that of the device 1, as far as the release of excess pressure is concerned. Thus, the device 30 is provided with a pin 1 7 having a head 1 8 which bears against an O-ring 19, the pin 1 7 being secured under tension by means of a nut 22 engaging a screw-threaded portion 20 of the pin 1 7. However, the device 30 of Figure 2 is adapted also to operate as an outlet valve for a pressure vessel.

The device 30 comprises a housing 31 which may be provided with means (not shown) by which it may be detachably secured to a pressure vessel. Alternatively, the housing 31 may be permanently secured to or part of the pressure vessel. The housing 31 affords a bore 6 which communicates with the interior of the respective pressure vessel, and which leads to a chamber 32 of reduced cross-section, which in turn leads to an outlet passage 33 of yet further reduced cross-section. Mounted within the bore 6 is a valve piston 34 having a central bore 35 in which the pin 1 7 is disposed. Radial bores 36 communicate between the bore 35 and the bore 6, and terminate adjacent the reduced diameter portion 21 of the pin 17.The head 1 8 of the pin 1 7 and the O-ring 1 9 are disposed in an enlarged diameter bore 37 of the valve piston 34, which bore is similar to the bore 1 2 shown in Figure 1. Radially extending spacers 38 serve to centre the valve piston 34 within the bore 6, and also afford axial passageways for the flow of pressure fluid within the bore 6.

One end of the valve piston 34 is provided with a frustro-conical surface 39, which engages with a corresponding surface 40 provided on the housing 31. The surfaces 39 and 40 are precision ground surfaces which serve to provide a seal when in close engagement. Alternative seals could be provided at this point, such as for example, a rubber 0ring or an insert of plastic, rubber or soft metal in one of the surfaces 39 and 40.

A projection 40 extends from the piston head 1 8 through a central bore provided in a support 41, which also affords passageways 42 for the throughflow of pressure fluid between the chamber 32 and outlet passage 33.

In use, pressure fluid from the respective pressure vessel flows in the bore 6 and urges the valve piston 34 to the left (as seen in Figure 2), to bring the frusto-conical surfaces 39 and 40 into close engagement and thereby provide a seal to the pressure fluid in the bore 6. To permit controlled outlet of the pressure fluid, a suitably formed part (not shown) engages with the projection 40 to urge the valve piston 34 to the right (as seen in Figure 2). Pressure fluid in the bore 6 then flows through the space defined between the surfaces 39 and 40, and out of the outlet passage 33 via the passageways 42. Upon releasing the force applied to the projection 40, the force of the pressure fluid within the bore 6 automatically urges the valve piston 34 into its closed position, and flow of pressure fluid ceases.

In the event of excessive built-up of pressure within the pressure vessel, increasing force is applied to the pin 1 7 until, in a manner analogous to that described above with reference to Figure 1, the reduced diameter portion 21 ruptures and the head 18 is ejected into the chamber 32, to permit the pressure fluid to be vented through the bore 37, chamber 32, passageways 42 and outlet passage 33.

It will be appreciated that the illustrated pressure release devices afford means of releasing excess pressure within a pressure vessel in a very safe, reliable and simple manner.

In particular, each pin 1 7 may be so designed that the force necessary to rupture the reduced diameter portion 21 is defined with a fairly high degree of accuracy, such that the excess pressure at which the pressure release device operates may be determined with a corresponding degree of accuracy. It may be further appreciated that there may readily be provided a plurality of different pins 1 7 having different pressure ratings. These ratings may be stamped on the pins 17, or the pins 1 7 may be coded in alternative ways. Thus, there may be readily provided a range of pressure release devices which may selectively operate over a wide range of excess pressures, simply by appropriate substitution of the pins 17.

The illustrated pressure release devices are particularly suitable for use where it is considered undesirable for them to be capable of being reset other than by skilled personnel, as the provision of replacement pins and appropriate tools is required in order to reset the devices.

Claims

1. A pressure release device comprising a housing adapted to receive pressure fluid and a valve element mounted in the housing, the valve element comprising a first part which provides a seal to pressure fluid in the housing and a second part which is adapted to rupture upon application of a predetermined force thereto, the arrangement being such that, upon a pressure greater than a predetermined value prevailing in the housing, said second part is caused to rupture and thereby release pressure in the housing.

2. A pressure release device as claimed in Claim 1 in which, when said second part is caused to rupture, said second part releases said first part at least to the extent of releasing the said seal to release pressure in the housing.

3. A pressure release device as claimed in Claims 1 or 2, in which the first part of the valve element cooperates with a resilient sealing member in the device to provide said seal.

4. A pressure release device as claimed in Claim 3 in which the resilient member comprises an O-ring.

5. A pressure release device as claimed in any preceding claim in which the second part comprises a reduced diameter portion of the valve element.

6. A pressure release device as claimed in any preceding claim in which the valve element is in the form of a pin which is secured under tension in the housing.

7. A pressure release device as claimed in any preceding claim in which the valve element is provided with a screw-threaded portion with which a screw-threaded fastener engages to secure the valve element in the housing.

8. A pressure release device as claimed in any preceding claim in which the valve element is secured directly to a part of the housing.

9. A pressure release device as claimed in any of Claims 1 to 7 in which the valve element is secured to a part of the device, which part is itself mounted in the housing.

1 0. A pressure release device as claimed in any preceding claim which is also arranged as an outlet valve for a pressure vessel.

11. A pressure release device as claimed in Claim 10 in which the valve element is secured to a valve piston which is slidably mounted within said housing and is operative to control normal outlet of pressure fluid through the housing.

12. A pressure release device as claimed in Claim 11 in which the valve piston is arranged to be urged under pressure within the housing into a closed position, and is provided with an external projection by which the valve piston may be urged away from its closed position.

1 3. A pressure release device as claimed in any preceding claim in which means are provided for removably securing said housing to a pressure vessel.

14. A pressure release device as claimed in any preceding claim including a member for limiting movement of the first part when said second part of the valve element ruptures.

1 5. A pressure release device as claimed in Claim 14 in which the member for limiting movement comprises a cap which is removable from the device.

1 6. A pressure release device substantially as herein described with reference to, and as shown in Figure 1 or Figure 2 of the accompanying drawings.