GB2265439A

GB2265439A - Pressure relief device

Info

Publication number: GB2265439A
Application number: GB9305240A
Authority: GB
Inventors: Dale J Stewart
Original assignee: SEABOARD LLOYD Ltd
Current assignee: SEABOARD LLOYD Ltd
Priority date: 1992-03-25
Filing date: 1993-03-15
Publication date: 1993-09-29
Also published as: GB9206482D0; GB9305240D0

Abstract

A pressure-relief device (2) is provided to permit escape of pressurised fluid from the cavity of a fluid valve, especially for fluid pressure rise due to temperature increase in a fire situation, the device (2) comprising a valve spindle (11) threaded to a movable holding member (12) which is urged against a fusible washer (15) by a spring (16). Normally the holding member (12) is stationary so that the valve spindle (11) can be screwed to a closure position preventing escape of fluid from the valve cavity, while in a fire situation the fusible washer (15) melts thereby permitting reverse movement of the holding member (12) carrying the valve spindle (11) so that the valve spindle takes up an open position enabling escape of pressure fluid from the cavity via a bleed duct (18). <IMAGE>

Description

"Pressure Relief Device" The present invention relates to a pressure relief device for use in fluid valves, and especially to a temperature actuated pressure-relief device for relieving pressure in a valve cavity where extreme temperatures exist due to a fire situation.

In fluid valves fluid can be trapped in the valve cavity when the valve is in a closed position. When the valve is exposed to elevated temperature, for example in a fire situation, the fluid trapped in the cavity will expand and this can lead to a dangerous overpressure in the valve. It is the principal object of the present invention to overcome this problem by the provision of a novel pressure-relief device.

Broadly the present invention provides a pressure-relief device for use in a fluid valve, comprising valve means settable to close a bleed ducting in the valve, and temperature responsive means causing opening of the valve means at elevated temperature conditions to permit escape of fluid from the valve cavity via the bleed ducting, and in particular the bleed ducting can feed back to an upstream side of the valve.

In a preferred embodiment, the valve means comprise a spindle valve screwed to a movable holding member whereby said valve means can be set in the closed position, and positioning means including a temperature responsive element for said spindle valve, said temperature responsive element responding at elevated temperatures to permit movement of the holding member whereby the valve means open for fluid bleeding from the valve cavity.

Preferably said temperatures responsive means comprises a fusible washer, and spring means can be provided to bias the holding member against said washer.

The valve means are preferably located in a heat intensified housing.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings wherein Fig. 1 shows a part-sectional view of a fluid valve embodying a pressure release device in accordance with the present invention; Fig. 2 shows a sectional side view of the pressure release device to a larger scale; and Fig. 3 shows a detail when the device is in the "open" position.

Referring to the drawings, the valve 1 comprises a main body 3 enclosing a valve cavity 4, an inlet portion 5 with inlet duct 5A and an outlet portion 6, the portions 5, 6 including flange 7 to facilitate connection of the valve 1 to pipework (not shown). The cavity 4 houses the gate and seat controlling fluid flow through the valve.

The pressure release by-pass device 2 serves to prevent a dangerous build-up of fluid pressure in the valve cavity 4 especially in a fire situation and comprises (referring to Fig. 2) a heat intensified block 8 secured to a recessed part 9 of the body 3 by screws 10, a metal ring seal 8A being present between the block 8 and the valve, and housing a fusible by-pass plug assembly. This assembly comprises a seal spindle 11 screwed via threading 12T onto an axially movable ring member 12, the axial movement of which is maintained by dowel 12A so that a frusto-conical head 13A of the spindle forms a tight metal-to-metal seal on a seating at a by-pass port 14 of the valve, and a fusible washer 15 against which the ring member 12 is pressed. A square operating head llA of the spindle is covered by a cap 17, which is retained by screws 17A.A bleed conduit 18 leads from the port 14 to the duct 5A, i.e. to the upstream side of the valve.

In normal operation, the port 14 is closed tightly by the head 13 and the valve 1 can operate normally. However, in a severe fire situation, the washer 15 melts permitting the ring 12, carrying the spindle 11, to be pushed back by a spring 16 and a frusto-conical head 13B on the spindle 11 makes a metal/metal seal with the block 8 as shown (Fig. 3): port 14 now opens enabling pressure fluid to pass from the valve cavity 4 to the valve upstream side at duct 5A via bleed conduit 18 thereby relieving any excess pressure in the cavity due to fluid expansion.

It will be understood that the fluid pressure in the cavity 4 will be higher, due to intensified heating, than the pressure of any fluid in the duct 5A, so enabling the bleed flow via conduit 18.

A particular advantage of the device 2 resides in the fact that the spindle valve 11, 13 is simply screwed into engagement with the by-pass seating so that in normal valve operations avoidance of leakage at the by-pass is ensured, whereas on the occassion of a severe fire situation effective pressure relief in the cavity 4 is achieved by the device 2.

Claims

1. A pressure relief device for use in a fluid valve, comprising valve means settable to close a bleed ducting in the valve, and temperature responsive means causing opening of the valve means at elevated temperature conditions to permit escape of fluid from the valve cavity via the bleed ducting.

2. A device as claimed in claim 1, wherein the bleed ducting feeds back to an upstream side of a fluid valve.

3. A device as claimed in claim 1 or 2, wherein the valve means comprise a spindle valve screwed to a movable holding member whereby said valve means can be set in the closed position, and positioning means including a temperature responsive element for said spindle valve, said temperature responsibe element responding at elevated temperatures to permit movement of the holding member whereby the valve means open for fluid bleeding from the valve cavity.

4. A device as claimed in any one of the preceding claims, wherein said temperatures responsive means comprises a fusible washer.

5. A device as claimed in claim 4, when dependent on claims 3, wherein spring means are provided to bias the holding member against said fusible washer.

6. A device as claimed in caim 3, wherein the spindle valve includes a head having a first sealing surface engagable with a seating to close said bleed duct and a second opposed surface engagable with a seating on the pressure relief device in the open position of the valve means.

7. A device as claimed in any one of the preceding claims, wherein the valve means are located in a heat intensified housing.

8. A device as claimed in claim 3, wherein a head is provided on the outer end of the spindle valve and is adapted to receive an actuating tool, and a removable cover serves to enclose said head.

9. A device as claimed in any one of the preceeding claims, including fastening means for securement of the device on the body of a fluid valve.

10. A pressure relief device subtantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.