GB2080496A

GB2080496A - Heat sensitive valve

Info

Publication number: GB2080496A
Application number: GB8116238A
Authority: GB
Original assignee: US Industries Inc
Current assignee: US Industries Inc
Priority date: 1980-07-23
Filing date: 1981-05-28
Publication date: 1982-02-03
Also published as: DE3126134C2; AT392678B; FR2487474B1; JPS5747076A; IT1171383B; DE3126134A1; IT8148891A0; JPH0362948B2; BR8103905A; NL8102757A; GB2080496B; CA1172543A; ATA302881A; MX153429A; FR2487474A1

Abstract

A valve for controlling fluid flow has a reciprocable valve stem (14) settable between open and closed positions. The structure for maintaining the valve stem in a set position against fluid forces acting in the valve to move the stem to a closed (or open) position includes a fusible plug (19) through which such forces are transmitted from the stem to a fixed cap (17). The fusible plug melts on the valve reaching an excessive temperature and the fluid forces force the stem to the closed (or open) position. The cap provides an enclosure for the fusible element and in one form (Figures 1-3) is apertured to allow controlled extrusion of the melting plug preventing excessively violent release of the stem. In another form (Figure 4) the plug may extrude more readily to allow faster stem release but is keyed in the valve to prevent explosive release of the plug. <IMAGE>

Description

SPECIFICATION Heat sensitive valve This invention relates to a valve which in normal operation can be moved between open and closed positions but which, when exposed to a selected high temperature level, will automatically be moved to a selected one of open or closed positions.

In many instances, it would be desirable to utilize a valve which, under normal circumstances, could be readily opened and closed to perform its normal valving function, but upon exposure of such valve to excessively high temperatures, such as in a fire, the valve would actuate to a selected one of open or closed positions. For example, such a valve could be used in refineries, chemical plants and the like as well as in Christmas trees and flow lines in producing oil and gas wells to be automatically closed in the event of fire as a safety precaution and to prevent the fluid normally flowing through such valves from further feeding the fire. Such heat sensitive valves would thus "fail" to closed position. On the other hand, there may be instances where it would be desired for the valve to "fail" to open position in the event of fire.For example, it might be desirable to vent fluid to a flare in the event of a fire. As indicated, with either type of valve, it would be desirable to be able to utilize the valve as a normal valve during day to day operations in the sense that the valve could be readily opened and closed at will.

Many valves have been proposed which contain a fusible element which will cause some sort of response when exposed to a temperature sufficient to cause the element to fuse or melt. In one such type of valve, the fusible element continuously maintains the valve in either open or closed position until exposed to the elevated temperature at which time the valve will move to its other position. This type of valve can not be normally operated between open and closed positions but remains in one position until exposed to the elevated temperature. Another such type of valve employs a fusible element in such a manner that the valve can normally be moved between open and closed positions but, when the fusible element melts, the valve can fail only to open position. This type of valve is illustrated in U.S.

Patent No. 3,618,627 to Wagner. In addition, the fusible element as shown in the Wagner patent is located in the interior of the valve and the latter must be dismantled in order to replace the fusible element.

A very significant problem encountered in designing valves having the desired characteristics mentioned above is to provide a fail safe operation which does not involve a portion of the valve becoming a "projectile" when the fusible element melts. Illustrative of this problem is the valve shown in U.S. Patent No. 3,842,854 to Wicke. In the Wicke patent, a valve operator is shown which becomes disengaged from the valve upon melting of a fusible member. When such a valve is used in reasonably high pressure operations, e.g.

5000 psi, line pressure acting across the main valve stem will cause it to move abruptly to closed valve position when the operator becomes disconnected. This movement is so abrupt and so forceful that it causes the operator to become a projectile in effect, so that it will travel several tens of feet before it comes to rest. Obviously, this can be extremely hazardous.

To further illustrate the forces involved when high line pressures act to move a gate valve to closed position without any restraint on such movement, it has been observed that these forces can actually cause the valve bonnet to be torn from the main valve body when the gate slams against the bonnet.

It is an object of this invention to provide a heat sensitive valve operable to be moved between open and closed positions during normal operations and, upon being exposed to excessive temperatures, being operable to automatically move to the closed position or, depending upon the design of the valve element, to the open position.

Another object is to provide such a valve which, upon being exposed to excessive temperature, moves to one position under the influence of line pressure without producing any pieces or mechanisms which could act as projectiles and present a hazard to nearby personnel and equipment.

Another object is to provide such a valve wherein the fusible element is arranged in such a manner as to dampen the movement of the valve element and prevent it from slamming against the valve body or bonnet with excessive force.

Another object is to provide such a valve wherein the fusible element is exterior of the valving mechanism per se so that the element can be readily replaced and so that the valving mechanism can act in its normal manner upon melting of the fusible element.

Another object is to provide such a valve which is constructed so that after melting of the fusible element and movement of the valve to its fail safe position, it will be readily apparent to an observer that the valve is in such position.

Other objects, advantages and features of the invention will be apparent to one skilled in the art upon a consideration of the written specification, the claims and the attached drawings wherein: Fig. 1 is a view, in half-section, of a gate valve embodying this invention; Fig. 2 is a partial cross-section of the upper portion of a gate valve showing another arrangement embodying this invention; Fig. 3 is a view similar to Fig. 2 except it shows the invention applied to a non-rising stem type of valve; and Fig. 4 is still another view of an upper portion of valve showing another embodiment of the fusible element employed in the invention.

Referring to Fig. 1, there is shown a gate valve having a conventional body 10, bonnet 11, valve element 12 and seats 1 3 (only one of which is shown). Valve element 12 is connected to a valve stem 14 extending from the bonnet and slidingly sealed thereto by means, for example, of a packing 15 and a packing nut 16.

The valve as thus far described is conventional and the various described elements can take other forms as long as a valve element is provided which can be moved between first and second position to control flow through the valve body and, also, there is provided a valve stem urged outwardly of the valve body and bonnet by pressure in the valve body acting over an area equivalent to that of the stem within the seal 1 5.

An actuating means is provided for reciprocating the valve element 12 and this actuating means can be functionally divided into three portions. In Fig. 1 the first portion is illustrated as a cap 1 7 fixed to the valve bonnet 11 by a series of cap screws 18. The second portion of the actuating means is shown as a hollow cylindrical fusible element 1 9 having its upper end bearing against an inturned shoulder 20 carried by cap 1 7. The third portion of the actuating means is illustrated as a nut 21 threaded to valve stem 14 and having an outturned shoulder 22 carrying a bearing 23 which in turn engages the lower end of fusible element 19.

A conventional handwheel 24 can be connected to nut 21 to rotate it to cause reciprocation of the valve stem and valve element.

With the foregoing arrangement, it can be seen that the thrust forces developed by valve stem 14 are transmitted across fusible element 1 9 to the cap 1 7 and thence to the bonnet 11. These thrust forces will consist primarily of the force developed by the pressure within the valve body acting across an area equal to that of the valve stem 14 within seal means 15.

When fusible element 1 9 is heated sufficiently, as by a fire in the vicinity, it will melt or fuse and the force generated by internal valve pressure acting on the valve stem will cause the melted material to be extruded out of openings 25 and 26 in cap 1 7. As the material is so extruded, the valve stem and valve element will move upwardly a distance sufficient that tapered shoulder 17 on the valve stem will engage a shoulder 28 on a bonnet to stop such outward movement. These respective shoulders are, of course, located so that they will engage after the valve element 12 has been moved to valve closing position as shown in Fig. 1.

Also, the length of fusible element 19 should be at least equal to the distance the valve stem must travel to move the valve element from its open to its closed position.

As indicated above, high pressures within the valve body (e.g. 5000 psi) can act, if unrestrained, to cause the valve stem to slam violently against the bonnet. This is prevented by selecting the number and size of openings 25 and 26 to be such that the melted fusible material is extruded therefrom at a rate which is sufficiently low that the outward movement of the valve stem is dampened and the impact of shoulder 27 on the valve stem against shoulder 28 on the bonnet is of an acceptable magnitude.

Referring now to Fig. 2, the arrangement is similar to that shown in Fig. 1 except that the actuator is designed to accommodate a rotating rising stem type of valve as contrasted to the nonrotating rising stem type of valve of Fig. 1.

Elements in Fig. 2 corresponding to the elements, of Fig. 1 have been numbered with like numbers with the suffix "a" being added.

In the actuating means of Fig. ?, the nut 21 A does not rotate and is held against rotation by a pin 29 engaging a radial slot 3Q in outturned shoulder 22A. Again, the thrust forces exerted by valve stem 14A are transmitted via nut 21A across fusible element 1 9A to cap 1 7A and thence to the bonnet 11 A. Thus the valve is susceptible of operation between open and closed positions by simply rotating handwhee!?4A. However, when the fusible element 1 9A melts, the pressure internally of the valve will again force the valve stem upwardly to close the valve. Of course, fusible element 1 9A is made iong enough so that when it is melted, the valve stem can move the valve element to its closed position.

Fig. 3 shows yet another arrangement of an actuating means wherein valve stem 148 is threaded to nut 21 B which is sealed to the bonnet by seal 1 5B. The thrust forces of valve stem 1 4B are transmitted by nut 21 B to the fusible element 1 9B and thence via cap 1 7B to the bonnet 11 B.

Reciprocation of the valve stem 1 4B is had by rotating handwheel 24B which in turn rotates nut 21 B. Endwise movement of the nut is prevented by capturing shoulder 22B between bearings 23B and 35. The operating principle of the actuating means of Fig. 3 is the same as the other actuating means in that upon melting of the fusible element 19B, the nut and the valve stem are moved outwardly under the influence of pressure within the valve body as the fusible element 1 9B is melted. Here again, the rate of outward movement is controlled by the number and size of openings 25B in the cap. Also, the length of shaft 21 B below, packing 1 5B is longer than the distance the shaft will move outward upon melting of the fusible element.

Referring to Fig. 4, there is shown an actuating means for a rising stem type of valve permitting relatively rapid movement of the valve stem upon melting of the fusible element. In this illustration, the first portion of the actuating means comprises the sleeve 50 mounted for rotation within the cap 51 by bearings 52 and 53 which capture outturned flange 54 therebetween. The hub of 55 of the handwheel 24C is also a part of the first portion and bears against fusible element 21 C.

the latter, of course, is the second portion of the actuating means. The third portion of the actuating means is the threaded upper end 86 of , valve stem 1 4C which has a threaded connection to the fusible element.

With this arrangement, it will be seen that rotation of the handwheel will also rotate cap 57 and fusible element 21 C to cause the latter to reciprocate the valve stem. The thrust forces involved in reciprocating the valve stem are transmitted from the latter to the fusible element, then to cap 57, hub 55, sleeve 50 and cap 51 to bonnet 11C.

When a fire or other elevated temperature condition heats the fusible element 21 C, it will loose its compressive strength and resistance to shear to a point where the outwardly directed force on the valve stem will cause the fusible element to shear in the vicinity of line 58. As a result, the valve stem can move rapidly upwardly carrying with it the sheared off plug of material still engaging the threads of the valve stem. This latter engagement prevents the sheared plug from acting as a projectile.

It will be noted in Fig. 4 that the fusible element has a conical outer surface 59 mating with a corresponding conical surface 60 on the inside of cap 57. As the valve stem applies an upward force against the fusible element, there will be a wedging action due to the conical arrangement to cause the fusible element to be thrust into tighter engagement with the threads on the valve stem.

As a result, if the material or the fusible element has any cold flow properties, such can be accommodated while maintaining the fusible element in proper threaded connection to the valve stem.

In general, the fusible elements can be made from materials which have physical properties suitable for undergoing the stresses and strains inherent to the normal operation of the valve. In addition, such material should have a softening or melting point which will permit the valve to be closed when the temperature in the vicinity of the actuating mechanism reaches a level selected by the designer of the valve. Ordinarily this level will be temperature within the range of 3000 to 4000for ambient service of the valve but can be higher or lower. An example of a preferred of one of such materials is an acetal resin marketed under the trade name Delrin. Other materials which can be used are nylon-6/6 marketed under the name Zytel, a polycarbonate marketed under the name Lexan, Noryl which is a modified polyelyphene oxide and Texin which is a polyurethane. Also, there are a family of lower melting point metal alloys which can be used including 30/70 bar solder, Woods metal, etc.

It will be understood that each of the objects of the invention stated hereinbefore refers to the invention as realised in one or more of the embodiments that have been described, and not necessarily as claimed.

Claims

1. In a valve wherein a valve element is reciprocated in a valve body assembly between inner and outer by an actuating means connected thereto; seal means providing a sliding seal between said actuating means and said body assembly; said actuating means having first, second and third portions with the first and third portions being connected respectively to the body assembly and the valve element and the second portion being a heat fusible element having connections with said first and third portions and normally transmitting valve opening and closing forces therebetween but when melted permitting the third portion to move outwardly with respect to the first portion under the influence of pressure in said body assembly sufficiently that the valve element can move to its outer position, the connections between the first and third portions and the body assembly and valve element being such that these portions remain so connected after the second element has melted.

2. The valve of claim 1 wherein the first portion includes a cap having an endwise shoulder, the third portion includes a rotatable nut having an endwise shoulder and wherein the fusible element is disposed between said shoulders to maintain them normally spaced apart and when the fusible element melts, allowing one of the shoulders to move toward the other.

3. The valve of claim 2 wherein'the cap surrounds the fusible element and has an opening therethrough restricting the rate of flow of the melted fusible element therethrough to limit the rate of movement of one shoulder toward the other.

4. The valve of claim 1 wherein the first portion includes an endwise shoulder, the third portion includes an endwise shoulder and a non-rotatable nut with a rotatable valve stem threaded thereto and connected to the valve element, and wherein said disposed element is designed between said shoulders to maintain them spaced apart and when the fusible element melts, allowing one of said shoulders to move toward the other.

5. The valve of claim 4 wherein the first portion surrounds the fusible element and has an opening therethrough restricting the rate of flow of the melted fusible element therethrough to limit the rate of movement of one shoulder toward the other.

6. The valve of claim 1 wherein the third portion is a valve stem and the second portion is non-rotatably connected to the first portion and the fusible element thereof has a threaded connection with the valve stem to transmit reciprocal movement to the stem when rotated and disconnecting the first and third portions when melted.

7. In a valve wherein a valve element is reciprocated in a valve body between valve open and valve closed positions by an actuating means attached thereto; seal means providing a sliding seal between said actuating means and said body assembly; said actuating means including a heat fusible element located outwardly of said seal means and arranged to transmit the force developed by said actuating means to reciprocate said valve element and when melted, to permit pressure within the valve body to move the valve element to one of its positions while maintaining said seal means effective to prevent escape of fluid from the valve body and while also maintaining the balance of the actuating means in position on the body assembly.

8. In a valve wherein a valve stem has a sliding seal with a valve bonnet and is connected to a valve element to move the same in a valve body between open and closed positions and wherein pressure within the valve body can act against an effective area on the stem or valve element to cause the same to move outwardly of the valve bonnet to move the valve element to one of its two positions, in combination therewith:: a nut having a threaded connection with the valve stem such that rotation of one of the nut or stem in one direction applies a force to the stem to open the valve and when one of the nut or stem is rotated in an opposite direction a force is applied to ciose the valve; means for so rotating one of the nut and stem and for linking the nut to the valve bonnet including a heat fusible element arranged to transmit the force applied to the stem or to the bonnet during normal operation of the valve, said element being of sufficient length so that when melted, the valve stem is permitted to move outwardly of the body under the influence of the pressure within the valve to position the valve element in one of its valve open or valve closed positions.

9. The valve of claim 8 wherein the nut is rotatable with respect to the stem and bonnet and wherein the fusible element is disposed about the nut and has an endwise force transmitting connection thereto and wherein the linking means also includes a cylindrical cap connected to the bonnet and having an endwise force transmitting connection to the other end of the element so that valve opening and closing forces are transmitted across the fusible element.

10. The valve of claim 9 wherein said cap closely surrounds the fusible element and has openings therethrough restricting flow of the material of the fusible element when the latter melts to thereby limit the velocity with which the valve element moves upon melting if the fusible element.

11. The valve of claim 8 wherein the nut is nonrotatably connected to the bonnet and wherein means are provided for rotating the stem, the nut having a first endwise facing shoulder, the linkage means including a cap connected to the bonnet and having a second endwise facing shoulder and wherein said fusible element is disposed between said shoulders to transmit forces therebetween.

12. A valve substantially as hereinbefore described with reference to any one of Figures 1 to 4 of the accompanying drawings.