AU621292B2 - Method of forming a thermally activated pressure relief valve - Google Patents

Description

mlmm

AUSTRALIA

Patents Act 621 2 ('OM PLETE SPECIFICATIONI

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: .:Priori ty *:Related Art: 0 APPLICANIrS REFERECE: US 043,830 Name(s) of Applicant(s): Aluminum Company of America Addesses)of Applicant(s): 1501 Alcoa Building, Pittsburgh, Pennsylvania 15219, UNITED STATES OF AMERICA.

o~Address for Service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Hark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the Invention entitled; MHODi1I OF FORMING A THERMALLY ACTIVATED PRESSURE RELIEF VALVE our Ref 91840 POF Code;o 1422/33194 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/1-1 1 THERMALLY ACTIVATED VALVE This invention relates to a thermally activated valve for attachment to a pressure vessel which can provide an outlet for the pressurized substance once a predetermined temperature value is reached, and to a ccmbination thermal or pressure activated relief valve, and to a method of forming a thermally activated pressure relief valve.

Pressurized containers such as compressed gas containers are normally equipped with temperature or pressure activated valves. Once the pressure within the container rises iiabove a predetermined value, the pressure activated valve will open to allow the internal gas to escape. Such containers can S* also be subjected to extreme heat, either through the action of a fire or otherwise, and the pressure within the container can **see: increase as the temperature increases. If the gas is not allowed to vent, the pressure can build until the stresses exerted on the inside walls of the container exceed the strength of the container itself. At this point, the cylinder could rupture explosively releasing the contents and potentially some shrapnel.

In the case of a fire, it is possible that the pressurized gas stored within the container can be heated to an extreme temperature very quickly, causing the montainer to explode even though the pressure activated valve has opened. The reason for this is that the gas cannot escape fast enough to prevent an explosion. Also, for some partially filled aluminum cylinders, the walls of the cylinders can soften and rupture even when the r pressure within the cylinder is below the relief setting on tt pressure activated valve.

Most pressure vessels are equipped with a relief valve to prevent catastrophic rupture in case of excessive temperature or pressure. Should the pressure vessel be in a fire, it is possible that the volume of liquid or gas contained therein '.-ll increase rapidly and reach a situation where the pressure is higher than it was at room temperature. For cylinders constructed of aluminum, Kevlar or plastic, this can pose a very critical problem. As the temperature increases, the material of which the container is constructed tends to stretch, soften or 'Ieaken and thereby is unable to hold the pressure for which the y..essel was designed.

ij To avoid such catastrophic failures, various types of ':"*.safety relief valves have been invented. U.S. Patents 2,040,776; 3,472,427; and 4,059,125 teach three different types of relief S'.*valves having a fusible material which can be ejected under 0'.*.'extreme temperature or pressure conditions. U.S. Patent S*:*4,352,365 teaches a safety valve which can be activated by either pressure or temperature. One drawback of these valves is that S the fusible material tends to extrude out of the bore after a .relatively short period of time. Such extrusion can cause leakage and premature failure of the valve itself. Other U.S.

patents of interest include: 1,211,173; 1,303,248i 1,876,938; 1,984,375; 2,020,075; 3,554,227; 4,335,734; 4,407,432; and 4,506,423. However, some of these devices have proved costly to manufacture and some are ineffective at high temperatures over long time periods.

Some of these valves use a fusible metal positioned within a narrow passageway which is design to melt at a predetermined temperature and be blown out by the pressure of the substance contained within the pressurized cylinder. One of the drawbacks with using a fusible metal is that when the valve is assembled a number of voids can occur within the passageway filled with the fusible metal. These voids shorten the life of the valve by allowing the fusible metal to extrude into the voids, thereby creating possible leaks. If the device is a combination rupture disc/fusible metal device, the

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voids may minimize support of the disc and lead to premature failure. The presence of any foreign minatter trapped within the fusible metal can also create a problem in that the relief valve is designed to release at a certain temperature or pressure, If *e Sforeign matter is present, the valve could release prematurely thereby minimizing its usefulness.

It can also be appreciated that a relief valve which opens at a certain pressure value gives some protection against overheating of the cylinder itself. However, under certain conditions, such as a partially filled cylinder or a cylinder made from a material which undergoes a relatively rapid decay in its tensile strength or other physical properties with increasing -3i -aL temperature, a pressure responsive valve may not be sufficient to relieve the pressure before the stresses induced in the cylinder exceed the r commended value.

Because of this, it is advantageous to employ a relief valve which has both a temperature and pressure sensing mechanism which are independent of each other.

Of the above patents, U.S. 4,352,365, issued to Boccardo et al, addresses the issue of providing both a temperature and pressure activated relief valve. However, Boccardo discloses a valve which uses a common outlet for releasing the pressurized fluid, while an embodiment of the present invention provides for two separate passageways which can allow for quicker venting.

The present invention provides a thermally activated .i 15 valve which essentially prevents a fusible material from extruding out, and a method of forming such valve.

According to the present invention there is provided a thermally activated valve comprising: a) a body having an inlet and an outlet in fluid communication with each other, said inlet adapted to be attached to a pressure source with said outlet communicating with an area having a lower pressure value than said pressure source, with said outlet having an internal bore which has an inner periphery; 25 b) an insert having an outer periphery, said insert being secured in said outlet through a portion of said outer periphery being fastened to a portion of said inner periphery, said insert having a helical groove in its outer periphery, the helical groove in co-operation with said inner periphery forming a helical passageway which provides a flou path between said inlet and sai outlet; and c) mate.ial means for normally blocking fluid flow through said k alical passageway and being fusible at a selected temperature to permit fluid flow from said pressure source to said area having a lower pressure value.

The invention also provides a method of forming a thermally activated pressure relief valve comprising the steps of: 4 1 r a) providing: 1) a body having an inlet and an outlet in fluid communication with each other, said inlet adapted to be attached to a pressure source with said outlet communicating with an area having a lower pressure value than said pressure source, with said outlet having an internal bore which has an inner periphery; and 2) an insert having an outer periphery, said insert being secured in said outlet through a portion of said outer periphery being fastened to a portion of said inner periphery, said insert having a helical groove in its outer periphery, the helical groove in co-operation with said inner periphery forming a helical passageway which provides a flow path between said inlet and said 1 5 outlet; b) introducing a molten fusible material into said helical passageway; c) exerting a force on said fusible material to cause movement of said material through said helical passageway thereby displacing any air or gas trapped therein and filling said passageway; and d) allowing said fusible material to solidify.

Briefly, the present invention relates to a thermally activated valve for attachment to a container 25 which houses a presurized liquid or gas. The valve is designed to open at a selected temperature and allow the pressurized substance to be released to the atmosphere or a lower pressure area thereby preventing rupture of the container. The thermally activated valve includes a body having an inlet and an outlet in fluid communication with each other. The inlet is attached to the container while the outlet is in communication with the atmosphere or a lower pressure area. An insert is secured to the outlet and includes a stem having a helical groove formed in the outer periphery thereof. The insert co-operates with the bodr to form a helical passageway. A fusible material is positioned within the passageway for normally blocking fluid flow therethrough. At a selected temperature, the material becomes fusible thereby opening the passageway to 4. 4 -5 permit the pressurized substance to be released.

Preferably, the outlet opening of the insert is smaller than the helical passageway thereby causing the fusible material to exhibit shear deformation which inhibits expulsion.

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An eibodiment of the present invention relates to a ccbination thermal or pressure activated relief valve for use on a pressurized container. The valve includes a housing having an inlet and an outlet portion separated by a wall. The wall is provided with a central passageway and at least two radially offset passageways which connect the inlet to the outlet by fluid communication. The inlet side of the housing is adapted to be attached to a pressure source such as a pressurized cylinder while the outlet communicates with the atmosphere or with an area having a lower pressure than said pressure source. An insert is e.

secured in the outlet and has a central passage formed S. therethrough which is axially aligned with the central passage formed in the housing. The insert also has a helical groove formed in its outer periphery which cooperates with the housing to form a helical passageway which fluidly communicates with the offset passageways formed in the housing. A fusible material is inserted into the helical passageway and normally blocks fluid flow therethrough while being fusible at a selected temperature to permit fluid flow from the pressure source to the lower pressure area. The helical passageway provides a separate te independent passage for relieving pressure within the pressurized *05 container when the material of which the container is constructed is subjected to an excessive rise in temperature.

-6i i ~i i I 1 In said embodiment of the invention, the valve also includes a second member which is secured to the insert and has a passage formed therethrough. The passage can be axially aligned with the central passage formed in the insert and provides fluid communication between the pressurized container and an area of lower pressure, such as the atmopshere. A pressure responsive lamina is positioned across the passage of the second member to normally block fluid flow therethrough and is designed to be rupturable in response to a selected pressure arising inside the container to permit the pressure to be released. The passage formed in the second member provides an independent passage to relieve excessive pressure from the container should the internal pressure within the container exceed a predetermined limit.

Also provided according to the present invention is a method of forming a thermally activated pressure relief valve which is designed to be used with a pressurized cylinder. The thermally activated pressure relief valve will be activated by excessive temperatures such that the pressurized substance within the container can be released before the cylinder catastrophically -7i ;61 ruptures. The valve includes a body having an inlet and an outlet which are in fluid communication with each other. The valve also contains an insert having a helical groove formed about its outer periphery.

The method includes securing the insert in the outlet so that the helical groove cooperates with the body to form a helical passageway. A molten fusible material is then introduced into the helical passageway while a force is exerted on the material to cause its movement therethrough. This force can either be a vacuum which causes the material to be drawn through the passageway or it could be a centrifugal force which pushes the material through the passageway. By exerting a force on the molten fusible material, the material can be drawn or pushed into and through the helical passageway, thereby displacing any air or foreign matter trapped therein. When a vacuum is applied to the material, a porous filter is used to allow air to escape from the vacuum side of the passageway while stopping the movement of the material itself. In the case of centrifugal force, a plug is used to block off one end of the passageway and the material is eos forced outward toward the plug. As the material flows outward toward 1dto plug, any trapped air, gas or fluxing residue will be S0. 6 displaced and can escape out of the entrance through which the molten material is entering. Once the passageway is completely filled, the molten material is allowed to cool and solidify.

-8- L -11- In the accompanying drawings: Fig. 1 is an assembly view of a pressurized cylinder having a flow control valve attached thereto which incorporates the thermally activated valve of this invention.

Fig. 2 is an exploded view of a the. activated valve.

Fig. 3 is an end view taken along line 3-3 of Fig. 2.

Fig. 4 is a sectional view taken along line 4-4 of Fig. 2.

Fig. 5 is a cross-sectional view of the assembled thermally activated valve showing the helical passageway blocked *0 by a fusible material.

Fig. 6 is an alternative embodiment of the insert ,having a groove formed therein with at least one 90° angular bend formed along its length.

Fig. 7 is still another embodiment of the insert S showing a helical groove formed at a desired angle.

0o Fig. 8 is still another embodiment of the insert showing a helical groove terminating into an axial groove segment adjacent the head end of the stem.

Fig. 9 is a cross-sectional view of a portion of the helical groove showing a rectangular cross-sectional configuration.

Fig. 10 is a cross-sectional view of a portion of the helical groove showing a semi-circular cross-sectional configuration.

-9- Fig. 11 is an alternative embodiment of the thermally activated valve showing the insert press fitted into the body and having the helical groove intersecting a circular groove formed about the insert.

Fig. 12 is a cross-sectional view taken along line 12-12 of Fig. 11 showing the circular groove.

Fig. 13 is a perspective view-of a combination thermal or pressure activated relief valve.

Fig. 14 is a cross-sectional view of the thermal or pressure activated relief valve shown in Fig. 13 taken along the line 14-14.

Fig. 15 is an end view of Fig,14 taken along the line 15-15.

Fig. 16 is a partial cross-sectional view of an alternative embodiment of the combination thermal or pressure S activated relief valve showing a pressure responsive lamina being an integral part of the cap.

Fig. 17 is an assembly view of a thermally activated Spressure relief valve and filling assembly.

Fig. 18 is a cross-sectional view taken along line 18-18 of Fig 17 and shows the internal helical passageway.

Fig. 19 is an exploded view of the thermally activated pressure relief valve and filling apparatus.

Fig. 2Qis a perspective view of a centrifuge holding six thermally activated pressure relief valves.

Fig. 21 is a schematic depiction of the thermally activated pressure relief valve and filling apparatus being rotated at an angle theta between a vertical orientation and a horizontal orientation.

Fig. 22 is a cross-sectional view of a thermally activated pressure relief valve and filling apparatus using a vacuum to draw a molten fusible material through the helical passageway.

.4 Referring to Fig. 1, a pressure vessel 10 is shown having a flow control valve 12 attached to an end thereof. The pressure vessel 10 can be a pressurized cylinder constructed of materials such as aluminum, Kevlar, plastic or other material subject to thermal degradation. The vessel 10 is designed to store or contain a pressurized liquid or gas, for example I hydraulic fluid, natural gas, industrial gas, nitrogen, oxygen, etc., at a specific service pressure. A service pressure of at least 3,000 psig at 70*F when fully loaded is a maximum standard for some industrial gases. Preferably, the vessel 10 can hold a I pressurized substance at 12,000 psig at ambient temperature and -11up to 6,000 psig at 180 0 F with a useful life of at least months. Today there are numerous uses for high pressure cylinders to store gases for industrial and medical uses, and specialty gases used to power vehicles, for beverage dispensers, for aerospace applications and for use on oil rigs.

The flow control valve 12 contains an outlet 14 as well as internal valving and passageways (not shown) which permits a substance stored within the pressure ve. il 10 to be expelled to the atmosphere or to an area or chamber having a lower pressure value. The flow control valve 12 can also contain an internal structure which permits a thermally activated valve 16 to be attached thereto. The thermally activated valve 16 can be :directly attached to an end of the pressure vessel 10 if desired.

Referring to Fig. 2, the thermally activated valve 16 has a body 18 with an inlet 20 and an outlet 22 formed therein.

The inlet 20 is preferably a bore having a screw thread 24 formed about its inner periphery. The screw thread 24 permits the body 18 to be threaded onto the vessel 10 or onto a flow control valve 12. In either case, the inlet 20 will be in fluid communication with the interior of the pressure vessel 10. The outlet 22 is in communication with the atmosphere or an area or chamber having a lower pressure value. The outlet 22 can be in the form of an internal bore which has a screw thread 26 formed about its inner periphery. The body 18 further contains a wall 28 which has at least one, and preferably two or more, small apertures 30 formed therethrough which fluidly connects the inlet 20 with the outlet 22. The apertures 30 can have a-cross-sectional area which is -12substantially less than the cross-sectional area of the outlet 22 if desired.

An insert 32 is designed to be secured within the outlet 22 of the body 18. As shown, the insert 32 contains an elongated stem 34 having a head 36, which can be an enlarged head, formed on an end thereof. The stem 34 contains an external screw thread 38 which is formed along a portion of its length which is designed to mate with the screw thread 26. However, in place of the screw threads 26 and 38, it is possible to press fit the insert 32 into the outlet bore 22 or to secure it in place by means of an adhesive or by using another type of mechanical fastener. Also formed in the stem 34 is a helical groove which extends below the root of the screw thread 38, The helical groove 40 preferably extends from an inner end 42 of the stem 34 to a point 44 located adjacent to the head 36. At the point 44, at least one, preferably two, and most preferably four or more small apertures 46 are formed through the head 36 which cooperate with the helical groove 40 to provide a through passageway. The greater portion of the passageway 48 iI helical in configuration and has a circular arc of at least 360°, preferably 720° and more preferably greater than 720°. It is also possible to form the helical passageway 48 in a solid body and avoid the use of the insert 32. In such a case, the body and passageway can be cast formed.

It should be noted that the apertures 30, which are formed in the body 18, can be the same size and can be arranged in the same configuration as the apertures 46 formed in the -13- 3 i I I 1L insert 32. In Fig. 3, four apertures 46 are shown arranged in a similar fashion to the arrangement of the apertures 30 shown in Fig. 4. The only limitation in this regard is that at least one and preferably all of the apertures 30 are in alignment with a portion of the helical groove 40. This will assure that the passageway 48 provides a flow path through the body 18 such that a liquid or gas contained within the pressure vessel 10 can be released once the passageway 48 is opened.

Referring to Fig. 5, the thermally activated valve 16 further contains a fusible material 50 which is deposited in the apertures 30 and 46 as well as in the helical groove 40 such that the entire helical passageway 48 is blocked off. The fusible material 50 can be a white lead or a fusible eutectic alloy having a melting point at a particular temperature or within a particular temperature range. Such fusible alloys are supplied by Cerro Metal Products, a division of the Marmon Group, Inc., P.

0. Box 388, Bellefonte, Pennsylvania 16823. The fusible alloys 0) normally include bismuth and antimony which are mixed with lead, tin, cadmium or indium. The eutectic alloys have the unique characteristic of having a melting temperature which coincides with their freezing temperature or, stated another way, there is no freezing range between liquidus and solidus. It is also possible to use a synthetic resin such as fluoride-containing polymers, nylon, etc. as the fusible material Experimentation has shown that for use in an aluminum cylinder, it is preferable to use a fusible material 50 having a melting point above 200 0 F, preferably at either 212*F or 217*F.

-14t- Referring- to Fig. 6; an alternative designed insert 33 is shown having a stem 34 with a step-shaped groove 52 formed therein. The step-shaped groove 52 has at least one angular bend formed along its length which is depicted by the angle alpha Although alpha is shown as a 90° angle, it can be any angle between 0* and 1800. The angular turn or bend assists in preventing extrusion of the fusible material 50 from the groove 52 over extended periods of time.

Referring to Fig. 7, another insert 35 is shown wherein the stem 34 has a groove 54 formed therein. The groove 54 is cut at an angle of either less than 400 or more than 55*, preferably greater than 65*, as measured relative to a longitudinal centerline. This angle, represented by the symbol theta has been found to be advantageous in prolonging the period of time it takes for the fusible material 50 to extrude out of the groove 54.

Referring to Fig. 8, still another insert 56 is shown

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S having a stem 58 which is only partially threaded at 60. By only partially threading the insert 56 the cost of producing it can be substantially reduced. The insert 56 also has a helical groove 62 formed therein which hai an axially oriented segment 64 formed along its length. It should be noted that although three alternative embodiments have been depicted herein, it is possible that other embodiments can also be utilized.

Referring now to Figs. 9 and 10, the helical groove can have a cross-sectional configuration which will assist in reducing extrusion of the fusible material 50. In Fig. 9 the i6 L I I helical groove 40 is shown having a rectangular cross-section while in Fig. 10 the helical groove 40 is shown having a semi-circular cross-section The surface of the helical groove 40 can also be roughened or coated with a material so as to cause it to be coarse. Such roughness or coarseness will assist in holding the fusible material 50 within the helical groove 40 thereby prolonging the period of time before extrusion will occur. It should also be noted that extending the length of the helical passageway 48 will also increase the force needed to extrude the fusible material ;Referring now to Figs. 11 and and 12, an alternative thermally activated valve design 66 is depicted having a body 68 with an inlet 70 and an outlet 72 formed therein. Both the inlet 70 and the outlet 72 are in fluid communication with each other.

Press fitted into the outlet 72 is an insert 74 having an elongated stem 76 with a head 78 formed at one end. Formed about the circumference of the stem 76 is a tapered helical groove having its head end communicating with an inner end 82 of the insert 74. The helical groove 80 can be tapered along only a portion of its length if desired and the taper can range from 1 to 30°. An opposite or narrow end 84 of the groove 80 intersects a circular groove 86 formed about the outer periphery of the stem 76. The circular groove 86 is located adjacent to the head 78 and provides an opening such that a substance stored within a pressure vessel can be released. Preferably, the circular groove 86 is aligned perpendicularly to the helical groove 80 and has a smaller cross-section than that of the helical groove 80. -It is -16i I possible for the cross-section of the circular groove 86 to be equal to or larger than that of the helical groove 80 but in these configurations the shear deformation of the fusible material 50 may not be as great.

Referring to Figs. 13and 14 a combination thermal or pressure activated relief valve110 is shown. The relief valve110 includes a housing or body112 which can be constructed of an easily machinable material such as brass. The housing112 has an inletll4 and an outletll6 formed therein which are separated by a 'wallil8. The wall118 contains a central passageway120 which is .surrounded by at least one and preferably two or more radially offset passagewaysl22. Fig.15 shows four passageways122 formed in the wall118. The purpose of the passages120 and122 will be explained below.

The inlet114 is shown having an internal thread124 "formed about its inner periphery. The thread 24 provides a means oo of attachment to a pressure source, for example, a pressurized cylinder (not shown). It should be noted that the inlet114 can be fastened to the pressurized cylinder by other known means as well. The outlet 16 communicates with the atmosphere or with an area having a lower preure value than said pressure source.

area having a lower pressure value than said pressure source.

-17- I I An insert126 is secured in the outlet116. The insert 126 includes an elongated threaded stem128 having a head130, preferably an enlarged head, formed on one end and a central passagei32 formed completely therethrough. The central passage 132 communicates with and preferably is in axial alignment with the central passagel20 formed in the housing112. The passages andl32 can have the same cross-sectional diameter and configuration if desired so as to facilitate fluid flow. The term "fluid flow", as used throughout this application, refers to pressurized liquid, gas or powder substances which may be contained within a pressure vessel.

The stem128 has a helical groove134 formed in its outer *0 S S. periphery which cooperates with the housing112 to form a helical passageway136 which fluidly communicates with the offset S passageways122 formed in the wall18. It is also possible to form the helical passageway136 in a solid housing and avoid the S use of the insertJ26. In such a case, the housing and passageway can be cast formed.

For ease of manufacture, the offset passageways22 should be in axial alignment with the end of the helical .".passageway 36 and each one should have a smaller cross-sectional S area than the helical passagewayi36. More preferably, the combined total cross-sectional area of all of the passagewaysl22 will be less than or equal to the cross-sectional area of the helical passagewayl36. The housingll2 is provided with at least one and preferably two or more outlet ports138 which are aligned perpendicularly to the helical passageway136. The outlet ports -18- 138 should have a cross-sectional area which is less than or equal to the cross-sectional area of the helical passagewayl36. The reason for this will be explained below.

A molten fusible materiall40 is inserted into the helical passageway136 and also occupies the passageways122 andj38 formed in the housing112. The fusible material 40 normally blocks fluid flow through the helical passageway 136 while being fusible at a selected temperature to permit fluid flow from the pressure source to the lower pressure area. The fusible material 140, which can be white lead or a eutectic alloy, can have a melting temperature which coincides with its freezing 0O temperature. The fusible material140 will have a melting point in the range of between 150* and 300*F, preferably between 2000 and 230 0 F, with a temperature of 2120 or 217*F being optimum.

Such fusible material140 is available from Cerro Metal Products, a division of The Marmon Group, Inc., P.O. Box 388, Bellefonte, Pennsylvania 16823.

Presently, the life of a pressure valve using a fusible material 140 is shortened by the fact that the fusible material240 tends to extrude out of its passageway over a period of time because of the internal pressure acting upon it. Experimentation has shown that by making the offset passageways122 and the outlet

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ports138 of a small cross-sectional area, the time period over which extrusion takes place can be extended. The reason for this is that even though the pressure acting against the fusible material140 is the same regardless of the cross-sectional size of the passageway122, by using a plurality of smaller openings, one -19- 1_ can reduce the absolute force exerted on the fusible By reducing the force acting on the fusible materiall40, it has been found that it will take a longer period of time to extrude the materiall40 from the passageway122. Experimentation has further proved that the helical passageway136 provides increased resistance to extrusion. This resistance can also be increased by roughening the surface such as by chemical etching or by using a coating so as to create more resistance.

As noted earlier, the helical passageway 36 is perpendicularly aligned to the outlet ports 138 such that the fusible material,140 has to make a right angle turn in order to be extruded. This right angle turn, in addition to the fact that i the ports138 have a smaller cross-sectional area than the helical passageway136, tends to increase the forced shear deformation which the fusible material 140 must experience in order to be displaced outward. Experimentation has shown that when the fusible material 140 exhibits forced shear deformation against itself that it will take a longer period of time before it will extrude, This design can substantially add months and in some instances years to the useful life of a relief valve.

The thermal or pressure activated relief valvell0 further includes a cap142 which is adapted to be secured to the insert126. As shown in Fig. 14, the cap 3I2 includes a threaded bore44 which engages a helical thread 16 formed on the exterior of the head 30. The cap 42 has a central passage 48 formed therethrough which is in axial alignment with the central passages 132 and120 formed in the insert126 and the housing.112, i i, i respectively. Preferably, the central passage14 8 will have a cross-sectional area at least equal to and preferably greater than the cross-sectional area of the passageJ 3 2 The central passagel48 cooperates with the passagesl20 and132 to provide fluid communication between the pressure source and the lower pressure area. Should the pressure within the cylinder rise above a predetermined value, the pressure will be able to be relieved or vented through the opening formed by the 132 and148. Since the thermal or pressure activated relief valve 110 is designed to be attached to a pressurized cylinder, it is advantageous to disperse the pressurized fluid in a radially outward manner so as to prevent the force of the relieving substance from knocking over the pressurized cylinder. In this S* regard, it is advantageous to utilize at least two and preferably S a plurality of radially aligned passagesl50 which are formed in the cap142. The passagesS50 enable the vented pressure to be dispersed in a number of different or opposite directions.

A pressure responsive lamina152 is positioned across the central passageway148 and serves to normally block fluid flow therethrough while being rupturable in response to a selected pressure arising inside the cylinder to permit fluid flow through 05 the passageway14 8 Such rupturable discs are commercially available from Superior Valve Company of Washington, Pennsylvania. Normally, the lamina 152 is constructed of a metal alloy such as rolled nickel, nickel-copper or Inconel. The pressure responsive laminal52 can be a separate member as shown -21-

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i Fig. 14or it can be an integral memberJ52' formed with a cap 154 as is shown in Fig.16.

A washerl56, preferably made of copper, brass or some other malleable material, is positioned between the insert126 and the pressure responsive lamina152 to provide a seal therebetween.

In safety relief valves, it is important that leakage be prevented between adjoining parts for it could adversely affect the operation of the valve itself. In the alternative embodiment of Fig. 16 the disc can be sealed in place without a washer and this can be accomplished by precisely machining the interconnecting parts or by using an adhesive.

Referring again to Fig. 14, a gasketl58 is also utilized between the housingll2 and the insert26 at the junction of the wall18. The gasketl58 is in the form of a ring with a central :ee opening to allow fluid flow through the central passages120 and 132 while preventing pressure leakage from the central 0* into either the offset passageway122 or the helical passageway S" 136. By providing independent passages for venting the.pressure, should either a temperature or pressure rise occur, the valvell0 has the unique feature of providing visible evidence at a later time of which type of problem occurred. For example, should the pressurized cylinder have been exposed to a very high heat condition, the fusible materiall40 would extrude out and the pressure would escape through the helical. passagewayi36. At a later time, an operator inspecting the cylinder and the could quickly determine that it was heat which caused the venting and not excessive pressure. The indepeendent passageways further -22in I I no~~ I facilitate venting in a situation such as a fire wherein both thetemperature of the cylinder as well as the internal pressure would cause their respective passageways to open, The use of two independent passageways will assist in venting the substance more quickly and thereby minimize, if not eliminate, ;he chance of a catastrophic rupture of the pressurized cyUlinder, Once again referring to Fig. 14, the ianert26 can contain an outer surfacei60 with a seat-62 formed thereon which will serve to sandwich the washer156 against the pressure responsive lamina152. The seat262 cooperates with the washer!56 to assure that an adequate sealing surface occurs. The seat162 can also reduce the cost of manufacturing the valvellO because it eliminates the need to maintain critical tolerances between two mating curfaces.

Referring to Fig. 17, a thermally activated pressure relief valvec1O is shown having a filling apparatus22 secured to it. As best seen in Figs. 18 and 19 the thermally activated pressure relief valvel10 includes a body,14 having an inlet1l6 and an outlet2.8 formed therein. The inlet2l6 and the outletZ18 e are fluidly connected by at least one and preferably two or more small aperturesI20 which can be arranged in a circular configuration. The inlet216 and the outlet118 are shown as bores having internal screw threads122 andI24 formed about their inner -23-

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0 to: 00: a a 0 peripheries. An external portion26 of the body..14 also contains a screw threadX28. It should be noted that other types of fastening means can be utilized in place of the screw threads, such as using a press fit between the parts.

The thermally activated pressure relief valve210 further includes an insert230 having an elongated steZ32 and a head34 formed on an end thereof. The outer periphery of the stem32 contains a screw thread%36 and has a helical groove38 formed therein. The bottom of the groove.38 extends below the root of the screw thread236 and the cross-sectional configuration of the groove can vary. Either a rectangular or semi-circular cross-sectional configuration is preferred since those are the easiest to machine. The head34 contains at least one and preferably two or more small apertures 40 formed therethrough.

The apertures 40 can be arranged in a circular configuration and are designed to intersect the helical groove 38 formed in the stem'32. The cross-sectional area of the apertures220 and2.40 should be less than the cross-sectional area of the helical groove238.

-24i I When the insert230 is inserted into the outlettl8 of the body214, the helical groove238 cooperates with the bodyZ14 to form a helical passageway142 which communicates with the apertures320 and240. This helical passageway42 provides an avenue of fluid communication between the inletl16 and the outlet 118. In normal use, the inlet216 is adapted to be attached to a pressure cylinder or container and is in fluid communication with a pressurized substance contained therein. The pressurized substance can be a liquid, powder or gas. The outlet218 of the S relief valve210 is normally opened to the atmosphere, although it may have a tube or hose connected to it so as to direct the pressurized fluid away to an area or chamber having a lower pressure value than that present in the cylinder.

One method of forming the thermally activated pressure relief valve10 is to secure the insert230 into the outlet.8 so I* that the helical groove.38 cooperates with the bodyll4 to form the helical passagewayS)42. Before doing this, it is advantageous to clean the bodyA14 and the insert'30 to assure the removal of any foreign matter, especially in the helical groovel38. This 9.* Scan be done ultrasonically or chemically. Once cleaned, it is advisable to submerge the parts in a rinse solution, such as acetone, and then air dry. A flux can be applied to either the r body1l4 or the insert230, or both, so as to assure that when they are assembled there will be no openings that could later provide a path for gas to leak out. This is particularly useful when the relief valvel10 is to be used as a safety valve on a high pressure cylinder.

A plug244 having a threaded projection46 is screwed into the inlet216 of the bodyUl4 so as to close off the apertures 220. Preferably, the plug.44 has a flat inner surface.48 which will mate in a flush manner with the inner end of the inlet bore 216. The flush fit assures that any molten fusible material that enters the apertures-20 can solidify without extending into the

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inlet216. This saves the need for having to grind off this portion of the fusible material at a later time. After the plug 244 has been secured to the inletU16 so as to block off fluid flow 0 fi therethrough, a hollow funnell50 is secured over the outlet218 by a bushing52. The bushingZ52 contains a through bore254 and has a threaded portionO56. The threaded portion256 will engage the screw thread;26 formed on the bodyl14.

A fusible material258, such as white lead or a eutectic S alloy, is introduced into the funnel50. The fusible material-58 can be a lead alloy, having a melting point between 150" and 300*F, preferably above 200*F, and most preferably either 212°F i L 4 1 or 217*F. The fusible material58 can also be of a-synthetic resin such as fluoride-containing polymers, nylon, etc. One supplier of such fusible material is Cerro Metal Products, a division of The Marmon Group, Inc., P. O. Box 388, Bellefonte, Pennsylvania 16823.

The fusible material258 can be preheated to a temperature above its melting point, preferably between 200 and 300°F, more preferably above 250"F, so as to become molten befo e it is introduced into the funnel250. It should be noted that it S is also possible to introduce solid fusible material or S semi-solid fusible material into the funnel.50 and then heat the funnel50 and the relief valve Q0 to a temperature above the melting point of the fusible material 2 58. Either approach is possible, although it is preferable to first heat the fusible material258 to a molten state. With the thermally activated pressure relief valveA10 in a vertical orientation, molten Sfusible material258 is added by pouring it into the funnel 250.

*soe It is also advisable to preheat the funneli50 and the valve210 so as to facilitate fluid flow and to prevent solidification. The material%58 will flow downward through the apertures'40, through the helical groove238 and into the apertures120 at the opposite end. The fusible material258 will have a certain density and viscosity that will displace any trapped air that may be present in the helical passageway24 2 This displaced air will be released upward and out into the funnel 50. It should be noted that as a convenience, the insertion of a predetermined amount of fusible material258 into tEe funnel.50 will reduce the necessity of having to grind off solid material from the outer face at a later date. However, it is also advantageous to add a little extra fusible materialZ58 so as to assure that the helical passageway42 will be free of any voids.

Referring to Figs. 20and 21 the thermally activated pressure relief valvetl0 and the filling apparatus212 are inserted into a centrifugel60 whereby they can be rotated at a relative centrifugal force. As depicted in Fig. 20, more than one valve210 and filling assembly212 can be inserted into the

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centrifuge260 so as to facilitate production of the relief valves 2.10. The centrifugeZ60 has a predetermined radius designated (r) and it can be rotated either clockwise or counterclockwise at variable revolutions per minute. The relative centrifugal force exerted on the molten fusible material58 can be calculated using: the radius (cm) times the rpm 2 times a constant .(.00001118). Experimentation has shown that a relative centrifugal force (RCF) of at least 150 centimeters/minute is n2 acceptable. A force of at least 175 centimeters/minute and 2 preferably about 190 centimeters/minute is sufficient to insure that any air or gas trapped in the helical passagewayt42 will be S displaced by the fusible material58.

Each thermally activated pressure relief valve40 can be inserted into the centrifuge260 such that it is held in place by a support structure262. The exact type of structure will change depending upon the shape and configuration of the relief Experimentation has shown that a time period of about 3 minutes is sufficient to assure that any air trapped in the -28- II i l I passagewaySA2 can be displaced. As depicted, in Fig. 21, it is preferable to tilt both the relief valve 10 and the filling apparatusl12 through an angle 0 which is approximately between and 90*, more preferably between 60° and 90°. This tilting places the plugZ44 to the outside surface of the and away from its center. Such action causes the helical passageway242 to lie in either an inclined or horizontal plane and this allows any air or gas trapped therein to have an avenue of escape as the molten fusible material258 is being forced into the passageway Z42 by centrifugal force.

S After the relief valve4O has been subjected to the o 0 ocentrifugal force, it is removed and the material58, which has solidified, is allowed to cool. At this time both the filling apparatusA12 and the plug 44 are removed and any solidified material28 that may project beyond the ends of the andS40 is removed by grinding, fracturing or some other means.

As a matter of convenience, it may be economical to preheat the centrifugeZ60 or to operate it in a temperature controlled housing. Such action will assure that the molten material258 will be allowed to flow into and through the helical passageway.42, thereby filling it completely without having to worry about any voids being present. This is important in very small size valves for the helical passagewayZ42 and the apertures 220 and240 tend to be very small.

Referring to Fig. 22, an alternative method of forming the thermally activated pressure relief valve210 is shown. In this-method a hollow tube264 having a threaded exterior portion -29- 166 is secured in the inletl16. As stated earlier, although threads are shown, a press fit or any other type of connection could be utilized. The tube264 contains an internal step68 which provides a seat for a porous filter270. The filter can be constructed of various types of porous materials, such that i will allow air to pass through it while stopping the flow oC molten material258. A second tube.72, having an external thread 274 located at one end, is threaded into an internal thread276 formed on the opposite end of the hollow tube264. The second S" tube274 forms a retainer for holding the porous filter270 in place. Again, other means of attaching the tubes164 and72

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together can be utilized as well as other means for holding the filter270 in place. The opposite end of the tube272 is connected to a source of vacuum78. The vacuum278 does not have to be very great in order to draw the molten material2.58 through the helical *9 passageway242.

Molten fusible material 2 58 is.then introduced into the opposite end of the valve110, as explained earlier, and the vacuum causes the material258 to be drawn through the apertures 240 and into the helical passageway2A2. The molten materialZ58 S" will be drawn through the apertures 220 and into a riser space180 which is formed above the filter.70. This riser space280, which is optional, enables any trapped air, gas or foreign matter that may be present to be expelled from the helical passageway242.

This riser spaceQ80 should have a sufficient cross-sectional area such that the displaced air or gas can come in contact with and pass through the porous filterT0.

1- As stated earlier, both the relief valveZJ0 and the filling apparatus1.2 can be preheated to a temperature above the melting temperature of the fusible material258. For example, when the fusible material258 has a melting temperature of 212° or 217 0 F, it is advantageous to preheat the relief valve210 and the filling apparatus212 to a temperature between 250* and 300*F. It is also advisable to clean the parts, either ultrasonically or chemically, before the insert330 is secured to the bodyA14.

Once the fusible material258 has been allowed to solidify, the parts can be disassembled and any excess material can be removed.

SWhile the invention has been described in conjunction with two specific embodiments, it is to be understood that many *s alternatives, modifications and variations will be apparent to those skilled in the art in light of the aforegoing description.

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Accordingly, this invention is intended to embrace all such *s alternatives, modifications and variations which fall within the spirit and scope of the appended claims.

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US

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Claims (4)

1. 2. The thermally activated valve of claim 1, wherein said insert comprises a stem with a head formed at one end with at least two apertures formed therein which communicate with said helical passageway, each of said apertures having a smaller c ross-section than the cross-section of said helical passageway thereby causing said material means to exhibit forced shear deformation to inhibit expulsion.
2. 3. The thermally activated valve of claim i, wherein said insert comprises a stem with a head formed at one end, said stem having said helical groove formed in its outer periphery and having a small aperture formed through said head which communicates with said helical groove.
3. 4. The thermally activated valve of claim 3, wherein said helical passageway has a circular arc of at least
4. 7200. The thermally activated valve of claim 4, wherein said helical passageway tapers downward to a smaller cross-sectional area adjacent to said head. 91L 6. The thermally activated valve of claim 3 wherein 91L_2 -r O 1 Z 4** said helical passageway has a rectangular cross-sectional configuration. 7. The thermally activated valve of claim 3, wherein said helical passageway has a semi-circular cross- sectional configuration. 8. A thermally activated valve of claim 1, wherein: a) said body has said inlet and said outlet connected by at least one aperture, said inlet adapted to be attached to a container and communicating with the interior thereof and said outlet communicating with the atmosphere; b) said insert comprising an elongated stem having a head formed at one end, said stem having said helical groove formed in its outer periphery, said helical groove 15 extending along the length of said stem and fluidly connected to said aperture formed in said body, and said head having at least one aperture formed therethrough which communicates with an opposite end of said helical groove. 20 9. The thermally activated valve of claim 1 or claim 8, wherein said helical groove has an arc of at least 360P. The thermally activated valve of claim 9, wherein said helical groove has an arc of at least 7200. 11. The thermally activated valve of claim 8, wherein said apertures formed in both said body and said head are smaller than :he cross-sectional area of said helical passageway. 12. The thermally activated valve of claim 11, wherein there are four apertures formed in said head. 13. The thermally activated valve of claim 8, wherein said helical groove tapers to a narrow opening adjacent said head. 14. The thermally activated valve of claim 8, wherein said insert is threaded into said body. 15. The thermally activated valve of claim 8, wherein said insert is press fitted into said body. 16. The thermally activated valve of claim 8, wherein said material means is a fusible material which exhibits forced shea deformation to inhibit expulsion from said 4 helical passageway. 9L -33- C ~S~Mci~t~ C C J 17. The thermally activated valve of claim 8, wherein said elongated stem has a screw thread formed along the length thereof which is engageable with a threaded outlet for securing said insert to said body and said helical groove extends below the root of said screw thread and forms said helical passageway when said stem is secured in said body, and said head having a plurality of small apertures formed therethrough which communicate with said helical groove. 18. The thermally activated valve of claim 1, wherein said insert comprises a stem having said helical groove formed in the outer periphery thereof which extends from one end along a portion of the length thereof, and a circular groove formed about the circumference of said 15 stem which intersects said helical groove and commui.icates with said area having a lower pressure value, 19. The thermally activated valve of claim 18, wherein said helical groove is tapered with the narrowest cross- section being located at the intersection with said circular groove. The thermally activated valve of claim 18, wherein S..said cross-section of said circular groove is smaller than said cross-section of said helical groove. 21. The thermally activated valve of claim 18, wherein 25 said cross-section of said circular groove is equal to the cross-section of said helical groove. 22. The thermally activated valve of claim 18, wherein said cross-section of said circular groove is larger than the cross-section of said helical groove. 23. The thermally activated valve of claim 18, wherein said circular groove is aligned perpendicular to said helical groove. 24. The thermally activated valve of claim 1, wherein in addition to the flow path between said inlet and said outlet formed by said helical passageway: a) said body has a first passage connecting said inlet and said outlet; b) said insert has a second passage formed therethrough, which is connected to said first passage to S4II I 1r4 provide a second flow path between said pressure source I k A ,91L -34 and said lower pressure area; and c) said second flow path is blocked in said second passage by means for normally blocking fluid flow through said second passage, said means being rupturable in response to a selected pressure arising inside said pressure source to permit fluid flow through said second passage to said lower pressure area. The thermally activated valve of claim 24, wherein said second passage is axially aligned with said first passage. 26. The thermally activated valve of claim 24, wherein there are two or more other passageways formed in said body fluidly connecting said inlet to said outlet, said other passageways being axially aligned with said helical 15 passageway. 27. The thermally activated valve of claim 26, wherein said other passageways formed in said body are radially spaced around said first passage. 28. The thermally activated valve of claim 27, wherein each of said other passageways fluidly communicates with Ssaid helical passageway and has a smaller cross-sectional area than said helical passageway. 29, The thermally activated valve of claim 24, wherein said outlet includes at least two ports perpendicularly 25 aligned to said helical passageway. The thermally activated valve of claim 24, wherein said means for blocking fluid flow through said second passage is a pressure responsive lamina, 31. The thermally activated valve of claim 24, wherein said outlet includes a plurality of ports perpendicularly aligned to said helical passageway, each having a smaller cross-sectional area than said hclical passageway whereby said material means is subjected to forced shear deformation against itself during said fluid flow of said material means. 32. A method of forming a thermally activated pressure relief valve comprising the steps of: a) providing: 1) a body having an inlet and an outlet in t fluid communication with each other, said inlet adapted to S91L h be attached to a pressure source with said outlet communicating with an area having a lower pressure value than said pressure source, with said outlet having an internal bore which has an inner periphery; and 2) an insert having an outer periphery, said insert being secured in said outlet through a portion of said outer periphery being fastened to a portion of said inner periphery, said insert hav.cg a helical groove in its outer periphery, the helical groove in co-operation with said inner periphery forming a helical passageway which provides a flow path between said inlet and said outlet; b) introducing a molten fusible material into said helical passageway; I*i 15 c) exerting a force on said fusible material to cause movement of said material through said helical passageway thereby displacing any air or gas trapped Stherein and filling said passageway; and d) allowing said fusible material to solidify, 33, The method of claim 32, wherein said force exerted on said fusible material is a centrifugal force applied by rotating said valve in a centrifuge with the valve .xis extending radially of the centrifuge. 34, The method of claim 32, wherein said force exerted 25 on said fusible material is a vacuum applied to one end of said helical passageway. The method of claim 32, wherein said body and insert are preheated prior to the introduction of the molten fusible material. 36. The method of claim 35, wherein said body and insert are preheated to a temperature above 250 0 F, 37. A method according to claim 32, comprising: a) inserting a plug into said inlet to block off fluid flow therethrough; b) securing a funnel over said outlet to form an assembly providing fluid communication with said helical passageway and orienting said assembly in a vertical position; 4 c) introducing molten fusible material through said I 9l0 funnel and into said helical passageway; A 991 a L -36- d) rotating said assembly in a centrifuge with the valve axis extending radially of the centrifuge to exert a centrifugal force on said fusible material thereby causing said material to flow toward said plug and displace any traiped air or gas present in said helical passageway; and e) cooling said assembly to solidify said fusible material. 38. The method of claim 37, wherein said body, insert and funnel are preheated before said molten fusible material is introduced. 39. The method of claim 38, wherein said body and insert are preheated to a temperature of between 2500 and 300 0 F. The method of claim 37, wherein said body and insert are cleaned and fluxed before bein. assembled. 15 41, The method of claim 40, wherein said body and insert are ultrasonically cleaned, 42. The method of claim 37, wherein said assembly is rotated at a relative centrifugal acceleration of at least *2* 150 cm/min. 43. The method of claim 42, wherein said assembly is rotated at a relative centrifugal acceleration of at least 190 cm/min. 44. A method according to claim 34, comprising: a) cleaning said body and insert to remove any no 25 foreign matter; b) securing a funnel over said outlet to form an assembly providing fluid communication with said helical passageway; c) ,,taching a tube to said inlet having a porous filter fitted therein, said tube being connected to a source of vacuum; d) introlucing a molten fusible material through said funnel and into said helical passageway and applying a vacuum to said tube to assist in drawing said material completely through said helical passageway and into contact with said porous filter, said filter allowing air or gas to pass through while blocking the passage of said material; and e) allowing said material to solidify. 0 45. The method of claim 44, wherein said porous filter a I 991L -37- is distally spaced from said inlet. 46. The method of claim 44, wherein said body, insert and funnel are preheated before said material is introduced. 47. The method of claim 46, wherein said body, insert and funnel are preheated to a temperature of between 2500 and 300 0 F. 48. The method of claim 44, wherein said body and insert are chemically cleaned. 49. The thermally activated valve of claim 1, substantially is herein described with reference to any one of the embodiments illustrated in the accompanying drawings. The method of claim 32, substantially as herein 15 described with reference to any one of the embodiments illustrated in the accompanying drawings. DATED: 3 January 1992 PHILLIPS ORMONDE FITZPATRICK Attorneys for:' ALUMINUM COMPANY OF AMERICA '1 e 1L -38- I x ii