CA2829815A1

CA2829815A1 - Cylinder valve having a device for reducing or closing off the flow in the event of a rise in temperature

Info

Publication number: CA2829815A1
Application number: CA 2829815
Authority: CA
Inventors: Claude Risse
Original assignee: Luxembourg Patent Co SA
Current assignee: Luxembourg Patent Co SA
Priority date: 2011-03-07
Filing date: 2012-02-29
Publication date: 2012-09-13
Also published as: LU91795B1; WO2012119901A1; US9151402B2; EP2683978A1; US20140053921A1

Abstract

L'invention a trait à un robinet bouteille 2 pour gaz sous pression. Le corps 4 du robinet 2 comprend une entrée de gaz 8, une sortie de gaz (non représentée) et un passage 10 reliant l'entrée avec la sortie. Le robinet 2 comprend également une vanne de fermeture/ouverture 26 (figure 2), un détendeur 12 et un dispositif de réduction ou de fermeture du passage de gaz entre ladite vanne et un détendeur 12. Le dispositif comprend un élément en alliage à mémoire de forme 16 disposé dans une cavité 14 du passage 10. Cet élément 16 comprend une partie active déformable dont le bord extérieur circulaire est apte à venir en contact avec la surface interne de la cavité 14 afin de fermer le passage suite à une élévation de température provoquée par une combustion. Une telle combustion peut être créée par une compression adiabatique lors de l'ouverture de la vanne 26.

Description

Description CYLINDER VALVE HAVING A DEVICE FOR REDUCING OR CLOSING OFF THE FLOW
IN THE EVENT OF A RISE IN TEMPERATURE
Background of the invention [0001] The invention relates to a tap for a pressurised gas container. More precisely, the invention relates fo a tap for a pressurised gas container fitted with a shut-off valve. While the invention is appropriate for applications involving various types of gases, it is particularly suitable for oxidising gases sensitive to adiabatic compression, more particularly for oxygen applications.
Prior art

[0002] The speeds involved in a tap for a high pressure (above 200 bar) gas container are very high. For gases such as helium the speeds can be much greater than the speed of sound. With such speeds some plastic seats or inserts in the regulator valve cannot resist the adiabatic compression shock and can burn in the presence of an oxidising gas. It is therefore useful to restrict the pressure and slow the speed of the gas to absorb the shock wave when opening the main valve of the tap for withdrawing gas.

[0003] ln the prior art filters were provided between the main valve and the regulator valve but these filters have the disadvantage of slowing the gas flow when the container is nearly empty. In addition, filters can become clogged. As a result, they suffer shocks every time they are opened and can generate particles. At high pressure, which can be of the order of 300 bars or more, when the gas cylinder is full, known filters pose no problems and do not interfere with the flow. However, filters cause a constant pressure drop, and at low pressures, below 50 bars, pressure disturbances begin and become particularly detrimental at 10 bars. These known filters that cause a constant pressure drop therefore choke the gas expansion curve at low pressure.

[0004] Other, less damaging, solutions have been developed for when the container pressure decreases.

[0005] For example, Patent EP 1500854 Al discloses a container tap provided with a non-sealing shutter located between an on/off valve and a regulator tap. The shutter is normally positioned across the flow area. When the valve is opened, the pressurised gas rapidly forces the shutter to a position across a restricted flow area so as to reduce the shock wave applied to the regulator valve. After the pressure equalizes across both sides of the shutter, the latter returns to its normal position across the full flow area.

[0006] Patent US 7,225,810 62 discloses a container tap with a shutter similar to that in the previous document and operating in the same way.

[0007] These shutters certainly provide an interesting solution; however, they have the disadvantage of complexity linked to a reliability constraint, as well as a disadvantage in that they do flot definitely prevent combustion when the valve is opened. Indeecl, in the presence of impurities in the tap pathway and, especially in the presence of oxygen under high pressure, combustion can still occur and cause serious safety problems. Indeed, in the event of combustion, times can escape from the tap and cause bums, damage to nearby equipment and/or cause &es.
Summaty of the invention The technical problem

[0008] The invention aims to provide a container tap that overcomes at least one of the problems mentioned above. More particularly, the invention has the objective of proposing a container tap that reduces the risk of fire and burns when operating the tap, especially with strong oxidising gases such as oxygen.
Technical solution

[0009] The invention relates to a tap for pressurised gas container, comprising a housing with a gas inlet, a gas outlet and a gas pathway connecting the inlet to the outlet, a shut-off valve for shutting off and/or reducing the gas path; wherein it further comprises a device for reducing or closing the path in response to a rise in temperature, the device being arranged in the housing downstream of the shut-off valve.

[0010] Such a tap is designed to operate at greater than or equal to 50 bars pressure, preferably to 100 bars, more preferably even at 200 bars.

[0011] According to an advantageous embodiment of the invention, the tap includes a regulator valve located downstream of the device for reducing or closing the passage, preferably in the tap housing. The regulator valve can be integrated into the tap body. The latter may consist of several assembled components.

[0012] According to another advantageous embodiment of the invention, the device for reducing or closing the passage is configured to reduce or close the gas flow when the temperature in the gas flow exceeds 100 C, preferably 120 C, more preferably 150 C.

[0013] According to a further advantageous embodiment of the invention, the device for reducing or closing the passage is mechanical. This device is indeed preferentially purely mechanical.

[0014] According to a further advantageous embodiment of the invention, the device for reducing or closing the passage comprises a shape memory alloy element that can be deformed when its temperature exceeds a preset level.

[0015] According to a further advantageous embodiment of the invention, the shape memory alloy element has a memory effect only when the temperature is raised.

[0016] According to a further advantageous embodiment of the invention, the device for reducing or closing the passage is configured so that the deformation of shape memory alloy element operates directly to reduce or close the passage.

[0017] According ta yet another advantageous embodiment of the invention, the shape memory alloy element comprises a deformable portion with a circuler edge designed to make contact with a fixed surface, preferably formed directly in the housing, so as to reduce or close the passage.

[0018] According to a further advantageous embodiment of the invention, the deformable portion of the shape memory alloy element is dome-shaped.

[0019] According to a further advantageous embodiment of the invention, the diameter of the circuler edge increases when the temperature exceeds the preset level, preferably more than 10% above 100 C, 120 C or aven 150 C.

[0020] According to a further advantageous embodiment of the invention, the shape memory alloy element comprises a generally elongated part attached to the deformable portion, the generally elongated part ensuring the fixing of the element to the housing.

[0021] According to a further advantageous embodiment of the invention, the generally elongated portion comprises a male thread mating with a corresponding female thread in the housing.

[0022] According to a further advantageous embodiment of the invention, the device for reducing or closing the passage comprises a cylindrical cavity with a first region with a first diameter receiving the deformable portion of the shape memory alloy element and a second region with a second diameter inside the first and upstream of the first region, so that the gas must flow around the circuler outer edge of the dome-shaped part.

[0023] According to yet another advantageous embodiment of the invention, the deformable part of the shape memory alloy element is dome-shaped with a circuler outer edge, located in the cavity so that the hollow of the dome is directed towards the second region of the cavity.

[0024] According to yet another advantageous embodiment of the invention, the cavity comprises a third region adjacent to the first region and opposite to the first, with a means for fixing the shape memory alloy element, preferably by a female thread.
Claimed benefits

[0025] The invention can take advantage of the increase in temperature caused by combustion when the on/off valve is opened, so to ensure closure or at least an automatic quasi-closure in a very short time. Given the fact that combustion in such a tap cannot be excluded, even in the presence of devices such as those described in the "Prior Art section, the tap in the invention provides a significant safety advantage.

[0026] The use of one (or more) shape memory alloy elements enables the response time to be very short and, above all, compatible with a very oxidising gas under very high pressure, such as oxygen. Indeed, automatic gas flow closure systems involving a fuse element are known, including anti-blowback functions in welding torches. Such a solution is obviously not applicable to a container tap where oxygen at a pressure of about 200 bars predominates.

[0027] Furthermore, the fact of using one (or more) shape memory alloy elements with an edge designed to corne into direct contact with a fixed surface so as to close off or reduce the passage is particularly interesting both because it is easy to implement as well as being reliable.
Short description of the diagrams

[0028] Figure 1 is a plan view of a container tap according to the invention.

[0029] Figure 2 is a sectional view of the shell of the tap in Figure 1, sectioned at 2-2.

[0030} Figure 3 is a sectional view of the tep closure device in the avent of a temperature rise in the tap of Figure 1, albeit with another design of shape memory alloy element, the device being in the open position.

[0031] Figure 4 is a sectional view of the tap closure device in the avent of a temperature rise in the tap of Figure 1, albeit with another design of shape memory alloy element, the device being in the closed position.
Description of the embodiments

[0032] The container tap 2 for pressurised gas comprises a housing 4 with a gas inlet 8, an outlet (flot shown) and a passage 10 connecting the inlet to the outlet. The housing comprises a male thread 6 to be screwed onto the neck of a gas cylinder.

[0033] The tap further comprises a shut-off valve 26 illustrated in Figure 2.
The latter is a sectional view of the tap in Figure 1, sectioned at 2-2. The duct for the passage of gas can also be seen. The shut-off valve 26 comprises an element movable in translation and rotation, and provided with a sealing ring mating with a seat formed in the valve housing. This movable element is actuated by a handwheel 24 accessible from the outside of the valve and located on the side of the housing,

[0034] Downstream of the on/off valve 26 is a device which is arranged to close the passage of gas when the temperature exceeds a critical threshold.
This device comprises a chamber 14 and a shape memory alloy element 16. The latter includes a head portion capable of changing its shape significantly. More particularly, the head of the shape memory alloy element comprises a circular outer edge designed to change its size in order to seal with the cavity 14 in which it is housed. ln the avent that the temperature of the head of the shape memory alloy element lises beyond a critical levai, it will change shape se that the diameter of its outer edge increases so that it cornes into contact with the inner surface of the cavity 14 and automatically closes off the gas passage.

[0035] ln Figure 1 the shape memory alloy element is in the closed position, that is to say the outer edge of that part of it intended to make contact with the cavity forms a seal with the said cavity.

[0036] Shape memory alloys (SMA) are among alloys with several new properties among metallic materials: the ability to remember an initial form and retum to it aven after deformation; the ability to switch between two previously stored forms when the temperature varies around a critical temperature;
and a super-elastic behaviour allowing elastic elongations greater than those of other metals. Among the main shape memory alloys there are a variety of nickel and titanium alloys as the main components in approximately equal proportions. Althoug h "nitinol" ("Nickel-Titanium Naval Ordnance Laboratory") is actually the name of one of these "quasi-equiatomic nickel-titanium" alloys this name has become commonly used in the literature to describe ail of these alloys, which have very similar properties. To a lasser extent soma brass and copper-aluminium alloys also have shape memory properties.

[0037] The active portion, in this case the head of the shape memory alloy element is designed to deform so that the diameter of its outer edge increases by at least 5%, preferably 10 %, more preferably 15%. Such super-elastic behaviour enabling elastic elongations can be achieved by a judicious choice of materials and suitable design of the active part of the element. The critical temperature can vary depending on the choice of material. ln the case of container taos, which typically operate at amblent temperatures of between 0 C and 30 C, the critical threshold will be set, at least approximately, to about 100 C, 120 C or aven 150 C. The closure valve must remain open over a broad temperature range, such as between -40 C and +70 C to cover the temperature extremes in which the valve is likely to need to function normally.

[0038] Particularly in the case of oxygen and when opening the tap's on/off valve 26, the pressurisation of the gas passage between the said valve and the regulator valve 12 may give rise to transient adiabatic compression, generating temperature increases and initiating combustion inside the valve housing. Such combustion may be made possible by the presence of residues or impurities in the valve.

[0039] In the event of combustion, flames can escape from the tap, particularly because of the large flow of oxygen. The presence of a self-closing device or, at least, one that reduces the gas flow to the tap provides a certain degree of safety in this problem area that, up till now, has had no real solution. lndeed, in the event of combustion starting when the valve 26 is opened, the shape memory alloy element will quickly heat up and exceed the critical threshold. lt will then, in a very short time directly linked to its thermal inertia, deform and corne into contact with the inner wall of the cavity. This contact closes off the passage of the gas, in this case oxygen, and thus stops the flames.

[0040] It should be noted that the contact between the outer edge of the active part of the shape memory alloy element and the inner surface of the cavity cannot be made completely gas-tight, especially in ternis of the surface state of the active part and the state of the corresponding internai surface of the cavity. The device may therefore be a device for reducing or decreasing the gas flow but not a device for closing it off completely.

[0041] The cavity 14 discharges upstream into a filter 20 located in a fitting 22.
The gas passing through the cavity 14 will therefore meet a first pressure drop generator from the narrowing formed by the filter and a second narrowing directly downstream at the regulator valve seat. The pressure drops created by these elements will increase the shock wave in the gas when the on/off valve is opened. This shock wave will be created in the cavity 14. Positioning the active part of the closure device in this cavity and adjacent to the filter and the regulator valve seat allows the response time of the device to be minimised and, thus, its effectiveness is increased.

[0042] With reference to the point made earlier about a device reducing the flow area, it should be noted that, depending on the application and its parameters, such a device significantly reducing this, for example by least 70%, preferably 80%, still more preferably 90%, the flow area could also increase the safety of the tap by limiting, in a known manner, the propagation of flames outside the tap.

[0043] Figure 3 illustrates the closure device of Figure 1, albeit with a design of shape memory alloy element that differs at the active part or head of the element. This latter 16 includes a first active domed portion 161 and a second generally cylindrical portion 162. The cavity 14 is generally cylindrical with a first region 141 of a fixed first diameter and wherein the active portion 161 of the element is located. The cavity 14 also includes a second region immediately adjacent to the first region 142 and in fluid connection therewith. The second region has a smaller diameter than the first. The dome-shaped portion 161 of element 16 is oriented so that its open end faces the second region 142 of the cavity 14. The cavity 14 is supplied with gas radially at the second region 142. The gas thus flows bypassing the rear portion and the outer edge of the dome-shaped portion.

[0044] The cylindrical portion 162 of element 16 ends with a male thread 163 inserted into a tomate thread formed in a third region 143 of the cavity 14.
The three regions 141, 142 and 143 of the cavity 14 are concentric.

[0045] When the on/off valve is opened, in the event of combustion caused by the adiabatic shock wave, the temperature in the first region 141 of the cavity 14 will increase. The temperature of the active domed part 161 of element 16 will increase and will deform to take the shape shown in Figure 4. The dome 161 is flattened and has increased its outer diameter so as to be in contact with the inner surface of the cavity 14. This super-elastic deformation thus enables the passage of gas to be stopped and the combustion to be stopped dead. Further, because the umbrella or dome shape of this part, oriented sa that its hollow is on the upstream side of the gas flow, allows this part to deforrn even further in the direction of closure from the effect of the shock wave triggered by its deformation.

[0046] Note that the shape memory alloy elements shown in Figures 1, 3 and 4 are purely examples. They can take many forms other than those shown.
List of part number references

[0047] 2: container tap

[0048] 4: housing

[0049] 6: male thread

[0050] 8: gas inlet

[0051] 10: gas outlet

[0052] 12: regulator valve

[0053] 14: cavity

[0054] 141: first region of the cavity 14

[0055] 142 : second region of the cavity 14

[0056] 143: third region of the cavity 14

[0057] 16: shape memory alloy element

[0058] 161: active dome-shaped part of the element 16

[0059] 162 : elongated part of the element 16

[0060] 163: male thread of the elongated part 162 of the element 16

[0061] 20: filter

[0062] 22: reg ulator valve seat and filter support

[0063] 24: handwheel of the on/off valve

[0064] 26: on/off valve

Claims

1. Pressurised gas container tap, comprising a housing with a gas inlet, a gas outlet and a passage connecting the inlet to the outlet;
an on/off valve in the gas passage;
wherein it further comprises a device for reducing or closing the passage in response to an increase in temperature, the said device being located in the housing downstream of the shut-off valve.

2. Container tap in accordance with Claim 1, wherein it comprises a pressure regulator valve located downstream of the device for reducing or closing the passage, preferably in the tap housing.

3. Container tap in accordance with one of Claims 1 and 2, wherein the device for reducing or closing the passage is configured to reduce or close the gas flow when the temperature in the gas flow exceeds 100°C, preferably 120°C, more preferably 150°C.

4. Container tap according to one of Claims 1 to 3, wherein the device for reducing or closing the passage is mechanical.

5. Container tap in accordance with one of Claims 1 to 4, wherein the device for reducing or closing the passage comprises a shape memory alloy element designed to deform when its temperature exceeds a preset level.

6. Container tap in accordance with Claim 5, wherein the shape memory alloy element has a memory effect only when the temperature is raised.

7. Container tap in accordance with one of Claims 5 and 6, wherein the device for reducing or closing the passage is configured so that the deformation of shape memory alloy element operates directly to reduce or close the passage.

8. Container tap in accordance with one of Claims 5 and 6, wherein the shape memory alloy element comprises a deformable portion with a circular edge designed to make contact with a fixed surface, preferably formed directly in the housing, so as to reduce or close the passage.

9. Container tap in accordance with Claim 8, wherein the deformable portion of the shape memory alloy element has the general shape of a dome.

10. Container tap in accordance with one of Claims 8 and 9, wherein the diameter of the circular edge increases when the temperature exceeds the preset level, preferably more than 10% above 100°C, 120°C or even 150°C.

11. Container tap in accordance with one of Claims 8 to 10, wherein the shape memory alloy element comprises a generally elongated part attached to the deformable portion, the generally elongated part ensuring the fixing of the element to the housing.

12. Container tap in accordance with Claim 11, wherein the generally elongated portion comprises a male thread mating with a corresponding female thread in the housing.

13. Container tap in accordance with one of Claims 8 to 12, wherein the device for reducing or closing the passage comprises a cylindrical cavity with a first region with a first diameter receiving the deformable portion of the shape memory alloy and a second region with a second diameter inside the first and upstream of the first region, so that the gas must flow around the circular outer edge of the dome-shaped part.

14. Container tap in accordance with Claim 13, wherein the deformable part of the shape memory alloy element is dome-shaped with a circular outer edge, disposed in the cavity so that the hollow of the dome is directed towards the second region of the cavity.

15. Container tap in accordance with one of Claims 13 and 14, wherein the cavity comprises a third region adjacent to the first region and opposite to the first, with a means for fixing the shape memory alloy element, preferably by a female thread.