GB2036905A

GB2036905A - Fluid Storage Vessels

Info

Publication number: GB2036905A
Application number: GB7848014A
Authority: GB
Original assignee: BOC Ltd
Current assignee: BOC Ltd
Priority date: 1978-12-11
Filing date: 1978-12-11
Publication date: 1980-07-02
Also published as: GB2036905B

Abstract

A fluid storage vessel 2 is provided with a closure assembly including a check valve, and a copper safety burst disk 9 for venting the vessel contents in the event of the vessel 2 being overpressurised. The valve has a moveable member 5 including an elastomeric sealing ring 4 urged against a seat 3 by the pressure of the vessel contents, and having a stem 6 by which it can be unseated for dispensing or refilling. A passageway 10 extends through the valve member 5 and the burst disk 9 is located within this passageway 10 at a position inboard of the fluid exit/entry port defined by the valve seat 3 and sealing ring 4, being held in a hollow member 7 crimped to the end of stem 6 by a hollow screw 8. <IMAGE>

Description

SPECIFICATION Fluid Storage Vessels This invention relates to storage vessels for pressurised fluid and is particularly, though not exclusively, concerned with bulbs and cylinders of relatively small volume (e.g. 10-500 cc) for the storage of gas or liquified gas under pressure.

It is known to provide vessels of the aboveindicated kind with a closure assembly including a form of check valve to facilitate gas dispensing and refilling. Typically the valve comprises an annular seat and a moveable valve member normally urged by vessel pressure into sealing contact with the seat, the valve member having a stem accessible from without the vessel whereby it can be unseated to permit gas to be dispensed or to permit the vessel to be refilled. It is also known to include in such an assembly a safety burst disk which is exposed to the pressure difference within and without the vessel and which will fracture to permit the vessel contents to be vented in the event of the vessel being overpressurised, by overfilling, overheating or otherwise.

The usual arrangement when employing such an assembly is to locate the valve and burst disk in a closure housing of brass or other high-grade material which is in turn screwed or otherwise secured to the body of the vessel. The valve assembly is outermost in the sense of gas flow from the vessel and disposed coaxially with the vessel axis, while the burst disk is inboard of the valve assembly and located in an opening in the side of the closure housing with its axis at right angles to that of the vessel.

This arrangement has the disadvantage, however, that a relatively long and wide housing member is required to accommodate the burst disk in the stated position and in addition an extra machining operation is needed to provide the opening for the location of the burst disk. The closure assembly is accordingly a relatively expensive item.

It is therefore a specific aim of the present invention to provide a construction of a closure assembly for a pressurised fluid storage vessel having facilities both for refilling and pressure relief and which, through suitable integration of the elements of the valve assembly and pressure relieving means, can achieve an economic advantage over the known types of closures indicated above.

Accordingly the invention resides in a closure assembly fDr a pressurised fluid storage vessel, comprising means defining a fluid port; a valve seat around said port; a valve member adapted to be urged into sealing contact with the valve seat by pressurised fluid when stored within a vessel provided with the closure assembly, thereby to close said port; the valve member having a portion in use accessible from without the vessel by which the valve member can be unseated thereby to open said port; and a passageway through said valve member normally closed by a device in use exposed to the difference in fluid pressure within and without the vessel and which, in the event of the vessel being overpressurised, is effective to vent excess pressure from the vessel through the passageway.

The invention also includes a storage vessel for pressurised fluid having a closure assembly as defined above.

In a particularly preferred class of embodiments the closure assembly comprises a tubular housing member adapted for securement to the body of the vessel and the inner end of which defines said port and surrounding valve seat; the valve member includes a stem extending, with clearance, coaxially through the interior of said housing member by which the valve member can be unseated; said passageway extends through the valve member coaxially therewith and with said housing member; and said device is disposed in said passageway at a location inwards of said port.

The terms "inner" and "inwards" as used herein mean "towards the interior of the vessel".

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a first preferred embodiment of a closure assembly in accordance with the invention, as installed in a pressurised fluid storage vessel; and Figure 2 is a similar view of a second preferred embodiment of a closure assembly in accordance with the invention.

Referring to figure 1, the illustrated closure assembly includes a tubular housing member 1 screwed into the neck of a small gas cylinder 2 which may be of the well-known type marketed by the present applicants under the registered trademark Sparklets. The inner end face 3 of member 1 constitutes an annular valve seat surrounding a gas port, and cooperates with an elastomeric sealing ring 4 forming part of a fabricated valve member 5. The valve member 5 is disposed coaxially with the housing member 1 and is made in five parts. A first part 6 constitutes a valve stem extending with clearance through the interior of member 1 and is crimped at its inner end to a ring 7, the sealing ring 4 being nipped therebetween. A second ring 8 is screwed into ring 7, a copper burst disk 9 being clamped between these two parts.The parts 6, 7 and 8 of the valve member cooperate to define a passageway 10 extending coaxially through the length of the valve member, gas flow through this passageway normally being prevented by the burst disk 9.

When the cylinder is charged with pressurised gas, the pressure acting on the inner portion of valve member 5 is effective to urge it upwards in the sense of the figure, so that elastomeric ring 4 is pressed into sealing contact with the valve seat 3 and gas flow from the cylinder is prevented. A spring 11 held between opposing shoulders 12 and 13 of the valve member 5 and housing member 1 also assists the valve-closing action and serves to keep the valve member seated when the cylinder is empty. When it is desired to dispense gas from the cylinder the valve stem constituted by member 6 is depressed to move the sealing ring 4 away from its seat 3 and permit gas to flow out of the cylinder through the annular space between members 6 and 1, as indicated by the arrows in the figure.Likewise the valve stem is depressed to unseat the sealing ring when the cylinder is empty and is to be refilled.

It will be appreciated that by virtue of its location in the passageway 10 the burst disk 9 is normally exposed to the difference in pressure within and without the cylinder. In the event of the cylinder becoming over pressurised for any reason the disk 9 is adapted to fracture under the pressure loading so that the cylinder contents can vent through passageway 10 even though the valve member 5 is seated and the normal gas port is accordingly closed.

Turning now to figure 2 this shows a second embodiment of a closure assembly functionally similar to that shown in figure 1 but differing in its construction. In this case the assembly includes a tubular housing member 21 clamped by a locking ring 35 to the neck of a small gas cylinder 22.

Alternatively the locking ring 35 may be dispensed with and member 21 welded in place.

The inner end face 23 of the member 21 constitutes an annular valve seat surrounding a gas port, and cooperates with an elastomeric sealing ring 24 forming part of a fabricated valve member 25 disposed coaxially with member 21.

The valve member 25 includes a part 26 constituting a valve stem extending with clearance through the interior of member 21 and crimped at its inner end to a ring 27, the sealing ring 24 being nipped therebetween.

A burst disk assembly is in turn crimped into the inner end of ring 27, this assembly comprising the disk 29 itself, a plastics (e.g. PTFE) ring 32 and a metal load-spreading ring 33. The parts 26 and 27 of the valve member cooperate to define a passageway 30 extending coaxially through the length of the valve member, gas flow through this passageway normally being prevented by the burst disk 29.

As before, when the cylinder is charged with pressurised gas the pressure acting on the inner portion of the valve member 25 is effective to urge it upwards in the sense of the figure so that the elastomeric ring 24 is pressed into sealing contact with the valve seat 23 and gas flow from the cylinder is prevented. The valve-closing action is supplemented by a spring 31 which in this case is held between the inner end of ring 27 and an opposing shoulder on a tubular member 28 which surrounds the valve member (with clearance) and is crimped to the housing member 21. As shown in the figure, the spring 31 may also serve to retain a fine mesh filter 34 for straining any particulate contaminants from the gas when dispensing or refilling.When it is desired to dispense gas from the cylinder the valve stem constituted by member 26 is depressed to move the sealing ring 24 away from its seat 23 and permit gas to flow out of the cylinder through the annular spaces between members 27 and 28 and members 26 and 21, as indicated by the arrows in the figure. Likewise the valve stem is depressed to unseat the sealing ring when the cylinder is empty and is to be refilled.

Again it will be appreciated that by virtue of its location in the passageway 30 the burst disk 29 is normally exposed to the difference in pressure within and without the cylinder and in the event of the cylinder becoming overpressurised for any reason the disk 29 is adapted to fracture under the pressure loading so that the cylinder contents can vent through the passageway 30 even though the valve member 25 is seated and the normal gas port is accordingly closed.

An advantage of the closure assemblies described above is that the housing members 1 and 21 which will usually be made of brass or a high-grade steel, are both axially shorter and of smaller diameter than equivalent elements of known cylinder closure assemblies including a check valve and burst disk. The remaining major elements 6, 7, 8 or 26, 27, 28 of the illustrated assemblies may be made from a less expensive material such as mild steel.

In a modified form of either assembly a ball 40 may be located in the space between the burst disk and valve stem, as indicated in broken line in the figures. This ball is intended to seat in the end of the valve stem member 6 or 26 under the pressure of the escaping gas in the event of the burst disk 9 or 29 rupturing, not to seal the passageway 10 or 30 but to leave a small leakage path between itself and its seat (as by making a "nick" in the end of member 6 or 26). In this way the cylinder contents can be vented in a controlled manner and the sudden and violent onrush of gas which might otherwise be experienced is avoided.

Although the invention has hitherto been described as including pressure relieving means in the form of a burst disk other such means may be employed and the disks 9 and 29 shown in the figures may, if desired, be replaced e.g. by a form of blow-off valve which in the event of overpressurisation is effective to vent excess gas from the cylinder through the passageway 10 or 30 but subsequently closes to retain the remaining gas within the cylinder when the cylinder pressure has reduced to its normal value.

Claims

1. A closure assembly for a pressurised fluid storage vessel, comprising means defining a fluid port; a valve seat around said port; a valve member adapted to be urged into sealing contact with the valve seat by pressurised fluid when stored within a vessel provided with the closure assembly, thereby to close said port; the valve member having a portion in use accessible from without the vessel by which the valve member can be unseated thereby to open said port; and a passageway through said valve member normally closed by a device in use exposed to the difference in fluid pressure within and without the vessel and which, in the event of the vessel being overpressurised, is effective to vent excess pressure from the vessel through the passageway.

2. A closure, assembly according to claim 1 comprising a tubular housing member adapted for securement to the body of the vessel and the inner end of which defines said port and surrounding valve seat; the valve member including a stem extending, with clearance, coaxially through the interior of said housing member by which the valve member can be unseated; said passageway extending through the valve member coaxially therewith and with said housing member; and said device being disposed in said passageway at a location inwards of said port.

3. A closure assembly according to claim 1 or claim 2 wherein said device comprises a disk which is adapted to rupture in the event of the vessel being overpressurised.

4. A closure assembly according to any preceding claim comprising means disposed in said passageway at a location outwards of said device which are adapted to restrict the flow of fluid from the vessel through the passageway in the event of the aforesaid venting.

5. A closure assembly according to any preceding claim further comprising spring means adapted to urge the valve member into sealing contact with the valve seat.

6. A closure assembly for a pressurized fluid storage vessel substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.

7. A storage vessel for pressurised fluid having a closure assembly according to any preceding claim.

8. A vessel according to claim 7 having a volume of not more than 500 cc.

9. A vessel according to claim 8 or claim 9 charged with gas or liquefied gas under pressure.