NZ260233A

NZ260233A - Gas cylinder installation with one cylinder insulated and filled with liquid gas for charging other cylinders with gas

Info

Publication number: NZ260233A
Application number: NZ26023394A
Authority: NZ
Inventors: Evelyn Arthur Shervington; Rohintan Sheriar Irani
Original assignee: Boc Group Plc
Priority date: 1993-04-23
Filing date: 1994-03-31
Publication date: 1995-02-24
Also published as: GB9406097D0; IE79083B1; GB2277370B; GB2277370A; IE940356A1

Abstract

A bank of gas cylinders 22 includes at least one cylinder 1 having a major portion of its body 2 coated with heat insulation material 4. To fill the cylinders 22, the cylinder 1 is first filled via a three way filler valve 6 with gas in liquid state which is subsequently allowed to boil. The boiled gas then passes through a gas line 24 via a one-way valve 26 and heat exchange 28 into the cylinders 22. The insulated cylinder may be of chrome molybdenum steel, stainless steel or aluminium and the insulation may be of high density expanded polystyrene. <IMAGE>

Description

<div class="application article clearfix" id="description"> i? /"> r^r a Patents Form 5 V*U| I ipiclw bpjCi;:_. L.^'ll [ "3/ *3 ,'jfy- pt*e,: .Fjn&$/?u : - r' ! 2ii FEB 1595 P.O. J .ju: No: N.Z. No. NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION GAS CYLINDERS We, THE BOC GROUP PLC, an English Company of Chertsey Road, Windlesham, Surrey GU20 6HJ, England do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - -1 - (Followed by 1A) - 1A- /■ (? f1 ~ GAS CYLINDERS The present invention relates to gas cylinder installations and in particular to high pressure gas cylinder installations for industrial applications. The costs involved in supplying compressed gases to industrial customers can be broken down as follows:- a) The cost of producing and/or purifying the gas; b) filling or compressing the gas into high pressure gas cylinders; and c) distributing the high pressure gas cylinders to the customer. It is an aim of the present invention to reduce the cost of filling and distributing high pressure gas cylinders to customers by using specially prepared gas cylinders in conjunction with liquefied gases to provide an economic means of recharging commercially available gas cylinders on the customer's premises. According to one aspect of the present a method of filling a bank of gas cylinders with a gas under pressure comprises the steps of: a) filling a gas cylinder having at least a major portion of its body coated with a heat insulation material with said gas in liquid state; b) allowing the liquid boil; and c) subsequently passing said gas through a gas line and into one or more of the bank of cylinders. According to a further aspect of the present invention, a gas cylinder installation comprises a bank of gas cylinders including at least one gas cylinder provided with a filler valve and having at least a major portion of its body coated with a heat insulation material, and a gas line extending from the filler valve and which communicates with the interior of one or more of the remaining gas cylinders of said bank of gas cylinders. An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which:- - 2 - Figure 1 is a cross-section through a gas cylinder; and Figure 2 illustrates the gas cylinder of Figure 1 forming part of a gas cylinder installation. As shown, a gas cylinder 1 includes an outer body 2 of, for example, a cryogenically compatible material such as chrome molybdenum steel, stainless steel or aluminium, the interior surface of which body 2 is coated with a heat insulation material 4. Preferably, the material 4 is a high density expanded polystyrene insulation material, for example, about 140 Kg/cm3 having a thickness of up to 20mm. The material 4 can be applied to the inner surface of the body 2 by any known technique, for example, by spraying. At the top (as shown) of the cylinder 1 is a three-way valve 6 having an inlet 8 for cryogenic liquid gas; an outlet 10 controlled by a ullage valve 12 and a further outlet 14 for gas. A particular advantage of the gas cylinder 1 becomes evident when it forms part of a gas cylinder installation on a customer's premises which installation includes a plurality of known commercially available cylinders 22. As shown in Figure 2, a gas line 24 extends from the further outlet 14 and communicates with the interior of each gas cylinder 22 in series before finally connecting with a customer's supply line. Located in the gas line 24 is a pressure relief valve 26 and a heat exchanger 28. In use, when it is desired to fill the bank of commercially available gas cylinders 22 with high pressure gas, the gas cylinder 1 is filled with a cryogenic liquid, e.g. oxygen, nitrogen or argon, via the inlet 8 in the three-way valve 6. The three-way valve 6 will allow the cylinder 1 to fill with liquid by allowing boil-off gas to bleed out during the filling operation through the outlet 10 and open ullage valve 12. Once the liquid is observed coming out of the ullage valve 12 the filling operation is stopped and the ullage valve 12 is closed. Boiling gas from the cryogenic liquid now passes through the further outlet 14 into the gas line 24 where it enters the interiors of the - 3 - cylinders 22. The gas take-off from the cylinder 1 will soon fill the bank of cylinders 22 due to the heat inleak through the insulation material 4 within the cylinder 1 which insulation 4 is selected and dimensioned to provide an inleak of heat to ensure that no embrittlement of the outer body 2 is possible. It has been found that under normal ambient temperature conditions the heat inleak will vaporise all the cryogenic liquid in the cylinder 1 within a period of 2 to 3 hours safely. The non-return valve 26 in the gas line 24 ensures that no impurities get back to the cylinder 1 and the heat exchanger 28 will ensure that cold gas does not get delivered to the bank of cylinders 22. The capacity or quantity of the bank of cylinders 22 will depend on the liquid gas capacity of the cylinder 1, that is, a 50 litre water capacity cylinder when insulated would hold 38 litres of liquid nitrogen which, if hydrostatically full, is equivalent to 26 m3 of gas or about three cylinders at 200 bar and six cylinders at 100 bar. Each cylinder 22 is in turn used until the overall pressure in the bank of cylinders has fallen below a predetermined economic operating pressure, for example, 25 bar at which point the cylinder 1 is refilled. In a preferred embodiment the gas cylinder 1 is rated to 200 bar operating pressure. A particular advantage of the gas cylinder 1 described in the above embodiment is that it is far cheaper and more robust than a vacuum insulated cryogenic vessel. Further, adequate pressures for normal use of compressed gases can easily be obtained and transport costs will be reduced as only cryogenic liquid rather than large quantities of steel cylinders need to be moved to a customers site. Still further, filling costs will be reduced as liquid fill will be quick and pressure raising in the cylinders 22 will be accomplished through natural boil-off from the enclosed cryogenic liquid in the cylinder 1. - 4 - 2 3 Although in the above described embodiment the interior surface of the outer body 2 is completely coated with the heat insulation material 4, it will be appreciated that depending upon the materials used and the local conditions only a major portion of the interior surface need be so coated. In an alternative embodiment particularly when an aluminium gas cylinder is used the outer surface of the aluminium gas cylinder can be covered with a heat insulation material. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> WHAT WE CLAIM IS A method of filling a bank of gas cylinders with a gas under pressure comprising the steps of: a) filling a gas cylinder having at least a major portion of its body coated with a heat insulation material with said gas in liquid state; b) allowing the liquid boil; and c) subsequently passing said gas through a gas line and into one or more of the bank of cylinders. A method as claimed in claim 1 comprising the step of passing the gas through a heat exchanger to elevate the temperature of the gas prior to delivery to said one or more of a bank of cylinders. A gas cylinder installation comprising a bank of gas cylinders including at least one gas cylinder provided with a filler valve and having at least a major portion of its body coated with a heat insulation material, and a gas line extending from the filler valve and which communicates with the interior of one or more of the remaining gas cylinders of said bank of gas cylinders. A gas cylinder installation as claimed in claim 3, in which the gas line includes -a non-return valve. A gas cylinder installation as claimed in claim 3 or 4, in which the gas line includes a heat exchanger. A gas cylinder installation as claimed in any one of claims 3 to 5, in which said at least one gas cylinder comprises an outer body having at least a major portion of its inner surface coated with a heat insulation material. A gas cylinder installation as claimed in claim 6, in which the outer body is made from chrome molybdenum steel or stainless steel or aluminium. A gas cylinder installation as claimed in claims 3 to 5, in which said at least one gas cylinder has at least a major portion of its outer surface covered with the heat insulation material. A gas cylinder installation as claimed in claim 8, in which the filer valve is a three-way filler valve. 10. A gas cylinder installation constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figure 2 of the accompanying drawings. 11. A method of filling a bank of gas cylinders substantially as hereinbefore described. THE BOC GROUP PLC By Their Attorneys HENRY HUGHES </div>