GB1558409A - Fluid storage vessels - Google Patents

Description

(54) FLUID STORAGE VESSELS (71) We, BOC LIMITED, of Hammersmith House, London W6 9DX, England, an English company, 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: This invention relates to fluid storage vessels of cylindrical form and particularly, but not exclusively, to cylinders suitable for storing gas or liquefied gas.

A large proportion of gas storage cylinders in use today were made 30 or more years ago and have rounded or domed bottom ends. Such cylinders, which are expected to be usable for many more years to come, are relatively difficult to manoeuvre manually for the following reasons.

Firstly, they cannot be stood upright on their bottom ends without additional support so that during handling they must frequently be lifted from horizontal positions on the ground. Secondly, the domed ends of the cylinders do not provide a surface suitable for rolling along the ground in the manner adopted for moving milk churns.

It has been proposed to attach a metal sleeve to the lower end of such a cylinder to surround the domed end thereof. The projecting end of the sleeve is turned inwardly to provide a rounded annular surface on which the cylinder can be stood in an upright position and also on which it can be rolled. For cylinders which are to contain gas at high pressures it is undesirable to weld the sleeve to the cylinders, as the cylinder's metallurgical properties can be affected adversely, so that the sleeves are shrink fitted. This has ben found to be unsatisfactorily costly owing to the fact that each sleeve has to be dimensioned to suit its respect cylinder.

The reason for this is that there tends to be relatively large variations in the external dimensions of the rounded or domed end type cylinders in use at present. Furthermore, corrosion tends to occur at areas adjacent to a narrow pocket which is defined between the sleeve and the bottom end of the cylinder and which can collect moisture.

The inventoin provides a fluid storage vessel of cylindrical form and having a domed closed end (as herein defined), provided with a base part of tough elastomeric or polymeric material (as herein defined) moulded in situ around said end of the vessel, the base part providing a substantially flat seating surface by which the vessel can be stood freely on the ground with its axis substantially vertical and an annular rolling surface having a mean diameter equal to or approximately equal to the outside diameter of the adjacent cylindrical wall of the vessel by which the vessel can be rolled along the ground by rotation of the vessel about its axis with the vessel axis at an acute angle to the ground.

The term "tough elastomeric or polymeric material" is used herein to mean a durable elastomeric or polymeric material which does not easily deform and which has a high resistance to impacts and abrasion. The term "domed closed end" is used herein to include any closed end which extends from the cylindrical wall of the vessel and which does not readily permit the vessel to be stood freely on the ground with its axis substantially vertical, for example closed ends which are not truly convex, e.g. originally convex ends which have been distorted or damaged in use, or ends which are conical or otherwise pointed.

The invention not only enables the large stock of existing gas storage cylinders to be readily provided with base parts by which they can be stood upright and rolled along the ground but also enables future cylinders to be made with domed ends for ease of manufacture, and because a domed end is generally the best configuration for withstanding fluid pressures, and subsequently provided with seating and rolling surfaces by molding thereto an aforesaid base part.

It is preferred that said seating surface of the base part is annular to give good stability when the vessel is placed on uneven surfaces.

It is further preferred that the annular rolling surface of the base part is rounded in radial cross-section which facilitates rolling of the vessel on account of the fact that it is not critical to maintain one specific angle of tilt of the vessel for such rolling.

It is further preferred that the base part has a cylindrical exterior and it may have an outside diameter substantially equal to the outside diameter of the adjacent cylindrical wall of the vessel to thereby effectively form an extension of said vessel wall. However, the base part may have an outside diameter slightly greater than that of the adjacent cylindrical wall of the vessel so that a portion of the base part encircles a portion of such vessel wall.

The base part may encapsulate the entire domed closed end of the vessel.

The invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a part-sectional view of a gas storage cylinder having a base part in accordance with the invention, and; Figure 2 is a sectional view on a larger scale of a mould for use in moulding the base part onto the cylinder of Figure 1.

Referring to Figure 1 of the drawings, a conventional gas storage cylinder 1, having a domed bottom end 11 is provided with a base part 12 in the form of a foot ring 13 made of tough elastomeric or polymeric material and moulded around the domed end 11 of the vessel and a portion of the cylindrical wall 10 adjacent thereto. The foot ring 13 is formed to have a cylindrical wall 14 which has a diameter slightly greater than that of the wall 10 for ease of filling the mould as described below.

The foot ring 13 has a flat bottom surface 15 to enable the vessel to stand freely on the ground in an upright position. The central area of the bottom of the foot ring is recessed, as denoted by reference numeral 16, in order to reduce the amount of elastomeric or polymeric material required for the foot ring and also to provide an annular flat seating surface 15 which gives greater stability when the vessel is placed on uneven ground. The annular edge 17 of the foot ring between surfaces 14 and 15 is rounded and provides a surface on which the vessel can be rolled along the ground by rotation of the vessel about its axis with the vessel axis at an acute angle to the ground.

Referring to Figure 2, a mould 18 for the foot ring comprises a base plate 19 and a cylindrical wall 20, the lower edge of which engages in an annular channel 21 in the upper surface of base plate 19. The area of plate 19 radially inwards of channel 21 is shaped to have a contour complementary to that required for the bottom surface of the foot ring. The lower end portion of the vessel is located in the mould.

The domed end of the cylinder engages a raised central area 22 of the contoured portion of plate 19. The wall 20 has an inner diameter greater than the outer diameter of the cylindrical wall 10 to define an annular space 23 therebetween.

The material of the footring is poured into space 23 until the mould cavity, defined between the mould 18 and the vessel 1, is filled.

One specific procedure for forming the foot ring using a mould as shown in Figure 2 will now be described. The vessel is shot-blasted to provide a surface suitable for receiving a bonding agent. The surface may if necessary be degreased using any suitable solvent, for example xylene followed by methyl ethyl ketone. A primer is then applied to the vessel by spraying or any other suitable technique. A suitable primer, which constitutes the bonding agent for the foot ring, is Thixon 1153 (marketed by Compounding Ingredients Ltd., Quay Street, Manchester). The primed surface is then forced dried in an oven under conditions which avoid bubbling. The time lapse between shot blasting and primer application should be as short as possible and should not exceed 8 hours. A further application of primer is then carried out.

A release agent is applied'to the inner surfaces of the mould 18 by spraying. A suitable release agent is Contour 1711 (marketed by Compounding Ingredients Ltd). The mould is then placed around the primed vessel and the mould and vessel assembly is heated until both are at about 100"C.

An elastomeric material found to be particularly suitable for the foot ring 13 is prepared from two compounds, namely Adiprene L-167 and MOCA (both trade marks of DuPont Limited). A quantity of Adiprene L-167 is warmed to 50"C and rolled. The required amount of such material is then taken and a dispersed pigment paste, e.g. CIBA GEIGY dispersed black 1102, is added. The mixture is heated to 1000C and degassed for 15 to 20 minutes at a maximum absolute pressure of Sm.m.I-Ig.

The required quantity of MOCA is taken and heated to 1200C to melt the material.

The two compounds are then mixed and poured into the heated mould 18 to fill the mould cavity. The elastomeric material is cured for 1 hour at 100"C. It is possible to remove the mould 18 after about 30 minutes of curing.

The above described material has been found to be particularly suitable as it has a high impact strength, good abrasion resistance and is fire resistant and self extinguishing thereby giving the foot ring a long useful life under arduous working conditions. Moreover, the material does not skid on wet surfaces as readily as an untreated vessel and it has an elastic memory so that even if it is deformed it will tend to recover its original shape.

Advantages of providing a gas storage cylinder having a domed closed end with a foot ring as described above are that the likelihood of damage to, and corrosion of, its bottom end is reduced, it can be stood upright otherwise unsupported, it is easier to move manually, noise during handling is reduced, less damage is inflicted e.g. on concrete surfaces by the vessel during handling, and the danger of sparking during handling is minimized.

It is expected that, in other embodiments of the invention, the mould wall 20 can be made of a size such that its inner diameter is substantially the same as the outside diameter of the cylindrical wall 10 of the vessel to produce a foot ring having a cylindrical wall which effectively forms an extension of the wall of the vessel. Suitable passages or pipes leading to the mould cavity would be provided in or through the mould wall 20 for introducing the elastomeric material into the mould and for allowing air to vent therefrom. It is desirable to make the foot ring so that it does not project radially beyond the vessel wall by an appreciable amount so that the number of vessels that can stand next to one another in a given storage area is not greatly reduced.

Furthermore, it is envisaged that the mould may be adapted to leave a space between the crown of the domed end of the vessel and the adjacent wall of the mould. In this way, the entire domed end is encapsulated thereby reducing still further the risk of damage and corrosion. In this case, the mould may be placed on the vessel when the latter is in a horizontal position.

WHAT WE CLAIM IS:- 1. A fluid storage vessel of cylindrical form and having a domed closed end (as hereindefined), provided with a base part of tough elastomeric or polymeric material (as herein defined) moulded in situ around said end of the vessel, the base part providing a substantially flat seating surface by which the vessel can be stood freely on the ground with its axis substantially vertical and an annular rolling surface having a mean diameter equal to or approximately equal to the outside diameter of the adjacent cylindrical wall of the vessel by which the vessel can be rolled along the ground by rotation of the vessel about its axis with the vessel axis at an acute angle to the ground.

2. A vessel according to claim 1 wherein said seating surface is annular.

3. A vessel according to claim 1 or claim 2 wherein said rolling surface is rounded in radial cross-section.

4. A vessel according to claims 1, 2, or 3 wherein the base part has a cylindrical exterior.

5. A vessel according to claim 4 wherein the base part has an outside diameter substantially equal to the outside diameter of the adjacent cylindrical wall of the vessel to thereby effectively form an extension of said vessel wall.

6. A vessel according to any preceding claim wherein the entire domed closed end of the vessel is encapsulated by the base part.

7. A fluid storage vessel of cylindrical form and having a domed closed end, substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. The required quantity of MOCA is taken and heated to 1200C to melt the material. The two compounds are then mixed and poured into the heated mould 18 to fill the mould cavity. The elastomeric material is cured for 1 hour at 100"C. It is possible to remove the mould 18 after about 30 minutes of curing. The above described material has been found to be particularly suitable as it has a high impact strength, good abrasion resistance and is fire resistant and self extinguishing thereby giving the foot ring a long useful life under arduous working conditions. Moreover, the material does not skid on wet surfaces as readily as an untreated vessel and it has an elastic memory so that even if it is deformed it will tend to recover its original shape. Advantages of providing a gas storage cylinder having a domed closed end with a foot ring as described above are that the likelihood of damage to, and corrosion of, its bottom end is reduced, it can be stood upright otherwise unsupported, it is easier to move manually, noise during handling is reduced, less damage is inflicted e.g. on concrete surfaces by the vessel during handling, and the danger of sparking during handling is minimized. It is expected that, in other embodiments of the invention, the mould wall 20 can be made of a size such that its inner diameter is substantially the same as the outside diameter of the cylindrical wall 10 of the vessel to produce a foot ring having a cylindrical wall which effectively forms an extension of the wall of the vessel. Suitable passages or pipes leading to the mould cavity would be provided in or through the mould wall 20 for introducing the elastomeric material into the mould and for allowing air to vent therefrom. It is desirable to make the foot ring so that it does not project radially beyond the vessel wall by an appreciable amount so that the number of vessels that can stand next to one another in a given storage area is not greatly reduced. Furthermore, it is envisaged that the mould may be adapted to leave a space between the crown of the domed end of the vessel and the adjacent wall of the mould. In this way, the entire domed end is encapsulated thereby reducing still further the risk of damage and corrosion. In this case, the mould may be placed on the vessel when the latter is in a horizontal position. WHAT WE CLAIM IS:-

1. A fluid storage vessel of cylindrical form and having a domed closed end (as hereindefined), provided with a base part of tough elastomeric or polymeric material (as herein defined) moulded in situ around said end of the vessel, the base part providing a substantially flat seating surface by which the vessel can be stood freely on the ground with its axis substantially vertical and an annular rolling surface having a mean diameter equal to or approximately equal to the outside diameter of the adjacent cylindrical wall of the vessel by which the vessel can be rolled along the ground by rotation of the vessel about its axis with the vessel axis at an acute angle to the ground.

2. A vessel according to claim 1 wherein said seating surface is annular.

3. A vessel according to claim 1 or claim 2 wherein said rolling surface is rounded in radial cross-section.

4. A vessel according to claims 1, 2, or 3 wherein the base part has a cylindrical exterior.

5. A vessel according to claim 4 wherein the base part has an outside diameter substantially equal to the outside diameter of the adjacent cylindrical wall of the vessel to thereby effectively form an extension of said vessel wall.

6. A vessel according to any preceding claim wherein the entire domed closed end of the vessel is encapsulated by the base part.

7. A fluid storage vessel of cylindrical form and having a domed closed end, substantially as hereinbefore described with reference to the accompanying drawings.