GB2284657A - Storage vessels - Google Patents

Abstract

A pressurised hot water storage cylinder comprises an outer, structural mild steel shell (1) lined with sheet copper (2). The cylinder comprises two cup-shaped halves (3, 3a) made by simultaneously deep-drawing superposed mild steel and copper sheets, the two halves being joined together by a circumferential weld (6) to form the finished cylinder which is provided with appropriate threaded bosses (not shown), for enabling connection of pipeworks to the cylinder, optionally, the provision of one or more electric immersion heater units. <IMAGE>

Description

Storage Vessels This invention relates to storage vessels, especially but not exclusively to hot water storage vessels for use in domestic or commercial, high pressure hot water supply systems.

The use of high pressure hot water supply systems has been commonplace for decades in many overseas countries and is now becoming more popular, instead of low pressure, cistern-fed systems, in the UK. In conventional low pressure systems, hot water is almost invariably stored in a relatively thin-walled copper cylinder which is able readily to withstand the lower pressures involved. Copper cylinders, too, may be used in high pressure systems in which the stored hot water is fed to points of use by incoming mains cold water reduced, typically, to a pressure of about 2 bar. However, it is then usually necessary to use a thicker-walled cylinder at considerably increased cost. As a consequence, it is common to use, in high pressure systems, mild steel cylinders that are lined in order to prevent corrosion problems.Typically, the lining comprises a thin enamel or plastics membrane but such linings have disadvantages.

It is an object of the present invention to provide an improved storage vessel, especially a hot water storage cylinder, comprising an outer structural shell having a corrosion resistant lining.

According to the present invention, therefore, there is provided a storage vessel, especially a hot water storage vessel, comprising an outer, structural shell of, for example, steel having a lining of a corrosion resistant metal sheet, for example, of copper.

Preferably, the structural shell comprises two separately formed portions, for example two substantially identical halves, each provided with a lining as aforesaid, the two portions being joined together to form the vessel. Preferably, each portion is of generally cylindrical form closed at one end by a dome-shaped wall and open at the other end, the respective open ends being brought together and then externally joined where they meet, for example by a welding operation. Where, as is preferred, the shell is made of mild steel and the lining is made of copper, each lined shell portion may be produced by simultaneously deep-drawing, using conventional techniques, a mild steel sheet of suitable gauge and a superposed copper sheet, again of suitable gauge.

Of course, when the two lined shell portions are externally joined together, it is necessary to ensure integrity of the lining. To that end, the joint between the two lined shell portions preferably has a configuration as shown in the attached drawings, which describe, by way of example, a preferred form of hot water storage vessel constructed in accordance with the invention and in which FIG 1 is a schematic sectional side elevation of the vessel, commonly referred to in the art as a "cylinder", and FIG 2 is a sectional detail of the region II of Fig 1 on a scale of about 2:1 actual size.

Referring firstly to Fig 1, the hot water storage cylinder, which in terms of external appearance is similar to a conventional all-copper cylinder, comprises an outer structural shell 1 of mild steel lined with a thin sheet 2 of copper. The wall thickness of the mild steel shell will typically be in the range of from 1.5 to 2.5 mm, for example about 1.6 mm, whilst the thickness of the copper sheet 2 will typically be in the range of from 0.5 to 1.0 mm, for example about 0.5 mm, thus enabling the cylinder to withstand up to about 10 bar working pressure.

The cylinder is, in fact, made up of two cup-shaped halves 3, 3a formed separately by simultaneously deep-drawing a mild steel sheet having a superposed copper sheet, using conventional techniques. The two portions are then joined together as will now be described in more detail with reference to Fig 2.

As can be seen from Fig 2, the open end of the lower half 3 of the cylinder 1 is belled as indicated at 4 whereas the open end of the upper half 3a is turned back on itself as indicated at 5. In the case of both halves 3, 3a, the copper sheet 2 terminates a short distance from the respective extremities of the mild steel shells. As can further be seen, the belled end 4 of the lower half 3 receives the turned-back end 5 of the upper half 3a, the extremities of the copper sheets associated respectively with the upper and lower halves 3, 3a being in contact with one another and being trapped between the extremities of the mild steel shells of the lower and upper halves 3, 3a.

A circumferential recess is defined between the extremities of the mild steel shells where they meet and this recess enables the two mild steel shells to be circumferentially fillet-welded together, as shown at 6, using, for example, a copper or copper alloy welding material such as a phosphor bronze or aluminium bronze. The circumferential fillet-weld 6 not only securely joins the upper and lower mild steel shells together, but also forms a bond with the edges of the copper sheets that project into the aforesaid recess. By using this joint configuration, during the fillet-welding process the heat input to the critical areas of the copper sheets, namely the radiused portions at the joint between the halves 3, 3a, is limited, being significantly dissipated by the mild steel, and they are thus preserved in their stronger, small grain structure form. Accordingly, a strong, watertight joint is formed between the two halves 3, 3a which, we have found, can withstand fatigue tests comprising hundreds of thousands of temperature change cycles.

The strength of the joint between the two halves 3, 3a may be enhanced by providing an equator band 7 in the form of, for example, a 3.3 mm thick mild steel pressing that surrounds the joint and that is itself joined by circumferential mild steel welds 8 and 9 to the mild steel shells of the halves 3, 3a respectively.

As will be appreciated, the cylinder will be provided with appropriate threaded bosses (not shown) for enabling connection of requisite pipes to the cylinder and, possibly, the installation of one or more electric immersion heater units.

Claims (10)

1. A storage vessel, for example for storing pressurised hot water, comprising an outer, structural shell having a lining of corrosion resistant sheet metal.

2. A vessel according to claim 1 wherein said shell comprises a steel.

3. A vessel according to claim 1 or claim 2 wherein said lining comprises copper or a copper alloy.

4. A vessel according to any one of claims 1 to 3 comprising two portions joined together to form an enclosed structure having a continuous lining of said corrosion resistant sheet metal.

5. A vessel according to claim 4 wherein each portion is of generally cylindrical form closed at one end and open at the other end, the respective open ends being circumferentially joined together to form said enclosed structure.

6. A vessel according to claim 4 or claim 5 wherein said portions are joined together by welding and/or brazing.

7. A vessel according to any one of claims 4 to 6 wherein each portion has been produced by simultaneously deep drawing appropriate, superposed, sheet materials.

8. A vessel according to claim 4 wherein the joint between said two portions has a configuration substantially as hereinbefore described with reference to the accompanying drawings.

9. A storage vessel substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

10. An unvented, high pressure hot water storage and supply installation including a storage vessel according to any one of claims 1 to 9.