GB2478015A

GB2478015A - Thin walled water cylinder

Info

Publication number: GB2478015A
Application number: GB1007696A
Authority: GB
Inventors: Gerard Joseph Mackle; Jason Bern Costello Cassells
Original assignee: WARMFLOW ENGINEERING Co Ltd
Current assignee: WARMFLOW ENGINEERING Co Ltd
Priority date: 2010-05-10
Filing date: 2010-05-10
Publication date: 2011-08-24
Anticipated expiration: 2030-05-10
Also published as: GB201007696D0; IE86068B1; GB2478015B; IE20110202A1

Abstract

A process for forming a thin walled cylinder is described. The cylinder comprises a cylindrical body 2 and end cap 6, where the cylindrical body has at least an end cap meeting edge 4 and the end cap has at least a body meeting edge 8. The process comprises the steps of forming the end cap meeting edge of the cylindrical body inwardly to decrease its diameter relative to the remainder of the cylindrical body, forming a lip 16 in the end cap meeting edge, and welding the so formed end cap meeting edge with the body meeting edge of the end cap. The lip forms filler material for the welding of the end cap meeting edge with the body meeting edge. Preferably, the thin walled cylinder is a closed hot water pressurised cylinder having a cylindrical body thickness in the range 0.5-1.5 mm. The end cap may comprise a dome having a circular bottom edge.

Description

Cylinder The present invention relates to a process for forming a thin-walled cylinder such as a water cylinder, particularly but not exclusively a pressurised hot water cylinder, and to a thin-walled cylinder.

Currently, pressurised hot water cylinders are formed by simple lap welding the body of a cylinder with a base and top plate to form a closed cylinder having sufficient strength to withstand the expected pressure and pressure changes therein. However, with the constant introduction of fresh water into such cylinders, such water generally being heavily oxygenated, the ready supply of oxygen means that any weakness in the inner surface of the cylinder, in particular any crack or crevice created by or left by the lap welding, provides an easy location for corrosion to start (using on the constant supply of oxygen in the fresh water).

Thus, many conventional cylinders are often easily corrodible, which defect cannot be seen within the closed or sealed cylinder once formed.

Any such corrosion will naturally effect product lifetime, and lead to potentially catastrophic leakage once the corrosion is sufficiently advanced.

It is an object of the present invention to provide an improved closed cylinder, as well as a process for forming a thin-walled cylinder that overcomes one or more of the above disadvantages.

Thus, according to one aspect of the present invention, there is provided a process for forming a thin-walled cylinder, the cylinder having a cylindrical body having at least an end cap-meeting edge, and an end cap having at least a body-meeting edge, comprising at least the steps of: (a) forming the end cap-meeting edge of the cylindrical body inwardly to decrease its diameter relative to the remainder of the cylindrical body; and (b) welding the so-formed end cap-meeting edge with the body-meeting edge of the end cap.

By decreasing the diameter of the end cap-meeting edge relative to the remainder of the cylindrical body, the end cap-meeting edge can be better directed towards the end cap, and can provide increased stability to the end cap-meeting edge during the subsequent welding step compared with an unformed or otherwise straight' edge.

The term "thin-walled" as used herein relates to a thickness from less than 1 mm, up to several millimetres, but generally not 10mm or above.

Generally, "thin-walled" may be in the range 0.1-5mm, preferably in the range 0.6-2mm, more preferably in the range 0.5-1.5mm. The example of the present invention as described hereinafter relates to a cylinder having a cylindrical body thickness of 0.8mm.

The cylinder is generally intended for use in a pressure or pressurised internal environment, generally a pressure above ambient pressure, such as in the range 3-15 bar.

The cylinder may be for use with any suitable liquid, including but not limited to water. The liquid may be heated, such as hot water. Heated liquid is usually more aggressive in relation to causing corrosion than cold or ambient liquid.

The cylinder is preferably a closed cylinder, and may include one or more ports for the entry and exit of one or more fluids, and may comprise one or more internal pipings, such as one or more coils, for the passage of hot liquids such as hot water thereth rough.

The cylinder body may have any suitable shape, size and dimensions.

Generally, the cylinder body is cylindrical, although the present invention is not limited thereto, and has a radius of several millimetres up to hundreds or thousands of millimetres.

The general shapes, sizes and designs of hot water cylinders are known in the art.

The end cap may have any suitable shape, size, design or configuration, at least having an edge intended to meet the end cap-meeting edge of the cylindrical body. The end cap may be integrally formed, or formed from a single piece of material, or be multi-formed.

Preferably, the end cap is formed from a single piece of sheet material such as sheet steel.

Preferably, the end cap has curvature and/or one or more arcuate portions, particularly at or near its body-meeting edge for meeting the end cap-meeting edge of the cylindrical body.

In one embodiment of the present invention, the end cap is a dome or otherwise having a domed shape, generally having a circular bottom edge intended to correspond with the end cap-meeting edge of the cylindrical body.

The end cap-meeting edge of the cylindrical body may be formed inwardly using any suitable process, apparatus or mechanism. This includes one or more of various swaging, roll forming, pressing, spinning and stamping processes, all known to the person skilled in the art.

Preferably, the end cap-meeting edge is formed inwardly to a degree or angle which is similar to, preferably wholly or substantially the same as, the relative angle of the body-meeting edge of the end cap in relation to the longitudinal axis of the cylinder.

The degree of inward forming of the end cap-meeting edge may be any number of degrees relative to the cylindrical plane of the remainder of the cylindrical body, such that the decrease in the diameter of the end cap-meeting edge after being formed inwardly is any decrease starting from >0mm. Similarly, the angle of the end cap-meeting edge relative to the plane of the remainder of the cylindrical body is >00.

According to another embodiment of the present invention, the process comprises the further step of forming a lip in the end cap-meeting edge.

Said lip may be formed either prior to, simultaneously with, or after the forming of the end cap-meeting edge inwardly.

The lip preferably extends circumferentially outwardly from the end cap-meeting edge, and preferably provides a suitable position for the location of the body-meeting edge of the end cap against the end cap-meeting edge.

According to another embodiment of the present invention, the lip provides a nested arrangement with the end cap that allows the cylindrical body in the end cap to be easily held in a secured manner during the welding of the formed edge with the end cap, such as in a suitable jig or the like, preferably being a self-jigging arrangement. That is, the nested arrangement allows the cylinder body to help hold' the end cap therewith.

The body-meeting and end cap meeting edges are preferably welded together using one or more known welding techniques that allow a weld to be formed having little or no defined edges within the inner surface of the cylinder, thereby reducing and/or preventing any cracks or crevices which may subsequently be weak or weakened points of the cylinder, in particular for the initiation of corrosion.

According to one embodiment of the present invention, the welding of the meeting edges includes at least an element of fusion welding. Where the end cap meeting edge includes a lip, preferably the lip forms part of the weld, that is it forms filler material or weld material for the welding of the end cap-meeting edge with thebody-meeting edge. Even more preferably, the lip is wholly or substantially burnt into the weld between the cylinder body and the end cap.

Preferably, the final form of the weld between the body and the end cap is, or has the form of, a butt weld, thus avoiding any crevices or cracks as discussed above.

The cylinder formed by the present invention may include a separate or integral base, optionally provided by using the process for forming as described herein.

The cylindrical body and end cap may be formed from the same or different materials, generally being metal or metal based, such as steel.

According to a second aspect of the present invention, there is provided a thin-walled cylinder comprising at least a thin-walled cylindrical body having an inwardly formed end cap-meeting edge, and an end cap welded thereto.

Preferably, the inwardly formed end cap-meeting edge is formed with a lip prior to welding with the end cap, said lip being as described hereinabove.

Preferably, the cylinder includes a base and forms a closed cylinder, more preferably a closed pressurised cylinder, particularly but not exclusively for a liquid such as water, in particular a heated liquid such as hot water.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a side view of a cylindrical body and end cap to form a thin-walled cylinder of the present invention; Figure Ia is an expanded view of Detail A of Figure 1; Figure 2 is a cross-sectional view of the detail in Figure 1 a and its meeting with the end cap in Figure 1; Figure 3 is a side view of the end cap of the cylindrical body and end cap in Figure I; Figures 3a, 3b and 3c are enlarged drawings of the Detail of Figure 3 showing conjoining steps; and Figure 4 is a side view of a closed cylinder according to the present invention.

Referring to the drawings, Figure 1 shows a cylindrical body 2 having an end cap-meeting edge 4, and an end cap 6 having a body-meeting edge 8.

Generally, the cylindrical body 2 is elongate, having a possible but non-limiting diameter in the range 400-500mm, and a possible but non-limiting height of 500-2000mm. Cylinders formed with such a cylindrical body are known in the art to have a capacity of tens, hundreds or thousands of litres.

The example in Figure 1 shows the end cap 6 having a domed shape, preferably having the same or similar thickness and material, such as 0.8mm or 1.0mm sheet steel, as the cylindrical body 2.

Optionally prior to or subsequent to the process of conjoining the end cap 6 with the cylindrical body 2, the cylindrical body 2 includes, integrally or separately conjoined, a base 10. With the addition of the end cap 6, the cylindrical body 2 and base 10 form a closed cylinder 12 such as that shown in Figure 4, which may be used with a pressurised internal environment and/or for hot liquids such as hot water. Thus, such a closed cylinder may be a pressurised hot water cylinder. Entry and exit ports for the closed cylinder 12 are not shown in the Figures herewith.

Figure 1 a shows in enlarged detail the uppermost part of one side of the cylindrical body 2 and the end cap-meeting edge 4 within Detail A of Figure 1. Figure 1 a shows the step of forming the end cap-meeting edge 4 of the cylindrical body 2 inwardly so as to decrease its diameter relative to the general circumferential plane 14 of the remainder of the cylindrical body 2.

The forming of the decrease in diameter and the end cap-meeting edge 4 may be carried out by swaging in a swaging apparatus.

Figure Ia shows an angle of e° between the cylindrical plane 14 of the cylindrical body 2 and the direction of the end cap-meeting edge 4. This angle may be as low as <10, or 10 20, 3°, 40, 5-10°, or greater.

In this way, the diameter of the innermost portion 4a of the end cap-meeting edge 4 compared with the inner diameter of the cylindrical body 2 is decreased, preferably a number of millimetres, more preferably by in the range 1-20mm.

As the cylindrical body 2 is a thin-walled cylindrical body, such as being 0.6, 0.8 or 1mm thick, and the height of the cylindrical body 2 can be >1 m and possibly up to 2m or beyond, the skilled man will be aware of the very flexible nature of the cylindrical body 2 when it is a straight' cylinder and not otherwise deformed. By reducing the diameter of the end cap-meeting edge 4 by even a small amount or proportion, in the manner defined herein to provide one end of the cylindrical body 2 having an overall reduced diameter, a significant degree of self-stability of the reduced-diameter end is achieved, which significantly assists overall stability of the cylindrical body 2 during the conjoining with a end cap 6 as described herein after.

Figure la also shows the formation of a lip 16 in the end cap-meeting edge 4, which lip 16 extends circumferentially outwardly in relation to the cylindrical plane of the formed end cap-meeting edge 4. The lip 16 can be formed in a similar manner to the forming of the end cap-meeting edge, being swaging or pressing.

Figure 2 shows the bringing together of the end cap 6 and the cylindrical body 2 such that the end cap-meeting edge 4 and the body-meeting edge 8 meet, and in particular the body-meeting edge 8 is nested in the lip 16.

Figure 2 also shows the general direction and plane of the body-meeting edge 8 being the same or similar to the general circumferential plane of the end cap-meeting edge 4.

Figure 3 shows a end cap portion of the cylindrical body 2 and the end cap 4 in a conjoined position, and shows in Figures 3a, 3b and 3c detail of the process of welding the end cap-meeting edge 4 the body-meeting edge 8 together according to a step of an embodiment of the process of the present invention.

Turning to Figure 3a, there is shown the meeting of the body-meeting edge 8 of the end cap 6 with the end cap-meeting edge 4. The lip 16 is particularly formed such that the body-meeting edge 8 is able to be nested within the shape of the lip 16, and to rest on a surface of the lip 16 that is wholly or substantially perpendicular to the base of the body-meeting edge 8. This allows for easy maintaining of the end cap 6 and the cylindrical body 2 together in the subsequent welding as shown in Figures 3b and 3c.

Preferably, the lip 16 is particularly formed such that the body-meeting edge 8 and the end cap-meeting edge 4 come together to form a secure arrangement that is self-jigging', especially remembering the thin-walled nature of the cylindrical body which is otherwise highly flexible. Optionally, or of desired, a number of simple and small placement or spot welds could then be added around the circumference to assist or provide initial conjunction of the end cap 6 and cylindrical body 2 together prior to fully welding same.

Full welding of the end cap 6 and cylindrical body 2 requires careful control where the thickness of the material is relatively thin. In a particular advantage of the present invention, the material of the lip 16 can be used to fully or partly provide the weld material or filler, such that in forming the weld between the end cap 6 and the cylindrical body 2, the lip 16 is transposed from being a projection outwith the plane of the cylinder surface to wholly or substantially forming the weld 20. (The size of the weld 20 in Figure 3c is exaggerated for clarity purposes.) Preferably, the final form of the weld 20 has the form of a butt weld, avoiding crevices and cracks as discussed hereinabove, and allowing the cylinder to maintain an internal pressure in use similar to conventional cylinders.

In this way, the lip 16 is a sacrificial' lip, providing both the advantage of initial placement of the end cap 6 and cylindrical body 2 together, following by providing filler material for forming a butt weld thereinbetween.

Figure 3a also shows the preferred arrangement of having a seemingly continuous cylindrical inner surface plane along the path between BB'.

This reduces the hoop stress in the fully formed cylinder as the inner surface of the cylinder is continuously curved as it extends from the main body towards the end provided by the end cap.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments.

Claims

Claims 1. A process for forming a thin-walled cylinder, the cylinder having a cylindrical body having at least an end cap-meeting edge, and an end cap having at least a body-meeting edge, comprising at least the steps of: (a) forming the end cap-meeting edge of the cylindrical body inwardly to decrease its diameter relative to the remainder of the cylindrical body; and (b) welding the so-formed end cap-meeting edge with the body-meeting edge of the end cap.
2. A process as claimed in claim I wherein the end cap-meeting edge of the cylindrical body is formed inwardly by swaging.
3. A process as claimed in claim 1 or claim 2 wherein the end cap-meeting edge is formed inwardly to a degree or angle which is similar to, preferably wholly or substantially the same as, the relative angle of the body-meeting edge of the end cap in relation to the longitudinal axis of the cylinder.
4. A process as claimed in any one of the preceding claims comprising the further step of forming a lip in the end cap-meeting edge.
5. A process as claimed in claim 4 wherein the lip extends circumferentially outwardly from the end cap-meeting edge.
6. A process as claimed in claim 4 or claim 5 wherein the lip provides a location of the body-meeting edge of the end cap against the end cap-meeting edge.
7. A process as claimed in any one of claims 4 to 6 wherein the lip provides a nested arrangement with the end cap.
8. A process as claimed in any one of claims 4 to 7 wherein the lip forms filler material for the welding of the end cap-meeting edge with the body-meeting edge.
9. A process as claimed in any one of the preceding claims wherein the weld formed between the body-meeting and end cap meeting edges is or is in the form of a butt weld.
10. A thin-walled cylinder comprising at least a thin-walled cylindrical body having an inwardly formed end cap-meeting edge, and an end cap welded thereto.
11. A thin-walled cylinder whenever prepared by a process as claimed in any one of claims I to 9.
12. A thin-walled cylinder as claimed in any one of claims 10 and 11 having a cylindrical body thickness of in the range 0.5-1.5 mm.
13. A thin-walled cylinder as claimed in any one of claims 10 to 12 being a closed cylinder.
14. A thin-walled cylinder as claimed in any one of claims 10 to 13 being a hot water pressurised cylinder.
15. A thin-walled cylinder as claimed in any one of claims 10 to 14 wherein the end cap is a dome having a circular bottom edge.Amendments to the claims have been filed as follows Claims 1. A process for forming a thin-walled cylinder, the cylinder having a cylindrical body having at least an end cap-meeting edge, and an end cap having at least a body-meeting edge, comprising at least the steps of: (a) forming the end cap-meeting edge of the cylindrical body inwardly to decrease its diameter relative to the remainder of the cylindrical body; (b) forming a lip in the end cap-meeting edge, and (c) welding the so-formed end cap-meeting edge with the body-meeting edge of the end cap, wherein the lip forms filler material for the welding of the end cap-meeting edge with the body-meeting edge.2. A process as claimed in claim 1 wherein the weld is formed having little or no defined edges within the inner surface of the cylinder.3. A process as claimed in claim I or in claim 2, wherein the end cap-meeting edge of the cylindrical body is formed inwardly by swaging.4. A process as claimed in any one of the preceding claims wherein the end cap-meeting edge is formed inwardly to a degree or angle which is wholly or substantially the same as, the relative angle of the body-meeting edge of the end cap in relation to the longitudinal axis of the cylinder.*. ,.* S * 5. A process as claimed ir any one of the preceding claims wherein the lip extends circumferentially outwardly from the end cap-meeting edge.6. A process as claimed in any one of the preceding claims, wherein the lip provides a location of the body-meeting edge of the end cap against the end cap-meeting edge.7. A process as claimed in any one of the preceding claims, wherein the lip provides a nested arrangement with the end cap.8. A process as claimed in any one of the preceding claims, wherein the weld formed between the body-meeting and end cap meeting edges is or is in the form of a butt weld.9. A thin-walled cylinder whenever prepared by a process as claimed in any one of claims I to 8.10. A thin-walled cylinder as claimed in claim 9 having a cylindrical body thickness of in the range 0.5-1.5 mm.11. A thin-walled cylinder as claimed in claim 9 or claim 10 being a closed cylinder. I...12. A thin-walled cylinder as claimed in any one of claims 9 to 11 being **.a hot water pressurised cylinder.13. A thin-walled cylinder as claimed in any one of claims 9 to 12, wherein the end cap is a dome having a circular bottom edge.