GB2051623A - Renovation of kegs and casks - Google Patents

Abstract

In the renovation of an aluminium keg or cask (1) having an internal lacquer coating, it is first cut into two parts (1a, 1b). These two parts are separated, joined back to back by means of wire ties (12) passing through aligned hand and drainage holes (6, 7) in end rings (3, 4) of the keg or cask, and placed in an oven (13). In the oven the two parts (1a, 1b) are heated to burn off the lacquer coating, and then removed and quenched in a water bath. The thus annealed parts (1a, 1b) are reshaped and/or otherwise repaired as necessary, and immersed in a brightening bath comprising an aqueous mixture of nitric and hydrofluoric acids. After washing off the parts (1a, 1b) are joined back together again, by a continuous peripheral seam weld, and the internal surface is relacquered with a heat-cured epoxy resin lacquer coating. <IMAGE>

Description

SPECIFICATION Renovation of kegs and casks This invention relates to the renovation of aluminium beer kegs and casks which have an internal lacquer coating, normally provided by an epoxy resin lacquer. The term "alluminium" is used herein in its customary sense to refer to the various aluminium alloys used in this field of endeavour.

During renovation and repair it is normally required to remove the old lacquer coating from an aluminium keg or cask prior to relacquering. Removal of the old coating presents problems and it is commonly achieved by filling the container with fuming nitric acid, with all the hazards attendant on the use of this dangerous liquid. To avoid the use of nitric acid the kegs or casks have been heated in an oven in order to burn off the internal lacquer coating, followed by an internal shot blasting process before relacquering. This is not entirely satisfactory and it is usually found that some residue remains which is covered by the new coating.

The object of the invention is to provide a method which avoids the hazards of the use of fuming nitric acid and which obviates the shot blasting process of the described alternative while at the same time providing complete removal of the internal lacquer coating.

According to the invention the renovation of an aluminium keg or cask includes the steps of cutting the key or cask into two parts and heating the separated parts in an oven whereby to burn off the internal lacquer coating.

It is found that with the container opened up into two parts in this manner the lacquer layer burns off completely, due to complete accessibility of the lacquered surface to the furnace atmosphere. A further advantage is that the heating anneals the metal so that the separated parts can readily be reshaped on an expanding mandrel, and otherwise repaired as may be necessary, prior to welding the parts back together to provide a completely renovated container. After the parts have been welded back together the cleaned internal surface can be relacquered, by coating with epoxy resin lacquer and heat curing, in the usual manner.

Preferably the keg or cask is cut into two across the middle to provide more-or-less equal parts which are conveniently temporar ily secured together, back to back, before placing in the oven to ensure that the parts of several containers do not become mixed up and hence that the same two parts are always joined back together. Securing the parts back to back in the case of a keg provides the additional advantage that the usual stainless steel insert in the end pressure collar of the keg is trapped in the cavity between the parts instead of falling to the bottom of the oven when the plastics insulating material in which the insert is mounted burns away. This avoids the inserts collecting at the bottom of the oven which would result in the need for regular clearing out of the latter to avoid interference with the air circulation within the oven.

Securing of the two parts back to back may be achieved, for example, by means of tack welding, which has in practice provided to be very satisfactory. However, during the practi cal development of the invention the use of ties which pass through the usual hand an ) d/or drain holes provided in the end chime rings of a keg or cask has proved to be a better procedure. Preferably the ties are pro vided by wire "twists" of the type as com monly used to tie up the necks of potato sacks, i.e. lengths of wire which are passed through said holes and twisted tightly to gether to hold the parts securely together. The use of these ties is quick, easy and cheap, and they are just as easily removed after leaving the oven.

Before re-assembling the keg or cask by welding the parts back together any repairs requiring access to the inner sides can readily be accomplished, for example bushing of a damaged shive or keystone hole in a cast or replacement of the pressure collar of a keg.

The presence of the shive precludes cutting of a cask into two exactly equal halves and it is desirably cut through close to one or other of the rolling rings normally provided on either side of the shive.

The renovation and repair of an aluminium cask by a preferred method in accordance with the invention is illustrated in the accom panying diagrammatic drawings and will now be described, by way of example, with refer ence thereto. In the drawings: Figure 1(a) and (b) are respectively front and side views illustrating a first stage of the repair; Figure 2 illustrates the next stage; Figure 3 is a detail view of Fig. 2 to a larger scale; and Figures 4 to 6 illustrate further stages in the repair.

The cask 1 is of the usual form, fabricated with a central closed container portion 2 to the ends of which are welded identical end rings 3 and 4. Two spaced rolling rings 5 are fitted around the container portion 2 towards the centre thereof. The end rings 3 and 4 provide chimes and as usual have holes (see particularly Fig. 3) which provide hand holes 6 and drainage holes 7.

In the illustrated method the cask 1 is first cut into two parts, close to and on one side or other of the two spaced rolling rings, this stage being illustrated in Fig. 1. Cutting is achieved by means of a narrow band saw 8 mounted on a pivotal jib 9 above a rotating fixture 10 with a headstock 11 by which the cask 1 is turned about its longitudinal axis while being cut through by the saw 8 which runs along a track in the jib 9 providing a depth stop which engages the outer surface of the cask 1. The separated parts 1 a anl b into which the cask is thus cut are secured together back to back as shown in Figs. 2 and 3. In this stage of the repair the parts 1 a and 1 b are stood, one upon the other, with the end rings 3 and 4 in juxtaposition and with the hand and drainage holes, 6 and 7, therein respectively aligned.Twist wires 1 2 are passed through the aligned holes 6, 6 and 7, 7 and twisted up to tie the two parts 1 a and 1 b securely together. Typically, the parts 1 a and 1 b will be tied together in this manner using four to six such wire twists 1 2. The latter are of the type commonly used to tie up sacks of vegetables, with blunt ends provided by bent-round end rings 1 2a which can be gripped to twist the ties up tight.

The two parts 1 a and 1 b, thus tied together, are placed in an oven 1 3 (Fig. 4) in which a plurality of separated casks are simultaneously heated to a temperature of about 540 degrees Centigrade which anneals the metal and at the same time burns off the internal lacquer coating.

After removal from the over 1 3 the parts 1 a and 1 b are cooled by quenching in water and separated by removing the ties 12, which may be untwisted or cut off, and the annealed parts are then reshaped and expanded on a radially expanding mandrel 14 (see Fig. 5) the expansion of which is limited at a position rendering the parts 1 a, 1 b slightly oversize as compared with the original radial dimensions.

This oversizing just compensates for the small amount of metal removed by the saw 8 and thus it restores the correct internal volume.

The two reshaped and expanded parts 1 a, 1 b are immersed in a brightening bath (not shown) comprising an aqueous mixture comprising 10% nitric acid and 3% hydrofluoric acid. Then the cleaned and separated parts are accurately clamped together with their now circular cut edges in contact. They are initially joined together by lightly tack welding and then placed (Fig. 6) in a rotary fixture 15 for automatic welding to provide a continuous seam weld 16 which rejoins the parts 1 a, 1 b and results in a completely renovated construction. Instead of tack welding the parts can be held together in accurate relative positioning in some other manner for the final welding operation. If the shive hole or the keystone hole is damaged it can easily be bored out and rebushed while the cask 1 is separated into the two parts 1 a, 1 b and after the annealing process, the bushing then being accessible for welding in position from the inner side. Similarly, in the case of a keg the pressure collar thereof can readily be replaced while the parts are still separate. Any other repairs necessary, such as the welding of leaks, can be done at the same time.

After the parts 1 a, 1 b have been welded together to provide a complete and repaired cask the cleaned internal surface is relacquered and to this end it is given an epoxy resin lacquer coating by means of a conventional electrostatic spraying process, after which it is baked in an oven to cure the resin and complete the relacquering process.

Claims (19)

1. The renovation of an aluminium keg or cask with an internal lacquer coating, including the steps of cutting the keg or cask into two parts and heating the two parts in an oven whereby to burn off the lacquer coating, prior to welding the parts back together to provide a renovated container.

2. The renovation of a keg or cask according to claim 1 wherein the separated parts, after removal from the oven are in an annealed condition and are reshaped on an expanding mandrel and/or otherwise repaired as may be necessary, prior to welding the parts back together.

3. The renovation of a keg or cask according to either one of the preceding claims, wherein the cleaned internal surface is relacquered, after the two parts have been welded back together, by coating with epoxy resin lacquer and heat curing.

4. The renovation of a keg or cask according to any one of the preceding claims, wherein the two parts are welded directly back together after removal from the oven.

5. The renovation of a keg or cask according to claims 2 and 4, wherein the annealed parts are reshaped on an expanding mandrel which renders them slightly oversize whereby to compensate for a small amount of metal lost when the keg or cask was initially cut into two parts, and hence to restore the correct original internal volume of the keg or cask.

6. Renovation of a keg or cask according to any one of the preceding claims, wherein the keg or cask is cut into two across the middle to provide more or less equal parts.

7. Renovation of a keg or cask according to any one of claims 1 to 5, wherein the keg or cask has a central shive positioned between two spaced peripheral rolling rings and is cut through, to provide said two parts, close to and on the outer side of one or other of the rolling rings.

8. Renovation of a keg or cask according to any one of the preceding claims, wherein the two parts are temporarily secured to gether, back to back, before being placed in and while in the oven.

9. Renovation of a keg or cask according to claim 7, wherein the keg or cask is one of several such kegs or casks the temporarily joined parts of which are heated in the oven simultaneously.

10. Renovation of a keg or cask according to claim 8 or 9, wherein an end pressure collar of the keg has a stainless steel insert mounted in plastics insulating material which burns away in the oven, leaving the insert trapped between the temporarily secured-together parts of the keg.

11. Renovation of a keg or cask according to any one of claims 8 to 10, wherein the two parts are temporarily secured together by tack welding.

1 2. Renovation of a keg or cask according to any one of claims 8 to 10, wherein the two parts are temporarily secured together by means of ties which pass through hand and/ or drain holes provided in end chime rings of the keg or cask.

1 3. Renovation of a keg or cask according to claim 12, wherein said ties are provided by wire "twists", i.e. by lengths of wire which are passed through said holes and the ends of which are twisted tightly together to hold the parts securely.

14. Renovation of a keg or cask according to any one of the preceding claims, wherein repairs requiring access to the inner sides of said parts is effected before they are welded back together.

1 5. Renovation of a keg or cask according to claim 14, wherein said repair comprises bushing of a damaged shive or keystone hole, and/or replacement of a pressure collar.

1 6. Renovation of a keg or cask according to any one of the preceding claims, wherein said removal from the oven the two parts are quenched in a water bath and before welding together the parts are immersed in a brightening bath comprising an aqueous mixture of nitric acid and hydrofluoric acid.

1 7. Renovation of an aluminium keg or cask according to claim 16, wherein said aqueous mixture comprises about 10% nitric acid and about 3% hydrofluoric acid.

1 8. A key or cask which has been renovated according to any one of the preceding claims.

19. The renovation of an aluminium cask substantially as herein particularly described with reference to the accompanying drawings.