Attaching the Column and Boiler
Attaching the Column to the Boiler
Stainless Steel Milk Cans
Adapting the stainless steel milk can for use as a still boiler is quite easy because the modifications are all made on the removable flat topped cap.
The modifications involve cutting a 2 1/8" hole in the cap and then either TIG welding the column directly to the cover, or building a small flanged adapter that will allow the column to be bolted to the cover.
The column should extend about an inch or two below the boiler cover so that brass screening can be used to cover the end. The screen keeps the tower packing (Raschig Rings) from falling into the boiler. A stainless steel hose clamp secures the screen to the bottom of the column.
If welding facilities are not available, a 2" copper adapter can be constructed as shown below.
Building this adapter is quite straightforward except that the outside diameter of the copper coupling is 2 1/8”. Unfortunately, in the U.S. the exhaust flanges are not made that size. And boring out a 2" flange is a very difficult job.
However, the problem can be avoided by first silver soldering a standard 2" coupling on top of the flange, and then making a collar that will pass up through the 2" hole and seat in the bottom of the coupling. Details of making this collar and pictures of the adapter are described in the "Building the Column Adapter" section below .
A cork flange gasket is also needed to fit the flange to the top of the boiler cap. Details of how that is made is described in the "Making the Gaskets" section below.
Stainless Steel Beer Kegs
As it stands, the biggest problem with the stainless half keg is that it doesn't have a good fitting to attach the reflux column to, and it is very difficult to clean and fill it without brewery filling and steam cleaning equipment.
At the very least, the ball valve assembly must be removed before the 2" reflux column can be attached. But even if this is done, it is difficult to attach the column with a flange fitting because of the curved top of the barrel. Furthermore, simply having a 2" opening at the top when the flange is removed will not be enough to allow the boiler to be cleaned well.
Modifying the Stainless Half Keg
We've found the best way to overcome these limitations is to start out by cutting out a large circle in the top of the keg so that a separate cover can be attached. We found that an 8" stainless steel mixing bowl with a 1/4" rimmed flange made a good cover.
To prepare for the cut you might find it easier to make a paper template by tracing and cutting out a circle inscribed around the rim of the mixing bowl as it is inverted over the paper.
The template center can then be found by using an ordinary compass. After the center is marked, draw another concentric inner circle 1/2" inside the first . Then cut the template around the inner circle line. The template will now be the correct size for cutting the hole.
To center the template on the top of the keg, you might find it easier to cut an X with about 3" legs through the center of the template. This will allow you to fit the paper over the ball valve on the top of the keg and then center the template.
When the template is centered, scribe a mark around it with a felt tipped pen. This will mark the top of the keg with the cutting line. The hole can be cut with an ordinary saber saw, but the cutting will go much faster if you have a larger reciprocating saw for this job. In either case, you will need to drill a pilot starting hole just inside the cutting line circle to start the cut.
When you've finished cutting the hole, use a round file or a die grinder to remove the burrs and smooth out the inside edges of the cut.
Anchoring the Cover
The mixing bowl cover is anchored to the keg by four 1/4" bolts. Since the metal on the top of the still is too thin to hold a thread, four 3/8" holes were drilled around the outside rim of the bowl flange to accommodate the insertion of threaded fastener nuts.
The bolts are inserted through 1 1/2" fender washers which clamp down on the outside rim of the mixing bowl cover. Because the top of the keg is domed, the washers were bent almost in half to compensate for the drop in elevation on each side of the bolt.
Building the Column Adapter
To allow fitting the still column to the keg cover, an adapter is made from a 2" automobile exhaust flange and a 2" copper coupling and bolted to the bottom of the bowl. And while these dimensions sound correct, they are unfortunately inside dimensions. That means that neither the column tubing nor the coupler can pass through the 2" hole in the exhaust flange.
Worse, the flanges are not made with 2 1/2" holes.
To avoid the expense of boring out the flange, it was decided that the coupling would be placed on top of the flange, rather than passing through it, and then silver soldered in place.
The consequences of that decision meant that the column tube would fit up to the coupling restriction on the top, but a connection to that coupling from the underside of the keg cover would not be able to pass through the flange opening of 2".
A connection from the underside of the coupler is needed, because the column is packed with Raschig rings or other distillation packing.
The connection will allow the column and cover to be removed from the keg as a unit.
With that in mind, you need to make up a collar of the right diameter and length to pass through the keg cover, and then seat into the coupling and flange from the underside.
This is best done by cutting a 5" nipple from 2" stock, and then making a hacksaw cut along its length. In that way you will be able to overlap the cut joint and reduce the diameter enough to pass through the cover, flange, and seat in the underside of the coupling. Notice how this appears in the photo at left.
The bottom end of this collar should pass through the flange and cover for about 3 inches. This will allow a covering of brass screen to be attached to the bottom end with a stainless steel clamp and ensure that the column packing will remain intact when the keg cover and column are disconnected.
Making the gaskets
Cork gaskets are used on both the top and bottom of the keg cover. This material is generally available at auto parts stores in 10" wide rolls of 1/8" sheet cork. Once the gasket outline has been drawn, the gaskets can be easily cut out with scissors or a sharp utility knife. The job of cutting out the small bolt holes is made much easier if a hollow punch set is available.
The rim of the keg cover is used to make the pattern for that gasket. Once the rim circle is traced on the cork sheet, draw a concentric inner circle so that a 1/2" wide circular gasket will be described. You may elect to use the pattern made for cutting the keg top for this.
The adapter flange (without the collar) should be used as a template to scribe the bolt hole locations and the flange hole on the bottom of the mixing bowl. The flange is also used to draw the outline pattern on the cork gasket material. Use the big circular piece left over from cutting the rim gasket for this.
A felt tip pen does a nice job on both these tasks.
Finishing the Keg Cover
The keg cover will be completed by cutting a 2" hole in the bottom of the bowl so that the collar can pass through it and seat in the bottom half of the flange coupling. It should fit quite tightly in the cover and flange holes and does not need to be soldered or pinned with a set screw.
The job of cutting the hole is made much easier if a bi-metallic hole saw is available. When this is finished, drill the marked flange bolt holes.
When all the cover holes have been drilled, insert the split collar through the cover as shown, and slip the gasket in place. The flange assembly can then be installed. At this point the cover assembly can be bolted together and set aside until it's time to attach the column.
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