A BOTTLER OF A BOILER

Now there is no real general rule for what you can use as a boiler. Even plastic containers are used (heated with an electric element). As long as it can take the heat, doesn't contaminate the beer, well anything can be used.

Now myself I love to cook with gas, so this naturally means I must use metal. I also want to boil 42 litre batches down to 38 litres, and this is where I had problems. Trying to find a large enough boiler is no real problem, any cooking supply shop has them, but the cost is terribly expensive. I needed a cheaper alternative, but most of all I wanted stainless steel for ease of cleaning.

It turned out easier than I thought. I managed to get a 50 litre keg that had a damaged top. Now there are two types of 50 litre kegs common in Australia. One is a squat 50 litre that CUB use, the other a taller narrower one used by Lion Nathan. I picked the taller narrow one, as it offered a smaller base. This means I can concentrate the heat on a smaller area.

So what did I do - First I had to prepare the base for the burner.

This is my burner. It's just a three ring low pressure LPG burner. This gives out more than enough heat to get a good rolling boil. In fact I only have to use the two outer rings. There is a lot of confusion out there how to use these burners. It is really quite simple. There is a round plate near the tap. This should be screwed out all way to allow as much air as possible to be sucked into the burner.

The flame is critical to get the best heat. You should adjust the flame so it is blue just rising off the burner. The odd flicker of yellow is ideal. This is then burning the gas most efficiently, giving off the greatest amount of heat. A yellow flame means a lot of soot will form on the bottom of the pot and the flame wont be as hot.

Now while a blue flame will be hot enough to get a good boil, you can help concentrate the heat with a few tricks. If you look at the bottom of kegs they are not shaped to trap heat. In fact they do the reverse, move heat away to the sides.

So how do you concentrate the heat?

I have modified the base of the boiler as you can see by the photo. You will notice that the base is 'inverted'. This allows the heat to rise to the middle of the base, instead of out at the sides. The boiler also sits nice and stable on the burner. So how do you do this. Well it's a matter of getting a hammer and a block of wood. Starting right at the middle bash the centre in. Then just keep working round the "edge", making the dent bigger and bigger, til you reach the rim of the keg. Now the volume the keg can hold will naturally drop from 50 litres to about 45 litres, but that still more than enough.

Also notice in the photo that I have removed the bottom rim off the keg. The rim did not allow enough of the exhaust gas to escape, in effect trapping it under the keg. This affected the height and efficiency of the flame. You may think the rim will help trap heat, but it also doesn't allow enough air to the flame. It was more efficient to remove it to get a bigger flame. Just leave a small edge that you can still stand the keg on the ground.

There is another advantage to having an inverted bottom. I am able to put the tap at the bottom of the keg. Thus I can drain the keg without the need of any unusual fittings. Speaking of fittings, the tap is just a 3/8 BSP thread blank stick welded to the side with a stainless steel ball tap fitted to that.

Now for the top.

As you can see the opening is not that large. Now I get the required evaporation rate of 10%-15% per hour with this size opening. Now there are a lot of arguments concerning oxidisation of the wort during boiling, whether it exists or not, and does it have a significant affect on flavour. While I will not go into the pros and cons of this debate, certainly there is no need to have an opening bigger than what you need. Mine I can get my hand in to clean. That's big enough.

But the real reason I had such a small hole is heat conservation. It traps a lot of heat, just like having a lid on a pot to help get it to the boil. You will be amazed how effective it is at trapping heat, yet allowing a good evaporation rate. In fact it has a similar shape to professional boilers.

And how did I cut the hole in the top. Well it's as easy as using an angle grinder and metal cutting blades. Cutting the hole will use two blades.

Finally, what do I use to filter out the trub and hops. You will see it in the photo on the boiler top. Its nothing more than a roll of Termi-mesh (stainless steel) that I roll up and put in the hole before I transfer the liquid. Notice you don't need a large screen to get good filtering and flow.

So that it! A cheap boiler that will last a lifetime.

Shout
Graham Sanders