Archive for October, 2012

October 30, 2012

Oooh shiny….

It doesn’t take much reading of the most popular brewing forums to realise that for many home brewers the construction of “stuff” for their brewery is almost as absorbing (and in some cases more so) that the actual brewing.  And that the shinier things are the more appealing they seem to be.  I’ll be honest, at the moment I spend much more time building bits of the brewery than I spend making beer. Mostly this is through necessity – having embarked on an exercise to upscale generally I’ve found more and more things that need to be built or modified or generally tinkered with before I can actually get the benefit of the increase in size.  But sometimes, it is very easy to get distracted by something that is more shiny and pleasing to the eye than actually a true necessity.

And so it was this weekend when, amongst a very productive attack on a number of other outstanding jobs, I had my first go at making a nice shiny spinning sparge arm.  For those of you who don’t know, sparging is the process when the mashed grain are slowly washed through with hot liquor (water) to extract all the sugars prior to the boil.  A common method in commercial breweries is a perforated pipe – the sparge arm – which rotates above the mash tun spraying the hot liquor over the top of the grain.  The rotation helps spread the liquor out across the grain rather than creating channels that cause the liquor to run straight through and miss those sugars that we’re trying to rinse through.  At least, that’s my understanding of it all…

In the home brewing world there are a variety of different approaches adopted to achieve the same end.  Sometimes it’s a mimic of the commercial rotating arm, other times it is a static version with more pipe and more holes to get a wider spread.  Watering can roses have been adapted for the purpose too, and then there’s the cruder but still effective sheet of foil with holes punched through.  And some people just gently run the liquor out onto the top.  It is arguable whether one method is actually significantly better than any other, and therefore questionable whether the extra effort makes the more technical solutions worthwhile or not, especially on this scale, but each to their own.

So armed with almost limitless enthusiasm for spending time potentially failing to achieve the more complicated of the various options, on Saturday night I set about building my own shiny spinny thing.  Here’s how I did it.

Parts list:
2 x 300mm lengths of 8mm diameter brass tube
2 x 8mm compression stop ends
1 x 8mm compression tee
1 x 8mm compression / 1/2″ BSP reducer

I should point out to start with that, when it comes to plumbing, I’ve found I’m much more successful when I don’t try soldering things any more than I absolutely have to.  Therefore, I went with compression fittings throughout.  This was slightly risky – they are of course heavier than soldered fittings and so the force (which comes purely from the flow of water through the sparge arm) required to spin the whole thing needs to be greater, so you might want to consider soldered stop ends if you’re copying this.  The tee needed to be compression though, as we’ll see shortly.

First step was to work out how long to make each arm.  My mash tun is 500mm across, but you need to allow for the size of the fittings too, and there’s no benefit in the end of the arms being too close to the edge of the tun, so in the end I went for about 160mm.  This meant, once the fittings were in place there was a total length of about 350mm, and there was a little over 100mm of tube between the fittings on each side.  This, in the event, worked out perfectly.  A piece of the remaining tube then became the downward feed to the whole thing.

Now for the holes.  Ten were marked out on each tube, 10mm apart, but the positions on one tube were offset at 5mm from those on the other tube to spread the spray out more.  The ten marks were in a straight line except for the outermost one, which was about 45 degrees further round so that it would direct the flow directly outwards whereas the others pointed down at about 45 degrees.  This was intended to provide a bit more of a push at the end to help the spinning.

In a rare display of caution I then drilled *half* of these holes, starting with the outermost and then drilling every other one.  I used a 2mm drill bit – it was that or 1mm and I quickly discovered that the 1mm bit is too small to fit in my drill so the choice was easy!  Two tips here: use a centre punch first so the the tube flattens slightly and the drill can get a good purchase; and then push the drill bit as far into the drill as you can, so you have as short a length exposed as possible.  A combination of these two approaches meant I was able to use the drill hand-held without any issues.

So, with 5 holes on each side, 20mm apart, the holes on one arm offset by about 5mm from those on the other arm, I then fitted and tightened the stop ends and fitted the arms into the tee and tightened up the compression joints there too.  The third branch of the tee needed different treatment though – this is the joint that is to provide the free rotation so if the joint is tight it won’t turn.  Instead, using a tip picked up from one of the forums I first fully tightened the compression fitting but with the piece of tube not actually pushed fully home so there was a slight allowance for movement.  Once tight the nut was removed again, and then I applied PTFE tape generously to the thread and refitted the nut.  The PTFE now prevents the nut being tightened up as much, so that once the joint is tight the tube is still free enough within it to spin.  Again using a recommendation from the forums I had also applied a little PTFE around the olive to help it move more freely, although with things being quite a tight fit this restricted the spinning at first, until the tape had worn away a little. 

So holding the one tube vertically, I could now spin the arms round.  So far, so good.  Adding the final fitting gave me a 1/2″BSP connection which I would then be able to connect up to my supply of water for sparging – obviously a different fitting might be more appropriate for a different setup so you’d have to choose what is most appropriate for your own arrangement.  At this point I tried holding the arm under a running tap.  With some effort , precise positioning and a “just so” speed of flow from the tap, we had movement!  The pressure of the water was just enough to start the arm spinning.  Not fast, but enough.

Next test was to connect up to the hot liquor tank and try it for real.  With 70 litres of water above it the flow rate had to be cut right back to prevent the whole thing spinning too fast.  Success!  It remains to be seen just how low the water level in the tank can drop before there isn’t enough force to keep the arm spinning, but it looks good so far.  Also, for the moment it will be suspended over the mash tun using some of the various bits and pieces of wood I’ve got cluttering up the place, but I guess at some point I’ll get round to doing something more permanent, so next time I need distracting from a more important task maybe I’ll put my mind to that…

So there you have it.  A spinning shiny thing.  It may or may not improve the quality of the beer.  It is, on the other hand, a very satisfying accomplishment and will no doubt be a most distracting piece of shinyness as it spins round doing its thing on a brewday.

It wasn’t all that expensive either.  The various fittings cost about £3.60 from an online plumbing supplier, and because these were ordered as part of a larger order there wasn’t any postage.  The brass tube was just over £8.00 delivered from eBay, and to be fair I spent about another £8.00 in order to connect up to my existing outlet on the hot liquor tank, including a quick disconnect fitting.  Still under £20 in total, and depending how it connects in your own system it can probably still be done for less than £15 even if you have to order things in specifically, as long as you shop around.

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