'How to' convert a thermo box into a mash tun

Discussion in 'Beer Brewing "How-To" Guides' started by Vossy1, Feb 18, 2009.

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  1. Feb 18, 2009 #1

    Vossy1

    Vossy1

    Vossy1

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    This is a guide on 'how to' convert a thermo box into a mash tun. It is not the easiest way to convert one, but I wanted a bottom drain and no dead space. It was awkward, and took more time than I thought it would. Hopefully it may be of help to someone intending to do the same sort of thing. My thanks go out to Derek Spedding of the NCBA and the CBA's Brewers Contact, for pointing me in the right direction on this project.

    Before starting the project I had to think about what I wanted from my mash tun. I was increasing brew length, so the mash tun had to be able to deal with 85ltr brew lengths of 5% beer. I wanted it to be bottom draining, and also wanted it to be insulated, so the mash temperature would remain fairly stable.

    The bits

    80ltr Thermo Box £84.85 from Catering - Service - FR on e-bay here
    ½” ball valve, part # 10397, £16.37
    ½” brass nipple, part # 6576 £1.08
    Both from http://www.bes.co.uk
    2 x ½” hole diameter stainless steel washers £0.90 from a local BSA parts shop (or from link below)
    M22 washers form B from here http://www.a2stainless.co.uk
    1 x 15mm compression 90 deg elbow, £1, local plumbers merchants
    1 x ¾ “ flange nut £0.50, local plumbers merchants
    1 x compression coupler ½” female to 15mm compression £1.20, local plumbers merchants
    6 x M3 x 12mm button head bolts, 6 x M3 spring washers, 6 x M3 nuts, in stainless steel (already had)
    JB Weld
    Masking tape and pencil

    False bottom 443mm circumference from http://www.hopandgrape.co.uk
    M3 x 6mm button head bolts x 60, stainless (boltmeup, E-bay) £4.48
    M3 spring washers x 100, stainless (Ultra Hardware, E-bay) £1.35
    M3 Nuts x 50, stainless (E-bay) £1.94

    Expanding foam and stainless sheet (already had)

    Total cost £173.67
    (not including consumables, labour and tools)

    Tools

    A drill, 20mm hole saw bit, 3mm HSS drill bit, angle grinder, dremmel, 15mm copper tube cutter, knife, tape measure.

    The job

    The first thing to do was to place the tun on a surface and ensure it was level using a sprit level. I put some masking tape at the top of the tun, roughly where I thought the centre of the tun was. I also put some masking tape on the bottom of the tun directly under the top piece of masking tape. I measured the distance between the 2 handles on the tun and marked the point on the masking tape half way between the 2. Using the spirit level vertically I marked the vertical position for the ball valve on the bottom piece of masking tape.

    [​IMG] [​IMG] [​IMG]

    Before I could mark the point at which to drill the hole for the ball valve, I needed to know where the inner skins base sat, in relation to the outer skin of the tun. To do this, I used a tape measure to measure the height of the inner skin from the top lip of the thermo box. I then measured the height of the outer skin and subtracted one from the other to give me a rough idea of the position of the base of the inner skin, making sure to factor in the height difference between the two skins. It just so happened to be in line with the recess at the base of the outer skin. Next I flipped the tun upside down so I could measure the centre point of the base of the tun. I then masked of the area of the base which I would need to remove in order to attach the bottom outlet and associated fittings. I drilled though the centre hole from the outside of the tun, through both inner and outer skins using the 6mm hole saw bit, the idea being I would then drill the main outlet hole from within the tun avoiding burrs. I flipped the tun back upright and got the first surprise. The centre hole on the outside of the tun did not match up with the centre of the inner skin, it was at least 10mm out. To make sure the take off was central in the tun I re marked the central point of the inner skin, and using a 20mm hole saw, drilled a new hole, which luckily meant the previously drilled hole was removed with the core taken out…phew.

    [​IMG] [​IMG] [​IMG]

    The next stage was to remove the outer skin from the base of the tun, so there would be room to attach the fittings for the take off tube and the ball valve….break out the angle grinder and safety glasses. The angle grinder did a great job of removing the bulk but it was necessary to use a dremmel type tool to finish the cuts at the right angles and near the lip of the tun. To remove the foam insulation I used a knife to cut it back to the inner skin, then the foam came out really easily, it was quite well insulated.

    [​IMG] [​IMG] [​IMG]

    [​IMG] [​IMG] [​IMG]

    With the foam removed I could re check the position of the ball valve before drilling the hole for it. As it turned out the hole needed to be moved as the inner skin was slightly higher than I had measured. I drilled the hole for the ball valve using a 20mm hole saw, using a constant supply of water to cool the drilled area and bit during the process. I used my dremmel to remove the burrs from the drilled holes. I thought I had drilled the ball valve hole high enough to avoid the lip of the outer skin, which I had removed….but I hadn’t. This necessitated the use of the dremmel to grind the lip down, so the compression coupler could be tightened up to the ball valve. I wanted a bottom draining tun for ease of cleaning. This means in the future, that I will be able to clean the tun without having to move it, as it’s quite heavy. I toyed round with ideas for the bottom take off before settling on this idea and mocking it up. It’s a standard 15mm compression elbow. I have removed the olive and nut from one end. I placed the elbow and a flange nut in a citric acid bath overnight, to ensure it was clean. I applied some JB Weld to the thread of the elbow and then attached the flange nut facing upwards, smoothing any JB Weld that was squeezed from the joint and allowed it to dry overnight. The flange nut is going to be attached from underneath the tun using 6 x M3 x 12mm button head bolts, nuts and spring washers, JB Weld will be used to form the seal being applied to the mating surfaces of the flange nut, tun, and elbow/flange nut combo, as in the mock up. I drilled 6 x 3mm holes in the flange nut.

    [​IMG] [​IMG] [​IMG]


    I masked the area immediately surrounding the previously drilled outlet hole in the inner skin of the tun, and secured the flange nut in position using a 1/2" nipple. I drilled through the holes in the flange nut, through the inner skin. These were the holes that I had all the trouble with. I removed burrs from the holes with my dremmel and keyed the mating surface with the dremmel also. I was now in a position to fit the tap and outlet assembly (see above right picture for exploded assembly) for easy reference. The washers have been cut down as the inner washer wouldn't fit neatly under the lip of the base of the thermo box and the outer washer went over the recess on the outside base of the thermo box. I applied plenty of PTFE tape to the nipple before screwing it into the ball valve. I pushed the ball valve nipple through the hole in the tun, and secured it with the coupler from the rear, using plenty of PTFE tape on the nipple before doing so. I then offered the outlet elbow to it's position on the inner skin. This gave me the length of 15mm copper pipe required to connect the outlet to the ball valve. I cut the pipe to length and then re-offered it to the elbow/valve combo to ensure that it all lined up. I treated the mating area of the elbow, the 6 bolts, nuts and washers to a citric acid bath and dry to get rid of any grease on their surfaces and also cleaned the mating surface of the thermo box with acid also. I liberally applied JB Weld to the elbows flange nut, and aligned it with the holes in the inner skin of the thermo box. I applied a small amount of JB to the button head of the bolt and passed them through the inner skin, securing on the underside of the thermo box with the spring washer and nut. On passing the bolt through an amount of JB came through with the bolt and this was enough to seal the bolt/nut/washer combo on tightening. It was then a case of tightening the compression fittings.

    [​IMG] [​IMG] [​IMG]

    I placed the thermo box upside down and put a tea light candle inside it to speed up the drying process, leaving the valve open to allow hot gases to escape. It was tested for water tightness the following morning, and there were no leaks. I filled the void around the drain assembly with expanding foam, and used a small piece of stainless sheet to seal the area, so as to minimise heat loss.
    I also bought a made to measure false bottom for the tun, which was supplied by John at the Hop & Grape. It was cut at 443mm, which I measured as the mash tuns interior circumference. I double checked the circumference by making a 'mock up' of the false bottom out of cardboard to make sure the measurement was correct before ordering. It has standard 3/8th beer line around the outer edge to take up any anomalies in the tuns circular shape, and it fits perfectly. It was supplied with no legs or handle as requested. I mapped out the leg positions using masking tape and then drilled 3mm holes in those positions. I used M3 x 6mm button head bolts as legs, secured with M3 spring washers and nuts.

    [​IMG] [​IMG] [​IMG]

    EDIT, Comments regards JB Weld. At the time of making this item JB Weld was, and still is, my option for use as a sealant. It is classed as inert once cured, but has not been tested as food safe. The reason for me using it is that I wanted the smallest rigid seal I could get with minimal surface area exposed to the process. I could have used food grade silicone sealant, but in my experience I have yet to use a mould PROOF silicone sealant, so as the brewery is always wet, silicone sealant was/is not an option. Whilst plastic and rubber washers are available, I view their potential leaching properties in just the same light as JB Weld.
    It's a personal choice as to what to use, I chose JB Weld.
     
  2. Feb 19, 2009 #2

    BrewStew

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    good stuff mate :thumb:
     
  3. Feb 19, 2009 #3

    A T

    A T

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    Nice work V :thumb:
     
  4. Aug 25, 2009 #4

    jamesb

    jamesb

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    V1, how much clearance is there from the inner skin to the bottom skin on the bottom of the box?
     
  5. Sep 2, 2009 #5

    Vossy1

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    About 2" on the 80ltr pots (see picture above) :thumb:
     
  6. Sep 2, 2009 #6

    jamesb

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    I found this which I'm going to use. Unlike you, I'm not a fan of JBWeld, and I don't want to drill as many holes.

    [​IMG]
     
  7. Sep 4, 2009 #7

    Vossy1

    Vossy1

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    :cool:
    There appears to be some confusion on this subject. I'm not a fan of JB Weld. I use it as I couldn't find anything else which had the same properties. I was looking for a rigid seal between surfaces, without welding. Due to the nature of the compressive forces between the surfaces, the area of solidified JB Weld exposed to the runnings or anything else is minimal, I would imagine less than a 1oth of a mm where the surfaces mate. There are other alternatives out there like food grade high temp silicon sealants, but I wanted a rigid seal, not a flexible one, besides leaching is a possible factor with rubber/silicon ect, just as it might be with JBW. Using rubber seals would give a far larger area of exposed material than JB Weld does. Natural fibre washers might provide a good alternative for sealing mating surfaces, as might plumbers sealant.
    I dont blame ya, it was a RPITA :lol:
     
  8. Jan 25, 2010 #8

    andysmok

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    I will get the camera out and photograph me ball'sing up a perfectly good 100l pot and 60l thermo box!! I make a new how to if it turns out OK, to be honest it will prob just read the same as yours Vossey. I've just ordered my qmax bits. the only other thing i am wondering about is the bottom drain conector, I realy dont fancy drilling holes if i dont really need to. Has any one come up with an easyer conector than the one Vossey used
     
  9. Jan 25, 2010 #9

    Vossy1

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    You can use a bog standard tank connector, it'll do the same job. It will leave some retention in the tun but next to nowt, so it's not worth worrying about :thumb: Might be tight getting the bend to valve right, but should be do-able.

    [​IMG]
     
  10. Jan 27, 2010 #10

    andysmok

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    I have ended up getting a basic tank connector and a 90 degree tap connector to fix straight onto it, Looks like it will work fine with a fibre washer inserted into the meeting point of the two (are fibre washers food grade)? The only issue looks to be a little extra dead space, but correct me if I'm wrong, I can understand it being an issue for batch sparging more so than fly sparging which Ill be doing.
    I have ordered my qmax cutters a 1/2" and a 20.4mm as i couldn't get a 20mm one, I hope .4 of a mill won't make much difference!
     
  11. Jan 27, 2010 #11

    Vossy1

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    The fibre washer will be fine and the dead space isn't worth worrying about :thumb:
    You'd be better putting a washer under the flange of the tank connector to seal it against the thermo box base. If you don't, wort coud get trapped underneath it and fester :sick:
     
  12. Jan 28, 2010 #12

    andysmok

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    What I was thinking was a smearing of JB weld under the flange to make a good bonded seal with the inside of the tun. I have read that you should have the black washer on the nut side of the tank connector but i can't see how this will create a good seal, if it was placed under the flange this would surly give an excellent seal and there would be no need for the JB weld. I can only think that this washer could leech out toxins?
     
  13. Jan 28, 2010 #13

    Vossy1

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    You are quite correct. The washer should go on the flange side of the tank connector.
    If you put the washer on the nut side, water can get in behind the flange and creep through the threads past the nut and hey presto...leak. The only way round that would be to PTFE the thread but that's a bit hit and miss.
    I wouldn't worry about toxins too much as there's such a small surface area of the washer exposed.
     
  14. Jan 28, 2010 #14

    Vossy1

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    You can buy rubber and plastic seals/washers from B&Q for tank connectors, plastic washers are even thinner then the rubber ones. JB Weld is not tested as food safe, it's just declared as 'inert' once cured. The benefit (if you want to call it that) of JB Weld is that when the joint is pulled together there's next to no JB exposed to the liquid, it really is minimal. You could always use high temp food grade silicone sealant as an alternative.
     
  15. Jan 29, 2010 #15

    tubthumper

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    surley vossy you could cut a bit off your 1/2 silicon tubing and use that a washer
    it would be inert
     
  16. Jan 29, 2010 #16

    Vossy1

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    Might do the trick, not sure if it'd be big enough for the diameter of the tank connector though, worth a try :thumb:
     
  17. Sep 3, 2013 #17

    djcorbetto

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    What component did you use to go through the side wall so that the valve can screw in? i have the tank connector for the drain and the elbow but I'm confused to whats needed at the other end
     
  18. Sep 4, 2013 #18

    Vossy1

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    Hi d, sorry for missing your posts :oops: and thanks for the pm prod :thumb:
    it's a compression coupler ½” female to 15mm compression one of these a 1/2" parallel nipple is then screwed into the female end, and then a ball valve onto that.....hope that makes sense.
     
  19. Sep 5, 2013 #19

    djcorbetto

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    Parts purchased thanks. Just got to figure out what holes to drill and sizes and purchase the cutters for this job and then time to finally build it
     
  20. Mar 12, 2014 #20

    Sanders

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    Hey,

    I have a 70l thermopot on the way(from hbb) but I was wonder firstly if I went with a 1/2" skin fitting then to a 90degree elbow from this to a 1/'2 male to 15mm compression fitting then to a length of 15mm pipe then back to another 15mm compression to 1/2" male then to the ball valve would this be a goer?
    Also I noticed chandlery has these (there would be a link but it's too spammy :/ basically 1/2 chrome plated fitting it's on the frontpage) on offer however I am was unsure of the safety of chrome if not I'll just go with stainless.
     

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