manticle
Standing up for the Aussie Bottler
I agree. Dremels are great for a variety of things but I'd be using my angle grinder for this.
Domed False Bottoms - How Domed Is Too Domed?
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Muscovy_333
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The big green shed has nice thin cutting blades for ss, couple of bucks each in the tool section.
The job will be done in under 10 minutes.
My keg top falsie cuts radiate from the centre out.
dicko
Boston Bay Brewery
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The moving FB is caused by the silicon hose.
You will need to install a solid tube between the FB and the tun outlet.
I made mine from s/steel with compressIon fittings but copper would be fine.
I would bet that the FB that manticle had collapse was fitted with a flexible hose of some kind as when they are set up with a solid tube it provides some rigidity to the system.
If you dont want to do this you may try underletting your mash at dough in and do not stir after the initial settling of the mash. This is still hit and miss and a solid tube will fix your problem.
Cheers
Helles
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Yer had this is about 12 inch not perfectly round yet
Could make 11inch Fb easily
You can have it
Thirsty Boy
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A lot of the issues of channeling and certainly of domed FBs collapsing, are really a matter of technique. You need to remember that there is a difference in the way "Lauter Tuns" and "Mash Tuns" work. Most home brewers primarily brew to the mash tun paradigm... and run into issues when they veer too close to lauter tuns.
Mash Tuns - have deep grain beds in taller narrower vessels and a slow sparge with the mash primarily floating off the plates. Wall channeling certainly happens, but so many mash tuns have full width FBs that it plainly isn't a big issue. Provided you do it right.....
Lauter Tuns - are wider with lower thinner grain beds. They run off considerably faster than MTs. While the mash still mostly floats early on in the sparge, its more "on" the plates than in an MT and eventually in all lauter tuns it will pull down onto the plates. Many lauter tuns have rakes to keep the flow going, or you need some serious technique and good design to stop it just clogging up. Because of the way they work, channeling, run-off point placement and other things like that are more important in LTs than in MTs to ensure even sparging, good quality wort and maximum efficiency.
Where you will get problems, is if you have a Mash Tun, but you try to run it like a Lauter Tun. The main problem is going to be simply running off too fast and pulling the grain down onto the plates. Thats maybe a big issue in Batch sparging where the object of the game is to get it the hell out of there ASAP - but in a continuous sparge situation... its just bad technique. Inverting a domed FB is - well - its spectacularly bad technique! And its nothing to do with the "weight" of the grain, how much does a kg of grain that's mainly floating in water weigh anyway?? Its to do with the differential pressure between the top of the FB and underneath it. You have lots of grain, floating in lots of water with a whack of head pressure related to the height of the liquid - clog up your FB by sucking the grain down onto the plates and then pulling on the bottom of the blockage by adding any head pressure from the hose that runs out of your MT..... that'll pull your FB inside out. BUT - keep the bed floating and the DP on either side of the plate nice and low.... you could have 100kg of grain in the tun and it wouldn't invert.
Now most HB Mash Tuns are usually a bit of a compromise between the two - not too many of us are running true fully floating mashes. Most of us don't care to spend the multiple hours running off that they require. But that doesn't mean we have lauter tuns either. A great way to learn whats happening in your tun and how your technique matches your equipment - is to take a bit of care when you are cleaning out the tun. After you cut your run-off, don't just open the taps on the MT to let it drain out and then don't just shovel it all in the bin. During the boil, let the MT drain fully at the same rate you were running off, then dig through the grain bed carefully and see whats happened. Try to take neat slices out of it. Is it all nice and fluffy or is it compacted? Is it OK on top but gets really dense towards the bottom? Is it fluffy at the edges but dense around the point where it runs off? Has it pulled significantly away from the edges of the tun?
What you want.... is a nice fluffy uniform grainbed, that's only pulled away from the walls a little (which it does as the liquid drain completely away). Dense spots are where you had channeling or high flow but then they clogged up. Big density differences between the top of the bed and the bottom mean you pulled it down onto the plates in a significant way. Pulling away from the walls a lot means you have either bad wall channeling and/or that you compacted the bed partially early on in the mash and that made the walls the easiest path, but that there was still some flow through the main bed... the wort (or just the sparge) was pulled down the walls and then some of it was pulled sideways into the main bed sucking it in from the sides as well as down onto the plate.
A grain bed that's floating two inches above the FB realistically means that the design of the FB is almost irrelevant - a grainbed that's hard down on the plates means the design of the FB, the void space (as MHB puts it), the slot pattern, the width, the number and placement of the runoff points etc etc are all really important. Your technique will determine how well your Mash-Tun design works out and conversely, your Mash-Tun design will determine what sort of technique will work best.
People manage to brew perfectly well with nothing but a stainless scrubby jammed onto a tube as their FB - or a coke can with a shitload of holes punched into it - its just a matter of understanding why things work the way they do and either matching your technique to the set-up you are brewing on, or building a brewery that you know will work with the technique you've decided to use.
Sermon over - sorry.
TB
Mash Tuns - have deep grain beds in taller narrower vessels and a slow sparge with the mash primarily floating off the plates. Wall channeling certainly happens, but so many mash tuns have full width FBs that it plainly isn't a big issue. Provided you do it right.....
Lauter Tuns - are wider with lower thinner grain beds. They run off considerably faster than MTs. While the mash still mostly floats early on in the sparge, its more "on" the plates than in an MT and eventually in all lauter tuns it will pull down onto the plates. Many lauter tuns have rakes to keep the flow going, or you need some serious technique and good design to stop it just clogging up. Because of the way they work, channeling, run-off point placement and other things like that are more important in LTs than in MTs to ensure even sparging, good quality wort and maximum efficiency.
Where you will get problems, is if you have a Mash Tun, but you try to run it like a Lauter Tun. The main problem is going to be simply running off too fast and pulling the grain down onto the plates. Thats maybe a big issue in Batch sparging where the object of the game is to get it the hell out of there ASAP - but in a continuous sparge situation... its just bad technique. Inverting a domed FB is - well - its spectacularly bad technique! And its nothing to do with the "weight" of the grain, how much does a kg of grain that's mainly floating in water weigh anyway?? Its to do with the differential pressure between the top of the FB and underneath it. You have lots of grain, floating in lots of water with a whack of head pressure related to the height of the liquid - clog up your FB by sucking the grain down onto the plates and then pulling on the bottom of the blockage by adding any head pressure from the hose that runs out of your MT..... that'll pull your FB inside out. BUT - keep the bed floating and the DP on either side of the plate nice and low.... you could have 100kg of grain in the tun and it wouldn't invert.
Now most HB Mash Tuns are usually a bit of a compromise between the two - not too many of us are running true fully floating mashes. Most of us don't care to spend the multiple hours running off that they require. But that doesn't mean we have lauter tuns either. A great way to learn whats happening in your tun and how your technique matches your equipment - is to take a bit of care when you are cleaning out the tun. After you cut your run-off, don't just open the taps on the MT to let it drain out and then don't just shovel it all in the bin. During the boil, let the MT drain fully at the same rate you were running off, then dig through the grain bed carefully and see whats happened. Try to take neat slices out of it. Is it all nice and fluffy or is it compacted? Is it OK on top but gets really dense towards the bottom? Is it fluffy at the edges but dense around the point where it runs off? Has it pulled significantly away from the edges of the tun?
What you want.... is a nice fluffy uniform grainbed, that's only pulled away from the walls a little (which it does as the liquid drain completely away). Dense spots are where you had channeling or high flow but then they clogged up. Big density differences between the top of the bed and the bottom mean you pulled it down onto the plates in a significant way. Pulling away from the walls a lot means you have either bad wall channeling and/or that you compacted the bed partially early on in the mash and that made the walls the easiest path, but that there was still some flow through the main bed... the wort (or just the sparge) was pulled down the walls and then some of it was pulled sideways into the main bed sucking it in from the sides as well as down onto the plate.
A grain bed that's floating two inches above the FB realistically means that the design of the FB is almost irrelevant - a grainbed that's hard down on the plates means the design of the FB, the void space (as MHB puts it), the slot pattern, the width, the number and placement of the runoff points etc etc are all really important. Your technique will determine how well your Mash-Tun design works out and conversely, your Mash-Tun design will determine what sort of technique will work best.
People manage to brew perfectly well with nothing but a stainless scrubby jammed onto a tube as their FB - or a coke can with a shitload of holes punched into it - its just a matter of understanding why things work the way they do and either matching your technique to the set-up you are brewing on, or building a brewery that you know will work with the technique you've decided to use.
Sermon over - sorry.
TB
Yob
Hop to it
No apologies... thats awesome
In the Name of The Grain The Wort and The Beer
Amen
In the Name of The Grain The Wort and The Beer
Amen
manticle
Standing up for the Aussie Bottler
Cheers TB.
Dumb question but can you tell me what you mean by DP?
False bottom squashing I witnessed didn't occur during sparging - not quite sure what happened but it was after 5 mins of a 55 degree protein rest and we started the pump to recirc and step up to sacch.
I'll keep what you say in mind - lots of great info there.
@hsb: Thanks for the offer - I'm probably going to grab one from Acasta as he is living close to my new home but appreciated anyway.
Muscovy_333
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Thirsty Boy
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yep DP = differential pressure
fb invert - pump on, too hard, grain pulled down onto plates, plates clog, head pressure from liquid height PLUS the pump's added head pressure makes very large DP and the FB is sucked inside out.
slower flow rate on the re-circ.
If it couldn't be made slow enough without becoming impractical, then you have just doscovered the design limit of the MT. A more robust FB wouldn't make a hell of a lot of difference.... it might have flowed for a little while longer, but if it was bad enough to pull the FB inside out, then you were on the way to stuck sparge - no flow territory anyway.
Thanks to Mark sharing his knowledge I've update my false bottom.
From this
To this
Now it's bigger than a 20cm (it's actually 39cm) false bottom, but I've gone from a void space of 2,255 mm2 to 4,631 mm2, and a cut length of 4.2m at 1.1mm wide. Out of interest this is about 40 times the sectional area of a 1/2" fitting. So flow while not optimum from the above calcs, it should be fairly slow.
QldKev
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