Lauter Tun Design

[cervezale]

I'm in the process of building a pilot plant in which to explore local tastes while I advance on all legal and tax matters involved with opening a brewpub. I'm building a 4hl , 3 vessel brewhouse with direct fire mash tun/ brewkettle with VFD agitator, lauter tun, and whp. I'm also importing some jacketed CCVs and BBTs from China. It's simple but the only way to start brewing on my budget. I'm hoping someone can help me establish lauter tun dimensions. Grist loads will be between 70-80kg. According to Kunze a false bottom loading between 150-200kg/m² will yield a grain depth between 25-34cm.. Do I calculate the weight of my mash (liquor and grist) and then relate to Kunze figures? So if I have 200L(kg) of water and 70kg grist do I need a false bottom with an area of 1.8m² at 150kg/m²? This would mean a radius of 0.75m and circumference of 4.7m. Am I doing this right?
I guess the other option is that false bottom loading refers only to grist load in which case 70kg grist would require a surface of 0.46m² so that at 150kg/m² this would result in a radius 0.38m and circumference of 2.4m.
Any comments welcome. Thanks

[dick murton]

Use the dry grist load to calculate the tun area.

But then calculate the volume of wet grist to make sure you have enough height above the plates.

And if you are sure the grist weight is the least you will ever use, go for the thinnest bed (bottom of the tun loading range) to start with, as this means you can increase the grist load a fair bit for specials, or even for routine operations. If you think you might want to use smaller grist weights, then you are probably better to go a little above the minimum of the quoted range of tun loadings.

[cervezale]

Very helpful confirmation. I believe a 75cm diameter and 100cm height will be perfect for gristloads starting at 70kg and going up to 90kg for higher gravity 4hl batches. Thank you.

[carontes]

false bottom holes

Hi,

I am designing a new 5 hl Mash/lauter tun and are dealing with conflicting views regarding the false bottom.

The tank is a 700 litres, with a diameter of 100 cm and heigth of 90 cm.

It has a 120 litre cone with a 20% slope at the bottom, all this volume under the false bottom.

We are using direct fire and no mechanical agitation (thanks to comment read here mostly from Dick Murton: thank a lot sir).

My question is about the best material to be used in the false bottom.

The easiest way to get the 30% oppening seems to be a tread mesh. Is it ok to use the mesh with some reinforcing frame?

thank you.

[dick murton]

That strikes me as a wastefullly large cone. With a total cylinder volume of 700 litres, grist volume I expect to be around 4 to 500 litres, then you will have to recyle 150 litres before you can start the runoff. This 150 litres will not be at the best temperature - circa 77 C but somewhat cooler so your extract is likely to be poorer than you could otherwise achieve.

I have never seen a mesh bottom, and in theory suitable mesh could be used if supported well. I would be reluctant to use it if only becasue of the risk of stretching it and particularly of tearing it when digging the grains out. Large commercial lauter tuns and mash tuns use about 7% surface area using wedge wire or milled plates, giving strength and adequate runoff area.

[parthamehendale]

Use the dry grist load to calculate the tun area.

But then calculate the volume of wet grist to make sure you have enough height above the plates.

And if you are sure the grist weight is the least you will ever use, go for the thinnest bed (bottom of the tun loading range) to start with, as this means you can increase the grist load a fair bit for specials, or even for routine operations. If you think you might want to use smaller grist weights, then you are probably better to go a little above the minimum of the quoted range of tun loadings.

So I've been facing the same problem while designing the mash tun. My tun diameter is 1.5m. The maximum amount of grains I'll be putting in is 450kg. So while designing the false bottom, should I use 450kg as the weight (which makes my grist load 254.78 kg/m2)? But shouldn't the weight of the wet grains be more? So if I consider that the grains absorb 1L/kg, the total weight would be 900kg. Which brings my grist load to 510 kg/m2. And hence the diameter reduces to 1.06m.

I've made two separate spreadsheets. In the first sheet, I've used the ideal 300 kg/m2 (which I've kept as a constant) as the grist load and then calculated the diameter of the mash tun based on the weight of grains. In the second sheet, I've kept the diameter of 1.5m as a constant, and then calculated the grist load based on the weight of grains.

So basically two questions-
1. Should I use the wet weight of grains while calculating the grist load?
2. Should I use the first sheet or the second sheet?

Thanks!

[dick murton]

Use the dry grain weight. The amount of water used for mashing is not used in a loading calculation apart from ensuring the structural loading is adequate, and that the internal volume is adequate to cope with the mix of grain and mashing water. once transferred above the plates.

I consider 250 kg dry grist m2 is better than 300 kg as runoff time will be shorter, extracts may even be very slightly better, and there is less risk of a set bed in a slightly shallower bed. So 1.5 metres diameter should be fine. Ideally, this should be the maximum weight you use, though you will be able to reduce the weight or increase it quite a bit and still have decent extracts etc., but don't forget to recalculate the height required for the maximum grist weight, and allow this height between the false floor and the sparge arms.

[parthamehendale]

Use the dry grain weight. The amount of water used for mashing is not used in a loading calculation apart from ensuring the structural loading is adequate, and that the internal volume is adequate to cope with the mix of grain and mashing water. once transferred above the plates.

I consider 250 kg dry grist m2 is better than 300 kg as runoff time will be shorter, extracts may even be very slightly better, and there is less risk of a set bed in a slightly shallower bed. So 1.5 metres diameter should be fine. Ideally, this should be the maximum weight you use, though you will be able to reduce the weight or increase it quite a bit and still have decent extracts etc., but don't forget to recalculate the height required for the maximum grist weight, and allow this height between the false floor and the sparge arms.

Alright so I'll use 450kg as the dry grain weight which makes my tun diameter 1.5m and the grist load comes to ~255kg/m2. Considering your experience, it sounds about right so I'll go ahead with that then! I have like 14" height in my mash tun extra after adding 450kg. But the height of false bottom from floor of tun (1.5"), the sparge arm height (~4") is not included in the 14". But still I'll have like 9.5" height extra.

Also, when you say "...once transferred above the plates". What do you mean by plates? You mean the false bottom, right?

450kg is the maximum weight of grains I'll be using, yes. But while making session ales, I'll be using grains as low as 150kg in weight. But even then, I'm getting a grain bed depth of around 10".

Thanks mate!