Hello everyone, I built a stainless steel tank for alcoholic beverages and I want to share with you how I built it and what to consider.
Here is the link to the build:
This is atmospheric, totally hermetic and watertight, with an airlock-type anti-return outlet. If it is isobaric type, it does not need airlock, it works with positive pressure of CO2 and air never enter.
The best construction always is conical cylinder, with a cone angle that depends if the yeast you use is sticky a lot or not, I tried 40 types of yeasts and only very few strains require a 60° cone, but if you have it better, I made it about 75° because I didn't want to spend more. The difference between an atmospheric and isobaric one, is its construction, an atmospheric one you can use stainless steel sheet from 1.5 to 2mm, while an isobaric one, minimum 2mm for small diameters up to 6mm for diameters greater than 1000mm. The isobaric needs the cone to be torus-conical in the widest area, for stress relief, and the cap must be torispherical or semi-elliptical to distribute stress and not deform. While the atmospheric withstands up to 1 bar of test pressure, an isobaric works between 0.5 and 3 bar, therefore its test pressure must be at least double.
Aisi 304L stainless steel alloy holds up very well for beers and wines, only 316L is recommended when it has a pH less than 3 and dissolved Chlorides up to 800 PPM. They are not stainless steel grades, I studied metallurgical engineering and specialized in stainless steels. It is a very common mistake to say that it is better quality, but the 316L has a greater resistance to corrosion, precisely because it has molybdenum in one of its alloys, there are better stainless steel alloys than these both in terms of resistance to corrosion and resistance mechanics that allows us to reduce thickness but costs us much more.
It is recommended to weld inside tank and polish the welds. Internal polishing must be well done to increase corrosion resistance. If it's done poorly, and it looks like everything is mirrored, over time darker areas will appear than more polished ones.
When welding, the opposite or internal side must be purged, with Argon gas, nitrogen (best option) or if there is no budget with CO2 gas.
Both the filler rods and the base metal must be extremely clean and degreased.
The rolling of the sheet must be checked with a sample of sheet metal with a calibrated radius. It is better to use veneers with vinyl on both sides.
To weld, you have to fix with welding points and use supports that ensure that the sheets do not move or deform.
The welding method I used is high-frequency micropulse TIG, which allows me to record the weld without damaging the camera and the welded area can be seen clearly, it also allows me to weld thin-thickness sheets with less deformation and less HAZ.
Discharge fittings should be of clamp type, as they are easier to clean and have less solid acumulated.
Here is the link to the build:
This is atmospheric, totally hermetic and watertight, with an airlock-type anti-return outlet. If it is isobaric type, it does not need airlock, it works with positive pressure of CO2 and air never enter.
The best construction always is conical cylinder, with a cone angle that depends if the yeast you use is sticky a lot or not, I tried 40 types of yeasts and only very few strains require a 60° cone, but if you have it better, I made it about 75° because I didn't want to spend more. The difference between an atmospheric and isobaric one, is its construction, an atmospheric one you can use stainless steel sheet from 1.5 to 2mm, while an isobaric one, minimum 2mm for small diameters up to 6mm for diameters greater than 1000mm. The isobaric needs the cone to be torus-conical in the widest area, for stress relief, and the cap must be torispherical or semi-elliptical to distribute stress and not deform. While the atmospheric withstands up to 1 bar of test pressure, an isobaric works between 0.5 and 3 bar, therefore its test pressure must be at least double.
Aisi 304L stainless steel alloy holds up very well for beers and wines, only 316L is recommended when it has a pH less than 3 and dissolved Chlorides up to 800 PPM. They are not stainless steel grades, I studied metallurgical engineering and specialized in stainless steels. It is a very common mistake to say that it is better quality, but the 316L has a greater resistance to corrosion, precisely because it has molybdenum in one of its alloys, there are better stainless steel alloys than these both in terms of resistance to corrosion and resistance mechanics that allows us to reduce thickness but costs us much more.
It is recommended to weld inside tank and polish the welds. Internal polishing must be well done to increase corrosion resistance. If it's done poorly, and it looks like everything is mirrored, over time darker areas will appear than more polished ones.
When welding, the opposite or internal side must be purged, with Argon gas, nitrogen (best option) or if there is no budget with CO2 gas.
Both the filler rods and the base metal must be extremely clean and degreased.
The rolling of the sheet must be checked with a sample of sheet metal with a calibrated radius. It is better to use veneers with vinyl on both sides.
To weld, you have to fix with welding points and use supports that ensure that the sheets do not move or deform.
The welding method I used is high-frequency micropulse TIG, which allows me to record the weld without damaging the camera and the welded area can be seen clearly, it also allows me to weld thin-thickness sheets with less deformation and less HAZ.
Discharge fittings should be of clamp type, as they are easier to clean and have less solid acumulated.
