I have a 50L American conical made by Hobby Beverage Equipment Co. and the lid just sits on top. No clamps, no seals, no blow off, no worries. The biggest problem was stopping the chief brewer from lifting the lid for a germ laden peek. I solved that one by fitting a small acrylic window in the lid. It's better than television.As with the Rims, i am looking into the idea of stocking stainless conicals. I know nothing about them though so would be interested in requirements.
Lid, what thickness? How should it seal? Should there be fittings for a blow off etc?