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My still uses a 20L drum for a boiler with an 1800W element. The column is 2m long filled with SS scrubbers. It has an offset head. The scrubbers dont appear to be in very tight because you can blow through it very easily and the scrubbers dont seem to inhibit this much at all.
However when i was running it the other day 3/4 full i could hear a strange noise so i took the lid of the boiler and wash went everywhere...
for the rest of the run i had to every coupke of minutes 'depressurise" it by opening the lid for a few seconds.
I have no idea what this is caused by. does anyone have ne ideas?

Buy or build a voltage control so you can lower the power to about 750W as you approach a boil.

Bottoms up, boozer

Hi zeff,
While cool the scrubbers are unexpanded they will seem loose enough. But if you heat them up they will expand and if they don’t expand up the reflux column (because you should have the bottom covered with a wire mesh (or split pin across to keep the scrubbers in place) they will tighten up but not completely block the column. But this will raise the pressure enough in the airspace above mash to instantly boil the mash when both pressures equalize.
From an old domestic pressure cooker lid take out the pressure release valve and fit it to your still boiler.
However that will solve a symptom, and not solve your problem.
This is an obvious blockage in the column. Strip it all down scrubbers and all and reassemble. Good luck and I hope you get it sorted.

While cool the scrubbers are unexpanded they will seem loose enough. But if you heat them up they will expand

I don't believe that stainless steel expands very much when heated 70C.

Yep. I'd bet the strange sound was a rough boil starting, opening it just made it go crazy.

Hi zeff,
While cool the scrubbers are unexpanded they will seem loose enough. But if you heat them up they will expand and if they don’t expand up the reflux column (because you should have the bottom covered with a wire mesh (or split pin across to keep the scrubbers in place) they will tighten up but not completely block the column. But this will raise the pressure enough in the airspace above mash to instantly boil the mash when both pressures equalize.
From an old domestic pressure cooker lid take out the pressure release valve and fit it to your still boiler.
However that will solve a symptom, and not solve your problem.
This is an obvious blockage in the column. Strip it all down scrubbers and all and reassemble. Good luck and I hope you get it sorted.

Dear guest
Do you know what the coefficient of expansion is of copper or stainless steel? Your explanation is not valid, for even if they were to expand significantly the column , being of the same material, will expand similarly and hence the status quo is maintained.
Secondally why would you want to complicate anything by putting such things as pressure releif valves, when the system is open to the atmosphere at the top (or should be).
Seems to me when the the pot is boiling over the simplest thing to do is turn down the heat. End of story.

Bottoms up; boozer