Lid on or off...?!

[EccentricDyslexic]

Yes this is asked quite often on here, but i noticed watching this vid- http://www.youtube.com/watch?v=zShNaDcCph8
they have a cover on thier boiler with a small vent pipe to release steam outside. If this is how comertial brewers are boiling then there should be no problems with us home brewers keeping the lids on our boilers and maybe just pop a vent hole through? should reduce evap losses quite significantly.

Another experiment coming up...

Steve

[boingy]

You do need to keep a reasonable rate of evaporation because it drives off undesirable stuff like DMS but I boil with the lid on and have fitted a 40mm waste pipe steam outlet. I posted some pics on this forum but don't have time to go searching for them now. You need to keep the pipe angled slightly downwards so condensate does not drip back into the beer and also you need to make sure you have a healthy amount of steam exiting the pipe. Works well for me.

[steve_flack]

I boil with the lid on but it's propped open with my measuring stick so steam does escape. I lose about 4L an hour from a preboil volumes of 45L which is about right (approx 9%).

[boingy]

Ok, so I couldn't resist searching for the pics:

viewtopic.php?f=5&t=19868#p227947

(and it's 32mm waste pipe not 40mm)

[boingy]

It doesn't get chance to condense on the underside of the lid - the whole space above the wort will be at 100 degrees or thereabouts. Those volatiles boil off at temperatures in the 30's and 40's and the steam pressure pushes them out of the pipe because they have nowhere else to go. I still lose between 5% and 10% to evaporation, just like I do if I leave the lid off. I boil with gas so the boil vigour is easy to control - once the boil is going I use the steam outlet as a guide to set the boil rate to a nice rolling boil.
I do think it is important to remove the lid when cooling though. As the temperature drops you will start to get some condensation.

[EccentricDyslexic]

Fab replys chaps! I noticed they also use wood for the lids, which will cause less condensate so maybe a wooden or insulated lid would be good, along with a vent pipe like boingy's. I live near burton on trent and can rarly smell boiling wort, if they were boiling with out a lid you'd be able to smell it miles away with the amount of beer brewed here!

Steve

[Aleman]

The large brewing kettles tend to use steam scrubbers to cut down on smells. They have a vent pipe coming out the side and pointing down to a drain a fine mist of cold water is directed down the vent pipe causing the steam (and any volatiles) to condense and run into the drain.

Then you have vessels that are completely enclosed an they boil under pressure . . .often in a separate heating chamber pumping the wort round to create turbulence . . . . Pressure released quickly at end of boil causes massive foaming and venting scrubbing the volatiles out of the wort.

Then you have kettles that are just bigger versions of ours with a vent pipe

[koomber]

would it be possible (I'm a chemist and geek) to build something similar, using a distillation tube to condense water coming of the boiler and collect it and all the other stuff in a little jug? Could use it to measure the volume of water boiled off and help minimise smell/steam.