de precoat

[farmerjoe]

was wanting some opinions on doing a precoat with beer vs. water. I have done it both ways with consistant results. pros and cons for both is what i am after. thanks a bunch
bob

[dick murton]

OK first a caveat - I have never used beer for precoating. However, to start the discussion off, a few thoughts

Whichever liquid you use, ideally it should be the same temperature or extremely close to the temperature of the beer to be filtered, ideally less than zero. So for a small brewery this probably is a plus for beer. From the breweries I have seen, most do not have chilled water.

It should be low in oxygen. This is to reduce the amount of oxygen in the final filtered beer, with the associated shelf life problems of high oxygen. Since beer should always be very low in oxygen, this is probably also a plus for beer, unless you have cold deoxygenated water to hand

It should be low in CO2 to minimise gas breakout in the filter, which will lead to poor precoating due to gas bubbles forming on the filter sheets. In this case then, water wins

It should not contain contaminants such as yeast or suspended proteins, or other haze particles which will help blind the precoat and filter support sheets. If using unfiltered beer to precoat - a definite win for water. If you can use previously filtered beer from a bright tank, then the water probably still wins, but by a very small margin.

OK, if I was having to filter beer under these sorts of conditions, I would be tempted to use previously filtered beer to precoat. HOWEVER, unless the filter is thoroughly purged with CO2 before introducing the beer, there would be a considerable wastage of beer whilst the high oyxgen beer at the start of the run is put to drain.

Particularly if using a plate and frame filter, I would fill the filter with water first to get the air out, then blow out the water with CO2, then introduce the filtered beer and precoat, then continue filtering as normal.

Thoughts ??

Cheers

[farmerjoe]

after sanitation the bell is pushed out w/ co2 so that the atmosphere will be void of oxygen. the water in house is niether chilled or deaerated. ive not noticed bad co2 break out in the filter here or the last job and the precoat always looks solid. the last job we had some beers that were heavy with particulate and could make it thru 200bbls (10 meter filter) no problem. did a 50bbl run last night (5 meter filter) ended just over 2 bar. my big thing is that it saves time to precoat w/ beer thanks a lot
cheers!
bob