your thoughts on the pre-coat...who precoats with water and who precoats with beer...advantages/disadvantages?
we currently precoat with water, and I personally have not done it with beer...was interested in doing it, but wanted your thoughts first.
I know from earlier posts on this site that there are at least a few who precoat with beer. However, and bear in mind that I don't operate a micro, I would prefer to precoat on water to reduce the potential blinding of the filter support sheets (assuming you are using a plate & frame filter), or potential protein & yeast residues on the discharge side of the filter - any type of filter. Having said that, a major problem with using water is getting the water supply cold enough - not more than 2 C to reduce the re-solution of haze forming proteins, and secondly, the inevitable dilution and losses at the interfaces unless you higher gravity brew to allow for the dilution.
Unless you have loads of cold deaerated water to flush through the filter after precoating to get the dissolved oxygen down, you are going to suffer high oxygen at the start of the beer run, almost whichever way you do it, due to entrained air in the precoat powders.
Precoating with beer has to be simpler for this reason. And often, simple is best.
Make sure your filter is gas purged out thoroughly though and or you flood fill from the bottom, and the beer is cold enough not to get too much gas breakout which might cause holes in the filter bed where bubbles break out.
I always precoat with beer. We use a 3 square meter DE filter. If the beer is young there is the trouble of excessive pressure build-up in the first few Hl's, though typically I can get through a 90Hl with ease. Our filtrations typically happen with about 750'000 to 1.5 million cells/ml.
When filling the bell I do so with gravity untill I get beer out the blowoff, I'll recirculate the beer through the bell (isolating the dosing tank for now) untill I see no more breakout. I then crack the blow off again to ensure there is no gas in the bell and top up if necessary. Then I'll start setting the precoats.
I will generally have about .75 BAR in the bell when I start pushing beer into the the bright tanks.
When I worked at BJ's we tried it both ways and had better filter when we precoated and recirculated with beer. give that a try and see how it goes.