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  • Basic Filtration Questions

    I realize that these are probably stupid questions but I am struggling to find answers anywhere else. Your explanations will mean a lot to me!

    I work at a chain of brew pubs and we use a lenticular filter (Pall Supradisc II) for the majority of our beers. We use K700 cartridges (7-15 micron). Because we are a chain, we get our beer tested on a regular basis (alcohol, clarity, colour, etc). The clarity target for our beers is <1.0 EBC, which I cannot achieve. I start my filter runs with a bar of pressure in both the filter and the bbt and gradually increase the speed of the pump during the run. I filter 24 bbl in approximately 60 minutes.

    To transfer our beer, we use a pump to push the beer to the filter and then into a bbt. We have two pressure gauges, one on top of the filter housing and one on the bbt. Here are my (many) questions about improving my clarity score:

    1) What gauges are measuring the differential pressure? Is the gauge on top of the filter the inlet pressure and the bbt is the outlet pressure? Are both the filter pressure and the bbt pressure the outlet pressure and the power of the pump is the inlet?

    2) What is an ideal differential pressure to maximize clarity? Is a lower differential pressure better than a higher differential pressure? Is there any way to change the differential pressure or is it just a matter of the condition of the cartridges?

    3) Does an increase in total filtration time always lead to clearer beer? Why?

    4) What role does pump speed play into clarity? Should I gradually increase the speed of the pump during the filtration run or just keep it steady?

    5) Does it matter if I start the filter run with pressure in the filter and the bbt?

    Based on my scores, I have determined that the single biggest factor in clarity is fermenter flocculation/time chilled in fermenter? Why does this occur if the filters have a set micron size? Shouldn't there be a "clarity limit" based on this? Obviously, the age and condition of the cartridges also has a big impact. The length of the filter run seems to have an impact but some results contradict this.

    Thanks for answering my horribly newb questions!

  • #2
    I'm not going to be able to answer many of your questions as I don't use a lenticular filter. But I can give you a few bits of advice.

    Your differential pressure is the pressure difference from the inlet of the filter to the outlet of the filter. the gauge on the bottom of the brite tank may be the same as the outlet of the filter but I'm not sure about that. (the bottom the brite tank will have extra pressure from the beer in the tank and any head pressure)

    Based on what you're aiming for the filter disk you're using may not be sized correctly. If I remember my microbio correctly the average yeast cell is 7 micron in diameter. And if that's the smallest opening on your filter you won't be getting all the yeast out during filtration. That would explain why longer cold crashing times are giving you clearer beer - there's less yeast in suspension.

    Cheers and good luck
    Manuel

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    • #3
      Yeast can typically measure 3micron cell size - get tighter micron filter discs and you should be able to hit your targets. Not sure about lenticular filters specifically, but 24bbl in an hour is a reasonable speed. The longer the beer sits in the FV, the less particulates there are to filter, even a 15 micron disc will filter out some of the smaller particulates.
      Last edited by theomuller; 09-19-2016, 10:53 AM.

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      • #4
        If you continue to have issues, contact Maria Peterson at Scott Labs. She's pretty much the filtration guru and does her best to take make time for helping with stuff like this.

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