Beer Filtering and Keg Transferring

by Graham Sanders

WHY FILTER ?

Not all commercial brewers filter their beer, that’s the first point I should make. Many pride themselves on the bottle conditioning and flavour of their unfiltered beer. Coopers Sparkling Ale would be a good example. But this does require more effort from the brewer to get the carbonation just right. It is far easier and cheaper just to carbonate the beer at packaging. All of the larger commercial brewers do this. But why do they filter their beer.

Due to very nature of their brewing practices, that is quick fermentation and minimum lagering, in other words quick thru-put, they have to ensure the final product presents perfectly, with utterly no flaws. Presentation is the key. They must ensure the product is the same batch to batch. So they filter their beer, to remove any suspended yeast, as well as any chill haze that has formed. This ensures when the consumer looks at the beer its perfectly clear – every time.

TIME IS THE KEY

Now craftbrewers have one advantage over commercial brewers – time. Where commercial brewers want their beer sold in as little as three weeks, craftbrewers can afford to let their beer settle out and lager for far longer periods. This should give exactly the same results filtering aims at, a crystal clear beer. And cold lagering works surprisingly well. Even chill haze will settle out if you lager your beer for an extended period of time. Yeast no matter how good it is at staying in suspension, will eventually give in to gravity and settle.

In fact if you own kegs this procedure is very easy.

KEG TRANSFERRING

After an extended period of lagering, you can transfer your cleared beer to a new keg. Simply attaching a line from the outlet pins of your keg and transferring the beer will ensure you leave the sediment behind. This method if you like is a primitive form of filtering, for all filtering is about is the removal of solid substances from a liquid. So in this picture I am removing the clear beer from the settled yeast and haze. The beer will be ready to drink and can be transported without any risk of getting a cloudy beer.

Now the question will always be, wont you suck up some of the sediment.

The answer is ‘it depends’. If the spear (pick up tube) of the keg goes all the way to the bottom of the keg, yes the first 200ml will contain sediment. You throw that away before you transfer your beer. Similarly just before you finish the transfer the last 200ml will again pick up sediment as it gravitated to the pick-up tube. You stop the transfer then. Another method to avoid picking up sediment is to cut 10mm off the pick up tube so it sits above the sediment. That way it doesn’t such up any and you stop when there is no more beer to transfer.

In my set up my spear goes all the way to the bottom, so I must stop it before it picks up the sediment. If you look at my transfer line you will see a tap in the line that I can turn off when I see the first signs of sediment pick up. The receiving keg (on the ground) has a pressure relief valve in the lid. This you have to bleed regularly causing a difference in pressure between the two kegs and the beer flows til the pressure stabilizes. The problem with this method is you are always going to the receiving kegs and having to bleed it. Also if the pressure difference is great there is a lot of foaming in the receiving keg that must settle before you can release pressure again, otherwise every time you bleed off pressure you get a lot of foam.

THE SECRET TO FILTERING AND KEG TRANSFERS

What is needed is a devise that keeps a slight pressure difference between the two kegs. Further the device must be adjustable to counter the different pressures you will have in your lagering keg. This is one such device

This attaches to the gas pin of the receiving keg. I can set it so it is a few kpa difference to the other keg and get a constant slow flow into the receiving keg. For those interested, it is the pressure relief value they use on jet fighter planes that releases pressure out of the fuel tanks when they quickly change altitude so the tanks don’t explode.

Its construction is really simple. It just a normal gas disconnect, to which I have attached the pressure relief value. The valve sits in that and is held there by a spring and screw on fitting. How tightly you screw it down determines at what pressure it releases gas. This model works up to 250 kpa.

The procedure is simple for easy beer transfer.

1.        Purge receiving tank with CO2

2.        Connect the transfer line between the two kegs (discard first 200ml if necessary before connecting)

3.        Wait until the pressure of the kegs stabilises

4.        Fit the bleed fitting to the receiving keg set at 250 kpa

5.        Slowly unscrew the adjuster until the beer just starts to flow.

6.        Check every half hour till it is at the right level in the receiving keg.

That’s it

BEER FILTERING

So what has this got to do with a craftbrewer wanting to filter his beer, and why would a craftbrewer want to filter it in the first place.  Well its generally the same reason the commercial brewers do it, either a time reason or to show off their beers. Now we craftbrewers have no difficulty drinking a cloudy beer, after all, we brew for either taste and/or price. But there are times or special events that demand the best of your skills to show thru, and filtering a beer will polish up a beer nicely. This is especially so for competitions, where it could make all the difference between first place or oblivion.

Now in Australia it is very difficult and expensive to get the filtering gear imported, and even more expensive to get the filter pads as well. But I have found a way that’s makes it so cheap you could filter all your beers if you like. Each filtering would cost you only a few cents.

THE BASIC IDEA

Most filters you buy work off the idea of filter pads. This requires specialised equipment, plus you are linked to the company that supplies the filter for their filter pads. This is unacceptable because you are locked into their price. I found thru research that commercial brewers use DME filters a lot. Now this is no different to what swimming pool filters work on. A further check determined that you can buy graded DME and filter easily down to 1 micron. At this level it will polish your beer nicely, removing yeast and impurities from your beer. Now I thought if it works with swimming pools, why not beer.

If you look at a pool filter its very simple device. Its basically a container of sand, which supports the DME that filters the water. The water is pushed thru under pressure and the DME filters it. So I thought, why not make one on a small scale for beer.

So I made one. And this is it (Click on it to see a close up view). Basically it’s a stainless steel pipe sealed and threaded at both ends. You will see my beer transfer line I use as well. Notice the blank in the line. When I use the filter I unscrew the blank and attach the line to each end of the filter. But before that you must first set up the filter.

PREPARING THE FILTER

You set the filter pipe up just like a pool filter. You put a fine stainless steel screen at the bottom (to keep the sand in) and half fill it with pool sand. You then flush the sand with water to compact it and wash out impurities. Then add a good inch of DME. (the more you add the finer the filtration).  Flush that with water. Now if you worried about infection heat the pipe in the oven at 130C for half an hour. I personally don’t worry about this as I drink the filtered beer straight away.

When you happy with the set up attach the line, with the flow going from top to bottom. Remember do not change the vertical orientation of the filter once its set up.

So the set up is

1.        Put a screen in the bottom of filter to stop the sand

2.        Half fill with sand

3.        Flush with water

4.        Add DME to filter

5.        Add more water to settle

6.        Sterilise if necessary

7.        Attach line.

SETTING UP THE FILTER BED

Now we need to set the filter bed and then run the filter. Pool filters do this by running water thru it, and once set then keeping the pressure constant. If you don’t keep the pressure constant you will disturb the filter bed. We will do the same thing.

So the procedure is

1.        Turn the tap in the line to off

2.        Attach the line to the keg you are transferring from

3.        Keeping the other end of the line open with a blank open the tap slowly and let the beer just flow thru

4.        It will fill up the filter and push out the water and air

5.        When the beer flows out the other side let about 200ml flow out

6.        Remove the blank and turn off the tap.

The filter and beer line is now at the same pressure as the keg. Now you transfer this beer the same way I mentioned earlier. You definitely need the bleed value so that the pressure remains constant.

RUNNING THE FILTER

Its very important you do not disturb the filter bed. This requires no sudden changes in the pressure in the line, or the filter bed is disturbed and wont work properly

So the procedure is

1.        Pressure the receiving keg to the same level as the transfer keg.

2.        Attach the transfer line

3.        Attach the bleed valve to the receiving keg and adjust it until it just let the gas escape

4.        Open the tap slowly

If you have done it right there should be little flow. Why - because the two kegs are the same pressure. Now you have to force the beer thru the filter. So you unscrew the receiving value slowly to get a flow. Once you get the beer flowing that’s fine. You may need to add extra pressure to the transfer keg if you cannot get a good flow.

Now that’s it. A simple cheap beer filter that works fine.

Shout

Graham Sanders