Ask The Brewmasters

Coming out of the discussions around centrifuge operation I stirred up some differing opinions on whether hydro-hermetic seal water needs to be deaerated water (DAW) or not. I stated in my experience for the machines I have worked on (Alfa-Laval and GEA/Westphalia btw), it does not. Both of those companies may make other models and designs where it is required. I added the caveat there can be other designs where the manufacturers require it as part of the design. For those of you that like getting lost in the weeds, come follow me...

On hydro-hermetic machines the seal water is a practical way to create a seal between the spinning bowl and the stationary parts. It's impossible to wear out flowing water and thus it creates a convenient seal between the air outside the bowl and the inert gas being pumped under the housing/cowling and near the paring disc. The liquid flow should be in balance with the inert gas that is occurring below it (near the paring disc). The seal water and inert gas have to also be in balance with the inlet beer pressure which is a function of many factors (flow in, paring disc capacity and the back pressure on the machine).

So, on a machine that is operating on the pump curve for the paring disc and the seal water and inert gas flow are correct settings then the seal water cannot come in contact with the process flow (beer). Where we get into trouble is when the inert pressure becomes too low due to (again) non-optimal flow in, paring disc capacity and the back pressure on the machine. When this out of balance occurs, we first start drawing in inert gas into the process flow and if the situation becomes dire enough, we could even draw in seal water. We don't ever want to get to the point that the seal water is pulled into the process (preferably not much inert gas either).

But why not just use DAW as seal water in case? There are arguably a few reasons. 

1. Cost of installing/piping DAW assuming it is even available
2. If we are drawing in plant water (generally carbon filtered for this application) we can actually detect it with oxygen meters and correct the seal water infiltrating our process 
3. Once we suck in "all" the seal water (with DAW we would not see this on the oxygen meters) then we will be hit with a lot more oxygen as the air starts sucking in.

As I said, this is all arguable. In fact, on GEA hydro-hermetic machines their own P&ID drawings show the seal water as "Hydrohermetic Water Inlet (DAW Preferred)" but not required (bold is my words). My guess is they are seeing it as an added layer of protection in case the machine is being run outside the design.

 If a brewer feels more comfortable running DAW seal water on a machine that it is not required for, then go for it. But I will stand by that (at least the many machines I have worked with) it does not have to be DAW. And to state again, if using DAW on a machine that it is not required for is helping DO, then we are drawing in seal water which is not optimal operation.

Hope that helps explain my perspective and let the arrows fly (nice, polite rubber ones)...

Centrifuge suppliers???

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Travis Audet
Slant Six Consulting
Hooksett NH
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Hey Travis,

I was probably the first person suggesting DAW seal water in that thread, and I'd say your prespective is 100% correct.  When we had DO issues early in the days of running our centrifuge, our GEA rep pointed us to this exact language and referred us to another brewery in San Diego with a similar machine who was using DAW.  While other issues ended up being the true cause of our DO spikes, we keep DAW on-hand for purging sanitized lines, pushing beer, etc. I suspect a decent portion of breweries that are large enough to have a centrifuge would also have DAW on-hand, making it just a question of plumbing and the cost/benefit analysis.  For us, seeing as nothing in breweries seems to work right 100% of the time, having DAW plumbed to the machine provides an extra layer of comfort and a longer window for troubleshooting if something fails.  If it saves 0 DO pickup 99% of the time but prevents a 30ppb pickup once a year, its certainly worth it for us.

Cheers!

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Jeremy Castellano
Director of Brewing Operations
Mission Brewing
San Diego, CA
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Hi Travis,

Just adding to the discussion- Hoping to help anyone making the decision to move forward with a large capital expense project including a DAW system. I was apart of the install, commission, and operation of two Alfa Laval Brew 350 Series separators at a large production plant (100K+ BBLs per year). We did not have a DAW skid and both machines were hooked up to city water. We processed a variety of different beer brands and RTD cocktails through the 350s. Operators were trained to monitor all critical control points you mentioned and we very rarely had any D.O. pick up in the separator. I credit the smooth operation and zero pickup to the training we got from our Alfa Laval technician, it made the difference during challenging spins. Obviously the need for a DAW skid will vary dependent on manufacturer/model, but in this case the 350s had no problem using city water as a utility.     

Tyler Walsh
Brewery Manager
pFriem Family Brewers
Hood River OR

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Tyler Walsh
Brewery Manager
Pfriem Family Brewers
Hood River OR
(541) 948-5320
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Hi Tyler,

I believe the Alfa Lavel 350 units use a mechanical seal on the bowl, not the hydro-hermetic seal that the GEA units use.   Unless they have different models that I'm not aware of that use hydro-hermetic in that 350 series.   So the type of water may not be as important on those models.   Glad to be corrected on this if I have the seal type wrong.   

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Curtis Holmes
Alaskan Brewing Co
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Original Message:
Sent: 01-11-2024 16:41
From: Tyler Walsh
Subject: The Great Centrifuge Seal Water Debate...

Hi Travis,

Just adding to the discussion- Hoping to help anyone making the decision to move forward with a large capital expense project including a DAW system. I was apart of the install, commission, and operation of two Alfa Laval Brew 350 Series separators at a large production plant (100K+ BBLs per year). We did not have a DAW skid and both machines were hooked up to city water. We processed a variety of different beer brands and RTD cocktails through the 350s. Operators were trained to monitor all critical control points you mentioned and we very rarely had any D.O. pick up in the separator. I credit the smooth operation and zero pickup to the training we got from our Alfa Laval technician, it made the difference during challenging spins. Obviously the need for a DAW skid will vary dependent on manufacturer/model, but in this case the 350s had no problem using city water as a utility.     

Tyler Walsh
Brewery Manager
pFriem Family Brewers
Hood River OR

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Tyler Walsh
Brewery Manager
Pfriem Family Brewers
Hood River OR
(541) 948-5320
------------------------------

Hi Curtis,

You are correct, the AL 350 is bottom fed with a mechanical seal. My apologies, I was not clear enough in my first message. I was trying to make a general point that operating water for these units didn't need DAW but operating utility water control by the operators is critical. Couple basic examples would be the OWMC for discharges and verified mechanical seal cooling during start up, stand by, and spin downs to preserve the seal. These are just a couple examples but it all led to zero DO pick up between services.      

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Tyler Walsh
Brewery Manager
Pfriem Family Brewers
Hood River OR
------------------------------

Original Message:
Sent: 01-15-2024 00:55
From: Curtis Holmes
Subject: The Great Centrifuge Seal Water Debate...

Hi Tyler,

I believe the Alfa Lavel 350 units use a mechanical seal on the bowl, not the hydro-hermetic seal that the GEA units use.   Unless they have different models that I'm not aware of that use hydro-hermetic in that 350 series.   So the type of water may not be as important on those models.   Glad to be corrected on this if I have the seal type wrong.   

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Curtis Holmes
Alaskan Brewing Co
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Original Message:
Sent: 01-11-2024 16:41
From: Tyler Walsh
Subject: The Great Centrifuge Seal Water Debate...

Hi Travis,

Just adding to the discussion- Hoping to help anyone making the decision to move forward with a large capital expense project including a DAW system. I was apart of the install, commission, and operation of two Alfa Laval Brew 350 Series separators at a large production plant (100K+ BBLs per year). We did not have a DAW skid and both machines were hooked up to city water. We processed a variety of different beer brands and RTD cocktails through the 350s. Operators were trained to monitor all critical control points you mentioned and we very rarely had any D.O. pick up in the separator. I credit the smooth operation and zero pickup to the training we got from our Alfa Laval technician, it made the difference during challenging spins. Obviously the need for a DAW skid will vary dependent on manufacturer/model, but in this case the 350s had no problem using city water as a utility.     

Tyler Walsh
Brewery Manager
pFriem Family Brewers
Hood River OR

------------------------------
Tyler Walsh
Brewery Manager
Pfriem Family Brewers
Hood River OR
(541) 948-5320