Ask The Brewmasters

I have a brew house centrifugal pump that has recently started to destroy its mechanical seals.  The pump is a YUY 3Kw pump with an ABB motor and serves multiple roles (vorlauf/lauter and transfer to the WP from the BK) on our 3 vessel 15bbl brew house.   A few months ago it started to whine a bit so I decided to swap the pump out with our identical spare so I could replace the seals.  All seemed fine for a few months then one day new spare pump started making a noise like a motor bearing had gone out.  I then swapped the original pump (with new mechanical seal back in place. The next brew it started leaking badly from the behind the seal mid lauter. After changing the seals again it did the same thing mid lauter on the next brew.  We run a 50L grant for vorlauf and lauter with automation to keep the pump from running dry and avoid running to dry when moving wort to the WP. These pumps run with stainless steel forward seal and carbon rear seal. On all instances of sever leakage the rear carbon seal was damaged (cracked or chipped).

The only thing I think of that might be causing it would be if the adjustable support feet for the pump were not properly supporting the motor and the motor was hanging by the pump housing putting stress on the drive shaft and mechanical seal, but I'm not even sure if that's possible. The bearing going out one the spare pump motor is a bit troubling as well.

Just wondering if anyone has seen or heard of a pump doing this before and if so what was the cause and more importantly the solution.  Happy to hear any and all thoughts or suggestions.
Thanks!


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Gary Heil
Cypress & Grove Brewing Co
Gainesville FL
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The most common cause of damage to the Carbon Rotary seals are;

1. Misalignment
2. Pump cavitation
3. Dry pump at start-up or shut down
4. Dirty pump cavity. As you know, beer or wort is very sticky when it drys.
5. For multi-purpose pumps, rapid fluid temperature changes. Don't flush pumps with cold water after hot liquids. In cold climates, run warm water before hot liquids.

Also, check the drive motor bearing. If it is a coupled drive pump, check the coupling alignment.

There are usually two reasons for pump seal failure, mechanical and operational.

Cheers







Sent from my iPhone

Original Message:
Sent: 10/19/2022 12:11:00 PM
From: Gerald Alvey
Subject: RE: Repeated mechanical seal failures on brewhouse pumps

The most common cause of damage to the Carbon Rotary seals are;

1. Misalignment
2. Pump cavitation
3. Dry pump at start-up or shut down
4. Dirty pump cavity. As you know, beer or wort is very sticky when it drys.
5. For multi-purpose pumps, rapid fluid temperature changes. Don't flush pumps with cold water after hot liquids. In cold climates, run warm water before hot liquids.

Also, check the drive motor bearing. If it is a coupled drive pump, check the coupling alignment.

There are usually two reasons for pump seal failure, mechanical and operational.

Cheers







Sent from my iPhone

Hi Gary,

Gerald's comments are spot-on. I would like to add a couple points. First, OEM parts are always best especially for pumps; side note, this is honestly why I don't buy Chinese pumps. Second, I have found that some high-temp rated pumps still have trouble with hot wort during w/p. If there is a small leak and you see wort coming out of the back, the problem is not only a sticky mess, but air ingress that can lead to floating trub in the w/p. One solution is to trickle a low-flow stream of water on the back of the pump which prevents air from entering. Of course, avoid water contacting electrical and opt for wash-down (sealed) motors whenever possible.

I hope you find a solution!

Cheers.

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Chris Bogdanoff
Head Brewer
Heroes Restaurant and Brewery
Rancho Cucamonga CA
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We experienced a repeated failure of pump seals on our kettle/whirlpool pump and found that misalignment (#1 in Gerald's list) was the cause. We hired a local mechanical crew to re-align our piping between the kettle/whirlpool/heat exchanger, which had fallen out of level through 10 years. It's not difficult to do yourself with a level, but our hard piping was somewhat difficult to re-align and we needed to make some slight changes in the piping structure. It was well worth it and corrected the issue.

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Marcus Powers
Co-Founder | Chief of Operations
Zipline Brewing Co
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our wort pump used to have seal failures often. 
I installed a cold water bleed that sprays directly on the back of the seal as it rotates and haven't had the issue in years.

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Michael Smith
Head Brewer
Eel River Brewing Co.
Fortuna, CA
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One additional item you may be seeing is cavitation due to high fluid temps. At the temperatures you'll see from the WK -> WP you are likely seeing flash boiling in the pump head. You are operating close to the boiling point and there is a slight pressure drop at the pump inlet that could be enough to cause cavitation. At two facilities we installed a small return line from the pump outlet to the pump inlet to help mitigate this problem. One I commissioned and the other happened to be installed before I started (just to say that it is not solely my crazy idea) and were both recommended by Fristam. 

The hot wort pump is often the most abused pump in the brewery. All of the suggestions above are excellent and a combination will get you on the right track. If you end up putting a double, flushable seal you can use the outlet water to cool another pump seal. On an older brewhouse, I didn't have a solenoid controlling flush water as Karl mentioned so at least we were flushing two pumps that typically ran simultaneously.

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Campbell Morrissy
Head Brewer
pFriem Family Brewers

PhD Candidate
OSU - Barley Project
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Original Message:
Sent: 10-20-2022 13:40
From: Michael Smith
Subject: Repeated mechanical seal failures on brewhouse pumps

our wort pump used to have seal failures often.
I installed a cold water bleed that sprays directly on the back of the seal as it rotates and haven't had the issue in years.

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Michael Smith
Head Brewer
Eel River Brewing Co.
Fortuna, CA
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All of the above suggestions are excellent advice, but do not forget the simplest cause. Repeated seal failures are often a sign that the shaft or sealing surface could be scratched or scored. Have you checked this?

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Garry Turnquist
Reliability Manager
Real Ale Brewing Co.
Blanco, TX
830-730-8397
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Has anyone switched from the carbon style mechanical seals to teflon seals the Thomsen pumps use?

Chris

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Chris Roberts
Red Crow Brewing Company
Olathe KS
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Original Message:
Sent: 10-24-2022 15:57
From: Garry Turnquist
Subject: Repeated mechanical seal failures on brewhouse pumps

All of the above suggestions are excellent advice, but do not forget the simplest cause. Repeated seal failures are often a sign that the shaft or sealing surface could be scratched or scored. Have you checked this?

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Garry Turnquist
Reliability Manager
Real Ale Brewing Co.
Blanco, TX
830-730-8397
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If the pump in question is a Thomsen #4 with an internal seal, Garry is correct in saying inspect ​the wear surfaces. Thomsen use the stainless backing plate as the stationary surface of the seal. Scoring of this rubbing surface is very common when the pump is used in brewhouse applications. We used to swap out the backing plate, or machine the race (if possible), when changing seals.

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Brad McQuhae
König Brewing Systems
Abbotsford, BC Canada
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Original Message:
Sent: 11-04-2022 10:39
From: Chris Roberts
Subject: Repeated mechanical seal failures on brewhouse pumps

Has anyone switched from the carbon style mechanical seals to teflon seals the Thomsen pumps use?

Chris

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Chris Roberts
Red Crow Brewing Company
Olathe KS
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Original Message:
Sent: 10-24-2022 15:57
From: Garry Turnquist
Subject: Repeated mechanical seal failures on brewhouse pumps

All of the above suggestions are excellent advice, but do not forget the simplest cause. Repeated seal failures are often a sign that the shaft or sealing surface could be scratched or scored. Have you checked this?

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Garry Turnquist
Reliability Manager
Real Ale Brewing Co.
Blanco, TX
830-730-8397

On wort pumps, a seal rinse extends the life.  But if it's a new issue, slight abrasion, wear, bent shaft or impeller wear can wreck them fast.  What is the pump manufacturer?

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Steve Saunders
Owner
Woodberry Fabrication, LLC
White Hall MD
(443) 992-5634
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Hi Gary,
Responding to this older post just in case you haven't found a cause yet.  We recently had a similar issue that has been baffling my crew where we'd have some seals last only a day, and other times the seal would last a week or two at most.     Our kettle wort pump has a water flush seal on it so it has two mechanical seals on it.  We finally figured out that the mechanical seals were being installed in the reverse location of where they were supposed to be.   Unfortunately one of my previous maintenance people had labeled the two different boxes of seal parts incorrectly and the manual from the manufacturer didn't list the seal locations at all.    So we were replacing seals  based on how the new seal looked compared to the old seal and just repeating a bad situation.  
After finally figuring this out by talking to the manufacturer, we found that the seals on the water side are cheaper materials (carbon & stainless) because they don't see the heat and friction of the high temperature wort side.  So if you put the seals in the opposite way of how they are designed, the cheaper material will burn up quickly.   A pump seal for high heat and friction should normally be made from Silicone Carbide from what I've read.  

I know your pump isn't a water flush pump, but many manufacturers make the same pump design and then just change the back housing to hold another seal.  I'm wondering if your pump supply company sent you the wrong seal type and it was actually supposed to be for a water flush side of a similar style pump, maybe they have the parts mixed up like we did?    Just something to look into.    I would highly recommend putting in a water flush pump on your wort pump though, it will save you a lot of headaches if someone runs the pump dry.

Let us know if you figured out the issue, I'm curious

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Curtis Holmes
Alaskan Brewing Co
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I'm finally getting around to following up with how this issue resolved and some things we discovered along the way, but first of all thanks to everyone for your insight, expertise and suggestions.

The pumps we have do not have fittings in place for seal rinse and a retrofit is not a high likelihood in the near future. All of the  pumps on our brew house are identical Chinese made YUY 3kW models of which we have one spare that we would swap out as needed when it came time to service in case of issues.  We did recently have a motor bearing go out on one of our pumps while it was being used for the MLT and that may have been the cause of the damaged carbon seal we saw.  I'd love to replace these pumps  with something more domestically sourced, but with the retrofitting of hard piping in out system it would require to match the configuration of a different pump head, that's not a project I'm ready to tackle at the moment. I do plan to look into retrofitting some water flush systemfor the rear seals. We do see a considerable amount of cavitation when transferring BK > WP but try to keep the pump speed low enough to keep this to a minimum without sacrificing a good spin.  I've always been careful to not start or run this pump dry, or deadhead as little as possible and have been diligent about everything getting a good hot water rinse at the end of a brew cycle.

After my original post I pulled the pump and took it apart expecting to find a damages rear seal, but to my surprise that was not that case. I inspected the shaft and all parts that made contact with the seal and found no damage. I did however find a considerable amount of spent grain between the seal and sealing surface of the pump. I also noticed as suspected that the leveling feet for the pump were not properly adjusted to support the motor and keep the drive shaft inline with the pump.   The grain, we discovered, was getting in through holes in our MLT false bottom vacated by  no less that 4 missing floor mounting bolts.  I replaced the bolts , lubricated the O-rings, reinstalled the seal, reinstalled the pump perfectly leveled and have not had any issues with the pump to date. We instituted a more regular preventative maintenance cycle for these pumps especially this one which aside from our HLT pump sees the most use so fingers crossed we continue running with no problems for good while.

Cheers
Gary

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Gary Heil
Cypress & Grove Brewing Co
Gainesville FL
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