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Thread: WP Pump Horror

  1. #1
    Join Date
    Aug 2012
    Location
    Santee, CA
    Posts
    20

    WP Pump Horror

    We have had an on-going issue with our WP pump making rattling/vibration noises straight out of a horror film. I have tried replacing seals, loosening/tightening the body, and trying different speeds with the VFD.

    It takes almost 8mins for any momentum to build-up to create a spin. Still there is slow spin. Kettle finings have been dialed in according to the manufacturer recommendation, but our trub pile is complete dog crap. No structure, flat as a pancake, very unappealing.

    The whirlpool pump outlet, into tangential inlet seems to be the source of the rattling/vibration. When we choke back the valve at the tangential inlet, the rattling goes away. However, the trub pile becomes egg-shaped. Some folks who have tried to help say the issue could be cavitation, but I can't figure how to alleviate that issue.


    I will be able to upload videos shortly, and I will post them here.

    This is running at 7/10 on my VFD


    from inside the kettle
    Last edited by SDDanC; 06-09-2015 at 03:27 PM.

  2. #2
    Join Date
    Jun 2011
    Location
    Richmond, VA.
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    395
    have you tried looking at motor rpm?

  3. #3
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
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    1,707
    "When we choke back the valve at the tangential inlet, the rattling goes away."

    Your pump is cavitating. Pure and simple. However the solution is not so simple. The problem is your wort is at boiling point and boils if the pressure is reduced, creating the bubbles at a slightly lower temperature than if at atmospheric pressure. It may help to reduce the distance from the kettle outlet to the pump, or the transfer pipe diameter, or you may simply need to replace the pump with one that has a very low NPSH at that temperature, in other words, doesn't suck very hard. However, to make even the new pump work, you will have to eliminate the restriction in the supply from the kettle to the pump, and may have to relocate the wort takeoff point as well.
    dick

  4. #4
    Join Date
    Aug 2012
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    Santee, CA
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    Quote Originally Posted by dick murton View Post
    "When we choke back the valve at the tangential inlet, the rattling goes away."

    Your pump is cavitating. Pure and simple. However the solution is not so simple. The problem is your wort is at boiling point and boils if the pressure is reduced, creating the bubbles at a slightly lower temperature than if at atmospheric pressure. It may help to reduce the distance from the kettle outlet to the pump, or the transfer pipe diameter, or you may simply need to replace the pump with one that has a very low NPSH at that temperature, in other words, doesn't suck very hard. However, to make even the new pump work, you will have to eliminate the restriction in the supply from the kettle to the pump, and may have to relocate the wort takeoff point as well.
    Dick,

    Would eliminating restriction require increasing the diameter of the supply? Earlier you mention reducing distance from K to Pump, or the transfer pipe diameter (to me, meaning reduce transfer pipe diameter).

    I will look into lower NPSH as well

  5. #5
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
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    1,707
    Sorry. You are right. That was confusing. Shorten the supply pipe length and or increase the diameter. However, unless you are familiar with pump curves, or have access to a tame process / mechanical engineer who does understand them, I would have a chat with a reputable pump supplier and check with them what you currently have and what the best way of resolving the problem is.

    Key to this is to determine what flow you require and the inlet velocity. Inlet speed should be between 1.5 - 4.5 m/s ( the smaller the whirlpool the higher the speed) (Kunze). Additionally, if using separate kettle and whirlpool, the transfer time is typically quoted as being 10 to 15 minutes for large WPs. I would aim for something like 10 minutes to get up to maximum rotational speed of the full contents. Unfortunately I have no idea who many volumes of the wort kettle is required to do this effectively. Perhaps someone else can enlighten me. I would have thought half to probably closer to one volume of the wort kettle, but this is purely a guess.

    So once you have determined the flow rate required, you can go back to your pump supplier and get them to spec up a suitable pump, not forgetting it should be hygienic, able to cope with boiling wort, and various CIP fluids. It might be worth getting the biggest they suggest, but fitting a variable speed drive, rather than throttling back the discharge.
    dick

  6. #6
    Join Date
    Mar 2011
    Location
    Fort Myers, Florida
    Posts
    50
    Something you might also try. This is going to sound a little odd, but if you have a center drain in your whirlpool that shares the same pump inlet with the kettle, open it in addition to the kettle drain as soon as it's covered with wort. My pump cavitates at full speed, and I discovered that opening the whirl drain I can get a much faster transfer from the kettle and much higher spin speed in my whirl.

    Hope that makes sense?

    Rob

  7. #7
    Join Date
    Nov 2009
    Location
    Moab, Utah
    Posts
    469

    Additional Considerations

    Dan what Dick has stated is correct and I will add to that.
    You should never restrict a pump at the inlet in any fashion, only on the discharge side can that be done.
    With that said it looks like you have a C-216 pump or equivalent. One good thing about those pumps is they are designed to operate in both the 1750 RPM and 3450 RPM range depending on the impeller used. If it is a Waukesha pump for example their application engineers can help with the calculations if you can give them the necessary minimum data required. This involves feet of head, PISG, and flow rates etc.
    What you have is an incorrectly built out system with possibly several areas that have to be corrected to run right.
    With corrected piping etc. and the pump curve charts in question the right pump configuration can be found.

    The pump inlet connection piping has to match the size of the pump. If that is reduced it will get you into trouble.
    The C-216 impellers can be gotten from something like 6 down to about 3 inches. One way to measure those 3 lobed impellers is to run a hose clamp down on them and then measure the DIA.
    I have a source for NON-OEM impellers that are just as good as factory for about 1/2 the price from a UT Dealer.
    Also I have 2 different size impellers for a c-216 that I can make sale of as we no longer need them.
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  8. #8
    Join Date
    Jul 2012
    Location
    Burnaby BC Canada
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    309

    A few more suggestions

    I agree with most of the suggestions above, definitely increase the diameter of the line to your pump to 2", the same as the inlet. A couple more points, the tee right at the inlet to the pump is a bad piping design you could try just changing that to a clamp in elbow and see if that helps.

    I would not suggest putting in a smaller impeller, that will reduce the flow but the pump becomes less efficient and will require a greater NPSH.

    I know this sounds counter intuitive but what I would do is use a VFD to slow the pump down and at some point the cavitation will stop and the pump will then be full of liquid and start pumping properly. It may be all you need to do.
    Your CPE Systems Team!
    CPE Systems Inc.
    800-668-2268
    CPEsystems.com
    Thinkpumps.com
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  9. #9
    Join Date
    Mar 2003
    Location
    Nashville
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    832
    Yeah, your inlet is way too small. It looks like 1-1/2" going to the pump where it goes up to 2"? To get the most flow, you will need to increase that pipe diameter. Don't run the pump with cavitation, you will destroy the impeller and housing and your ears.

    But... you may not have to. You said your trub pile looks flat, but they all look flat at the end of the knockout. It's only a cone-shape while the wort is covering it. Are you getting excessive amounts pulled into the pump? Is it clogging your HX? If, not, then set the VFD speed to where the cavitation goes away, and just live with it.
    Linus Hall
    Yazoo Brewing
    Nashville, TN
    [url]www.yazoobrew.com[/url]

  10. #10
    Join Date
    Jul 2012
    Location
    Burnaby BC Canada
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    309

    Cavitation problem

    How did you make out? Have you managed to settle your pump down?
    Last edited by CPESystems; 08-19-2015 at 10:23 AM. Reason: Fixed my spell'n
    Your CPE Systems Team!
    CPE Systems Inc.
    800-668-2268
    CPEsystems.com
    Thinkpumps.com
    sales@cpesystems.com

  11. #11
    Join Date
    Jul 2012
    Location
    Burnaby BC Canada
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    309
    By the way - and I know this is a little old now - we put together a blog post explaining cavitation a bit and recommend that anyone who is suffering from a similar problem check it out.

    THE STRANGE RELATIONSHIP BETWEEN PRESSURE AND STATE
    You probably already know that the boiling point of water is 100°C (212°F) but what you might not know is that that only holds true when water is at 1 atmosphere of pressure. If you’re brewing at the top of the Mt. Everest, where the atmosphere is thinner, your water would boil at ~73°C (163°F). Pressure and temperature are closely related. At different pressures water boils differently and less pressure requires less heat for your fluids to approach a phase change. In fact, at 0 atmospheres water will boil at just ~20°C deg (70°F).

    This may seem little more than a thought experiment but your brewing system changes pressure all the time and the resulting water vaporization can be massively damaging to your pumps and equipment...
    Read more
    Last edited by CPESystems; 03-01-2018 at 09:47 AM.
    Your CPE Systems Team!
    CPE Systems Inc.
    800-668-2268
    CPEsystems.com
    Thinkpumps.com
    sales@cpesystems.com

  12. #12
    Join Date
    Jul 2015
    Location
    Ocean, NJ
    Posts
    21
    that Tee right in front of the pump inlet and that concentric reducer opening up from 1.5 to 2" right as you enter the pump are bad news for sure, as others have mentioned. I'd address that and consider adding a water cascade (there's a little threaded hole at the top of the cage for a fitting to be screwed in). A steady drip of water goes a long way toward keeping the seal faces cool and helping with cavitation. We have water cascades on all our pumps that push hot wort... near-boiling, high sugar content sticky liquid is a tough thing to pump under even ideal circumstances... factor in your piping shortcomings and cavitation is bound to be an issue.

    we run water cascades on our main brew house pump and wort pump. We've gotten away without them on HLT pumps so for us the fact that it's wort combined with the temp seems to be the issue. We've had pumps that run like crap with a lot of cavitating, and the solution was always a little bit of better plumbing (straight as possible inlet with a larger diameter than the outlet), seal material selection (though good old carbon seems to be just fine if you add the cascade) and water to cool where necessary.

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