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Thread: Hot Side Pump Seizing

  1. #1
    Join Date
    Apr 2018
    Dearborn Heights, MI, USA

    Hot Side Pump Seizing

    Hey All,

    We have a Thomsen centrifugal pump that we use for hot a cold side. After boil, we'll hook our pump to the kettle, then to the heat ex. After knock out, if we shut the pump off, it will seize up, requiring it to be broken down to clean out and cool off. Our particular model did have a recall for the seal, but the replacement hasn't seemed to work in this situation. There is no visible damage to the plate or o-ring, and it never has trouble cold side.

    Just wondering is anyone has dealt with this issue, it's never been a problem for me in other breweries. The pump head is held on by a clamp instead of bolts, is this a pressure issue?

  2. #2
    Join Date
    Sep 2005
    Louisville, KY
    My brewhouse has two Thomsen pumps. The mash/lauder pump has an internal seal, the kettle has an external. The external is held in place with a spring so it can only take so much back pressure. The difference is the external is designed for high temps, the internal is for under 180f. When I first started working with this brewhouse the kettle seal would wear out every 6 months b/c it was replaced at some point with an internal seal backplate. I changed it and have not had a problem since. Mine never seized, just leaked. Are you sure this is not a wet seal? What exactly is causing the seizure is it dried up malt glue, the seal, bearings?
    Joel Halbleib
    Partner / Zymurgist
    Hive and Barrel Meadery
    6302 Old La Grange Rd
    Crestwood, KY

  3. #3
    Join Date
    Mar 2003
    I used to have a couple of Thomsens. If I recall, you had to have about a credit card's width of clearance between the impeller and the back plate. If the impeller is too close to the backplate, it may be rubbing once it gets hot. I can't remember how to adjust it - I think it had a set screw that locked it to the motor shaft.
    Linus Hall
    Yazoo Brewing
    Nashville, TN

  4. #4
    Join Date
    Jul 2013
    Idyllwild, CA, USA
    My brew house pump has an external seal and I added a small bit of tubing that sprays water on it while brewing. It keeps the seal cool and lubricated and also prevents the sugars from building up. I just turn the valve enough so there's a steady stream of water hitting it. Haven't had any squeaks or problems with it in two years.


  5. #5
    Join Date
    May 2019

    Thomsen Pumps Seal Deal

    The brewery I work for uses only external seal pumps. They all have water nozzles to cool and clean the sealing surfaces; all but the hot liquor pump, because it has no contact with the wort. Thomsen Pumps with external seals come with a ceramic seat. The seat is the part that sits in the pump back plate. Those were primarily designed for dairy or food service. In a brewery the pump is most often used in pumping sugary liquid at high temps.
    With temperature extremes of going from boiling and whirlpooling to rinsing afterwards, the ceramic experiences thermal shock and will crack. The cracks then fill with wort that doesn't completely rinse out, especially if rinsing the copper gets delayed for an hour or two. It creates a very thick adhesive that seizes the carbon seal to the seat. When the pump is turned on the shaft spins inside the seal bellows often accompanied by a high pitched squeal that is the spring spinning against the washer. Once the seal starts spinning the squeal subsides. Eventually the washer is destroyed and it releases the spring pressure holding the seal to the seat. Leakage accompanies this. Leakage can occur initially when the ceramic cracks.
    To prevent thermal shock to the seat, order your pump with a silicon carbide seat, or repair kits with a silicon carbide seat. Silicon carbide is not affected by thermal shock. Thomsen sells them. And if your pumps that deliver wort don't have water nozzles be sure to install them. Ours were made in house. Sorry if I over simplified, but some might be less experienced.

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