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Knocking

Dave Faust
Dave Faust Member Posts: 51
in THE MAIN WALL
One of my responceabilities concerns a steam to water heat exchanger that supplies hot water for the heating system of a building. The other (unseasonably warm) day I shut off 4 of the 7 water circulators that serve this system. After about thirty minuits a slight waterhammering noise started coming from the newly installed but uninsulated heatexchanger. It got progressively louder, and was definatly cyclic. After another forty minuits of this I got so nervous that I turned back on all of the circulators. Within 60 seconds the noise subsided.
The old heatexchanger didn't do this. There are drip/traps imidately upstream of the control valves (a parellel arangement). Come to think of it the controll valves are new too. The other valves were two different sizes. The new ones are identical. Anybody ever experienced anything like this?
Thanks,
Dave

Comments

  • Ken_8
    Ken_8 Member Posts: 1,640
    It is possible

    That the steam side of the HX was percolating. I assume by your outline, the day was warm. The steam boiler probably was off. If all it feeds is the HX, a vacuum would produce flash steam which would perc. The pipes being great sound transmitters, may have made the percolation noises (sort of popping, crackling type sound?)

    Also, if the HX got hot enough, the water side may have also experienced impellor cavitation. It depends somewhat on the location of each circulator's PONPC and whether the circ. pumps pump into - or away from the HX.

    More info, please.

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,054


    Thats a "one third"- "two thirds" situtation on the control valves. Supposed to get better control with two valves.They are supposed to be diferent sizes. I am assuming they are pneumaticly controlled valves probably normially open valves. The system starts with both valves wide open. As the load drops off (inc pneumatic air pressure) starts to throttle the larger(two thirds) valve closed-as the load continues to drop the larger valve is completly closed and the smaller (one third) valve which is still open starts to throttle back toward the closed position. The reverse happens when the load picks up.

    Some possibilities for the noise. Do you have a vacuum breaker installed somewhere between the control valve outlet and the steam trap inlet?? Is the steam in the shell or in the tubes?? Is the sensor that operates the steam valve on one of the hot water loops you shut off??

    ED
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