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vacuum steam systems

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dfaulk
dfaulk Member Posts: 2
Can anyone tell me why there is a second check valve on the equalizing line on the vacuum tank to the boiler, I understand why its by the boiler but don't understand why there's another one and a vent by the vacuum tank ?

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  • Pumpguy
    Pumpguy Member Posts: 663
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    Reading from left to right, the first check valve is a pressure vent.

    If the vacuum pump is running on float only, or if the vented air volume exceeds the air removal capacity of the vacuum pump, steam pressure will push out air through this check valve to atmosphere.

    The check valve on the right is for equalizing the pressure between the steam side and return side of the system. When steam stops flowing in a properly tight system, an induced vacuum will occur due to the volume change between steam and water. When this happens, there is a high vacuum on the steam side. If this were not equalized with the return line pressure (vacuum), condensate would not gravity flow back to the vacuum pump.

    If you look closely, you will see these 2 check valves are installed to allow flow in opposite directions. The pressure vent check valve allows flow to atmosphere. The equalizer check valve allows flow toward the boiler.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.
    Noel
  • dfaulk
    dfaulk Member Posts: 2
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    In what application would you have float only vacuum pump, I would think you would want it on float and vacuum ?
  • Pumpguy
    Pumpguy Member Posts: 663
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    True, except when condensate is too hot for producing a vacuum due to leaking steam traps or other causes.

    Other times are when there are air leaks in the system that exceed the vacuum pump's air removal capacity, and in summer when steam is not used for building heat.

    Perhaps also when vacuum producing pump parts are too worn, or if vacuum pump is undersized for the system. This last scenario, not enough air removal capacity in terms of CFM, is a far too common situation.
    Dennis Pataki. Former Service Manager and Heating Pump Product Manager for Nash Engineering Company. Phone: 1-888 853 9963
    Website: www.nashjenningspumps.com

    The first step in solving any problem is TO IDENTIFY THE PROBLEM.