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Steam main check valve

WeilWeil Member Posts: 15
Can anybody tell me the purpose of a check valve in the main steam supply off of a 175 HP low pressure steam heating boiler? Below is picture. 80 year old government building. Not sure if it was a vacuum system but it is two pipe. Stockholm 12C is model #. Engineer wants it removed. I want to confirm its purpose first.


  • SteamheadSteamhead Member Posts: 13,766
    Are there or were there two boilers in that building? If so, the check was probably there so steam wouldn't back into the inactive boiler.

    And what's that pipe coming off the bottom of the check?
    All Steamed Up, Inc.
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  • GrallertGrallert Member Posts: 442
    edited September 2017
    I doesn't look like it goes anywhere. It looks like that gate is the end of the line. Or the beginning of an abandoned run. I don't see any piping connected to that gate valve. If that's right that whole run could be removed and capped down by the boiler. Maybe?
  • DanHolohanDanHolohan Member, Moderator, Administrator Posts: 14,979
    I agree with Steamhead.
    Retired and loving it.
  • Danny ScullyDanny Scully Member Posts: 1,221
    edited September 2017
    I'd guess the pipe coming off the bottom is a support. I agree with @Steamhead as well.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,930
    You do not need a check valve unless you have two boilers or two sources of steam such as district steam and a back-up boiler.

    High pressure steam boilers in battery (two or more ) require two stop valves in series on each boiler as well as a check valve on each boiler. It is common procedure to use 1 stop valve and 1 non-return valve (which is a combination stop valve and check valve in one body) There is also supposed to be a manual drain valve between the two stop valves (usually 3/4")

    In some circumstances the inspectors may allow the extra valves to be omitted IF the boilers do not have a manhole on the boiler (no one can crawl inside)

    Valves are required so one boiler can be safely worked on while the other one continues to operate

    In most locations HP steam is inspected by the state or an ASME certified boiler inspector.

    I wouldn't alter anything without checking with the inspector
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