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Why does the steam not go out of the air vents?

I read this in a trade magazine:
"For a steam system to operate correctly, the air has to be removed from the pipes and replaced with steam. Since the two gases — steam and air — cannot occupy the same space, steam at a higher pressure will push the air from the pipes through the air vents or traps."
ethicalpaul

Comments

  • JUGHNE
    JUGHNE Member Posts: 11,021
    The vents and traps have a high temp thermostatic valve that closes upon the arrival of the steam.

    Keep reading, a good book is "We Got Steam Heat!", easy and interesting read .
    ethicalpaul
  • BUSTERBATBOY
    BUSTERBATBOY Member Posts: 6
    Aha! Thank you kindly.
  • dean_20
    dean_20 Member Posts: 16
    An even better one is "The Lost Art of Steam Heating". And I'm just a homeowner who just happens to have a one pipe steam system.
  • JohnNY
    JohnNY Member Posts: 3,226
    But, as with all things mechanical, those thermostatic valves do fail at times. They're one of the very few moving parts in a simple steam heating system and they need attention once in a great while. Just saying.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
  • ChrisJ
    ChrisJ Member Posts: 15,433
    JohnNY said:

    But, as with all things mechanical, those thermostatic valves do fail at times. They're one of the very few moving parts in a simple steam heating system and they need attention once in a great while. Just saying.

    How long do they generally last, assuming the velocity through them is low as to not carry rust, debris etc and assuming dry clean steam?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Jamie Hall
    Jamie Hall Member Posts: 22,878
    ChrisJ said:

    JohnNY said:

    But, as with all things mechanical, those thermostatic valves do fail at times. They're one of the very few moving parts in a simple steam heating system and they need attention once in a great while. Just saying.

    How long do they generally last, assuming the velocity through them is low as to not carry rust, debris etc and assuming dry clean steam?
    If they have never been abused -- particularly overpressure, or steam in the returns -- a long time. The ones in Cedric's home were installed in 1930, and are fine.

    Even a relatively short overpressure, though, can ruin them pretty fast.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    Also, if the steam fills the radiator too fast and/or is wet, it will mix and you get a lot of warm vapor that is too cool to close hte trap but will spit out the vent. Solution is properly near boiler piping and slowing the radiator vents and speeding up the main venting.

  • Gordo
    Gordo Member Posts: 852
    @BUSTERBATBOY : Here is a YouTube video showing and trying to explain what goes on inside a typical steam radiator vent.
    Sorry about the low volume sound (Earphones might help).

    https://www.youtube.com/watch?v=U1HZUxhEFO4
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
    https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
    Dave in QCAethicalpaul
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    I see you have a Hoffman 1A vent there. You happen to have a stash of those? It’s a really slow vent and I’m considering converting back to vacuum. They apparently last forever too. The one I have I think is original from about 1907.
  • BUSTERBATBOY
    BUSTERBATBOY Member Posts: 6
    Thank you all. :)