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  • Air Vents

  • Air Vents

    Whether it’s a one-pipe or two-pipe steam system, the introduction of air and non-condensable gases within the system is inevitable.

    In a steam system, when the system is shut down, it will cool and all of the steam within the system will condense.  This creates a vacuum which will cause air to be drawn into the system.  When the system is brought back on line, all of that air which was introduced into the system by the shut-down, must be removed before steam can replace it.  When boiler feedwater and returned condensate which has been exposed to the atmosphere are heated in the boiler, dissolved gases are released and are carried with the steam into the distribution system.  These too must be removed.  If you have ever felt the top of a cast iron radiator and found it to be cool while the bottom is hot – chances are good that there is entrapped air within the radiator.

    For steam systems, air vents are typically designed with temperature sensitive devices that react to the surrounding medium.  Air, being cool when compared to steam, will pass through the air vent; when steam reaches the air vent, the thermostatic device will react to the increase in temperature and close, keeping the steam within the system.

    Features:

    • Common sizes: ⅛”, ¼”, ½”, ¾”, but available up to 2 inches
    • Angle or vertical connections
    • Automatic or manual operation

    Applications:

    • Removing air from equipment at a high point before the point of use
    • Removing air along main or distribution lines
  • Available Air Vents for Steam Systems

  • VENT-RITE (For Steam)

  • Model No. Connection Main Use Max O.P. Height
    1 1/8" Male Angle Free Standing Radiator (1-pipe system) 3 3-1/4"
    11 1/8" Male Angle Free Standing Radiator (2-pipe system) 6 2-3/4"
    31 1/8" Male Convector, Short Mains, Risers 6 3-3/4"
    33 1/4" Male Convector, Short Mains, Risers 6 3-3/4"
    35 3/4"M x 1/2"F Mains 3 3-1/4"
    75 3/4"M x 1/2"F Mains 5 4-4/5"
    77 3/4"Mx1/2"F Mains 3-1/2 4-5/8"
    57 3/4"Mx1/2"F Unit Heaters 20 4-5/8"
  • WATTS (For Steam)

  • Model No. Connection Main Use Max O.P. Height
    SVA 1/8" Male Angle Free Standing Radiator (1-pipe system) 1-1/2 3-1/8"
    SV 1/8" Male Angle Free Standing Radiator (2-pipe system) 6 3-1/8"
    SVS-1 1/8" Male Free Standing Radiator (2-pipe system) 6 3-7/16"
    SVS-2 1/4" Male Free Standing Radiator (2-pipe system) 6 3-7/16"
  • HOFFMAN (For Steam)

  • Model No. Connection Main Use Max O.P. Height
    74 3/4"M x 1/2"F Unit Heaters 35 6-1/8"
    75 3/4"M x 1/2"F Mains 3 6-1/2"
  • Hydronic heating systems can contain excess air which harms their ability to function properly. Air takes up valuable space in mains and distribution lines, reducing the volume of water transported through the system. When air accumulates in heating equipment like radiators or coils, it acts as an insulator that reduces the amount of heat transferred to the space.

    For hydronic systems, automatic air vents are typically float devices which remain open allowing air to escape. When the rising liquid level reaches the air vent, the liquid causes the float to rise and seal the air vent opening. As long as the liquid creates a positive pressure on the float, no liquid will escape. When the liquid level falls below the float level, the accumulated air escapes and the process is repeated. They are installed at high points in the system can be found on mains, distribution lines and at points of use like radiators.

    Manual air vents are opened with a screwdriver, button or knob and are found at points of use like radiators and heating coils. They are installed at the highest point in the equipment.

    Features:

    o Connection sizes: ⅛”, ¼”, ½”, ¾”, 1”
    o Vertical or horizontal mounting
    o Automatic or manual operation

    Applications:

    o Removing air from equipment at a high point before the point of use
    o Removing air along main or distribution lines

  • Available Air Vents for Hydronic Systems

  • Hoffman (For Water Service)

  • Model No. Connection Main Use Max O.P. Height
    77 1/8" MNPT Radiators and Convectors 50 3-1/4"
    78 3/4" MNPT Main Lines 150 6-1/2"
    79 1/2" FNPT or 3/4" MNPT Main Lines 75 6-5/8"
    790 1/8" MNPT Radiators and Convectors 30 4-1/4"
    791 1/4" MNPT Radiators and Distribution Lines 50 4-7/8"
    792 3/4" FNPT Inlet x 1/2" FNPT Outlet Main Lines 250 7"
  • MAID 'O MIST (For Water Service)

  • Model No. Connection Main Use Max O.P. Height
    7 1/8" Female Vertical Mount Mains, Pipe Lines, Unit Heaters, Chillers, Convectors, Radiant Panels, Coils 75 4-3/8"
    27 1/8" Female Horizontal Mount Radiators, Convectors, Fan Coil Units, Baseboard Radiation, Mains, Radiant Panels, Small Unit Heaters 50 2-1/2"
    37 1/8" Male Horizontal Mount Radiators, Convectors, Fan Coil Units, Baseboard Radiation, Mains, Radiant Panels, Small Unit Heaters 50 2-1/2"
    67 1/8" Male Vertical Mount Convector Radiators, Baseboard Radiation, Radiant Panels 50 3-3/4"
  • Note: Additional models are also available.

  • Watts (For Water Service)

  • Model No. Connection Main Use Max O.P. Height
    DuoVent 1/8" MNPT Distribution Lines 150 3"
    FV-4M1 1/8", 1/4", 1/2", 3/4", and 1" Distribution Lines 150 2-15/16" to 3-1/2"
  • Keystone Steam Supplies is here to help you get the Air Vents you need.