Brochure

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Selection Guides
Hoffman Specialty
®
Selection Guidelines
Selection Guidelines – Steam Vents
Steam vents are used in one-pipe steam heating systems. As such, steam vents are primarily replacement items.
Information required for sizing and selection:
1. Type of service
Determine the type of service where the vent
is to be installed.
a) Radiator Vent
b) Convector Vent
c) Main Vent
Model Radiator Convector Unit Thermostatic
Number (Angle type) (Bottom Inlet) Heater Mains Vent (only)
1A X
1B X
3 X
4 X
4A X
8C X
40 X
41 X
43 X
45 X
70A X
71A X
71B X
71C X
74 X
75 X
75H X
76 X
508 X
2. System operating pressure
Determine the operating pressure of the steam system.
(a) The rated operating pressure of the vent must be higher than the maximum operating pressure in the steam
system. When the system pressure exceeds the vent operating pressure rating, the vent cannot open and
air will remain in the system. Air in the system produces inefficient steam system operation.
(b) On steam systems with pressures up to 125 psig, Thermostatic Traps such as Model 8C and 9C may be
used as air vents.
(c) Determine if the vent is to be installed in a vacuum system. The Model 76 Main Vent is for vacuum service.
It should be used on systems with a vacuum pump or a vapor system with a coal or wood fired boiler.
Systems converted from coal or wood fired to oil or gas should use non-vacuum vents such as the Model 75.
3. Connection size
Determine the NPT connection size where the vent is to be installed.
Steam and Water Vents