Float and Thermostatic Steam Traps

Armstrong Float & Thermostatic (F&T) steam traps combine a ball float for continuous condensate drainage with a balanced-pressure thermostatic air vent for rapid air and CO₂ removal. The B and BI Series are ideal for heating service where continuous drainage with high air-venting capacity is required, operating from vacuum to 30 psig.

Learn more about Armstrong F&T steam traps

How It Works

The ball float rises and falls with the condensate level, continuously modulating the valve to drain condensate as fast as it forms. A separate thermostatic air vent element responds to the steam saturation curve, opening to discharge air and CO₂ at temperatures slightly below steam temperature. This dual mechanism provides both continuous condensate drainage and rapid air venting in a single trap.

Due to the wide use of vacuum returns in heating systems, the thermostatic air vent element is charged to provide compensated response to the pressure-temperature curve of steam at any pressure from less than 20″ Hg vacuum to 30 psig gauge. All B Series traps (except ½″ and ¾″) have inlet connections on both sides of the body for piping flexibility. The BI Series features in-line connections with the same internals as the B Series.

Armstrong F&T Models

Model	Max Capacity	Max Allowable Pressure	Max Operating Pressure	Connection Size
B2 / BI2	1,410 lb/hr	125 psig @ 353°F	30 psig	½″
B3 / BI3	1,410 lb/hr	125 psig @ 353°F	30 psig	¾″
B4 / BI4	2,250 lb/hr	175 psig @ 377°F	30 psig	1″
B5	2,750 lb/hr	175 psig @ 377°F	30 psig	1¼″
B6	4,200 lb/hr	175 psig @ 377°F	30 psig	1½″
B8	8,100 lb/hr	175 psig @ 377°F	30 psig	2″