Float and thermostatic traps are mechanical units that operate on both density and temperature principles. The float valve operates on the density principle. A level connects the ball float to the valve and seat. Once condensate reaches a certain level in the trap, the float rises, opening the orifice and draining condensate. A water seal formed by the condensate prevents live steam loss.
Since the discharge valve is under water, it is not capable of venting air and non-condensables. When the accumulation of air and con-condensable gases causes a significant temperature drop, a thermostatic air vent in the top of the trap discharges them. The thermostatic vent opens at a temperature a few degrees below saturation, so it’s able to handle a large volume of air-through an entirely separate orifice-but at a slightly reduced temperature.
* Float-Thermostatics steam traps complete by the differential temperature type exhaust valve and the float ball stem and valve seat.