Float and Thermostatic Steam Traps

The Armstrong and Spirax Sarco 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.