Control orifice:

A control orifice runs by the disk from top to bottom that is considerably smaller at the top than at the bottom. A bottom category of the disk extends by and beyond the orifice within the seat. An upper part of the disk (involving the flange) is within a cylinder. A cylinder tapers inward, so the amount of clearance among the flange and the cylinder varies according to the position of the valve. While the valve is open, the clearance is greater than while the valve is closed.

While the trap is first placed in service, pressure from the inlet (chamber A) acts against the underside of the flange and lifts the disk off the valve seat. Condensate is therefore permitted to pass out by the orifice in the seat; and, at the similar time, a small amount of condensate (called control flow) flows up past the flange and within chamber B. The control flow discharges by the control orifice, within the outlet side of the trap, and the pressure in chamber B remains lower than the pressure within chamber A.

As the line warms up, the temperature of the condensate flowing by the trap rise. The reverse taper of the cylinder varies the amount of flow around the flange until a balanced position is reached within that the total force exerted above the flange is equivalent to the total force exerted below the flange. It is significant to remember that there is still a pressure difference among chamber A and chamber B. A force is equalized since the effective area above the flange is larger than the effectual area below the flange. The difference within working area is such in which the valve manages at an open, balanced, position while the pressure in chamber B is around 86 percent of the pressure in chamber A.

While the temperature of the condensate approaches its boiling point then a few of the control flow going to chamber B flashes inside steam as it enters the low pressure area. Since the steam has a much greater volume than the water from that it is produced, pressure builds up in the space above the flange (chamber B). While the pressure inside this space is 86 percent of the inlet pressure (chamber A), the force exerted on the top of the flange pushes the whole disk downward and closes the valve. Along with the valve closed, the only flow by the trap is past the flange and through the control orifice. While the temperature of the condensate entering the trap drops slightly and condensate enters chamber B without flashing inside steam. Pressure in chamber B is therefore decrease to the point whereas the valve opens and permits condensate to flow by the orifice within the valve seat. The cycle is repeated constantly.

Within a normal condensate load, the valve opens and closes at often intervals, discharging a small amount of condensate at every opening. Inside a heavy condensate load, the valve remains open and permits a continuous discharge of condensate.