The steam trap is an essential element of a steam distribution piping system. As steam flows through a pipe, it cools off due to heat losses and converts into hot water; this hot water is called condensate. The function of a steam trap is to bleed off hot water so that only steam remains in the system. In addition to condensate removal, a steam trap also performs air venting function, thereby increasing the thermal efficiency and reliability of the steam distribution system.

A typical steam trap assembly consists of a number of components which enable the successful operation of the system.

1.       Stop Valves: To control (stop or allow) the steam flow through the system.
2.       Strainer: To remove debris from the steam; if debris is not removed, it might damage the trap.
3.       Check Valves: It stops the condensate from flowing back to the system.
4.       Trap: To catch water and allow the steam to flow through.

In normal practice, strainer and check valves are built in with the steam trap.

Under normal operation, bypass stop valve remains closed and the other two stop valves remain open. Steam flows through the trap, where condensate is removed and drained while the steam returns to the steam mains. In some plants, condensate is recovered and returned to the boiler feed water tank. This results in significant savings in terms of energy and water usage.

In case of repair or replacement of steam trap, bypass valve is opened and both stop valves, before and after trap, are closed. After performing the repair or replacement activity, the stop valves are opened and stop valve closed to their normal position.