This month we are going to look at steam traps.

A steam trap’s function is to allow air and condensate to leave the radiators and steam piping and prevent steam from entering the condensate return piping.

There are various types of steam traps in use. For our purposes we are only going to cover the two main types used in steam heating systems.
The most common is the thermostatic radiator trap. Every radiator is equipped with one, with the exception of a one pipe system.

Radiator traps come in two main types – angle and straight way. Both types have similar construction, a body, cap, thermostatic element, and a union tail.

The thermostatic element is the heart of the trap, It expands and contracts with the steam and condensate temperature. When the element is in contact with the steam it expands closing off the exit opening thus preventing the steam from entering the return piping. As the steam is condensed the lower temperature condensate causes the element to contract opening the exit opening allowing the condensate to clear the radiator. As the steam comes in contact with the element the cycle starts over again. This expansion and contraction eventually causes the element to fail.

It can be difficult to determine when an individual trap is leaking, usually the first indication is loss of vacuum, or steam issuing from the condensate tank vent. This happens when an element fails open or the radiator is not heating when the element fails closed.

The second type of trap is the float and thermostatic trap. This trap is used to rapidly remove large amounts of air and condensate and is generally found at the end of the steam mains or on unit heaters.

The operating mechanism consists of a float valve and a thermostatic element. In most cases these traps can be rebuilt.

Repair parts for most steam traps are still available. Call for more details!