Bimetallic steam trap ( BST )

As the name implies, bimetallic steam traps are constructed using two strips of dissimilar metals welded together into one element. The element deflects when heated. (Figure 3):
There are two important points to consider regarding this simple element:

Balanced pressure steam trap ( BPST )

Balanced pressure steam trap with replaceable capsule

A large improvement on the liquid expansion trap is the balanced pressure trap, shown in Figure 2 Its operating temperature is affected by the surrounding steam pressure. The operating element is a capsule containing a special liquid and water mixture with a boiling point below that of water. In the cold conditions that exist at start-up, the capsule is relaxed. The valve is off its seat and is wide open, allowing unrestricted removal of air. This is a feature of all

Liquid expansion steam trap ( LEST)

 Liquid expansion steam trap

This is one of the simplest thermostatic traps and is shown in Figure 1 An oil filled element expands when heated to close the valve against the seat. The adjustment allows the temperature of the trap discharge to be altered between 60°C and 100°C, which makes it ideally suited as a device to get rid of large quantities of air and