Steam Trap

A steam trap does not remove air. Instead, it allows condensate (liquid water) to pass through while stopping the passage of steam.

That's right, but if it's any help to Yogananth, a steam trap turned upside down can be used to release air from a liquid system.

Cheers..........Codey

There are many kinds of steam traps.

Steam traps with thermostatic bellows will remove air until the vapor inside the bellows expands and closes the air vent valve. When the air has been expelled the remaining steam heats up the bellows. The bellows are very susceptible to damage by water hammer.

In the common float and thermostatic trap, condensate will be forced by the pressure difference across the valve until the float drops and pushes the needle against the seat.

When a steam trap removes air and condensate from a steam system the condensate and air is expelled into to the condensate line.

Do not confuse steam traps with air eliminators or air vents for steam systems.

In low pressure steam systems as often used in older buildings air is often expelled from the system by air eliminators that sometimes are located on the steam mains, but nearly always on the radiator and other heat-emitting devices. Either closed by a thermostatic element or a float, the air is released to the atmosphere.

During startups:

The Ball Float Steam Traps have built-in air vent valve to remove air .

The Inverted Bucket Steam Traps have a small hole on the top of the bucket to remove air, however an air vent is recommended prior the steam trap.

The bi-metallic & Thermostatic steam traps are temperature-sensative and hence face no problem in removing air.

If you have excessive air then you can also install an automatic air vent prior each steam trap/s.

Suggest you log on to www.spirax.com site to see these in details. The www.tlv.com site shows you animation to help you understand better.