Bimetallic Trap

Bimetallic Steam Trap Operating Principles

The bimetallic trap operates on the temperature principle using two layers of metallic elements, each with different expansion coefficients.

Careful choice of materials and surface treatments in bimetallic traps makes them highly resistant to the erosive action of flash condensate and prevents wear on the trap's valve and seat material.

How It Works

		Step 1 In bimetallic traps the valve is operated by metal strips made of alloys with different coefficients of expansion that are bonded together. At start-up, the trap is cold and the bimetallic element is relaxed. The valve is wide open.

		Step 2 When steam enters the trap, it surrounds and heats the strips, which begin to expand at different rates. The element pulls directly on the valve stem, closing the valve against the pressure differential. As heat radiates from the trap, the strips begin to cool. When the element has cooled sufficiently, it relaxes, opening the valve.

Armstrong Bimetallic Trap Features

	1.	Vents non-condensables at low pressure.
	2.	Resists corrosion damage.
	3.	Handles light loads well. May need to pre-set operation range.
	4.	Handles start-up loads well.
	5.	Easily clogged by dirt.
	6.	Available in a number of connecting types and sizes as well as a range of pressures and capacities. Robust construction resistant to water hammer.
	7.	Operates well in freezing environments.
	8.	Sub cools condensate. Only the trap capacity is affected by increased back pressure.