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Mechanical steam traps rely on the density difference between steam and condensate to operate. One common mechanical trap is called an F&T or float-and-thermostatic trap. In this trap, the inlet is near the top of the body and the outlet is near the bottom. A float on a hinge moves a valve plug which controls the flow of condensate through an orifice in the outlet. The float is positioned such that when the level of the condensate in the body is slightly above the outlet orifice, the valve is closed. As more condensate enters the body, the float rises, pulls the valve plug away, and opens the orifice. Any steam entering the body must force condensate out before it can escape. But as the condensate level falls the orifice closes and the steam is contained.