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INVERTED BUCKET TRAPS normally fail in the open position because the trap loses its prime. This condition means a complete
blow-through, not a partial loss. The trap will no longer operate intermittently. Aside from a continuous rushing sound, another clue
for steam blow-through is the sound of the bucket clanging against the side of the trap.
A FLOAT AND THERMOSTATIC trap normally fails in the "closed" position. A pinhole leak produced in the ball float will cause
the float to be weighted down or water hammer will collapse the ball float. Since the trap is totally closed - no sound will be heard. In
addition, check the thermostatic element in the float and thermostatic trap. If the trap is operating correctly, this element is usually
quiet; if a rushing sound is heard, this will indicate either steam or gas is blowing through the air vent. This indicates that the vent has
failed in the open, position and is wasting energy.
THERMODYNAMIC (DISC) traps work on the difference in dynamic response to velocity change in the flow of compressible and
incompressible fluids. As steam enters, static pressure above the disc forces the disc against the valve seat. The static pressure over a
large area overcomes the high inlet pressure of the steam. As the steam starts to condense, the pressure against the disc lessens and the
trap cycles. A good disc trap should cycle (hold-discharge-hold) 4-10 times per minute. When it fails, it usually fails in the open
position, allowing continuous blow-through of steam.
THERMOSTATIC TRAPS (bellows & bi-metallic) operate on a difference in temperature between condensate and steam. They build
up condensate so that the temperature of condensate drops down to a certain level below saturation temperature in order for the trap to
open. By backing up condensate, the trap will tend to modulate open or closed depending on load.
In a bellows trap, should the bellows become compressed by water hammer, it will not function properly. The occurrence of a leak
will prevent the balanced pressure action of these traps. When either condition occurs, the trap will fail in its natural position either
opened or closed. If the trap falls closed, condensate will back up and no sound will be heard. If the trap falls open, a continuous
rushing of live steam will be heard.
With bimetallic traps, as the bimetallic plates set due to the heat they sense and the cooling effect on the plates, they may not set
properly which will prevent the plates from closing completely and allow steam to pass through. This will be heard as a constant
rushing sound.
NOTE: A complimentary Steam Trap Trouble Shooting Guide is available. Contact UE Systems directly by phone or fax.