Inverted Bucket Steam Traps Introduction
INVERTED BUCKET TRAPS . Operation:
Due to its weight, the inverted bucket within the trap will rest on the bottom of the trap body keeping the valve open and allowing condensate to be discharged ( Figure A ). In the top of the bucket there is a small bleed hole which allows air to escape from inside the bucket and exit through the outlet port ( Figure B ). When steam arrives through the inlet of the trap, it fills the inverted bucket which makes it buoyant and rise to the top of the trap, closing the valve ( Figure C ). As steam condenses and/or is bled through the small bleed hole in the top of the bucket, the bucket loses buoyancy which causes it to sink to the bottom of the trap. The valve then opens allowing condensate to be discharged from the system ( Figure A ). The bucket trap must maintain a certain amount of water (prime) in order to operate. If the trap loses its prime, the bucket will not be able to float when steam enters; keeping the valve in the open position which allows steam to escape ( Figure D ). Due to the balance of forces required between the incoming pressure and internal trap components, several orifice sizes are required to accommodate various differential pressure ranges. For this reason care must be used to select a trap model with an equal or higher PMO rating than the steam pressure.
A) Discharging Condensate
B) Discharging Air
A) With condensate completely filling the trap, the bucket is in the down position with the valve open, allowing condensate to be discharged. B) Small amounts of air will pass thru the bleed hole on top of the bucket and be discharged. (Note: Large amounts of air will lift the bucket and close off the trap, temporarily air locking the system.) C) When steam enters the trap, the inverted bucket fills with steam and floats to the surface, closing off the valve, preventing steam from escaping. Bucket traps must maintain a water prime to function properly. If the prime is lost, the bucket will remain in the down position with the valve open, and live steam will be discharged from the system. D) Potential Failure Mode:
Bleed Hole
Valve (Open)
Valve (Open)
Inverted Bucket
D) Potential Failure Mode Loss of Prime
C) Closed (Trapping Steam)
Bleed Hole
Valve (Open)
Valve (Closed)
Air
Steam
Condensate
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