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Posted by Tony Conner on February 21, 2002 at 08:31:09:
In Reply to: URGENT! Low-Low Water Cut Off set. posted by BoilingMan on February 21, 2002 at 06:50:21:
It's likely an operational requirement. I've seen boilers where the low drum level alarm and low-low cut off were set too close together. The first thing that happens when relatively cold feedwater hits the boiler, is the level shrinks for just a moment. On the boilers where this is a problem, once you get a low water alarm, you'll get a trip no matter what you do. If you don't add water, the level will fall, and it'll trip. If you DO add water, the level drops a fraction of an inch for just a second before it starts to come back up, and it'll trip.
I'd say the low-low trip should be set to protect the boiler. The low level alarm should be set maybe an inch above that. Hard to day without seeing it.