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Posted by ringle on July 06, 2002 at 04:23:57:
In Reply to: overheating and overpressure posted by Russ on June 29, 2002 at 22:03:31:
: I work at a plant that has hog fired hot water boilers that heat kilns to dry wood. The kilns are controlled by a computer, and occasionally crash. When the computer has a problem the valves leading to the kilns close and the water stops circulating resulting in extreme temperature and pressure in the boilers. Even if the fuel feed system stops, there is still enough fuel in the boilers to continue to create lots of heat.
: The safety valves do there job, but it still shakes the building enough to break hot water unions and valves.
: My question is: Should we just change out the valves so that they fail open, or is there more to it than that?
You might want to consider putting in a pid controlled vent. I work with a fluidized bed fired boiler burning industrial waste. Control is good under normal operating conditions but since there is aprox. 100 tons of hot sand in the combustor fast turn downs can be a problem. To solve this we added a full flow vent that uses a standard pid control loop to vent excess steam pressure to atmosphere (through a silencer)
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