Heating furnace damper
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In an emergency situation, should the damper control valve of the heating furnace be fully open or fully closed? Basis or reason?
It should be fully open; in the event of an accident, the fuel valve must be fully closed while the air valves must be fully open to prevent explosions.
This must be an FO, start in case of an accident; there’s no room for negotiation.
If it wasn’t an accident caused by a power outage, with the blower still running and the air valves fully open, could there be a sudden positive pressure flashback?
Interlocked with the fan for quick opening of the air damper； In an accident condition, the blower stops operating; when the pressure at the blower outlet (which is controlled by a three-out-of-two interlock system) falls below the set value, the quick-opening damper will open. So, the situation you mentioned doesn’t exist.
I’m not talking about quickly opening the air damper; I’m referring to adjusting the air damper, also known as an air duct adjustment flap
Similarly, the flue baffle is interlocked with the exhaust fan. It automatically opens fully when the inlet pressure of the exhaust fan is higher than the set value. However, in some companies, the opening of the flue dampers remains locked in place during shutdown. (This instrument setting can be achieved.)
I’m sorry, I misread it. The air ducts in our company are adjusted manually; there is no automatic switching. Generally, air doors are opened to quickly reduce the temperature inside the furnace chamber and prevent excessive temperatures there. However, the influx of large amounts of cold air can cause oxidation and peeling of the furnace tubes. In the case of a minor accident, the furnace flame goes out; the gas manual valve on the pipeline is used, and re-ignition is carried out after ventilation and purging.
Previously, we also used manual valves for regulation; switching to instrument control has made things much more convenient. But what should be considered regarding the valve position in case of an accident?