Emergency shutdown conditions

(1) The MFT action will be triggered if any of the following conditions are met: Manual MFT； Bed temperature higher than 990°C (average) ； Abnormal water level (high water level or low water level) ； High furnace pressure (typically +2489 Pa with a 5-second delay) ； Low furnace pressure (typically -2489 Pa with a 5-second delay) ； All exhaust fans tripped ； All primary fans tripped ； All high-pressure fluidization fans tripped ； All coal feeding fans trip and the bypass doors are not opened (with a certain time delay) ； The main steam valve of the turbine is closed ； If the total air volume at the outlet of all primary fans is less than 25% of the rated air volume, a 5-second delay is applied ； The bed temperature is below 650°C and no start burner has been activated ； Exceeding 3600 s from the start time (referring to the time it takes to start the burner: failure to ignite within 3600 s) ； DCS power supply lost ；

To ensure the safe operation of gas boilers, operators can take various measures. If advanced computer control systems are used in gas boilers, considering the varying levels of management and skill among personnel in society, the presence of tens of thousands of such boilers scattered across urban areas poses numerous safety risks. So under what circumstances can an emergency shutdown of the unit be carried out? (1) The operating conditions and parameters reach the set values that trigger the accident shutdown protection, but the protection fails to activate. (2) All the feedwater flow meters are damaged, resulting in abnormal main steam temperature; or although the main steam temperature is normal, the flow meters fail to return to normal within half an hour. (3) In the event of a burst in the main feedwater and steam pipelines. (4) In the event of an explosion inside the furnace or flue, causing severe damage to the equipment. (5) When the steam pressure exceeds the limit pressure, the safety valve fails to operate or the exhaust valve cannot open. (6) After the medium-pressure safety valve operates, it does not return to its original position; as a result, the pressure and steam temperature in the reheater drop, reaching a level that makes operation impossible. (7) When the power supply to the main instruments is lost, making it impossible to monitor the operation of the unit. (8) When the low-load boiler has unstable combustion and large fluctuations in furnace pressure (with a rapid drop in steam flow). (9) When the four tubes of a boiler burst, posing a threat to the safety of adjacent tubes. (10) When all the drum level gauges are damaged or malfunctioning, making it impossible to monitor the water level. (11) The drum water level is too high or too low.