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Boiler furnace safety monitoring system 1: System Overview The Boiler Furnace Safety Supervisory System (FSSS, Furnace Safeguard Supervisory System) is a control system responsible for boiler furnace fuel safety and burner management. The FSSS system can continuously monitor the operating status of the relevant auxiliary equipment of the boiler during each working condition of the boiler (including starting, running, and stopping). The FSSS system performs logical operations and judgments based on the operating status of the equipment, allowing the auxiliary equipment to complete necessary operations or processing according to established procedures to avoid near-miss accidents. Ensure the safety of the boiler furnace and combustion system. It plays an important role in preventing boiler furnace explosions caused by operator misoperation and equipment failure. The system host adopts Siemens programmable logic controller (PLC), which can respond quickly and agilely to machine, furnace and auxiliary machine failures and generate corresponding operations to ensure the safety of the boiler. The boiler has a total of four burners and is arranged on the front wall of natural circulation. ； The main fuel can be both gas and heavy oil. ； The ignition method adopts combination air gun ignition, that is, the combination air gun is ignited first, and then the flame of the combination air gun is used to ignite gas or heavy oil. Details are as follows: The main oil gun ignition method is: High-pressure igniter → GAS → fuel, the main oil gun adopts steam atomization method. 1． System function: Logical function of the system ① Full furnace purge logic The purpose of the full furnace purge function is to completely remove the combustible mixture in the furnace and flue before the boiler is started in cold state or after the MFT is shut down, to prevent the combustible mixture accumulated in the furnace and flue from exploding when encountering a fire source (such as ignition, high furnace temperature, etc.) and endangering the safety of the boiler. The purging conditions are: (Fuel main valve closed ； All support valves closed ； Gas main valve closed ； All bronchial valves closed ； All fire detection probes have no fire ； Any blower is put into operation ； No MFT trip condition ； ) The full furnace purge function is used before each start of the boiler. All purge conditions must be met. After the conditions are met, the system will issue a "purge request" and the operator will issue a start purge command. After the completion of purging is confirmed, operators and operators are required to establish the first set of flames in the furnace within 15 minutes, otherwise the boiler needs to be purged again before starting. ② MFT logic MFT (main fuel trip) function is the mandatory shutdown measure taken by the system to protect the safety of the boiler when working conditions endanger the safety of the boiler. When shutting down the furnace, remove all fuel entering the furnace ； Shut down auxiliary machinery related to the boiler ； And give alarm signal and accident record signal ； After the MFT, the operator must start the furnace purging command to purge the furnace after the natural ventilation channel of the boiler is established. The boiler can only be restarted after the furnace purging is completed and the MFT is manually reset by the operator. The conditions that cause MFT include the following nine:: All furnace flameout ； All blowers are stopped ； Furnace pressure too high ； (Two out of three) ； Gas pressure too low ； (Two out of two) ； Steam drum water level is too high ； Steam drum water level is too low ； fuel loss ； Manual MFT ； Ignition delay. Note 1: Fuel loss, that is, all oil fuel and gas fuel are lost. The loss of oil and fuel means that all the oil branch valves are closed or the supply and return main oil valves are fully closed. ； Loss of gas fuel means all branch valves are closed or the main gas valve is closed. When both oil fuel and gas fuel are lost and the boiler is put into operation, it is considered that the entire furnace fuel is lost, causing MFT of the boiler system. Note 2: Manual MFT is an operating interface specially provided by the system for operating personnel. When the operating personnel discover working conditions that seriously affect the safety of the boiler and believe that an emergency shutdown of the boiler is required, the forced boiler shutdown signal is implemented by the operating personnel. Note 3: Ignition delay, that is, the furnace purge is completed and the MFT is reset for 15 minutes (the time is adjustable) and the boiler has not yet performed the ignition operation. ； At this time, in order to ensure the safe ignition of the boiler and send out the MFT signal, the operator is required to purge the furnace again. The ignition delay system is specially designed to ensure the safety of starting the furnace when the furnace is cold. ③Judgment logic of full-furnace flameout. The logic of full-furnace flameout means that when the gas valve or oil valve of the boiler is put into operation, all the burners in the furnace have no fire. Full-furnace flameout is one of the causes of MFT, and MFT is caused by full-furnace flameout. First trip reason display: When the MFT operates, in addition to closely monitoring the execution of the "furnace purge" function, the cause of the MFT operation should be checked and analyzed clearly. The function of "MFT first cause display" is to display the first condition that causes MFT (in the order of time) among the conditions that generate the MFT trip signal. Leak test: In order to ensure that the valves and pipes in the gas and oil pipeline system in front of the furnace do not leak, a leakage test is required before the furnace is purged. specific steps: When the main oil pipe shut-off valve is opened in place and all angle oil valves and main pipe oil return valves are closed, oil is supplied through the oil pump to pressurize the oil pipeline. When the pressure behind the main oil pipe shut-off valve is >500KPa (oil gun working pressure), close the main oil pipe shut-off valve and the pressure charging is completed. After that, within 2 minutes, observe whether the pressure behind the main oil pipe shut-off valve can be maintained at 500KPa. If so, a "leak test successful" instruction will be issued. ； Otherwise, a "leak test failed" indication will be issued. 2． Fire detection system: For the entire boiler combustion status, we have configured 4 integrated fire detection probes to detect the flame combustion status of the boiler burner. These fire detection devices send the switching signals of the detected flame status to the FSSS system as the basic conditions for the flame judgment logic in the FSSS system. At the same time, the FSSS system also collects fire detection fault signals. Based on the presence or absence of fault signals, it determines whether the flame status signal sent by the integrated fire detection probe to the FSSS system is valid. Regarding the power supply, installation and wiring, detection principle, operation and maintenance of the integrated fire detection probe, please refer to the relevant drawings of the fire detection part of the FSSS system supplied by our company and the intelligent integrated fire detection instructions. 3． Operation introduction: Since the host computer touch screen provided in the FSSS system is only used to display the status of the controlled object, based on unit safety considerations, there is no operating interface and interface for the controlled object on the touch screen. There are six paintings on the touch screen, namely: The status screen of the four burners, the main valve screen and the MFT initial screen. Boiler cold start: ①After debugging is completed, the system power supply controller is placed in the running state. After each part is powered on, the controller can generally enter the running state automatically. ②Leak test: The centralized control room operator confirms that the leakage test conditions are met ； Issue the "Start Leak Test" command from the centralized control room ； After the leak test starts, the operator can obtain relevant information about the leak test from the DCS operator station. ； Regardless of whether the leak test succeeds or fails, the operator can get leak test information prompts from the DCS operator station. ； When the leak test fails, the operator can issue a "leak test reset" command to eliminate the leak test failure signal. And find out the cause, eliminate the fault, and re-perform the leak test until the leak test is successful. ； The leakage test success signal will automatically disappear after any angle oil valve or air valve is opened. ③Furnace purge: Prepare purge conditions ； After the purging conditions are met, the operator can get the "Purge Allowed" message prompt from the DCS operator station. The operator can issue a purge start command from the centralized control room ； After the system receives the command to start purging, it starts purging timing. At this time, the system will send a "purging" signal to the centralized control room ； After 5 minutes of purging timer, the centralized control room will receive a "Purge Completed" message. Within 5 minutes of the purge timer, if any purge condition is not met, a "Purge Interruption" signal will appear on the DCS operator station. After the purging is interrupted, the purging conditions should be prepared again and the purging program should be entered again. After "Purge Completed", it indicates that the entire furnace purge process is completed. At this time, the "Purge Complete" signal resets the "MFT" signal (requires manual reset), and the system enters the ignition stage. “The "Purge Completed" signal will automatically disappear when any oil supply valve or air valve is opened, 20 minutes after the purge is completed, or at MFT. ④Burner start: The start-up of a single burner confirms that the ignition conditions are met, and the operator issues the "Start #1 burner" command, and the oil burner enters the program-controlled start-up process. If the normal system is started, first start the high-pressure igniter of the combined air gun, then open the 1# ignition branch quick-closing valve, the igniter ignites the GAS device, and the ion fire detector of the combined air gun detects the flame signal. During the startup process, if there is no fire in the ignition air gun 15 seconds after the ignition branch valve leaves the original position or the ignition process exceeds 60 seconds, it will be considered that the ignition failed, and the system will feedback the "start failure" alarm signal to the DCS operator station, and the system will automatically stop the burner. If ignition failure occurs, the cause should be identified and properly handled before the burner can be restarted. If the 1# burner is started successfully, the oil burner or gas burner can be started according to the situation. If the oil burner is started, the oil main valve and atomization air main valve should be opened. The "Allow oil ignition" sign appears on the operation screen. At this time, you can "start the 1# oil burner". When the steam pressure meets the atomization requirements, you can switch to steam atomization. Also turn off air atomization. If the gas burner is started, the main relief valve should be closed and the main gas valve should be opened. The "Allow gas ignition" sign will appear on the operation screen. At this time, you can "start the 1# gas burner". ⑤Boiler burner out of service: Normal shutdown: Stop each burner in sequence according to the operating procedures and the following operating methods. Stopping a single burner: The operator believes that a certain burner should be stopped and issues a "stop burner No. X" command. If the stopping process is normal, for oil burners, the oil support valve should be closed and the corresponding steam purge valve should be opened. For gas burners, the bronch valve should be closed and the corresponding relief valve should be opened. If an abnormality occurs during the stopping process, manual operations should be carried out immediately on site. And identify the cause and eliminate the fault to prevent hidden dangers from causing accidents. Note: Normal shutdown of the boiler will also end with MFT (caused by "no fire in the whole furnace"). The MFT here (caused by "no fire in the furnace") itself should not be considered an accident, it is a protection strategy imposed on the boiler, that is, after the boiler is shut down, it must be re-purged to reset the MFT, and then the boiler is allowed to be restarted. two: Maintenance In order to ensure that this system operates efficiently and accurately, in addition to correct operation, careful maintenance is essential. Regular dust removal and maintenance should be carried out, and faults should be eliminated promptly. In addition, during use, operators must pay special attention to the following situations:: 1． When the high-pressure igniter is in use, the time for ignition alone should not exceed 30 seconds, and the time interval between two ignitions should be >1 minute. 2. During use, the ignition operation must not be performed when the high-voltage igniter is in an open circuit state, that is, when the spark rod is not connected, otherwise the internal components of the high-energy igniter will be damaged. 3. For valves and electric devices, the cover must be assembled and the screws must be tightened. 4. For valves, the surface of the electric device should be wiped regularly and should not be splashed by water or oil. 5. During use, do not touch the various parts of the high-voltage igniter, and you should also be careful during maintenance! 6. During use, the cooling air of the flame detector probe cannot be interrupted, otherwise the probe will be damaged. 7. After the boiler is shut down, if the temperature in the furnace has not dropped to normal temperature, the cooling air of the flame detector probe cannot be interrupted, otherwise the probe will be damaged due to high temperature radiation. Attachment 1: Chain logic diagram OR cut button furnace pressure PS8145ABC 2 out of 3 1: Shutdown condition cut off button Blower shut down cut off button cut off button cut off button cut off button cut off button Manual stop button Ignition delay Full furnace fire extinguishing BS8131-BS8134 All fuel gas lost Fuel main pipe pressure low low PS8133 Bubble level high high LT8103 Gas main pressure low low PS8131AB Two out of two Bubble level low low LT8103 Stop signal cut button Cut off button description: When the furnace pressure PS8154ABC is interlocked, the bubble liquid level is high and high, LT8103 is interlocked, the liquid level is low and low, LT8103 interlocking, the gas main pipe pressure PS8131AB is interlocked, and the fuel main pipe pressure is PS8133. When the whole furnace is extinguished, the fuel is lost, the blower is stopped, and the ignition is delayed. If one of the nine conditions is met, it will cause the furnace to shut down. The "cut button" is used to determine whether the condition is activated. Press it to activate the chain. In an emergency, the furnace can be shut down manually. Allow startup step: 1: Conditions for allowing leakage: Allow leak test light to start Leak test Leak test successful Leak test failure Description: When the leakage test allowed light is on, the leakage test button can be started, and the light below can show whether the leakage is successful. 2: Purge conditions: The conditions for a purge are met to start the furnace purge. The purge is completed and the purge is interrupted.: When the purging conditions are met, the light will light up and the button can be started to start purging the furnace. The lower indicator light shows whether it is completed or interrupted. 3: MFT reset: MFT MFT reset button allows ignition, allows oil ignition, allows gas ignition, turns off burner #1 4: combustion system: Switch allows 1# gas ignition. Gas switch allows 1# oil ignition. Oil steam air to steam air switch. Gas start. 1# burner allows 1# ignition. Stops 1# burner flame detection signal. Flame detection signal description.: After the leakage test, furnace purging and MFT reset, the ignition permission signal will appear, and then the gas ignition of the 1# burner will be carried out. When the flame is detected, oil ignition or gas ignition will be carried out. If 1# fuel is allowed to ignite, the front indicator light will light up and the fuel inlet valve will open. If 1# gas is allowed to ignite, the front light will light up and the gas inlet valve will open at the same time. The whole process is automatic. Comment: Burners 1#, 2#, 3#, and 4# are the same as the above pictures, and the operations are the same.