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Case analysis of a multi-purpose furnace explosion
Explosive condition
The explosion will occur under certain conditions, and the necessary conditions for the multi-purpose furnace type explosion we currently use have three points: the explosive mixing ratio of combustible gas and air (or oxygen); the ignition gas and air mixture ignition temperature and A source of ignition; a mixture of combustible gas and air combusts a relatively confined space.
2. Process description
After the equipment is shut down for a short time, the furnace door is opened, the furnace door is open, the temperature reaches 760 °C, and the air supply is opened (supply RX gas). After the gas supply is opened for 1 hour, the temperature of the heating chamber rises to 900 °C. At this time, the two holes of the middle door rise a certain length. The stable flame opens the front door fire curtain and closes the front door. After the front door was closed for 15 minutes, the heating chamber in the furnace exploded, the front door flew out, and the heating room guide rail and the furnace wall were seriously damaged.
3. Reason for troubleshooting
The equipment was opened in accordance with the normal operation process, but exploded. The reason is firstly that the ratio of combustible gas to air in the furnace reaches the range of explosive mixing ratio. Secondly, the temperature in the furnace reaches the ignition point of the mixture. After closing the front door, a relatively closed space for gas combustion is formed in the furnace. The three prerequisites for the explosion were reached.
(1) Customer feedback Closing the front door process When the front door is closed, the two doors of the middle door emit a stable flame; when the front door is closed, the front door fire curtain burns and is highly stable; the exhaust gas ignition burner after the front door is burned stably; the various media supply is normal and safe. Gas supply is normal; on-site feedback did not hear high-pressure nitrogen sound after closing the front door.
(2) Check the high-pressure nitrogen control system pressure (see Figure 1) and the hand valve is open; when the front door is simulated, the high-pressure nitrogen solenoid valve cannot be turned on; the front chamber pressure in the control cabinet is found. The switching relay is closed (see Figure 2), which means that the front chamber pressure meets the front chamber pressure switch setting (actually there should be no pressure, and the atmospheric pressure should be zero). The front chamber pressure switch setting value is 80Pa (see Figure 3). The set value is normal. It is suspected that the switch detection hole is blocked and the pressure switch is lightly tapped. At this time, the pressure switch relay in the control cabinet is disconnected, and the front door lower limit high pressure nitrogen supply is simulated. normal. The anterior chamber pressure switch was disassembled and found to be clogged with carbon black powder. After cleaning and re-installation, the high-pressure nitrogen filling was simulated after repeated simulation tests.
4. Investigation conclusion
The pressure in the furnace detected by the front chamber pressure switch blocked by the front chamber pressure switch is inaccurate, and the pressure is too high, resulting in failure to fill the high pressure nitrogen filling furnace pressure and the replacement furnace in time when the negative pressure is formed in the furnace after closing the front door. The inner air, while the RX gas continues to pass to the back chamber of the furnace. When the ratio of CO+H 2 and oxygen in the rear chamber reaches the explosion range, the equipment is exploded in the heating chamber after closing the front door for 15 minutes, and the huge impact force is heated. The furnace tanks on one side of the chamber are all shattered, the middle of the middle door is raised to the outside of the furnace, the furnace wall bricks on both sides are damaged to varying degrees, and the front door is broken out and damaged (see Figure 4).
5. Preventive measures
Customized complete maintenance plan, list complete maintenance list, customize strict inspection and maintenance standards, and implement strict maintenance process. Safety must be based on prevention, killing hidden dangers in the bud, avoiding major casualties and property losses.
About the author: Liu Jiucheng, Sibo Bauer (Tangshan) Technology Co., Ltd.