Case Studies of Boiler Operation Accidents--8
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On September 8, 2000, an accident resulting in casualties occurred at a power plant. The sequence of events was as follows: On that day, at 2:30 a.m., while Unit 2 of Shift C at the power plant was operating normally, with a load of 150 MW, a main steam pressure of 13.6 MPa, and a main steam temperature of 537°C, the chemical team requested that Unit 2 undergo regular blowdown. Around 2:40 a.m., the boiler operator prepared to carry out the blowdown process; the second assistant boiler operator went outside to perform this task. At 2:45 a.m., the control room staff heard a loud noise accompanied by vibrations. Not knowing what was happening, they quickly checked the instruments on the control panel, but none of them showed any changes. When they went outside, they found that large amounts of steam were coming from the stairwells at both the A and B sides at zero meter level. The drain valve located at the bottom of corner B behind the furnace was open, and the drain valve at corner D in front of the furnace was also open. Meanwhile, close the water gates placed at the bottom of the D angle in front of the furnace and the B angle behind the furnace. The pipeline stopped emitting steam after the blasting; people were sent to the zero-meter mark and found the second boiler operator lying on the ground. He was rushed to the hospital for treatment, where it was determined that he suffered second-degree burns covering 70% of his body. Despite all efforts by the medical staff, he died from respiratory failure at 22:30 on September 9th. After the accident, a recheck of the valve positions at the site revealed that the primary drain valve at angle B behind the furnace had rotated 1.2 turns.
Analysis of the accident cause: Preliminary analysis shows that while going to the bottom to remove waste water, the assistant boiler operator should have opened the regular drainage primary and secondary valves at corner D in front of the furnace and corner B behind the furnace. Instead, he mistakenly opened the upper drain valves located at the same locations as the regular drainage primary and secondary valves. Due to leaks from some of the electric control valves, high-pressure steam and water from the furnace side flowed into the low-pressure pipelines, causing the pipes of the upper drain system to burst. A large amount of high-pressure steam was released, which knocked the assistant boiler operator who was there to the ground level, resulting in burns; despite attempts to save him, he died. The operators are not familiar with the system and the equipment; when draining waste, they do not carefully check the names of the valves, resulting in the wrong valves being opened.
Accident summary: 1. Strengthen safety management in all aspects of work, increase supervision and corrective actions, to ensure the safety of production equipment and the working environment. 2. Various forms of safety awareness education should be carried out regularly to enhance employees’ awareness of safety protection and enable them to master relevant methods. 3. Regular examinations on safety regulations should be conducted for key production personnel to clarify their safety responsibilities and enhance their safety awareness. 4. All employees should be regularly trained in first aid techniques, especially to ensure they are proficient in first aid measures for electric shock. 5. Strengthen the safety management of all tasks, increase the intensity of supervision and corrective actions, to ensure the safety of production equipment and the working environment. 6. In each hydrophobic pipeline, the piping material downstream of the throttle valve should be the same as that upstream of the valve, to prevent overpressure in the pipe downstream of the valve once it is opened.
Lack of familiarity with the production process is indeed a problem, and this issue is quite common~~~~