[Haichuan: Lessons from Others] Utilizing the major overhaul to maintain flame detection probes, ensuring the safe operation of the unit

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“Repair of 32 flame detection probes, restoration of 13 brackets, and replacement of 4 sleeves – all completed in just 6 days. This also resulted in savings of over 100,000 yuan on materials! ” On August 6, at the site of the major overhaul of Unit 4 at PetroChina Electric Power Thermal Power Company No. 1, the technicians from Shift 4 of the Thermal Control Section under the Electrical Maintenance Department spoke about the recently completed maintenance of the flame detection system. Pride was evident on their sun-tanned faces. This race against time in repairs showcases their perseverance in tackling tough challenges, as well as their ingenuity in repurposing and reusing old materials. Due to the fact that flame detection probes are constantly exposed to high temperatures and dusty environments, nearly 40% of them occasionally experience a “decrease in flame detection intensity”. Even when there is actually a flame burning in the boiler, the probes seem to be “slow to respond”. Flame detection serves as the “eyes” for monitoring the operation of burners. Any misjudgment may trigger the FSSS fire-extinguishing protection logic, resulting in a boiler shutdown, which directly affects the safe operation of the unit. In April this year, the major overhaul of Unit 4 commenced. Shift 4 of the Thermal Control Team included flame detector maintenance in their “must-complete tasks” list, conducting a comprehensive inspection of all 32 flame detectors. After the furnace was shut down, it was completely dark inside. The crew members carefully climbed in, and using the flashlight light from the lift platform, they searched for a long time before identifying the root cause of the problem. Many flame detection brackets had developed cracks or even come loose due to prolonged exposure to the furnace’s vibrations and high temperatures; as a result, the probes became misaligned, deviating from the center of the furnace flame ； Some protective sleeves were charred, and the internal fiber optic cables were damaged. “The probe was positioned more than half a meter off-target, and the flame detection fiber optic cable also got damaged. No wonder the measurements were inaccurate. ”Class monitor Yu Dong held the worn-out sleeve in his hand and spoke while looking at the dents on its wall. Time was tight and the tasks were numerous. Squad leader Yu Dong checked the spare parts in the warehouse and found that the new brackets and casings wouldn’t arrive for another week—nowhere near enough time to meet the deadline. At this point, Deputy Class Leader He Dejun suggested, “During the recent maintenance of the flame detectors on the oil burners of Furnace No. 4, several sets of flame detectors were replaced; some of their components are still in good condition!” ”They immediately retrieved the unused devices. Upon disassembly and inspection, they found that the brackets and sleeves of four of them were intact, and their dimensions matched perfectly. “Repair and reuse! ”Everyone pitched in: they carefully removed, cleaned, and calibrated the good parts one by one, then reinstalled them onto the probes that needed replacement. In this way, they managed to save the time required for waiting for spare parts. Collaboration during maintenance is even more of a delicate task. The interior of the furnace is quite cramped; the highest point is nearly 20 meters above the ground. The workers wear safety harnesses as they move between the supports. They must keep the level steady in their hands before they dare to adjust the angle of the probe. “OA layer flame detection probe, deflect 3 degrees to the left! ”“Raise the OB layer flame detection probe by another 10 centimeters, aiming at the center of the flame! ”The people inside give instructions via walkie-talkies, while those outside monitor the DCS screen to check the intensity of the flames. A single probe often needs to be adjusted four or five times until the monitoring signal becomes stable. Over a period of 6 days, the team of 8 people worked in shifts, spending nearly 10 hours each day on site. They even ate their lunch on the platform in a hurry before getting back to work. Now that the maintenance is complete, the effectiveness can be verified once the boiler is ignited. This maintenance work was completed 10 days earlier than scheduled; by recycling waste materials, over 100,000 yuan in material costs were saved. Moreover, it completely eliminated the fire detection malfunction that had been a problem for two years. “Maintenance isn’t just about fixing equipment; it’s about tackling problems and paying close attention to details. ”Class monitor Yu wiped the sweat from his forehead and gazed in the direction of the furnace—where lay their familiarity with the equipment, as well as their confidence in the safe operation of the unit.