Measures for Temperature Rise of the Fire Pipe Unions (Part Two)
Posted: 10/19/2023 03:19:56 Hits: 18
3. Cause analysis
(1) According to the design and drawing requirements, the generator fire ring pipe and joints are made from stainless steel. However, the internal structure and composition of the ring pipe joints have changed in the manufacturing process, making them magnetic. When the unit is running, the magnetic joint is in the magnetic field generated by the generator rotor. Under the action of the magnetic field, the joint continuously generates heat, resulting in abnormal temperature of the fire joint.
(2) It is generally required that the upper and lower ring pipe joints of fire protection pipelines should be installed directly or use matching sealing gaskets to prevent overheating. In the installation process, to prevent the joints from leaking, the installation unit used raw material tape to seal the joints. The main material of raw tape is polytetrafluoroethylene, which is an insulating material. Wrapping raw tape around the threaded joint increases the resistance there, and a large amount of heat is generated when the current generated in the magnetic field of the joint passes through the pipe joint.
(3) The upper ring pipe of the generator fire ring pipe is between the windshield ring and the wind guide plate. The cooling air circulation in this position is not smooth, and the heat generated by the generator stator core, rotor yoke and joint cannot be effectively taken away for cooling in time, resulting in abnormal joint temperature.
4. Solutions and suggestions
After the problem was discovered, it was tracked and monitored. During weekly inspections, infrared thermometers were used to measure the generator fire ring pipe joints, especially when the load on the unit was great. Measurement frequency was increased and records were kept. In the tracking and monitoring process, the temperatures of the fire ring pipe joints were all within 270°, with no obvious upward trend.
Connect the wires into a closed loop, and the current will flow through. A large amount of heat is generated when an electric current passes through the ring pipe joint, causing the temperature of the joint to rise abnormally. This article describes in detail the actual measures taken by the power station to deal with this problem and some suggestions for subsequent treatment were put forward.
(1) During the maintenance period, the fire ring pipe joints of the generator of Unit 3 were disassembled and the raw material tape at the joints was completely removed. The joints of No. 1, No. 2, and No. 4 machines were not disassembled, and only the raw material tape outside the threaded threads was removed.
After the maintenance was completed, the temperature of the fire ring pipe joints was measured and monitored when the unit was at full load. The maximum temperature of the fire ring pipe joints of Unit 3 was 160°, and the maximum temperature of Unit 4 was 210°. The temperature of Unit 3 dropped from 270° to 160°.
(2) It is recommended that when conditions permit, an aluminum plate with a thickness of 10mm should be used to make a sealed box to cover the fire ring pipe joints to prevent the joints from being in the generator magnetic field.
(3) Replace the connector and replace the current magnetically conductive connector with a non-magnetic conductive connector.
5. Conclusion
The generator fire ring pipe joint is in the magnetic field generated by the generator rotor and moves relative to the magnetic field. When wires cut magnetic lines of force, they can generate an induced electromotive force. When the wires are connected into a closed loop, current will flow through them. A large amount of heat is generated when an electric current passes through the ring pipe joint, causing the temperature of the joint to rise abnormally. This article describes in detail the actual measures taken by the power station to deal with this problem and some suggestions for subsequent treatment were put forward.
(1) According to the design and drawing requirements, the generator fire ring pipe and joints are made from stainless steel. However, the internal structure and composition of the ring pipe joints have changed in the manufacturing process, making them magnetic. When the unit is running, the magnetic joint is in the magnetic field generated by the generator rotor. Under the action of the magnetic field, the joint continuously generates heat, resulting in abnormal temperature of the fire joint.
(2) It is generally required that the upper and lower ring pipe joints of fire protection pipelines should be installed directly or use matching sealing gaskets to prevent overheating. In the installation process, to prevent the joints from leaking, the installation unit used raw material tape to seal the joints. The main material of raw tape is polytetrafluoroethylene, which is an insulating material. Wrapping raw tape around the threaded joint increases the resistance there, and a large amount of heat is generated when the current generated in the magnetic field of the joint passes through the pipe joint.
(3) The upper ring pipe of the generator fire ring pipe is between the windshield ring and the wind guide plate. The cooling air circulation in this position is not smooth, and the heat generated by the generator stator core, rotor yoke and joint cannot be effectively taken away for cooling in time, resulting in abnormal joint temperature.
4. Solutions and suggestions
After the problem was discovered, it was tracked and monitored. During weekly inspections, infrared thermometers were used to measure the generator fire ring pipe joints, especially when the load on the unit was great. Measurement frequency was increased and records were kept. In the tracking and monitoring process, the temperatures of the fire ring pipe joints were all within 270°, with no obvious upward trend.
Connect the wires into a closed loop, and the current will flow through. A large amount of heat is generated when an electric current passes through the ring pipe joint, causing the temperature of the joint to rise abnormally. This article describes in detail the actual measures taken by the power station to deal with this problem and some suggestions for subsequent treatment were put forward.
(1) During the maintenance period, the fire ring pipe joints of the generator of Unit 3 were disassembled and the raw material tape at the joints was completely removed. The joints of No. 1, No. 2, and No. 4 machines were not disassembled, and only the raw material tape outside the threaded threads was removed.
After the maintenance was completed, the temperature of the fire ring pipe joints was measured and monitored when the unit was at full load. The maximum temperature of the fire ring pipe joints of Unit 3 was 160°, and the maximum temperature of Unit 4 was 210°. The temperature of Unit 3 dropped from 270° to 160°.
(2) It is recommended that when conditions permit, an aluminum plate with a thickness of 10mm should be used to make a sealed box to cover the fire ring pipe joints to prevent the joints from being in the generator magnetic field.
(3) Replace the connector and replace the current magnetically conductive connector with a non-magnetic conductive connector.
5. Conclusion
The generator fire ring pipe joint is in the magnetic field generated by the generator rotor and moves relative to the magnetic field. When wires cut magnetic lines of force, they can generate an induced electromotive force. When the wires are connected into a closed loop, current will flow through them. A large amount of heat is generated when an electric current passes through the ring pipe joint, causing the temperature of the joint to rise abnormally. This article describes in detail the actual measures taken by the power station to deal with this problem and some suggestions for subsequent treatment were put forward.
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