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Chinese1. Reduce equipment leakage points
Strengthen the detection methods, and strive to minimize the leakage of equipment in the manufacturing process of DVE vacuum pumps. When the air condenser is produced in the manufacturing plant, the single tube of each heat exchanger undergoes a 0.8MPa air tightness test, and the welded joint between the tube end of the fin tube and the tube sheet is inspected for penetrant flaws. After the entire air-cooled heat exchanger is assembled, perform a hydraulic test. According to the requirements of the "Pressure Vessel Safety Technical Supervision Regulations", the air-cooled tube bundle is filled with water and the air in it is exhausted. At the same time, the surface of the tube bundle is kept as dry as possible to facilitate Check for leaks. When the wall temperature of the tube bundle is close to the liquid temperature, slowly increase the pressure to the design pressure of 0.15 MPa. After confirming that there is no leakage, continue to increase the pressure to the test pressure of 0.18 MPa to ensure that it does not change for 30 minutes. Then the pressure drops to 0.144MPa, and the pressure is maintained for a certain period of time for inspection. During the inspection, the pressure remains unchanged, which means that the water pressure test is qualified.
Strengthen the detection methods, and strive to minimize the leakage of equipment in the manufacturing process of DVE vacuum pumps. When the air condenser is produced in the manufacturing plant, the single tube of each heat exchanger undergoes a 0.8MPa air tightness test, and the welded joint between the tube end of the fin tube and the tube sheet is inspected for penetrant flaws. After the entire air-cooled heat exchanger is assembled, perform a hydraulic test. According to the requirements of the "Pressure Vessel Safety Technical Supervision Regulations", the air-cooled tube bundle is filled with water and the air in it is exhausted. At the same time, the surface of the tube bundle is kept as dry as possible to facilitate Check for leaks. When the wall temperature of the tube bundle is close to the liquid temperature, slowly increase the pressure to the design pressure of 0.15 MPa. After confirming that there is no leakage, continue to increase the pressure to the test pressure of 0.18 MPa to ensure that it does not change for 30 minutes. Then the pressure drops to 0.144MPa, and the pressure is maintained for a certain period of time for inspection. During the inspection, the pressure remains unchanged, which means that the water pressure test is qualified.
2. Improve installation quality
Perform flaw detection on the joints, and minimize the joints during on-site installation in the design, so that the amount of welding for on-site installation work is as small as possible.
Perform flaw detection on the joints, and minimize the joints during on-site installation in the design, so that the amount of welding for on-site installation work is as small as possible.
3. Reasonable choice of DVE vacuum pump
The amount of air entering the system is not only related to the amount of steam, but also mainly related to the tightness and installation quality of each equipment under vacuum. The tightness of the vacuum system is generally assessed by the rate of vacuum drop. All interfaces of large-scale direct air condensers are generally welded, and valves, pumps and other equipment use water-sealed structures, which greatly improves the tightness of the system and greatly reduces the amount of air leaking.
The amount of air entering the system is not only related to the amount of steam, but also mainly related to the tightness and installation quality of each equipment under vacuum. The tightness of the vacuum system is generally assessed by the rate of vacuum drop. All interfaces of large-scale direct air condensers are generally welded, and valves, pumps and other equipment use water-sealed structures, which greatly improves the tightness of the system and greatly reduces the amount of air leaking.
China’s GB/T5578 "Technical Conditions for Stationary Thermal Power Turbines" stipulates that for units larger than 100MW, the vacuum drop speed shall not be greater than 0.266kPa/min. Some domestic projects that have been constructed stipulate that the air-tightness test of the air condenser and its system shall be carried out, and the test pressure shall be 0.04MPa. The test standard is: the average pressure drop in 24 hours, the partial test is controlled within 0.2 kPa/h, and the system pressure drop is controlled within 0.4 kPa/h.
From the perspective of the manufacturer, in order to maintain the vacuum of the unit, the quality of the product must be improved so that the air-tightness of the air condenser is in an excellent state. The design should also consider minimizing the workload of on-site installation and welding to reduce the possibility of poor sealing. Coupled with the reasonable selection of the DVE vacuum pump, the operation of the air-cooled unit can meet the requirements of economy and safety.
