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1 Problem exists: The heat exchanger before the methanol tower was converted from the condenser of the original ammonia synthesis system; it makes use of the shell of the original high-pressure vessel. The new internal components use the positioning steps originally used to hold the components inside the cylinder as the sealing surface for the heat exchanger, and these steps are only 10 mm wide. Its gasket uses a wave-tooth composite gasket, namely a flat gasket made of stainless steel wrapped with expanded graphite. During the installation of the internal components, it was found that due to errors between the manufacturing of these components and the cylinder, they were eccentric; as a result, this sealing surface is underused. Moreover, the sealing surface of the new components is a non-machined surface, so it cannot ensure the required flatness and surface roughness. After opening the upper cover of the heat exchanger and performing a pressure test with system gas, it was found that a large amount of gas leaked from the graphite wound gasket, confirming that the reduction in the system’s circulation rate was caused by the failure of the graphite wound gasket. After analysis, it was decided to use a comprehensive method to seal the leaks in the pre-tower heat exchanger. 2 Operating Procedure (1) Fill the packing. Due to the highly uneven gaps between the internal components and the cylinder shell, 3–5 mm thick aluminum and lead wires were first mixed with silicone rubber sealant 1587 to fill and level out the larger gaps. At the tube sheet on the internal components, 10 mm × 10 mm graphite gaskets were placed at the junction between the flange of the internal components and the cylinder shell, using sealant 1587. (2) Process a special sealing flange to compress the packing. A custom flange is manufactured based on the dimensions of the flange on the upper tube sheet of the internal component; the outer circumference of its lower surface is turned at an angle of 5×45°. Using the 20 M16 internal threads along the circumference of the upper tube sheet of the internal component, a double-headed bolt is used to tightly connect the custom flange to the flange on the upper tube sheet, thereby compressing the graphite gasket and providing sealing in both axial and radial directions. (3) Inner component positioning. Due to the presence of the special flanges, there is no space left to install the positioning plates used to hold the internal components in place within the cylinder. Therefore, 4 specially designed positioning bolts with tapered surfaces were fabricated and secured to the cylinder; the tapered surfaces of these bolts are used to hold the internal components in place. Together with the 7.6 tons of weight of the internal components themselves, this ensures that they do not move axially. 3 Conclusion After 24 hours of continuous maintenance work, the comprehensive leak-sealing plan was successfully implemented. After the system was restarted, the tower temperature could be controlled smoothly, the circulation rate increased significantly, the system operated normally, and the leak-sealing effect was excellent.