Leakage area

The leakage of heat exchange pipes in pressure vessels generally occurs in two places, the connection of the pipes and the leakage of the pipes.

Methods for handling leaks at pipe connections

There are three methods for connecting pipes and tube sheets: welding, expansion joint, expansion joint and welding. Due to temperature and pressure fluctuations, as well as uneven deformation caused by temperature differences, the expansion joint causes the pipe to detach and loosen from the tube sheet, resulting in leakage. Expansion can be used to eliminate leakage, If it is ineffective, it can be done again. Expansion should not be more than three times, otherwise it will cause the material at the tube plate hole to harden and the expansion joint to be not tight.

In case of ineffective expansion, it is necessary to replace the pipes or use welding methods. It should be noted that after welding, the surrounding pipes need to be expanded again, because the thermal expansion and contraction of the tube plate after welding can cause leakage of other tube expansion joints around the welding area. If the weld seam between the pipe and the tube sheets leaks, it can be polished and repaired by welding.

Methods for handling pipe leaks

Due to abrasion, erosion, corrosion, sedimentation corrosion and other reasons, heat exchange tubes often have perforations, cracks and leaks. Leakage of pipes is generally irreparable. If the number of leaking pipes is not large, conical metal plugs can be used to block both ends of the pipe. If the pressure of the pipe is high, it is more rigorous to plug it tightly before welding. The length of the metal plug is generally twice the inner diameter of the pipe, and the diameter of the small end should be equal to 85% of the inner diameter, with a taper of 1:10.

The hardness of the plug material should be lower than or equal to the hardness of the pipe. When using blocked pipes to eliminate leaks, the number of blocked pipes should not exceed 10%. When one end of the stainless steel heat exchange tube is damaged, the pulling tube repair method can also be used, because the elongation of the stainless steel tube is 40%~45%. When the total elongation of the pulling tube does not exceed 12%, the tube can be pulled multiple times.