Timing of ammonia leak detection test

Thread Content

Our company has a U-tube heat exchanger. The design pressure for the shell side is 1.2 MPa, while that for the tube side is 4.2 MPa. The drawings specify that the weld joints between the heat exchange tubes and the tube sheet must undergo an ammonia leak test. Two different opinions arose during the process planning: one was to first conduct a hydrostatic test on the shell side, carry out the ammonia leak test after it was successful, and finally perform a hydrostatic test on the tube side； Second, conduct a hydrostatic test on the shell side first; once it passes, carry out a hydrostatic test on the tube side, and finally perform an ammonia leak detection test ； The first method is carried out in accordance with the requirements specified in GB/T151. The second method takes into account the fact that the hydrostatic test pressure for the tube side is too high; after the hydrostatic test, problems may arise at the welding joints between the heat exchange tubes and the tube sheet. I would like to ask the experts here: which method is better? The second method requires the tube box to be disassembled and reassembled once more.