Abstract: There are two major problems in the operation and maintenance of the thread-locking ring heat exchanger: internal leakage and seizure during the assembly and disassembly of the thread-locking ring. None of the existing thread-locking ring heat exchangers can avoid the above two problems at the same time. Design improvements were made for the φ1 800 mm high-high pressure thread-locking ring heat exchanger in two steps. The first step is to improve the process, namely to exchange the medium between the tube side and shell side to make the tube side pressure greater than that of the shell side. The pressure difference was used for self-tight sealing, which mainly solved the problem of internal leakage. The second step is to use D-shaped bolts instead of the main thread connection to reduce the weight of the tube box by about 25% to 30%. After these improvements, the total weight and the cost of the original heat exchanger was reduced and the two major problems of internal leakage and seizure during assembly and disassembly of the thread-locking ring was solved.

Key words: thread-locking ring, internalleakage, tube and shell side medium interchange, D-shaped bolt