Abstract: With the development of large-scale hydroprocessing units, two different forms of nozzle connection began to be applied in some special high pressure vessels, such as threaded ring lock heat exchangers. But the specific selection principles for nozzle connection forms are not mentioned in applicable pressure vessel codes and standards. This paper compares and analyses the merits and demerits of the two connection forms of tube and shell side inlet and outlet of the threaded ring lock heat exchanger in hydroprocessing unit from various perspectives and recommends a choice from the two forms, which can provide reference for the optimization design of nozzle connection of the threaded ring lock heat exchangers in hydroprocessing units.

Key words: threaded ring lock heat exchanger, nozzle connection type, flange connection, welded connection