Determining Useful Life of Reactor Pressure Vessels

The length of useful life of the reactor vessel is much more questionable than the estimate of a probable breakdown. It particularly arises as a need and an obligation after regular technical inspections. The problem of determining the remaining life of the vessel is especially arises when there are errors or cracks on the vessel walls. Research on high quality vessels leads to the conclusion that hydraulic tests are harmful, which was confirmed by a large number of cracks that appeared after these hydraulic tests. This fact gives a basis for evaluation of these tests and their adjustment depending on the length of exploitation. The analysis of causes for a change in material properties from manufacturing all the way to the removal from exploitation was performed on over fifty vessels in oil processing. Special attention was given to a reactor vessel that operates under heavy operating conditions and with a complex catalytic chemical process using hydrogen. Changes in material characteristics were monitored from the production of the reactor vessel until its shutdown and removal from service. The causes for crack occurrence and expansion in vessel walls and heads were analyzed. The occurrence of new cracks and expansion of old cracks was particularly considered during hydraulic tests.