In 2014, there was depressurization of reactor vessel at the fluid catalytic cracking unit. Based on the thermal inspection results, wall temperature in the depressurization area reached 224 °C. Thermal testing diagram is presented in the picture
Internal examination revealed the shotcrete fall-out with exposure and through erosion wear of the wall metal in the attachment point of the peripheral cascade tray second from the top.
Structural and stress condition of the metal in the shortcrete damage and depressurization area (inspection of metal damage areas) was inspected according to STO 00220302/67-006-2012 “Coercivity measurement of vessels and apparatuses”. In the areas of most thermal stresses (maximum risk areas), under the influence of cyclic temperature strains, the metal may have increased coercive force values standing for deterioration of its quality.
Coercivity measurements (by demagnetization curve) were made on the external surface of the reactor, the points of measurement are marked on the thermal testing diagram. Measurement results gave the values not exceeding the critical values that confirmed feasibility of repair welding.
Upon completion of repair welding, during the pneumatic testing of the reactor, acoustic emission control was also performed, “passive” sources of acoustic emission were identified, no active zones were detected.