This paper details with the unexpected cracking encountered in the outlet nozzles of all three reactors for Platformer unit, during a scheduled shutdown. The unit was commissioned in 1957 and the reactors metallurgy is as per withdrawn ASTM standard, A301 Gr. B (1Cr-1/2Mo). The isolated cracks were located at the upstream edge of the inset nozzle and running vertically down. The cracking in the high-pressure fixed bed reactor outlet nozzles was successfully repaired in-situ. This paper reviews the circumstances which led to these failures and highlights the lessons learned from each failure.