The 112,000-bpd gasoline-producing Residual Catalytic Cracking Unit (RCCU) was shut on March 7 for a planned overhaul, the sources said. Shell began preparing the unit for restart on May 12.

The company began restarting production on Thursday.

The 50,000-bpd gasoline hydrotreater malfunctioned on Sunday and is expected to return to normal operation between Monday and Wednesday, the sources said.

The RCCU is unlike most gasoline-producing catalytic cracking units in that it uses residual crude oil as its feedstock for making unfinished gasoline.

The more common fluidic catalytic cracking unit uses gas oil.