The refinery has been struggling to complete a restart following a Jan. 16 plant-wide power outage after temperatures fell below 20 degrees Fahrenheit (minus 7 degrees Celsius).

A company spokesperson did not reply to a request for comment.

On Wednesday, the company reported multiple upsets in heaters for the refinery's 150,000-bpd ACU-1 and 40,000-bpd ACU-2 crude distillation units along with the 51,000-bpd and 60,000-bpd vacuum distillation units as well as the 60,000-bpd DCU-2 coker were affected by the Wednesday malfunction, according to the TCEQ filing.

CDUs break down crude oil into feedstocks for all other units while VDUs further refine gunky residual crude oil from CDUs into feedstocks for other units.

The coker finishes the refining of crude oil by converting residual crude from the VDU into motor fuel feedstocks or petroleum coke.

The refinery's 76,000-bpd fluidic catalytic cracker-2 was also in operation, according to the sources.

(Reporting by Erwin Seba; Editing by Chris Reese and Josie Kao)

By Erwin Seba