The 350,000-bpd VPS-5 CDU and the 110,000-bpd DCU-2 coker are scheduled to remain shut for a 45-day planned overhaul.
A Motiva spokesperson did not reply to a request for comment.
In November, Motiva moved the overhaul’s scheduled start from from March to January to avoid equipment failure on DCU-2 that would cause an unplanned shutdown.
VPS-5, the largest of three CDUs at the refinery that break down crude oil into feedstocks for all other units, also needs equipment repaired and replaced, the sources said.
The addition of VPS-5 in 2012 more than doubled the capacity of the refinery.
VPS-5 feeds residual crude oil to DCU-2, which converts it into either motor fuel feedstocks or petroleum coke, which can be a substitute for coal.
A sulfur recovery unit will also be shut for work while the CDU and coker are shut, the sources said.
(Reporting by Erwin Seba; Editing by Kim Coghill and Rashmi Aich)