(Adds company no comment, details on refinery)
HOUSTON, Nov 30 (Reuters) - The large coking unit at MotivaEnterprises' 603,000 barrel per day (bpd) PortArthur, Texas, refinery was back in production on Monday afterbeing shut for about two hours on Sunday night, said sourcesfamiliar with plant operations.
A Motiva spokesman said one of the refinery's unitsmalfunctioned on Sunday.
"For reasons of commercial confidentiality, we do notprovide details about the operational status of individual unitsor information on supply," Motiva spokesman Ray Fisher said.
A compressor on the 110,000 bpd Delayed Coking Unit-2stopped running, triggering the shutdown on Sunday night, saidthe sources, who requested anonymity because they are notauthorized to speak publicly about the matter.
Energy industry intelligence service Genscape reportedflaring at the refinery on Sunday related to DCU-2. Motiva fileda notice with the Texas Commission on Environmental Qualityabout flaring at the Port Arthur plant, citing the coker as asource of emissions in excess of permitted levels.
The Port Arthur Refinery is the largest in the UnitedStates. Motiva is a 50-50 joint venture between Royal DutchShell Plc and Saudi Aramco.
A 54,000 bpd coker at the refinery remained in operationwhile DCU-2 was malfunctioning.
A coker increases the amount of refinable material obtainedfrom a barrel of oil. The unit also converts residual crude intopetroleum coke, which can be used as a coal substitute.
(Reporting by Erwin Seba; Editing by Richard Chang)