(Adds company no comment, details on upset)
HOUSTON, Jan 20 (Reuters) - BP Plc's 413,500 barrelper day (bpd) Whiting, Indiana, refinery returned to normaloperations by late Wednesday morning following a malfunction ona diesel hydrotreating unit (HTU), sources familiar with plantoperations said.
A BP spokesman declined on Wednesday to discuss operationsat the Whiting refinery.
The upset had a minor impact on production at the refinery,the sources said. They did not identify which of twohydrotreaters removing sulfur from distillates had themalfunction.
The two hydrotreaters are of similar size with a 36,000 bpdHTU used in ultra-low-sulfur diesel production and at 40,000 bpdHTU used for distillate production.
Energy industry intelligence service Genscape reported therefinery used its safety flare for three hours on Wednesdaymorning. Refineries operate their flare system when hydrocarbonfeedstocks cannot be processed normally. (Reporting by Erwin Seba; Editing by Cynthia Osterman andAndrew Hay)