UPDATE 2-BP Texas City upset has no impact on output-source

(Updates with source info, BP no comment, changes dateline from prev. NEW YORK)

HOUSTON, July 7 (Reuters) - A Tuesday morning upset in a crude unit at BP Plc's (BP.L) 475,000-barrel-per-day (bpd) refinery in Texas City, Texas, had no impact on production, a source said.

The 80-minute malfunction that triggered flaring at the refinery "was a non-event," according to the source familiar with refinery operations.

A BP spokesman declined to discuss refinery operations.

After the upset "personnel reduced the temperature which decreased the pressure in the system alleviating the upset" in the unit, called Pipestill 3B, according to a notice filed Tuesday with Texas Commission on Environmental Quality.

The Texas City refinery is the third largest in the United States and BP's largest U.S. refinery.

BP in late June entered into an agreement with the Texas attorney general to improve environmental compliance at the Texas City refinery, including investigations into malfunctions that trigger flaring. (Reporting by Erwin Seba in Houston and Rebekah Kebede in New York)