UPDATE 1-Shell restarts CDU at Deer Park, Texas, from maintenance -sources

(Adds company statement; background about work, units)

HOUSTON, Nov 12 (Reuters) - Royal Dutch Shell Plc is finishing a planned multi-unit overhaul as it begins restarting the large crude distillation unit (CDU) at its 340,000 barrel-per-day joint-venture Deer Park, Texas, refinery on Tuesday, said sources familiar with plant operations.

The 270,000 bpd DU-2 CDU was shut on Sept. 23 at the start of the multi-unit overhaul planned to last for about two months, the sources said.

Shell spokesman Ray Fisher said planned work was still underway at the Deer Park refinery, which is a joint-venture between Shell and Mexico's national oil company Petroleos Mexicanos.

In addition to DU-2, Shell shut the 92,000 bpd coker, the 67,000 bpd hydrocracker and 40,900 bpd gas oil hydrotreater along with several other units.

The gas oil hydrotreater restarted on Tuesday. The hydrocracker is preparing to restart along with DU-2. The coker will restart along with the CDU or shortly after it, the sources said.

DU-2 is the larger of two CDUs doing the primary breakdown of crude oil into hydrocarbon feedstocks for all other production units at the refinery.

The coker converts residual crude oil from distillation units into feedstocks for motor fuels or petroleum coke, a coal substitute. Hydrocrackers use hydrogen under high pressure and high heat with a catalyst to convert gas oil into motor fuels, primarily hydrogen.

Hydrotreaters remove sulfur from motor fuels in compliance with U.S. environmental rules. (Reporting by Erwin Seba, editing by Louise Heavens and Marguerita Choy)