By Brian Ellsworth

PUNTA CARDON, Venezuela, Dec 14 (Reuters) - Years of shoddy maintenance and mounting shortages of spare parts have left Venezuela's second-largest oil refinery barely capable of functioning, three sources at the refinery told Reuters.

State oil company PDVSA's 300,000 barrels per day Cardon refinery is currently operating at minimal rates because four of its six steam boilers are out of service, leaving the facility without enough steam to keep units functioning, the three sources said.

Cardon normally uses the steam from five boilers and holds the sixth in reserve, the sources said.

"They don't have the equipment. There are no spare parts, and they don't have them because they are not experienced enough to get them," said one of the refinery sources, all of whom spoke on condition of anonymity.

PDVSA officials did not return calls seeking comment on operations at Cardon.

Venezuela, once one of United States' main suppliers of gasoline, has suffered numerous refinery problems in recent years that have slashed exports and forced it to periodically import gasoline blending components.

12 MAJOR OUTAGES

This year alone there have been 12 major outages, almost half of which have been blamed on power failures. At least nine workers have been hurt in refinery accidents in 2007.

PDVSA has struggled with operational problems at its refineries since hundreds of refinery workers and engineers were fired after they joined an anti-government strike meant to force President Hugo Chavez from power in December 2002.

Chavez purged the company of his political opponents in 2003 and turned it into the financial engine of a social development campaign that has built up his political support.

The government's critics say shortages of skilled staff have hampered investment in the oil industry, leading to falling oil output and increasing unplanned shutdowns.

Most of Cardon's units are currently in a standby mode, after a power surge this month shut the refinery and led to massive emergency flaring of partially refined oil.

A recent attempt to restart the gasoline-making fluid catalytic cracking unit with insufficient steam pressure failed and damaged the unit's compressor, the sources said.

"This is a product of a lack of investment in maintenance," said a second refinery source.

The refinery sources said PDVSA was resorting to installing portable boilers in an effort to restart the refinery as the facility's staff have not been able to acquire the replacement parts to repair the principal boilers. (Editing by Walter Bagley)

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