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By Julia Symmes Cobb
BOGOTA, April 17 (Reuters) - BHP Billiton has shut an oven at its Cerro Matoso ferronickel plant in Colombia after equipment damage, cutting output by as much as three quarters, the president of the union representing the plant's workers told Reuters on Friday.
Damage to a crane stopped production of one of two ovens at the world's sixth-largest ferronickel producer on Thursday afternoon, union leader Domingo Hernandez said.
The second oven on site is producing at half its capacity, he said. It was not initially clear whether that was linked to Thursday's incident.
"The cables that suspend the container [from the crane]broke, which caused damage to the equipment and as they can't feed the oven without the crane, the oven is out of operation," Hernandez told Reuters, referring to the first oven.
Neither Cerro Matoso S.A., nor parent company BHP Billiton were immediately available to comment.
The operation, located in northern Cordoba province, produced over 41,000 tonnes last year.
The shutdown and production cut come as a strike by half of the mine's 1,000 workers protesting longer working hours enters a fourth day.
Three-month nickel prices on the London Metal Exchange are languishing at six-year lows around $12,500 per tonne amid a global surplus and lackluster demand from the stainless steel industry, the biggest user of the metal. (Reporting by Julia Symmes Cobb; Additional reporting by Nelson Bocanegra; Editing by Josephine Mason, Alden Bentley, Dan Grebler and Bernard Orr)