U.S. oil refinery managers are going to the mats, literally, during the biggest fight with union workers in 35 years, bedding down for a third strike week that experts and some employees say raises concerns over safety and operations. At the 135,000 barrel-per-day refinery just outside of Toledo, Ohio, run by BP Plc and Husky Energy Inc , most of the nearly 300-person staff have been calling the refinery home since Feb. 9. For the last week, they have slept on recently purchased mattresses inside rental trailers to rapidly respond to any problems and avoid striking workers, sources say. On Tuesday, a van full of washing and drying machines gingerly cut through about a dozen United Steelworkers carrying pickets and walking a strike line at the facility's front gate.