sentences:  That same year, Weatherford completed its acquisition of V-Tech International, a pioneer in the development of mechanical power tong systems in the North Sea to improve rig safety.In May 2010, Weatherford's Leetsdale, Pennsylvania, facility accidentally released a cloud of ammonium persulfate that resulted in the evacuation of 500 workers from the surrounding industrial park.In April 2014, Weatherford announced that its board of directors approved the relocation of its legal domicile to Ireland from Switzerland.