Specialist engineering company Rotork has bought US company Flow-Quip Controls.Rotork is paying $8m in cash for the Tulsa, Oklahoma based company, of which $1m will be deferred for 12 months.The acquired company will join Rotork's Fluid System division, and will add around $14m of annual revenue to the division.Rotork said Flow-Quip's current returns are marginally behind the rest of the Fluid System division's.'Flow-Quip brings with it additional products to add to our portfolio together with well established customer relationships in the United States and South America, markets we have identified as having potential for further growth,' said Peter France, chief executive of Rotork.