Check Valve And Control Valve Manufacturer | DFT® Valves, Since 1943 DFT® Inc. has manufactured world class, problem solving, in-line, axial flow, nozzle style silent check valves and severe service control valves. Whether it is "in stock", or a "custom engineered, special order", the DFT® sales and engineering staff will respond quickly to your requirements. DFT® is the only company that specializes in a broad spectrum of spring assisted, in-line silent check valves with materials ranging from ductile iron to exotic alloys, and are.