... double eccentric structure reduces friction of the sealing ring, providing the valve a long service life.2. "T" ... 3. Replacing materials of the disc ring, "O"-ring, disc and shaft, the valve can be used for various medium ... ball valves, plug valves strainers, etc.in accordance with the latest international standards of ANSI,DIN, JIS,BS ... cooperation and visit our company. butterfly type check valve