Valve & Seat Double Support Valve has 3 web & 4 web valve; Full Open Valve has Integral Forged Valve and Friction Welding Valve. Sinotai offer all types of double support valve bodies and seats that conforming API Spec 7K. . They are made of high quality alloy structure steel,through special mechanical process and treat. The valve body, seat and its nut are manufactured by forged steel.