The center vertical pin shaft. When the valve is open, the resultant force of fluid is on the center of sealing face of valve clack, while the point of action of counter spring support force is on the center of valve clack surface so that the root of valve clack opens firstly. It avoids wearing of sealing face of old conventional valve when valve opens, and increase the persistence of valve seal. When flow slows down, counter force of torsion spring makes the valve clack moves to valve seat, and the valve is in slow off stage. When fluid flow backwards, the closing of valve clack is correspondingly increased and enters the rapid closing stage under force of backflow fluid on valve clack and counterforce of torsion spring. The influence and harm of water hammer is effectively reduced. When closed, the spring force closes the top of valve clack firstly so that bite phenomenon on root of valve clack is prevented to guarantee longer service life of valve sealing face. API 594 single clack wafer check valve is single clack swing wafer connecting check valve that prevents backflow of medium. They are all ultra-thin check valves. Single clack swing wafer connecting check valve is designed to be connected through wafer. stainless steel or stellite build up welding may be applied for sealing face of valve body and valve clack. The valve is suitable for clean medium, and not suitable for medium with solid particles and great viscosity. Main advantage of tilting disc check valve is overcoming shock, water hammer in operating condition of swing check valve and lifting check valve to realize shock-free operation.