Check Valve

Check valve is also known as one-way valve or non-return valve. It's a kind of valve with opening and closing part opens and closes automatically driven by flow and force of medium to prevent backflow of medium. Check valve is automatic valve, and mainly applied on pipeline with medium flows in one direction. The medium is allowed to flow only in one direction to prevent accident. ZAF mainly manufactures four types of check valve: swing check valve, lifting check valve, tilting disc check valve and wafer check valve.

API 6D/BS 1868 Swing Check Valve

1. As the channel within the valve is in streamline form, the flow resistance is smaller than lifting check valve, it's suitable for low flow large-caliber application without frequently change in flow. However, it's not suitable for pulsating flow for sealing performance poorer than lifting check valve. 2. Swing check valve is suitable for various operating conditions of pipeline for petroleum, chemical, pharmaceutical, chemical fertilizer and electric power industry. 3. Swing check valve is suitable for clean medium like water, oil, steam, acid medium, and not suitable for medium with solid particles and great viscosity.

API 602 Check Valve

Check valves serve an important application—namely to prevent flow in one direction while allowing it in the other. A check valve is self-actuated and designed to prevent fluid from flowing back into the system (prevent reverse flow). Real-life applications include preventing backflow into an injection line or into a pump.

API 594 Check Valve

The butterfly plate of API 594 double-clack check valve is two semicircular. The check valve uses spring-loaded valve clack which hanged on 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

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