what is a swing check valve? 

The swing check valve operates automatically by the action of fluid pressure and the self-weight of the valve disc. Unlike other check valves( like the lift type check valves, wafer butterfly type check valves,etc), the disc of the swing type check valve rotates around the rocker shaft in the body cavity instead of moving up and down. The swing check valve can also play a role in preventing the back flow of the medium. 

Swing type check valve can be divided into three types: single disc swing check valve(single plate swing check valve), double disc swing check valve(dual disc swing check valve, or dual plate swing check valve), and multi disc swing check valve. 

What are components of swing check valve? 

Swing type check valve is mainly composed of valve body, valve bonnet, valve disc and rocker,etc.