Check Valve: According to the structure, it can be divided into three types: lift check valve, swing check valve and butterfly check valve. Lift check valves are available in both vertical and straight versions. The swing check valve is divided into three types: single-lobed, double-lobed, and multi-lobed. The butterfly check valve is divided into a butterfly double flap and a butterfly single flap. The above several check valves can be divided into four types: a screw connection, a flange connection, a welding and a clip type connection.