Swing check valve is a kind of check valve series widely used, swing check valve disc, rotating movement around the shaft, so that the channel in the valve into a linear shape, flow resistance is small, suitable for low flow speed and flow does not often change in large caliber occasions, swing check valve is divided into single disc type, double disc type and half type, these three forms are mainly divided according to the valve caliber, Effectively relieve the disc and valve body seal flush out of the medium backflow, thus extending the service life of the valve.​