Check valves include swing type check valves and lift type check valves.Swing type check valve has a hinge mechanism and a door - like disc that rests freely against the tilted seat surface. To ensure that the disc reaches the right position on the seat face each time, the disc is designed in a hinged mechanism so that the disc has sufficient swing space and that the disc is truly and fully in contact with the seat. Disc may be made entirely of metal, may be inlaid with leather, rubber, or synthetic covering, depending on performance. Swing check valves offer virtually unimpeded flow pressure when fully open, so the pressure drop through the valve is relatively small.The flap of the lift check valve is located on the seat seal face of the valve body. This valve in addition to the disc can be free to rise and fall, the rest of the same as the globe valve, the fluid pressure makes the disc from the seat sealing surface to lift, the medium backflow causes the disc to fall back to the seat, and cut off the flow. Depending on service conditions, the disc may be of all-metal construction or may be in the form of a rubber pad or ring mounted on the disc holder.Like globe valves, the flow through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than the swing check valve, and the swing check valve flow is less restricted.