The valve plays an important role in cutting and throttling the medium in its pipeline. Cut-off valve as a very important cut-off valve, its seal is through the valve stem torque, valve stem in the axial direction to the disc pressure, so that the disc sealing surface and the seat sealing surface close together, to prevent the media along the seal surface gap leakage. The seal of the cut-off valve is made up of the disc sealing surface and the seat sealing surface, and the valve STEM drives the disc along the center line of the seat for vertical movement.
Cut-off valve opening and closing process is relatively small, easy to adjust the flow, and easy to manufacture and repair, pressure applicable to a wide range. And in the industrial production of another commonly used truncated class valve one by one alarm valve, structurally speaking, the cut-off valve is simpler than the former, easy to manufacture and repair. From the service life, the cut-off valve sealing surface is not easy to wear and abrasion, valve opening and closing process between the disc and _ seat sealing surface without relative sliding, so the seal surface wear and abrasion is small, so improve the seal of the service life of the valve in the whole closed process of the disc stroke small, its height relative to the smaller valve. The disadvantage of the cut-off valve is that the opening and closing torque is larger and difficult to achieve rapid opening and closing, because the valve body flow channel more twists and turns, fluid flow resistance, resulting in fluid power in the pipeline loss of larger.