Vertical Check Valve: The valve is opened or closed by overcoming spring resistance due to the pressure action of the medium at the inlet end of the pipeline. When the medium pressure at the inlet end is lower than that at the outlet end, the spring pushes the spool toward the valve seat and closes the valve, preventing the medium from countercurrent, thus playing a check role. Vertical check valves are widely used in chemical, liquefied petroleum gas, fluids and other industries. Check valves are divided into lifting check valves, swing check valves and butterfly check valves according to their structure.