Drain valve is a valve that automatically discharges condensate and prevents steam from discharging with water. It is generally used in steam system and gas system. Each type is used for many purposes, and it needs to be selected according to the requirements of working conditions. The most representative is the high-temperature and high-pressure steam type, which is used as the diversion and confluence or flow direction switching device of the medium in the pipeline. It adopts the top mounted structure, which reduces the connecting bolts of the valve body under the conditions of high pressure and large diameter, enhances the reliability of the valve, and can overcome the influence of the system self weight on the normal operation of the valve.