its structure, operation and environment were improved. The first is to increase the limit welfare of flat key I, and add a 3mm thick stainless steel packing pad to the lower packing of PTFE material, so as to prevent the packing from getting dirty and limiting the valve stem. When the valve is closed, if the valve can not be closed, it should not be forced to close, but open the valve, flush it with fluid for a period of time, and then close it again and again. If it still can not be closed, the grinding sealing surface should be checked. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open, so as to extend the service life of the valve stem and its sealing components. When installing the stop valve with thrust ball bearing on the upper part of the valve stem, it is necessary to avoid the condensation water dripping directly on the valve stem and causing the stem corrosion.