5 Conclusion High temperature and high pressure metal seat pneumatic ball valve is an energy saving and consumption reducing product that we focus on organizing and developing. After the product is applied locally, there is still much room for promotion. In addition to the advantages of R&D conditions, there is also an important advantage, that is, its convenient industrial test conditions can be repeatedly tested on the operating unit. At present, a large amount of data has been obtained, and a small number of samples have begun to conduct experiments. The experiment shows that the project can be used for the ultra supercritical steam turbine generator unit boiler, steam turbine body and pipeline drainage system, reaching the same level as imported products from western countries, and can replace imported products, with huge energy saving value.

2. Packing leakage: after packing is loaded into stuffing box, axial pressure is applied to it through gland. Due to the shaping of the packing, it generates radial force and is in close contact with the valve stem, but this contact is not very uniform. Some parts are contacted tightly, some parts are contacted loosely, even some parts are not contacted; During the use of a single seat pneumatic control valve, there is a relative movement between the valve stem and the packing. With the influence of high temperature, high pressure and highly permeable media, the packing box of a single seat pneumatic control valve is prone to leakage. Solutions: 1) In order to facilitate the packing, chamfer the top of the stuffing box and place a metal protective ring with small erosion resistance clearance at the bottom of the stuffing box to prevent the packing from being pushed out by the medium pressure. 2) The metal surface of each part of the stuffing box in contact with the packing shall be finished to improve the surface finish and reduce the friction of the packing. 3) Flexible graphite is selected as the filler because of its good air tightness, small friction, small change after long-term use, small burning loss of wear, easy maintenance and other characteristics. The above points can ensure the reliability and long-term performance of the packing seal.