At the end of the 20th century, several representative hard seal pneumatic ball valve improved processes were basically formed at home and abroad based on the original floating pneumatic ball valve and fixed pneumatic ball valve seat structures,
1. The valve structure mainly improves the hardness and elasticity of the sealing surface. To extend the service life of the sealing material, the improved mechanical transmission mode is used to get rid of or reduce the friction contact between the ball and the sealing surface to prevent scratches, so as to improve or extend the service life of the valve.
2. The advanced HVOF spraying technology at home and abroad is used to make the sphere and the sealing surface form an ultra hard seal, and the hardness of the sealing surface is HRC 73. HVOF spraying is a high-tech recently developed by our company, which is in the research and development period and gradually forms a set of mature experience.
3. Maximizing the hardness of the ball and the sealing surface is the key to ensure the service life of the sealing surface under the conditions of high temperature, high pressure, corrosion and granular media.
4. Improving the traditional sealing mechanism design of pneumatic ball valve is an innovation of new structure pneumatic ball valve. The traditional pneumatic ball valve design adopts the linear contact between the ball and the sealing surface. The sealing ring bears excessive specific pressure, and the deformation of the sealing ring is the main factor for the low service life of the pneumatic ball valve. The sealing surface of the ultra hard sealing pneumatic ball valve adopts a new structure, and the bearing specific pressure of the sealing surface is relatively reduced, which provides a guarantee for improving the service life of the pneumatic ball valve. High temperature and corrosion resistant springs (plate spring, cylindrical spring) are used to ensure the sealing reliability of high temperature and high pressure valves under low pressure. Metal skeleton packing is used to ensure reliable valve stem sealing under high temperature and pressure.
5. Advanced processing technology and assembly technology are adopted, and advanced thermal spraying technology is adopted for ultra hard sealed pneumatic ball valve, which provides process guarantee for ultra hard sealed pneumatic ball valve. The manufacturing precision, smoothness and coincidence of the ball, seal ring and sealing surface are the key technologies for the successful development of the ultra hard sealed pneumatic ball valve. Ultra hard sealing materials such as Cr2O3, ZrO2, Al2O3, Ni base alloy and WC can meet the requirements of sealing function conditions under high temperature, high pressure and corrosive granular medium conditions. At the same time, it also brings difficulties to product manufacturing, processing and assembly.
6. Processing technology The hardness of the sealing surface of the super hard sealing pneumatic ball valve ball and the sealing ring is 1000~1300HV (69~75HRC). On the basis of this hardness, the manufacturing accuracy and smoothness of the ball and the sealing ring, and the coincidence between the ball and the sealing ring are the key to the success of the product development. The ball is rough machined, shaped, and sprayed with super hard sealing materials (special equipment, tooling) Ultra hard sealing surface grinding (special equipment, special fixture, special abrasive) polishing. Rough machining and forming of valve seat are sprayed with superhard sealing materials (special equipment, tooling), and the superhard sealing surface is polished (special equipment, special fixture, special abrasive). When assembling the valve body and valve cover, adjust the matching size of the valve seat and the ball to ensure that the ball center is concentric with the valve stem shaft, and ensure the sealing reliability of the pneumatic ball valve. For floating pneumatic ball valve, first adjust the valve seat width, and then adjust the gasket thickness. For fixed pneumatic ball valve, first adjust the valve seat width, and then adjust the spring preload. After the assembly of the whole machine, the valve can be opened flexibly, and the fitting degree between the ball and the sealing surface of the valve seat is 100%. After the torque meets the design requirements, the shell test and sealing test shall be carried out according to the standards. The use of metal hard seal is an effective measure to achieve high parameters of valve use. The metal valve seat seal must be matched to produce a certain specific pressure to achieve sealing. Under normal conditions, the service life of the ball and metal valve seat seal can be extended only when the ball is rotated under the condition of no friction or less friction, which is difficult to achieve and the service conditions will be greatly limited. The super hard sealed pneumatic ball valve can effectively solve this problem, showing the special function of the pneumatic ball valve.

Structure enhancement measures of pneumatic butterfly valve
The pneumatic butterfly valve used to compensate the tank foundation subsidence and the hose with small lateral compensation and large bending radius used in other places abroad mainly adopt the construction mode of corrugated pipe armored steel belt mesh sleeve.
To analyze the strength of the metal wire mesh sleeve, first make clear the structural parameters and the relationship between them.
The net sleeve is made of several strands of metal wires with diameter d, each of which has several wires. It is wrapped on the cylindrical surface of the corrugated pipe with certain rules.
Therefore, in order to reasonably use the strength of the metal wire mesh sleeve, it is necessary to understand the bearing capacity of the bellows.
Since the rubber hose with wire mesh sleeve as the "tendon" is the predecessor of modern pneumatic butterfly valve, before analyzing the strength of the wire mesh sleeve of modern pneumatic butterfly valve, let's first discuss the condition of the wire mesh of the rubber hose under the stress condition. The rigidity of the rubber hose is very small, so the load caused by the medium pressure is basically accepted by the wire mesh. Pneumatic butterfly valves are different from rubber hoses because their lateral stiffness is much greater than the longitudinal stiffness. Therefore, a large part of the transverse load caused by the medium pressure is accepted by the bellows, while the longitudinal load is mainly accepted by the wire mesh.