If the high-temperature electric pneumatic ball valve driven by the power supply has coking condition in the valve when the torque of the valve driving device is insufficient, the failure cause analysis and countermeasures of the high-temperature pneumatic ball valve for coking and the abnormal shaking of the actuator during the valve operation, and the shaking is increasing with the operation of the device, it indicates that the coking in the valve has been serious. At this time, remove the valve for maintenance. When disassembling and maintaining the high-temperature pneumatic ball valve that has not been difficult to operate, it focuses on cleaning the internal coking of the valve, especially the parts between the bellows and the bottom of the ball and the valve body, as well as the sealing surface. Sometimes a thin layer of hard coke is formed on the spherical surface of the sphere. For cleaning this part of coke, a special soft metal scraper should be used to remove it. The coking in the corrosion pit shall be removed by a similar method, and then the corresponding materials shall be selected for repair welding and grinding. For valves with abnormal conditions, after cleaning and coking, the valves shall be comprehensively inspected, and then targeted inspection shall be carried out for the abnormal conditions. Because the flow medium contains sulfur, the corrosion of the valve sealing surface is inevitable, that is, the repair of the valve sealing surface is essential. The damage of sealing surface mainly includes corrosion, abrasion or scratch. For corrosion, corrosion pits can be generally solved by grinding. For local wear, slight wear can be solved by grinding. If the wear is serious, local repair welding is required. Then grind. For scratches, repair welding is required for the scratched parts, then machining and finally grinding; If the repair welding area is large or the depth is deep, the part shall be calibrated before machining. For the maintenance of bellows, once there is coking at the bellows, it is difficult to separate the bellows from its guide cylinder, so it needs to be disassembled with special tools with its waveform. If there is coking at the bellows, the distribution of the coking block on the bellows is usually uneven, and the bellows may have been deformed (the two ends of the bellows are not parallel, and the same wave has deviation in different phase wave distance), so it is necessary to level its two ends, and adjust the wave distance appropriately to maintain the rigidity of the bellows.

Functions of pneumatic butterfly valve
As a flexible element in the car exhaust system, the pneumatic butterfly valve plays an important role in absorbing and slowing down the vibration of the starter, bearing load, heat dissipation, falling noise, and compensating the displacement of the starter and the installation tolerance between various pipe fittings.
2.1 Damping
The uneven rolling of the initiator during operation will cause oscillation. The vibration generated by the starter will be transmitted to the pneumatic butterfly valve through the connecting rigid pipe. However, due to the vibration absorption function of the flexible buckle structure of the pneumatic butterfly valve, the amplitude will gradually decrease from the maximum value until it disappears, and then the effect of vibration reduction will be achieved. Generally speaking, the oscillation is concentrated at 1/3 of the end of the pneumatic butterfly valve close to the starter. In practice, the pipe is often easy to crack at this part, so the length of the pipe should be 2.5 times greater than the pipe diameter.
2.2 Compensating displacement and installation tolerance
Because the subdivision structure of the pneumatic butterfly valve reduces the internal stress of the metal material itself during processing, its flexible fastening planning can complete the axial, radial and even circumferential displacement within a certain range, which solves the problem of pipe cracking caused by metal fatigue during oscillation during hard pipe connection, and extends the service life, It also deals with the inconvenience of installation caused by the size fault of components, and can withstand the displacement caused by oscillation during the operation of the initiator. The annular buckle structure inside the pneumatic butterfly valve makes it impossible for the noise sound wave emitted by the initiator to pass through the pipe straightly, which can play a certain role in noise reduction. Since pneumatic butterfly valves are operated at high temperature, they are made of stainless steel materials that are resistant to high temperature and corrosion.
2.3 Transmission effect
As the internal surface of the stainless steel pneumatic butterfly valve is lubricated, the exhaust gas will not be turbulent when passing by, and can be smoothly escorted to the following parts. The high-quality pneumatic butterfly valve can ensure a low disclosure rate even under high temperature and pressure, satisfying the requirements of maintaining the environment.
2.4 Bearing load
When the vehicle moves along with the shaking of the vehicle and the oscillation of the starter, the pipe should bear various alternating loads such as axial, radial and circumferential shear. Assuming that the pipe is made of all materials, stress concentration will occur, making the pipe easy to crack; The pneumatic butterfly valve adopts a flexible ring buckle structure, which can release the stress in time when bearing axial and radial loads. With the planning that can be changed circumferentially, the purpose of bearing circumferential shear load is achieved.
3. Primary function comparison between pneumatic butterfly valve and bellows
The similarities and differences between the primary functions of pneumatic butterfly valve and bellows can be seen from the following table. Among all functional indicators, only the air tightness of bellows is better than that of pneumatic butterfly valve. Since the bellows is made of all materials, and the pneumatic butterfly valve is a flexible component wound with stainless steel tape, it is impossible to prevent slight air leakage. However, as the technology of pneumatic butterfly valve progresses from time to time, its air tightness will become higher and higher.
4 Application and installation of pneumatic butterfly valve
Although the pneumatic butterfly valve can be tightened or stretched, if it is not installed in the correct direction, it will crack quickly. Generally, pneumatic butterfly valves can be divided into three lengths: the first is the tightening length, that is, the length when the hose is tightened to the limit position; The second is the installation length, which is the length of the hose in the middle of half of the maximum displacement; The third is the stretching length, which is the length when the hose is stretched to the maximum limit. When installing the hose, the hose should be in the middle position. The functional advantages of the exhaust pneumatic butterfly valve and its application in commercial cars are now in the domestic commercial vehicle manufacturers that use pneumatic butterfly valves. Most of them are still using ASS type products. There are also single commercial vehicle manufacturers that have begun to use or are preparing to use SSS type products, and companies in the automotive industry are all using pneumatic butterfly valves. With the implementation of the new environmental protection regulations and the continuous improvement of official and large users' requirements for the quality of the whole vehicle, more and more domestic commercial vehicle manufacturers will choose pneumatic butterfly valves with increasingly excellent functions to improve the quality and market competitiveness of the whole vehicle.