How to make pneumatic ball valve balls with high requirements for surface roughness and geometric accuracy on an ordinary lathe? Finishing is required after finishing. At present, for the final finishing of large diameter ball, our factory usually uses the abrasive belt grinding process on the special ball turning machine tool. Due to the limitation of the structure of the belt grinding device, the final finishing of small diameter spheres is generally done by hand grinding, but this process method often fails to meet the needs of practical use in terms of efficiency and quality. For this reason, we have designed a device for honing ball on C620 ordinary lathe, and the effect is good through verification.

The following is a brief analysis of the failure modes and causes of various types of thin-walled stainless steel pneumatic butterfly valves consumed by our company in practice. Analysis of failure mode of pneumatic butterfly valve
The thin-walled stainless steel pneumatic butterfly valve is structurally composed of flexible bellows and joints. The flexible bellows is covered with stainless steel wire mesh sleeve for maintenance and pressure bearing. The joint is divided into the part connected with the bellows (internal connection part) and the part connected with the engineering pipeline (or engine body) (external connection part). The failure modes of stainless steel pneumatic butterfly valves are generally as follows.
1. The bellows in the pneumatic butterfly valve cracked and leaked (1) Weld cracking The flexible bellows section in the pneumatic butterfly valve mostly adopts longitudinal seam welded pipe. Due to the quality defect of longitudinal seam welding itself, the pipe strength is not enough to cause cracking and destruction at the weld. This damage is a quality problem of longitudinal weld of bellows, so the control of weld quality should be strengthened. (2) When the pressure of the bellows is not enough, the blasting will happen because the pressure and temperature of the recommended medium are too high and the pressure of the bellows is not enough. This kind of damage is caused by the design and selection error, so the selection should be stopped strictly according to the hose design and selection specification, and the parameters of corrugated pipe and net sleeve should be affirmed. (3) Corrosion perforation damage Because corrugated pipes are mostly made of austenitic stainless steels such as lCrl8Ni9Ti, OCrl8Ni9, etc. These stainless steels contain more non-metallic inclusions (such as silicate, oxide, TiN, etc.) When the pipeline is filled with corrosive media, corrosive penetration micropores will be formed at the edge of the weld fusion line or other thin spots. The corrugated pipe material is very thin, usually between 0.15 and 0.8. It is easy to form corrosion penetration on such a thin material. To avoid such damage, it is necessary to select qualified stainless steel strips (sensitization and other series of experiments are qualified), and it is also necessary to avoid the destruction of bellows caused by external mechanical damage during consumption and transportation. (4) Fatigue failure Under the dynamic working state, the pneumatic butterfly valve is often damaged by fatigue cracks under the cyclic load. Such destruction is normal failure. In order to extend the service life, it is necessary to ensure that the hose design and selection are correct, the device is accurate, and no additional stress such as twisting occurs to the hose.
2. The stainless steel wire mesh sleeve in the pneumatic butterfly valve is mainly used to maintain the bellows and accept the medium pressure (mainly axial force) in the bellows. The mesh sleeve is wrapped outside the corrugated pipe, and both ends are welded with the corrugated pipe, end ring and joint. (1) Due to the reason of welding quality, the corrugated pipe, ring and wire mesh sleeve form a part of steel wire false welding (burning or final welding) during the trinity welding process. In this way, after the hose is installed in the pipeline, due to the uneven stress on the steel wire, under the effect of the medium pressure, the steel wire at the faulty weld will pull off first, which will pull off the entire steel wire mesh sleeve, causing the failure of the bellows drum, which is dangerous. In order to eradicate this situation, the welding quality should be improved. Before the hose leaves the factory, the water pressure and air tightness test should be stopped. Only after it is qualified can it leave the factory. (2) Improper device causes the wire mesh to break the hose. In the process of installation, the hose will be stretched and twisted due to improper device or high pressure. When the stress generated by stretching or twisting exceeds the ultimate strength of the hose wire mesh sleeve, the mesh sleeve at the welding part of the hose trinity or the mesh sleeve at other parts will be pulled off, thus causing the outer drum of the bellows to be stretched and damaged, It causes medium leakage, so the design and model selection shall be accurate and the device shall be correct.
3. The welding quality defects of the pneumatic butterfly valve joint (internal connection part) lead to the leakage failure of the hose. When the hose body is welded with the hose joint, when the operation is not correct, it will produce welding defects, which are difficult to find during the pressure test inspection. When the hose is connected to the medium pipeline, it will crack or break at the defect due to fatigue and other reasons after long-term use, and finally form the medium leakage of the escort pipeline.
4. The joint of pneumatic butterfly valve (local internal connection) is corroded and fails, causing the hose medium to leak. The joint of pneumatic butterfly valve is made of 1Crl8Ni9Ti or SUS304 stainless steel. Inclusions (such as silicate, oxide, etc.) in stainless steel are sometimes in chain dispersion state. When they are affected by welding heat or acid medium, they will form through micropores, causing medium leakage in the hose. To avoid such failure, it is required to select qualified stainless steel joint data and reasonable welding process.
5. The fatigue damage of the external connection part of the pneumatic butterfly valve joint makes the hose invalid;