Pneumatic valve lever switch is ineffective

） Conduct operations, pneumatic valve stem thread damage;
　　） The lack of lubricating oil or lubricant failure;
　　） Pneumatic valve rod;
　　） Pneumatic valve rod surface finish is not enough;
　　） Pneumatic valve stem thread fit tolerance, biting too tight;
　　） Pneumatic valve stem nut tilt;
　　） Pneumatic valve stem nut or pneumatic stem improper material selection;
　　） Pneumatic valve stem nut or pneumatic stem is medium corrosion;
　　） Open-air lack of maintenance of pneumatic valve, pneumatic valve stem thread covered in dust sand or corrosion by rain and dew frost and snow, etc. ;
　　） When the cold shut tight, when hot bulge;
　　） Packing gland and pneumatic valve rod gap is too small or gland partial stuck door rod;
　　） Too tightly on the packing.