; 2 The main factors affecting the tightness of pneumatic ball valves The main factors affecting the tightness of pneumatic ball valves are the roughness of the sealing surface and the roundness of the ball. As we all know, no matter how advanced processing technology is used, it is impossible to completely eliminate the roundness error of the sphere and the micro defects of the sealing surface. Therefore, in order to achieve a good sealing effect and ensure that the processing process can be achieved, it is necessary to determine appropriate sealing surface roughness and ball roundness parameter values. Relevant data recommend that the maximum allowable roughness Ra value of the ball sealing surface is 0.4; The maximum allowable roughness Ra value of the seal seat is 0.8 when PTFE is used as the sealing material. The roundness tolerance of spherical surface shall be in accordance with Level 6 accuracy in Table 2 of GB/T1184.

Pneumatic ventilation butterfly valve, characterized by a slit between the valve plate and valve seat, is suitable for use in the environment with poor air circulation.