The tightness of the stainless steel ball valve is mainly determined by the roughness of the sealing surface and the roundness of the sphere. In fact, no matter how advanced the processing technology is, the roundness error of the sphere and the small defects of the sealing surface cannot be completely eliminated.
Therefore, in order to ensure a good sealing effect and ensure that the processing process can be achieved, it is necessary to confirm the appropriate sealing surface roughness and spherical roundness parameter values. Relevant information shows that the maximum allowable value of the roughness Ra value of the sphere sealing surface is 0.4µm; the maximum allowable value of the Ra value of the sealing seat roughness is 0.8µm when PTFE is used as the sealing material. The roundness tolerance of the spherical surface is more suitable according to the 6-level accuracy of GB/T1184 Schedule 2.