According to Article 11.6 of GB 3836.2-2010, for non penetrationExplosion proofThe screw holes or double headed bolt holes on the shell wall should have a remaining thickness of at least one-third of the diameter of the bolt or double headed bolt on the explosion-proof shell wall, with a minimum of 3mm.

Q: Is the "remaining thickness" of the explosion-proof shell wall here referring to the thickness below the hole or the thickness around and below the hole?

A: The "remaining thickness" of the explosion-proof shell wall here is explained as: when the hole is perpendicular to the shell, there is only a requirement for the thickness of the shell wall below the hole (3mm or 1/3 diameter, whichever is larger). This explanation is based on the fact that there is no specific material thickness requirement for the explosion-proof shell, so the material around the hole is not restricted. Explosion proof testing should consider most blind holes, such as impact testing and overvoltage testing.