5.2.4.4 Spigot joints where, to the edges of the holes, the joint consists only of the plane
part (see Figures 7 and 8), in so far as plane joints are permitted (see 5.2.7)
The distance l is the width of the plane part between the inside of the enclosure and a hole,
where the hole is outside the enclosure (see Figure 7), or between a hole and the outside of
the enclosure where the hole is inside the enclosure (see Figure 8).
5.2.5 Conical joints
Where joints include conical surfaces, the width of the joint and the gap normal to the joint surfaces
shall comply with the relevant values in Tables 1 and 2. The gap shall be uniform through
the conical part. For electrical apparatus of Group IIC, the cone angle shall not exceed 5°.
NOTE The cone angle is taken to be the angle between the vertical axis of the cone and the surface of the cone.
5.2.6 Joints with partial cylindrical surfaces (not permitted for Group IIC)
There shall be no intentional gap between the two parts (see Figure 9a).
The width of the joint shall comply with the requirements of Table 1.
The diameters of the cylindrical surfaces of the two parts forming the flameproof joint, and their
tolerances, shall ensure compliance with the relevant requirements for the gap of a cylindrical
joint as given in Table 1.