5.2 Non-threaded joints
5.2.1 Width of joints (L)
The width of joints shall not be less than the minimum values given in Tables 1 and 2. The
width of joints for cylindrical metallic parts press-fitted into the walls of a metallic flameproof
enclosure of a volume not greater than 2 000 cm3 may be reduced to 5 mm, if
– the design does not rely only on an interference fit to prevent the part being displaced
during the type tests of Clause 15, and
– the assembly meets the impact test requirements of IEC 60079-0, taking the worst-case
interference fit tolerances into account, and
– the external diameter of the press-fitted part, where the width of the joint is measured, does
not exceed 60 mm.
5.2.2 Gap (i)
The gap, if one exists, between the surfaces of a joint shall nowhere exceed the maximum
values given in Tables 1 and 2.
Where the maximum constructional gap (ic) is less than that required by Table 1 or 2, the value
shall be stated in the certificate and the apparatus shall be marked according to 27.2 item i) of
IEC 60079-0. In addition, this condition for safe use shall be specified in the manufacturer’s
instructions.
The surfaces of joints shall be such that their average roughness Ra (derived from ISO 468)
does not exceed 6,3 μm.
For flanged joints, there shall be no intentional gap between the surfaces, except for quickacting
doors or covers.
For electrical apparatus of Group I, it shall be possible to check, directly or indirectly, the gaps
of flanged joints of covers and doors designed to be opened from time to time. Figure 1 shows
an example of construction for indirect checking of a flameproof joint.