The new standard of cable entry The Standards which regulate the installation criteria of electrical products and equipment for use in...
The new standard of cable entry
The Standards which regulate the installation criteria of electrical products and equipment for use in hazardous areas have been constantly updating. Particularly, it has been recently amended the standard of cable entry/exit from 'Ex d' junction boxes, whether for IIB or IIB + H2 or IIC group.
For this reason, we face in this study the changes introduced by updating the technical article of May 2014.
The updated Standard is the IEC 60079-14/EN 60079-14/IEC 60079-14 and, especially, has been changed the concept of cable entry, as described below:
(hereinafter named only as 60079- ...., as virtually identical).
Before this change, the design had to be carried out considering the following basic criteria:
This modification has involved a radical change of concept: the volume limitation for the installation of not barrier cable glands or sealing fittings, the need to verify, with tests, the cable seal or the systematic adoption of barrier cable glands or sealing fittings, the first placed directly into the threaded hubs of the junction box and, the second, in the extreme vicinity of the enclosure, respecting the provisions of the paragraph 13.5.3 of the 60079-1 Standard.
In order to make a correct sizing of enclosures for the uses described above, it is essential that all parameters are systematically taken into account and used as a method of calculation for determining the size of such cases.
(hereinafter named only as 60079-..., as virtually identical)
This task belongs mainly to the manufacturer of such equipment, as prescribed by the regulations listed above; however, we intend to provide our customers a wide description of the criteria that we usually take to realize the sizing.
• “Directly” cable entry, type (‘Ex d’ way of protection)
• "Indirect" cable entry, type (‘Ex de’ way of protection).
The "Directly" cable entry provides for the entry of cables directly in the "Ex d" Panel board with the use of sealed cable glands, if you adopt the concept described in paragraph 10.6.2 b), or barrier cable glands if you adopt the concept described in paragraph 10.6.2 point a), which not allows to a possible explosion within the Panel board to propagate outside. In this case, the choice of the cable gland or of the sealing fitting shall meet the standard requirements, such as Figure 1.
The "indirect" entry involves the use of an increased safety "Ex e" junction box for input/output cables, within which are housed the increased safety terminal blocks. From this enclosure are derived all the links from and to the "Ex d" explosion-proof enclosure. The passage between the two enclosures will be through sealed locking devices and/or sealed bushings, always in ‘Ex d’ way of protection. In this case, the choice of the sealing fittings and/or the sealed bushings has to comply with the requirements of standard, such as Figure 2.
Typical of “Ex de” “indirectly” entry
If the cable glands and the cables used are certified as unique and indivisible part of the equipment (enclosure), it is not required the conformity, according to what is written in paragraph 10.6.2 of the standard 60079-14 (see Note 2 of paragraph 10.6.2 of the same rule).
As regards the mechanical and electrical dimensioning, we refer to what is described in the technical article by May 2014.