Cylindrical Threads #
The threaded part shall be at least 8mm in length (for enclosures > 100mm3), and must have at least 5 full threads as per IEC60079-1
| Cylindrical threaded joints | |
| Threads engage | ≥ 5 |
| For Volume ≤ 100cm3 | Depth ≥ 5 mm |
| For Volume > 100cm3 | Depth ≥ 5mm |
Entry by Cable Gland or Conduit #
The thread engagement requirements for cable and conduit entries are specified in the standard IEC 60079-01. Only threaded entries are allowed for cable glands or conduits entering flameproof enclosures – clearance entries are not permitted.
Six threads are minimum usually provided as per older standards. This allows for a margin of error or for thread undercut.
Ex thread adaptors and stopping plugs #
A flameproof adaptor (or reducer) may be used if the entry hole thread is not the same as the cable gland thread.
An unused cable entry shall be sealed with a flameproof stopping plug (blanking element).
Adaptors and plugs must have at least five full threads of arrangement
Stoppers should be fitted with their certification details visible, for ease of inspection.
IEC60079-1 clarifies that
“Each entry shall have no more than one thread adaptor fitted” and
“A blanking element shall not be used with a thread adaptor”
An unused cable/conduit entry in a flameproof enclosure must be closed using ONE ‘component certified’ metal stopper with the correct thread size, engaged by at least 5 full threads. Stoppers should be fitted with the certification details visible, for inspection.
If a cable gland has different thread form the cable entry, then use a ‘component certified’ metal thread adaptor with the correct thread sizes, engage by at least 5 full threads.
Plastic Stoppers are unacceptable.
Cable Glands #
Cable Glands – ‘Direct’ and ‘Indirect’ entry to enclosures:
Where glands are used for direct entry into an Ex ‘d’ enclosures the following can be used, depending on criteria given in the ‘Wiring Systems’ unit :
- Ex ‘d’
- Ex ‘d’ / Ex ‘e’ dual certified (universal)
- Barrier glands
Cable glands which can be used for Ex ‘d e’ flameproof equipment.
(Ex ‘d’ enclosure with an indirect entry Ex ‘e’ terminal box).
- Ex ‘e’
- Ex ‘d’ / Ex ‘e’ dual certified (universal)
Note: Higher ratings could be used but this would be over specification.
Drilling and tapping of cable gland entries should only be carried out by the manufacturer of enclosure, or his approved agent.
The threads of the entries must be compatible with those of the glands or conduit, since flamepaths exist at the entries – type of thread, thread pitch, & clearance tolerance.
Correct alignment of the threaded entry is also important, since the flamepath length at one side will be reduced if the cable gland or conduit is not fitted perpendicular to the face of the enclosure.
Strength of the enclosure may be impaired if the number and size of entries exceeds that permitted in the original certified design.
