Standards and certification
iTB and iSTB enclosures are designed for use in hazardous locations and are manufactured in accordance with the following standards:
- IEC/EN 60079-0:2018 — General requirements
- IEC/EN 60079-7:2015 — Increased safety protection (Ex e)
- IEC/EN 60079-11:2012 — Intrinsic safety (Ex ia) — terminal box assemblies only
- IEC/EN 60079-1:2014 — Flameproof (Ex d) — control panel variants only
- IEC/EN 60079-31:2014 — Protection by enclosure for dust (Ex tb)
These instructions are based on the Ex e component certificates for enclosures and terminals, the Ex e, Ex ia and Ex e ia certificates of conformity for assemblies, and EN/IEC 60079-14 (Code of Practice for the selection, installation and maintenance of electrical apparatus for use in potentially explosive atmospheres). Only those components listed on the relevant certificate may be used.
The external certification label must remain legible at all times. Observe the type of protection, gas group and temperature class shown on the label. The maximum permitted surface temperature is 135 °C (T4). The permitted ambient temperature range is defined on the relevant certified drawings (IEL00013 / IEL00014 for assembly variants; IEL006CML for control panel variants).
Alterations or modifications to the enclosure or its contents may invalidate the certification. Any proposed change must be discussed with indEx Enclosures before it is carried out.
Mounting
The enclosure must be mounted on an even surface with each fastening point resting evenly on the mounting surface. Use appropriate fixings at every point provided — a minimum of M8 (8 mm diameter) bolts or screws is recommended.
Do not force the enclosure against an uneven surface, as this may distort the enclosure body and compromise the lid seal and IP rating.
Glanding and cable entry
All cable glands and stopping plugs must be appropriate for the application:
- Gas and vapour atmospheres (Ex e): cable glands must be certified Ex e and rated to a minimum of IP66.
- Dust atmospheres (Ex tb): cable glands must provide a minimum ingress protection of IP6X.
The installer may drill cable entries only in the areas specified on the certified drawings. Entries drilled outside these areas may invalidate the certification.
Where a gland plate is provided with an auxiliary earth stud, it must be connected to the main enclosure earth stud using an appropriately sized conductor.
External identification labels may be fitted by the installer, provided they maintain a minimum protection of IP54 for gas/vapour applications or IP6X for dust applications. For certified and approved labelling methods, contact indEx Enclosures.
The enclosure assembly must not operate beyond the maximum ambient temperature range defined on the relevant certified drawings.
Terminals and wiring
All conditions and limitations stated on the relevant terminal component certificates must be observed. The following requirements apply to all iTB and iSTB assemblies:
- Conductor insulation must have a temperature rating appropriate to the T-class of the apparatus.
- Wiring within the enclosure must not be grouped or bunched in a way that could cause hot spots to form.
- Only one conductor per terminal clamp is permitted.
- All terminal screws — used and unused — must be fully tightened.
- Any cross-connected terminal must be mounted and used subject to the limitations given in the certification documents for that terminal.
- Conductor insulation must extend to within 1 mm of the terminal block clamp or cable lug. All strands of the conductor must enter the terminal clamp.
- Minimum creepage and clearance distances specified in IEC 60079-7 (Ex e) or IEC 60079-11 (Ex ia), as applicable, must be maintained at all times.
- The minimum wiring distances specified on the certified drawings must be observed.
Intrinsically safe circuits
Where both intrinsically safe and non-intrinsically safe terminals are housed in the same enclosure, they must be separated by a minimum of 50 mm. This separation may be achieved through physical spacing or by fitting the correct certified partition between the two terminal groups, in accordance with the relevant certification documents.
Control operators — panel variants
This section applies only to iTB and iSTB enclosures supplied as control panel assemblies (Ex e / Ex d combined protection).
Control panel enclosures are built with pre-defined configurations of control operators as specified at the time of order, in accordance with drawing IELO005CML. The equipment permitted for use is listed on drawing IELO002. No modifications to these configurations may be made by the end user at any time.
The following requirements apply during installation and wiring of control operator panels:
- The recommended tightening torque for the lock nut on each control operator head is 1.1 Nm. The module mounting must be firm and reliable.
- During wiring, the creepage distance of bare current-carrying parts must exceed 10 mm and the electrical clearance must exceed 6 mm.
- A routine electric strength test must be conducted in accordance with EN/IEC 60079-7, clause 6.1, before the panel is placed into service.
Should any control operator component fail in service, the end user or installer must inform indEx Enclosures so that a replacement can be supplied. Replacement devices may only be supplied as complete units (panel-mounted component and contact blocks together). Repair of flameproof joints must be made in compliance with the structural specifications provided by the original equipment manufacturer and must not be made solely on the basis of the values specified in EN 60079-1, Table 3.
It is the user's responsibility to ensure that the equipment is connected to earth appropriately — refer to the user manual for the specific control apparatus.
Torque values
The following torque values must be applied after installation and verified during each periodic inspection:
| Fastener | Torque |
|---|---|
| Lid screws | 2 Nm |
| Gland plate screws | 4 Nm |
| Earth stud (M10) | 10 Nm |
| Control operator lock nut | 1.1 Nm (panel variants only) |
For larger enclosures with multiple lid fixing points: tighten the top and bottom fixings first until the enclosure door is parallel with the edge of the enclosure body, then torque all remaining fixings to 2 Nm.
Special conditions for safe use
The following special conditions apply to all iTB and iSTB enclosures and must be observed by the installer and end user:
- Dust layer thickness: precautions must be taken to prevent the accumulation of dust layers exceeding 5 mm on the external surface of the enclosure. In dust explosive environments, the user must implement a regular cleaning regime to prevent excessive dust build-up.
- Service temperature: the enclosure must not be operated outside the ambient temperature range defined on the certified drawings. The service temperature range is –50 °C to +135 °C.
- Previously certified devices: the installer must take into account any restrictions or special conditions for safe use that are stated in the certificates of any previously certified devices fitted inside the enclosure.
- Operation: do not open the enclosure when it is energised.
Inspection and maintenance
A visual inspection must be carried out at a frequency appropriate to the installation environment. An annual inspection is the recommended minimum — more demanding environments may require more frequent checks, in accordance with EN/IEC 60079-17.
What to inspect
- Certification label — verify all details are clearly legible.
- Lid and gland plate screws — verify they are secured to the correct torque values.
- Lid gasket — after opening, inspect visually to confirm no damage and no foreign objects that could interfere with the sealing function.
- Enclosure interior — check for any ingress of dust or liquid.
- Cable glands — check that all glands are in good condition and properly secured.
- Earth connections — verify that the main earth stud and any auxiliary earth connections are secure and in good order.
Additional checks for control panel variants
- Check for any cracks in explosion-proof modules.
- Confirm that all control apparatus is still fixed firmly and reliably.
- Check that all wiring connections remain secure — no loose terminations.
- Inspect the flameproof joint surfaces for any visible signs of damage or corrosion.
Cleaning
During each inspection, clean the external surfaces of the enclosure with a damp cloth. Do not use solvents or abrasive cleaning products that could damage the enclosure finish or gasket material.
Gasket replacement
If the lid gasket is found to be damaged during any inspection, it must be replaced before the enclosure is returned to service. Operating with a damaged gasket will compromise both the IP66 ingress protection and the ATEX certification. Contact indEx Enclosures for replacement gasket materials and fitting instructions.
For any queries regarding these installation or maintenance instructions, or to report a component failure, contact indEx Enclosures at [email protected] or call +44 1233 801 890.