Do cable glands need to match the IP rating of the enclosure?
Abstract
Yes. The cable entry must keep the degree of protection of the enclosure, and at least the IP the type of protection and the location need. The gland's IP only counts when it is fitted as its instructions say, often with a sealing washer or O-ring on the entry thread.
Yes, in practice. IEC 60079-14 expects cable entry devices to maintain the degree of protection of the enclosure they are fitted to, so the installed entry must give at least the IP that the type of protection requires and the IP that the location requires. A gland only achieves its own rated IP when it is installed exactly as its instructions say, which often means a sealing washer or O-ring between the gland and the enclosure wall.
Short answer
- The enclosure is only as tight as its weakest opening. An IP66 box with an IP54 entry is an IP54 box.
- Two minimums apply: the IP needed by the type of protection (for example Ex e or Ex t) and the IP needed by the environment (rain, washdown, dust). The higher one governs.
- The gland's certificate or instructions state its IP and the conditions: thread type, sealing washer or O-ring, cable diameter range, and sometimes the surface finish of the entry.
- Second numerals 7 and 8 do not include 5 and 6. A gland marked only IP68 is not proven against water jets unless it is dual coded, for example IP66/IP68 (IEC 60529).
- Unused entries need blanking elements suitable for the type of protection; on Ex e enclosures they must keep at least IP54 or the IP the location requires, whichever is higher (the same rule applies to the glands themselves).
Why the entry decides the IP of the enclosure
The IP code of IEC 60529 describes how well a complete enclosure keeps out solid objects, dust and water. Every hole cut for a gland is a new path for water and dust. If water collects inside an increased safety (Ex e) terminal box, it can cause tracking and arcing between terminals; if conductive dust gets into a dust-protected (Ex t) enclosure, the protection is lost. For these types of protection the IP rating is part of the explosion protection, not just a reliability feature.
Damaged or poorly fitted glands and seals are among the recurring findings of regulators' inspections of hazardous area installations, together with corrosion of the equipment behind them.
IP that the type of protection needs
| Type of protection | Minimum IP from the product standard | Notes |
|---|---|---|
| Ex e (increased safety) | IP54 with bare live parts, IP44 with only insulated live parts (IEC 60079-7) | Outdoor use usually needs more |
| Ex i apparatus enclosure | IP20 (IEC 60079-11) | Environment usually decides the real need |
| Ex t, dust IIIC | IP6X for ta, tb and tc | Conductive dust |
| Ex t, dust IIIB | IP6X for ta and tb, IP5X for tc | Non-conductive dust |
| Ex t, flyings IIIA | IP6X for ta, IP5X for tb and tc | |
| Ex d (flameproof) | None from the flameproof concept itself | IP for the environment; the entry must also keep the flameproof joint |
The 2024 edition of IEC 60079-14 added an informative annex listing the IP code by type of protection, and the equipment certificate can set a different or higher value. Restricted breathing equipment (Ex nR) is a special case: its entry must keep the restricted breathing property, which is a tightness test of its own rather than just an IP code.
How the sealing washer and the thread fit in
Most glands seal on the cable with an inner and an outer seal, and on the enclosure with a face seal. On a plain, parallel-threaded hole in a sheet-metal or plastic box, that face seal is usually a sealing washer or O-ring under the gland body; without it, water runs along the thread into the enclosure. On taper threads the instructions may call for a suitable thread sealant instead. The 2007 edition of IEC 60079-14 notes that, for Ex e, a threaded entry device screwed into an entry plate or wall at least 6 mm thick, with its axis at right angles to the surface, needs no extra seal to reach IP54. The installer must follow the gland's instructions, not guess.
Flameproof (Ex d) enclosures add one more condition: the entry thread is itself a flamepath. IEC 60079-14 allows a sealing washer under a parallel-threaded flameproof gland, adapter or blanking element only if the required thread engagement is still achieved after the washer is fitted; any grease used must be non-setting. Nothing that hardens may be put on the joint unless the documentation allows it.
Example: An IP66 Ex e junction box is mounted outdoors with four M20 entries. Three glands are fitted with sealing washers; on the fourth the washer was forgotten. The box now behaves like an enclosure with an unknown IP below its rating, and rain can reach the terminals. The inspector records it as a defect, and the remedy is to refit the gland with the specified washer, not to add sealant around it.
Common mistakes
- Buying a gland by its headline IP without checking it was tested in the same configuration (thread, washer, cable size).
- Leaving out the sealing washer because the gland "screws in tight".
- Using a gland outside its cable diameter range or building up the cable with tape to fit, so that the seal no longer works as tested.
- Closing a spare entry with a plastic transit plug instead of a certified blanking element.
Related on excodex
- Cable glands for hazardous areas: barrier glands, compound glands and selection
- Common Ex inspection findings and how to fix them
- What does IP66 on an Ex label have to do with explosion protection?
- Can silicone sealant be used to improve the IP rating of Ex equipment?
- Standards space: IEC 60079-14
Standards and further reading
- IEC 60079-14, design, selection and installation of electrical installations (edition 6, 2024), cable entry devices, unused openings and the informative annex on IP codes: preview
- IEC 60079-14:2007 (edition 4), quoted where the text names that edition; public text as AS/NZS 60079.14:2009
- P. Thurnherr (convenor of IEC maintenance team MT 60079-14), presentation on the requirements of IEC 60079-14 edition 5, IECEx International Conference 2014: slides
- P. Thurnherr (convenor of IEC maintenance team MT 60079-14) and G. Schwarz, "Electrical installations: design, selection, erection and inspection", presentation on IEC 60079-14, IECEx International Conference 2015, Gdańsk: slides
- IEC 60079-7, increased safety "e"; IEC 60079-11, intrinsic safety "i"; IEC 60079-31, dust ignition protection by enclosure "t"; IEC 60079-1, flameproof enclosures "d"
- IEC 60529, degrees of protection provided by enclosures (IP code): catalogue entry
- NSW TestSafe, dust ignition protection and IP requirements for Ex t: nsw.gov.au
- NOPSA (now NOPSEMA), Safety Alert 33, hazardous area electrical equipment: PDF
This article is general technical information prepared by the excodex editorial team. It does not replace the applicable standards, the equipment certificates and instructions, national regulations or the assessment of a competent person.