ATEX Zones for Explosion-Proof Enclosures in Pakistani Refineries

A loose terminal inside the wrong junction box at PARCO's hydrocracker can ignite a hydrogen-rich atmosphere from a single 1 mJ spark. Most installation problems trace back to the moment someone specified a Zone 2 enclosure for a Zone 1 area, or signed off an IIB-rated control station in a hydrogen service.

For Pakistani refineries, petrochemical plants, and gas processing terminals, hazardous-area electrical specification runs through IEC 60079 [2] and the ATEX directive its harmonised standards underpin [4]. This guide covers how to select Alloy Industry explosion-proof enclosures against the zone and gas-group framework that governs every Pakistani refinery's E&I specification.

What ATEX zones actually mean

IEC 60079-10-1 [3] defines three zones for explosive gas atmospheres by frequency of presence:

• Zone 0 — explosive gas atmosphere present continuously or for long periods. Inside vessels, mixing tanks, sumps; on the surface of stored flammable liquids.
• Zone 1 — likely to occur in normal operation. Around pump seals, sample points, vent stacks, routinely-opened process connections.
• Zone 2 — unlikely in normal operation and, if present, only briefly. Most of an outdoor process area; secondary zones around Zone 1 sources.

Dust atmospheres get a parallel classification — Zone 20, 21, 22 — under IEC 60079-10-2. The area-classification drawing is the responsibility of the facility's process safety engineer, not Pacific; we supply equipment to match an already-classified site.

ATEX vs IECEx: which does Pakistan need?

Both schemes test against the same IEC standards but route certification differently [4]:

• ATEX is the EU's mandatory directive, CE-marked, with the manufacturer accountable for compliance. Its category structure (1/2/3 for gas) maps directly to zone usage.
• IECEx is the voluntary international scheme operated under the IEC, third-party certified, accepted in ~35 countries including most Asian and Middle Eastern markets.

For Pakistani projects, IECEx is the simpler default — accepted by every major refinery and EPC contractor. Some European parent-company specs require ATEX; Alloy Industry typically provides both, and the certificate number must be verified on the specific supplied product.

Zone 1 vs Zone 2 in practice

The procurement rule is one-directional: equipment certified for a more onerous zone can be used in a less onerous zone, never the reverse [5].

• Zone 1 equipment uses one of several IEC 60079 protection concepts: flameproof "d" (IEC 60079-1) [6], increased safety "e", intrinsic safety "ia"/"ib", encapsulation "m", or pressurised "px". Alloy Industry's JBE, TBE, and DJB enclosure series target Zone 1 with flameproof "d" [1].
• Zone 2 equipment can use the simpler "n" concept (IEC 60079-15) or any Zone 1 method. Most Zone 2 areas use dual-certified equipment since the price delta is small.

A Zone 1 enclosure in Zone 2 is compliant but overspecified. A Zone 2 enclosure in Zone 1 is a fundamental safety violation — and the refinery HSE audit will find it.

Gas group IIB vs IIC: when does a Pakistani refinery need IIC?

IEC 60079-0 [2] divides gas atmospheres into three groups by ignitability:

• Group IIA — methane, propane, most light hydrocarbons.
• Group IIB — ethylene, town gas, most refinery process streams.
• Group IIC — hydrogen, acetylene, carbon disulphide. The hardest to contain because the minimum ignition energy is lowest.

For a Pakistani refinery: hydrocrackers, hydrotreaters, hydrogen plants, and any unit handling H₂ recycle need IIC-rated equipment. General hydrocarbon process areas (atmospheric distillation, vacuum distillation, FCC) typically need IIB. IIC equipment can be used in IIB/IIA areas; IIB cannot be used in IIC. Default to IIC where the gas group is not formally characterised; de-rate to IIB where the area-classification drawing supports it.

Selecting Alloy Industry equipment by zone

Pacific's Alloy Industry catalogue maps to a typical Pakistani refinery as follows:

Application	Zone	Alloy Industry product family
Junction boxes (cable consolidation, instrument loops)	Zone 1, IIB/IIC	JBE / TBE / JBE2 / TBE2 flameproof enclosures [1]
Empty enclosures for custom panel build-up	Zone 1 or 2	DJB / DER / WJB series
Field control stations (start/stop, ESD, local-remote)	Zone 1	EPB / DCU / DCT / DCR push-button series
Energised disconnect at maintenance points	Zone 1	ESN snap switches; DCR3-CB / DRCS / DPG interlocked plugs
Process lighting (high-bay, floodlight, tank light)	Zone 1 or 2	DNGV / DFP / DFPE / DFDR2 / DFXT fixtures
Cable entry at any of the above	matched to enclosure	DAC / DNA / DNAF cable glands, barrier glands, sealing fittings

Cable entry is where most field installations fail Ex inspection. Unsealed glands turn a flameproof enclosure into an open one. IEC 60079-14 [5] specifies cable-entry rules — barrier or compound-filled glands are mandatory where flammable gas can migrate through the cable interstices.

Common specification pitfalls

Procurement errors on hazardous-area projects cluster in five places:

• Specifying "explosion-proof" without naming the protection concept. Flameproof "d", increased safety "e", and intrinsic safety "i" are not interchangeable — each has its own installation rules under IEC 60079-14 [5]. Name the concept on the BOQ.
• Treating the certificate as brand-wide. Certificates are per-product-per-batch, not per-manufacturer. Verify the certificate number against the specific Pacific-supplied unit.
• Mismatching gas group to area. A IIB-certified control station in a hydrogen unit is non-compliant regardless of how recently it was installed.
• Omitting cable-entry seals. Bare cable glands defeat the enclosure's protection at the interstice. IEC 60079-14 [5] specifies when barrier or compound seals are mandatory.
• Forgetting that grounding and surge protection still apply. Ex equipment does not exempt the installation from equipotential bonding or transient overvoltage protection — see the grounding and lightning protection guide for Pakistani industrial sites and the CITEL surge protection tiers guide.

Sourcing and support in Pakistan

Pacific Engineering & Automation is the authorized Alloy Industry reseller in Pakistan. We supply the full Alloy Industry hazardous-area range — explosion-proof enclosures, junction and terminal boxes, cable glands and conduit fittings, control stations, interlocked switches and plugs, and Ex-rated lighting fixtures — with technical support on zone selection, gas-group matching, and IEC 60079 conformance from our Karachi office. Alloy Industry pairs with Kumwell grounding systems and CITEL surge protective devices for complete hazardous-area electrical infrastructure.

For a hazardous-area equipment specification or product quotation, request a catalogue or contact our engineering team.

Field-derived case studies will be added to this post as Pacific Engineering & Automation accumulates engagement records. The current version is grounded in published specifications, regulatory documentation, and standards body references.

Sources

1. Alloy Industry — official product portal
2. IEC 60079-0:2017 — Explosive atmospheres, Part 0: Equipment, General requirements (7th ed.)
3. IEC 60079-10-1:2020 — Classification of areas, Explosive gas atmospheres (3rd ed.)
4. ATEX vs IECEx — Industry comparison on regulatory scope, certification routes, and global acceptance
5. IEC 60079-14:2024 — Electrical installation design, selection, and installation of equipment (6th ed.)
6. IEC 60079-1:2014 — Equipment protection by flameproof enclosures "d" (7th ed.)
7. PARCO — Pak-Arab Refinery Limited corporate website
8. PRL — Pakistan Refinery Limited corporate website