Technical Guidance
ATEX & IECEx zones, selection checks, and offshore inspection reality
Hazardous area zone classification defines the boundary. Offshore compliance and clean close-out depend on verification detail: protection concept suitability, correct entries and glands, certificate scope, and evidence that matches the installed condition.
This page gives the practical decision inputs that reduce late NCRs: gas and dust zone considerations, gas group and temperature class checks, and the items inspectors challenge most during verification.
What drives acceptance
Hazardous area zone classification sets the boundary. Acceptance is won or lost on verification detail: nameplate and marking evidence, certificate scope and any special conditions, entry and gland selection, installation method, enclosure integrity, and traceable evidence linked to tag and location.
What inspectors typically request
Certificates and datasheets, nameplate evidence, installation condition checks, cable entry details, earthing and bonding continuity, and documented deviations with justification.
What reduces punch items fastest
Consistent equipment standards, fewer variants, correct entry and gland selections, clear Ex marking evidence, and documentation tied to tag, location, and the register.
Hazardous area zones at a glance (gas and dust)
Hazardous area zones describe the likelihood of an explosive atmosphere being present. Zone classification is only one input, selection also depends on gas group, temperature class, protection concept, ambient limits, and the installation environment.
| Atmosphere | Zone | Meaning (simplified for project use) |
|---|---|---|
| Gas / Vapour | Zone 0 | Explosive gas atmosphere present continuously, for long periods, or frequently. |
| Gas / Vapour | Zone 1 | Explosive gas atmosphere likely to occur occasionally during normal operation. |
| Gas / Vapour | Zone 2 | Explosive gas atmosphere not likely in normal operation; if it occurs it will be short duration. |
| Dust | Zone 20 | Explosive dust atmosphere present continuously, for long periods, or frequently. |
| Dust | Zone 21 | Explosive dust atmosphere likely to occur occasionally during normal operation. |
| Dust | Zone 22 | Explosive dust atmosphere not likely in normal operation; if it occurs it will be short duration. |
Offshore examples that drive selection
Offshore selection is rarely about one component. It is about how the system is installed and maintained: cable construction, entries and sealing, vibration, corrosion, seawater exposure, accessibility, and inspection evidence.
Open deck equipment and luminaires
Marine exposure and corrosive environments drive material choice and the entry system. For replacements, dimensional fit and thread compatibility can be as important as certification.
Instrumentation and Fire and Gas field devices
Rework often comes from interfaces: junction boxes, terminations, marshalling, shutdown devices, and evidence capture for verification.
Enclosures, JB locations, and cable routing
Enclosure type alone is not enough. Confirm terminals, earth bars, breathers and drains, IP rating, mounting hardware, and the correct gland system for the cable.
Dust exposure and Ex t considerations
Dust zones can be location-specific. Ex t selection depends on surface temperature, IP rating, ambient limits, and installation condition. Missed assumptions often fail inspection.
Diagram: Gas group and temperature class checks
Gas group affects ignition sensitivity. Temperature class limits maximum surface temperature. Standardisation can reduce mismatch risk, but certificate scope and installed conditions must still match.
Selection checklist used for fast quotation
For a fast, low-rework first pass, send a one-page summary with the items below. It reduces mismatch risk and speeds selection of equipment, entries, accessories, and documentation scope.
| Input | What to provide |
|---|---|
| Area summary | Hazardous area zone classification (gas and dust where applicable), gas group, temperature class, ambient conditions, and any dossier constraints. |
| Protection concept | Preferred protection concepts (for example Ex d, Ex e, Ex i, Ex t) plus any client or class constraints. |
| Cable data | Armoured or unarmoured, diameters, screens, and any EMC requirements (drives gland selection and accessories). |
| Material preference | Stainless, aluminium, or GRP, coatings, corrosion category, and material grade specifications. |
| Replacement evidence | Photos of nameplates and Ex markings, thread type, existing part numbers, and any fit-up constraints. |
| Close-out needs | Certificate pack expectations, tagging format, inspection evidence requirements, and document structure expected by the project. |
Ex marking decoder (project practical)
Ex marking is a compact summary of suitability. Selection should be checked against the certificate and installation notes, particularly for entries and glands, sealing method, ambient limits, and any special conditions.
What matters most for procurement
Match protection concept to the installation, confirm gas group and temperature class, confirm ambient range, and capture clear evidence of marking and configuration.
Where projects often slip
Entries and glands are treated as an afterthought. Offshore, the entry system and installation method drive most failures. Treat glands and accessories as part of the equipment selection.
Inspection-ready handover
A good package can be installed, inspected, and closed out without ambiguity. MurphyEx supports selection, supply, documentation, and installation or rectification support when required so close-out runs clean.
Evidence that supports inspection and acceptance
Nameplate evidence, certificate alignment, installation condition checks, and documented deviations linked to tag and location so verification does not stall.
Fewer late NCR triggers
Controls on entries and glands, enclosure condition, dust assumptions for Ex t, and consistent equipment standards reduce rework and close-out friction.
Send this for a fast response
Asset type and location, Hazardous area zone classification summary (gas and dust), gas group and temperature class, preferred protection concepts (including Ex t where applicable), cable types, material preference, and any existing part numbers. Add photos of nameplates and entries if it is a replacement or rectification scope.