How Does Extronics Inspect Flameproof Enclosures to Meet Ex d Requirements?

We inspect flameproof enclosures using GD&T (Geometric Dimensioning and Tolerancing) controlled verification, detailed flame path inspection, and calibrated measurement of threads and surface finishes to ensure full compliance with Ex d standards for explosion protection in hazardous areas.

The iWAP107 aluminium enclosure is one example of how this inspection process is applied in practice.

Inspection First: Our Approach to Flameproof Enclosures

At Extronics (BARTEC’s IoT and Connectivity Brand), inspection is a core part of how we deliver safe, compliant equipment.

Every flameproof enclosure is treated as a safety critical system, meaning each machined feature must perform exactly as intended to prevent ignition in hazardous areas.

Our process is built around key standards:

• BS EN 60079-0 – General requirements for equipment in explosive atmospheres.
• BS EN 60079-1 – Requirements specific to flameproof enclosures (Ex d).

Such standards define how flamepaths must behave, as well as surface finish, gap control, and thread engagement.

We apply these requirements using GD&T, ensuring every feature of the enclosure is measurable, repeatable, and compliant.

Why Flamepath Inspection Is Critical

In Ex d protection, a flameproof enclosure must contain an internal explosion and withstand the resulting explosion pressure, preventing it from igniting the surrounding atmosphere.

A flamepath is any route between the inside and outside of the enclosure. They include:

• Flange joints- the flat, machined surfaces where two parts of the enclosure meet and bolt together, forming a controlled gap that acts as a flame path.
• Threaded entries- machined holes with internal threads used for cable glands or stopping plugs, supporting inputs (power and data) and outputs (antenna).
• Machined interfaces- precisely machined surfaces or features where components fit together, contributing to the enclosure’s ability to contain and control internal pressure and flame propagation.

These paths control and cool escaping gases, but in a controlled way that cools them below ignition temperature.

If a flamepath is damaged, incorrectly machined, or out of tolerance, that protection is lost.

Flange Joints and Flamepath Surfaces

Flange joints are one of the most crucial flamepaths, formed by flat surfaces that meet to generate a controlled interface.

We inspect them to ensure:

• The surfaces are smooth and continuous.
• There are no gaps, dents, or protrusions (overhangs).
• The flamepath behaves exactly as defined in the standard.

No flamepath should allow energy to escape in a way that could cause ignition outside the enclosure.

Visual Inspection, Assessing Flamepath Condition

Visual inspection is important because it identifies issues that measurements alone may miss.

We use focused lighting (such as a torch) to examine Flamepaths for:

• Porosity- small holes in the material.
• Scratches or dents- that create escape paths for gases.
• Foreign object damage- trapped washers during assembly.
• Machining marks- signs of poor finishing.

Defects of this kind directly affect safety. Should a flamepath be compromised, the enclosure will be rejected.

Surface Finish Measurement, Making “Smooth” Measurable

Flamepaths must meet defined surface finish limits under BS EN 60079-1.

We measure this using a United Kingdom Accreditation Service (UKAS) calibrated surface finish tester, which drags a probe across the surface and records its profile.

Key measurements include:

• Ra (Average Roughness)– the overall smoothness of the surface.
• Rp (Peak Height)– the height of the highest point on the surface.

Why this matters:

• If the surface is too rough gases can escape too quickly.
• If peaks are too high surfaces may not seal correctly.

When a defect is found:

• Measurements are repeated (typically five times).
• The entire affected area is measured, not just a single point.

This ensures the results are accurate and representative.

Coating Inspection, Protecting Long-Term Integrity

The enclosure coating provides protection against corrosion in harsh environments.

We inspect for:

• Scratches or dents.
• Coating inconsistencies.
• Any exposed areas that could corrode.

Even small defects can develop into corrosion paths over time. Coatings are excluded from certified flamepath surfaces but inspected for environmental protection.

Threaded Entries as Flamepaths

Threads are an integral part of the flame path system, not just a mechanical feature.

Under BS EN 60079-1, threaded entries must:

• Have sufficient engagement length.
• Be correctly sized and formed.
• Prevent flame transmission.

We inspect for:

• Cracks or damage.
• Clean, complete thread profiles.
• Correct engagement length.

GO/NO-GO Gauges – Simple Tool, Vital Check

To verify thread size, we use GO/NO-GO plug gauges.

Here’s how they work:

GO gauge

• Should fully screw in.
• Confirms the thread is not too small.

NO-GO gauge

• Should not fully screw in.
• Confirms the thread is not too large.

This matters because:

• An oversized thread causes too much clearance, and gas can escape too easily.
• An undersized thread causes risk of damage or poor assembly.

Each threaded hole is checked individually to confirm it meets the required tolerance.

GD&T Verification – Ensuring Everything Lines Up

GD&T ensures that features are the correct size and in the correct position.

We verify:

• True position and runout checks: Is the feature located exactly where it should be?
• Perpendicularity: Is the hole drilled straight (90° to the surface)?

Misalignment can:

• Affect sealing.
• Reduce flame path effectiveness.
• Cause assembly issues.

These checks help deliver consistency across every enclosure produced.

Protection After Inspection

Following inspection, protective covers are applied to flame paths and threaded entries to prevent damage or contamination.

This is intended to:

• Prevent surface damage during handling.
• Avoid contamination from debris or dust.
• Safeguard critical surfaces prior to assembly.

Such protective measures preserve the flameproof enclosure’s verified condition through to final assembly and delivery.

Traceability and Compliance

Once inspection and protection are complete:

• Flame paths are covered for handling.
• A GII inspection (Inspection Compliance Record) sheet is completed.
• All inspection data is recorded in our ERP (Enterprise Resource Planning) system.

This provides:

• Full traceability.
• Evidence of compliance.
• A permanent inspection record.

Inspection as a Safety System

By combining:

• Standards-based requirements (BS EN 60079).
• GD&T-driven verification.
• Experienced inspection teams.

We ensure every flameproof enclosure performs as expected in hazardous environments.

If you require verified Ex d compliance and repeatable inspection processes, contact us to discuss your requirements.