Deployment Strategies for Explosion-Proof Instruments in Hazardous Environments

In industries such as oil & gas, chemical processing, mining, and grain handling, hazardous environments are a daily reality. Flammable gases, combustible dust, and volatile vapors can turn a minor spark into a catastrophic event. Explosion-proof (Ex d) instruments are engineered to contain internal explosions and prevent ignition of the surrounding atmosphere—but their safety depends as much on how they are deployed as on their design.

This article outlines key strategies for installing and maintaining explosion-proof instruments to ensure safety, compliance, and long-term reliability.

1. Understand the Hazardous Area Classification

Before selecting or installing any instrument, determine the hazardous area zone or division:

• Zone 0 / Class I, Division 1 – Continuous presence of explosive atmosphere.
• Zone 1 / Class I, Division 1 – Likely presence during normal operation.
• Zone 2 / Class I, Division 2 – Unlikely presence, and if present, only for short periods.

Matching the instrument’s certification (ATEX, IECEx, UL, FM) to the correct zone is the first step toward safe deployment.

2. Choose the Right Protection Method

Explosion-proof instruments are one of several protection concepts:

• Explosion-Proof / Flameproof (Ex d) – Enclosure contains any internal explosion and cools escaping gases below ignition temperature.
• Intrinsic Safety (Ex i) – Limits electrical and thermal energy to safe levels, preventing ignition entirely.
• Pressurization (Ex p) – Maintains a protective gas inside the enclosure to prevent ingress of explosive atmosphere.

In some cases, combining methods (e.g., Ex d enclosure with intrinsically safe signal circuits) offers optimal safety and flexibility.

3. Installation Best Practices

1. Seal Fittings and Conduits – Install explosion-proof seal fittings within 18 inches of the enclosure to prevent flame propagation through wiring systems.
2. Cable Selection – Use armored or shielded cables rated for hazardous locations; avoid cable types that can transmit gases through the core.
3. Mounting Location – Position instruments away from high-vibration zones, direct heat sources, and areas prone to mechanical impact.
4. Ingress Protection – Ensure enclosures meet IP66 or higher for dust and water resistance in harsh environments.
5. Accessibility – Allow safe access for calibration, inspection, and maintenance without compromising safety barriers.

4. Grounding and Bonding

Proper grounding ensures that any fault current or static discharge is safely dissipated:

• Bond all metallic parts to a common ground grid.
• Avoid multiple ground points that can create loops.
• Verify continuity during commissioning and periodic inspections.

5. Maintenance and Inspection

Explosion-proof systems require regular inspection to remain compliant:

• Visual checks – Look for cracks, corrosion, or missing fasteners on enclosures.
• Seal integrity – Verify that gaskets and flame paths are intact and free of debris.
• Certification labels – Ensure markings remain legible for audits and inspections.
• Functional testing – Confirm that instruments operate within specified parameters.