IEC 60079-26 Explained: Equipment with Separation Elements

Most explosion-protected equipment is designed for a defined hazardous-area classification. Some equipment, however, is installed across a boundary where different explosion protection requirements apply to different parts of the equipment.

In these applications, the equipment design must account for the boundary between the different hazardous environments. The separation arrangement and the protection provided to each part must be suitable for the conditions in which that part operates.

IEC 60079-26 specifies additional requirements for equipment with separation elements and certain arrangements using combined Levels of Protection. It works with the general requirements of IEC 60079-0 and the applicable protection standards.

What Is IEC 60079-26?

IEC 60079-26 is part of the IEC 60079 series for equipment used in explosive atmospheres. It addresses specific equipment arrangements involving different Equipment Protection Levels (EPLs), separation elements, or defined combinations of protection.

The edition identified in this guide is IEC 60079-26:2021, Edition 4.0. Confirm the applicable edition against the project specification and the equipment certification documents before making a compliance decision.

IEC 60079-26 is not a standalone protection method equivalent to Ex d, Ex e or Ex i. Instead, it adds requirements for equipment configurations that fall within its scope.

What Is a Separation Element?

A separation element forms part of the equipment arrangement where different sections are subject to different explosion protection requirements.

It should not be treated as an ordinary mechanical partition. Its function and construction must be appropriate to the protection concept and the conditions on either side of the boundary.

The equipment must be assessed in its intended configuration. Evaluating two individual components separately does not, by itself, demonstrate that the complete assembly meets the applicable requirements.

Equipment Protection Level (EPL)

An Equipment Protection Level indicates the level of protection assigned to equipment for use in explosive atmospheres. The required EPL depends on the hazardous-area classification and the application.

Common EPL designations include:

Atmosphere	EPL Designations
Explosive gas atmospheres	Ga, Gb, Gc
Combustible dust atmospheres	Da, Db, Dc

The equipment installed on each side of a boundary must meet the requirements applicable to that location. The correct EPL cannot be selected from the physical boundary alone; the hazardous-area classification and equipment design must also be considered.

Related guide: Equipment Protection Level (EPL) Explained

Types of Boundary Applications

Gas-to-Gas Boundaries

Equipment may cross a boundary between gas hazardous areas with different protection requirements. The design must provide suitable protection for the relevant conditions on each side and maintain the required separation arrangement.

Dust-to-Dust Boundaries

Equipment can also be installed across boundaries between combustible dust hazardous areas. The assessment must account for the applicable dust protection requirements, including relevant dust characteristics and temperature limitations.

Gas-to-Dust Boundaries

A more specialized application occurs when equipment crosses between an explosive gas area and an adjacent combustible dust area.

Gas and dust atmospheres have different classification and equipment-protection considerations. The equipment arrangement must therefore address the applicable requirements for both environments.

These examples describe boundary situations addressed by IEC 60079-26; they do not mean that every product crossing a Zone boundary automatically requires the same construction. The applicable requirements depend on the actual equipment configuration and standard scope.

Combined Levels of Protection

IEC 60079-26 also addresses specified arrangements that combine protection levels. The 2021 edition includes requirements for combining two Types of Protection, each with EPL Gb, to achieve EPL Ga.

This is a defined engineering and certification arrangement. Two EPL Gb protection methods do not automatically become EPL Ga simply because both are present in one assembly.

Electrical and Non-Electrical Equipment

IEC 60079-26:2021 covers electrical and non-electrical equipment within its scope. This distinction matters because mechanical equipment can also present potential ignition sources.

For non-electrical equipment, ignition hazard assessment may be required in accordance with ISO 80079-36, depending on the equipment and applicable requirements.

The assessment should consider the complete equipment configuration, including relevant electrical and mechanical ignition hazards, rather than focusing only on electrical components.

Relationship With IEC 60079-0 and Other Standards

IEC 60079-0 establishes general requirements for Ex equipment. IEC 60079-26 supplements and modifies those requirements for equipment within its scope. Where provisions conflict, the applicable requirements of IEC 60079-26 take precedence for the matters it specifically addresses.

Standard	Primary Subject
IEC 60079-0	General requirements for Ex equipment.
IEC 60079-1	Flameproof enclosure protection “d”.
IEC 60079-5	Powder filling protection “q”.
IEC 60079-6	Liquid immersion protection “o”.
IEC 60079-7	Increased safety protection “e”.
IEC 60079-11	Intrinsic safety protection “i”.
IEC 60079-18	Encapsulation protection “m”.
IEC 60079-26	Equipment with separation elements or specified combined Levels of Protection.

The applicable protection standard or standards depend on the equipment design. IEC 60079-26 does not replace the requirements of the protection method used by the equipment.

Construction and Testing Considerations

Equipment within the scope of IEC 60079-26 must be assessed as a complete arrangement. The detailed requirements depend on the selected protection concept and equipment configuration.

Engineering review may need to consider:

• The required EPL for each relevant equipment section.
• The location and function of the separation element.
• The applicable Types of Protection.
• Electrical and mechanical interfaces between sections.
• Relevant ignition hazards and operating conditions.
• The tests and assessments required by the applicable standards.
• The complete assembly and its certification scope.

The specific construction and testing requirements must be taken from the applicable standard and certification documents. A generic checklist cannot establish conformity.

Marking and Certification

Ex marking and certification provide the information needed to assess whether equipment is suitable for its intended hazardous-area application.

When reviewing equipment involving separation elements or combined protection levels, check:

• The complete Ex marking.
• The EPL and equipment group applicable to the installation.
• The Type or Types of Protection used.
• Temperature classification or maximum surface temperature, as applicable.
• Ambient temperature limits.
• The certificate number and certified model or configuration.
• Any specific conditions of use, including conditions identified by an “X” suffix.
• The manufacturer's installation and operating instructions.

The marking should be reviewed together with the certificate and technical documentation. An Ex marking alone does not prove that the equipment is suitable for every boundary arrangement.

Practical Engineering Review Checklist

Review Item	What to Verify
Area classification	Hazardous-area classification on each side of the boundary.
Required EPL	Required protection level for each relevant equipment section.
Boundary location	Physical location of the boundary relative to the equipment.
Separation element	Function and construction as defined by the certified design.
Protection concept	Applicable Types of Protection for the equipment arrangement.
Interfaces	Relevant electrical and mechanical interfaces.
Ignition hazards	Potential electrical and mechanical ignition sources.
Temperature	Applicable temperature limits for the atmosphere and equipment.
Certification	Certificate scope, model designation and equipment configuration.
Specific conditions	Conditions for safe use and installation.

Procurement and Technical Bid Evaluation

For EPC and procurement teams, the main task is to establish that the offered equipment is certified for the actual application, including the boundary arrangement where different EPLs are required.

During technical bid evaluation, review:

• Compliance with the applicable IEC 60079 standards.
• Complete Ex marking and required EPLs.
• The separation element or combined protection arrangement.
• The equipment certificate and its scope.
• Manufacturer's technical documentation.
• Installation requirements and specific conditions of use.

Do not evaluate the offer solely on the basis of a general Ex certificate or a datasheet statement. The certificate and supporting documents must cover the actual model and protection arrangement being offered.

Inspection and Maintenance

After installation, the equipment must remain in the certified configuration. Inspection should identify damage, unauthorized modifications or other changes that could compromise the protection arrangement.

Relevant checks depend on the equipment design and may include:

• Mechanical damage to the equipment or separation arrangement.
• Unauthorized changes to the assembly.
• Damage to interfaces or sealing arrangements, where applicable.
• Changes to cable or process connections that affect the certified design.
• Evidence of overheating or abnormal operation.

Maintenance and repair should follow the manufacturer's instructions and the applicable inspection and maintenance requirements of the IEC 60079 series.

Common Misunderstandings

IEC 60079-26 Is Only About EPL Ga

No. The standard addresses equipment with separation elements and specified combined protection arrangements. The EPL Gb-to-Ga combination is one particular application.

A Separation Element Is Just a Mechanical Partition

Not necessarily. It forms part of the protection arrangement and must meet the requirements applicable to the certified design.

Two EPL Gb Protection Methods Automatically Achieve EPL Ga

No. The combined arrangement must comply with IEC 60079-26. The result cannot be inferred from the labels alone.

IEC 60079-26 Applies Only to Electrical Equipment

No. The 2021 edition covers electrical and non-electrical equipment within its scope.

Any Ex Equipment Can Cross a Hazardous-Area Boundary

No. Suitability depends on the equipment design, hazardous-area conditions, required EPLs and applicable certification.

Frequently Asked Questions

What is IEC 60079-26?

IEC 60079-26 specifies requirements for equipment with separation elements or defined combinations of Levels of Protection in explosive atmospheres.

What is a separation element?

It is a part of an equipment arrangement that provides the required separation between sections subject to different protection requirements.

Does IEC 60079-26 cover gas-to-dust boundaries?

Yes. Its scope includes equipment mounted across boundaries involving gas hazardous areas and adjacent dust hazardous areas, as well as relevant gas-to-gas and dust-to-dust boundaries.

Can two EPL Gb protection types achieve EPL Ga?

IEC 60079-26 specifies requirements for certain arrangements combining two Types of Protection, each with EPL Gb, to achieve EPL Ga. Compliance with the standard is necessary; the result is not automatic.

Does IEC 60079-26 cover non-electrical equipment?

Yes. IEC 60079-26:2021 includes electrical and non-electrical equipment within its scope.

Conclusion

IEC 60079-26 addresses specialized Ex equipment arrangements involving separation elements or defined combinations of protection levels. It is particularly relevant where equipment crosses hazardous-area boundaries or where a specified combination of protection methods is used.

For engineering and procurement teams, the essential checks are the hazardous-area conditions, required EPLs, certified equipment configuration, separation arrangement and applicable protection standards. The complete assembly must be suitable for the intended installation and supported by the appropriate certification and documentation.

Related Reading

• Equipment Protection Level (EPL) Explained
• Zone 0 vs Zone 1 vs Zone 2
• Zone 20 vs Zone 21 vs Zone 22
• IEC 60079-10-2 Explained: Classification of Combustible Dust Areas
• IEC 60079-1 Explained: Flameproof Enclosure “d” Protection
• IEC 60079-7 Explained: Increased Safety “e” Protection
• IEC 60079-11 Explained: Intrinsic Safety “i” Protection

References

• IEC 60079-26:2021 — Explosive atmospheres – Part 26: Equipment with Separation Elements or combined Levels of Protection.
• IEC 60079-0 — Explosive atmospheres – Part 0: Equipment – General requirements.
• ISO 80079-36 — Explosive atmospheres – Part 36: Non-electrical equipment for explosive atmospheres – Basic method and requirements.