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CAN/CSA C22.2 No. 60079-1-16: A Technical Guide to Flameproof Enclosures for Hazardous Locations
Understanding the Requirements for Equipment Protection by Flameproof Enclosures ‘d’ in the Canadian Electrical Code Framework
Scope
CAN/CSA C22.2 No. 60079-1-16 is the Canadian adoption of the international standard IEC 60079-1, Edition 7.0 (2014), titled Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures “d”. Published by the Canadian Standards Association (CSA Group) as part of the C22.2 series of standards for electrical equipment, this standard specifies the construction, testing, and marking requirements for electrical equipment protected by flameproof enclosures intended for use in explosive gas atmospheres.
The primary principle of flameproof protection is to contain an internal explosion and prevent the propagation of the flame to the surrounding explosive atmosphere. The enclosure must withstand the pressure of an internal explosion without rupturing, and its joints must be designed such that escaping hot gases are cooled sufficiently to prevent ignition of the external atmosphere.
The standard applies to all electrical equipment that employs a flameproof enclosure as a means of protection, including motors, lighting, junction boxes, and control stations. It covers gas groups IIA, IIB, and IIC (acetylene and hydrogen) and assigns Equipment Protection Levels (EPL) Da, Db, and Dc, corresponding to Zones 0, 1, and 2 respectively. It does not apply to dusts or hybrid mixtures, which are covered under separate standards.
Technical Requirements
The technical requirements of CAN/CSA C22.2 No. 60079-1-16 are comprehensive and build upon the general requirements of IEC 60079-0. Key areas include:
Construction
Flameproof enclosures must be made from materials that are resistant to the expected mechanical, thermal, and chemical stresses. The enclosure must have a minimum ingress protection rating of IP54. Joints are designed in one of several configurations: flanged, threaded, or cylindrical (spigot). Each joint type has specific dimensional requirements for gap, length, and surface roughness.
Joints and Gaps
The standard defines maximum permissible gap widths based on the volume of the enclosure, the gas group, and the length of the flameproof joint. A typical table for flanged joints is reproduced below.
| Gas Group | Enclosure Volume V (cm³) | Minimum Joint Length L (mm) | Maximum Gap Width i (mm) |
|---|---|---|---|
| IIA | V ≤ 100 | 12.5 | 0.30 |
| IIA | V > 100 | 25 | 0.40 |
| IIB | V ≤ 100 | 12.5 | 0.20 |
| IIB | V > 100 | 25 | 0.25 |
| IIC | V ≤ 100 | 12.5 | 0.10 |
| IIC | V > 100 | 25 | 0.15 |
Table 1 – Example of maximum gap widths for flanged joints (gap length L = 25 mm or 12.5 mm as indicated). Actual values in the standard vary with joint configuration and material.
Overpressure and Explosion Testing
Each enclosure design must undergo type testing to verify its ability to withstand the explosion pressure. The reference pressure is determined by igniting the most explosive mixture inside the enclosure. The enclosure must then pass an overpressure test at 1.5 times the reference pressure. For non-metallic enclosures, additional pressure tests at elevated temperatures are required.
Temperature Requirements
The equipment must not exceed the temperature class (T1–T6) determined by the maximum surface temperature. The standard specifies test conditions for determining thermal stability and maximum temperatures.
Cable Entries
Cable entries and conduit entries must maintain the flameproof integrity. They must be tested to the same pressure requirements and may require sealing compounds or certified flameproof cable glands.
Tip: When designing flameproof joints, always consult the maximum experimental safe gap (MESG) for the specific gas group. IIC group requires extremely tight tolerances – a minor scratch on the gap surface can render the joint ineffective.
Implementation Highlights
Implementing CAN/CSA C22.2 No. 60079-1-16 requires careful integration of design, manufacturing, and quality assurance processes. The following points are critical for successful implementation:
Design for Manufacturability
Flameproof enclosures often require precise machining of flanges and threaded elements. The designer must account for tolerances that ensure the maximum gap is never exceeded over the life of the equipment, including after thermal cycling and mechanical wear. Gaskets are generally not permitted for the flameproof function; compressible seals should not be relied upon to meet the gap requirements.
Testing and Certification
All new designs must undergo type testing by an accredited laboratory. CSA Group is a primary certification body in Canada, but other NTRL/NRTLs such as Intertek and UL are also recognized. Routine production tests include a pressure test on every enclosure and verification of gap dimensions.
Marking
The equipment must be marked with the protection concept (Ex db, Ex db eb, etc.), the gas group, temperature class, EPL, and certificate number. The marking must be durable and legible. Canadian adoptions may also require the CSA mark and the C22.2 number.
Documentation
A technical file must be compiled containing drawings, calculations, material certificates, test reports, and instructions for safe use. The manufacturer must provide detailed installation and maintenance instructions.
Compliance Success: Products fully compliant with CAN/CSA-C22.2 No. 60079-1-16 are accepted across all Canadian provinces and territories under the Canadian Electrical Code (CE Code). This streamlines market access and reduces duplication of testing.
Compliance Notes
Adherence to CAN/CSA C22.2 No. 60079-1-16 is mandatory for any electrical equipment installed in Class I hazardous locations in Canada. While the standard is technically identical to IEC 60079-1, there are important Canadian-specific considerations:
- Jurisdictional adoption: Each province and territory enforces the CE Code as regulation. Compliance with the CSA C22.2 series is considered a means of meeting the Code requirements.
- Certification body requirements: Certification must be carried out by an organization accredited by SCC (Standards Council of Canada).
- Canadian deviations: The C22.2 version may include national differences, such as requirements for conductor sizes, ambient temperature ranges, and conductor materials.
- Field modifications: Any repair or modification that affects the flameproof joint gap, enclosure strength, or cable entries requires re-certification.
- Maintenance: Regular inspection of flameproof joints is essential. Joints must be kept clean and free from paint, rust, and debris.
Warning: Never install a flameproof enclosure with missing or damaged bolts. The rated internal pressure resistance depends on the clamping force of the fasteners. Use only fasteners with the specified strength grade and corrosion protection.
For manufacturers exporting to Canada, it is not sufficient to have an IECEx or ATEX certificate alone; a separate certification to the Canadian adoption is required. However, if the design already meets IEC 60079-1, the incremental work to gain CSA certification is often minimal, involving only verification of national deviations and submission of the technical file to a Canadian-recognized body.
Critical: The use of compressible gaskets or O-rings on flameproof joints is strictly prohibited unless they are specifically tested and shown not to compromise the gap dimensions under any service condition. Most gaskets will compress over time, increasing the gap beyond the safe limit.
Frequently Asked Questions
Q: What is the difference between “Ex d” and “Ex db” protection levels?
A: “Ex d” is a broad designation for flameproof enclosures. With the introduction of Equipment Protection Levels (EPL) in Edition 7 of IEC 60079-1, “Ex db” indicates a protection level suitable for Zone 1 (EPL Gb), while “Ex dc” is for Zone 2 (EPL Gc). “Ex da” is for Zone 0 applications but is rarely used due to stringent requirements. CAN/CSA C22.2 No. 60079-1-16 includes all three levels.
A: “Ex d” is a broad designation for flameproof enclosures. With the introduction of Equipment Protection Levels (EPL) in Edition 7 of IEC 60079-1, “Ex db” indicates a protection level suitable for Zone 1 (EPL Gb), while “Ex dc” is for Zone 2 (EPL Gc). “Ex da” is for Zone 0 applications but is rarely used due to stringent requirements. CAN/CSA C22.2 No. 60079-1-16 includes all three levels.
Q: Is a product certified to IEC 60079-1 automatically acceptable in Canada?
A: No. While CAN/CSA C22.2 No. 60079-1-16 is technically identical to IEC 60079-1, Canadian regulations require certification according to the Canadian adoption by a recognized certification body. However, manufacturers can often leverage existing IEC test data to expedite CSA certification.
A: No. While CAN/CSA C22.2 No. 60079-1-16 is technically identical to IEC 60079-1, Canadian regulations require certification according to the Canadian adoption by a recognized certification body. However, manufacturers can often leverage existing IEC test data to expedite CSA certification.
Q: What are the main changes in Edition 7 compared to earlier editions?
A: Edition 7 introduced the EPL classification system (da, db, dc), aligned with the IEC 60079-0 general requirements. It also tightened gap requirements for IIC group (from 0.15 mm to 0.10 mm for some configurations) and introduced more rigorous testing for non-metallic enclosures.
A: Edition 7 introduced the EPL classification system (da, db, dc), aligned with the IEC 60079-0 general requirements. It also tightened gap requirements for IIC group (from 0.15 mm to 0.10 mm for some configurations) and introduced more rigorous testing for non-metallic enclosures.
Q: Can I use an O-ring to seal a flameproof joint for weather protection?
A: Yes, but only if the O-ring is confined to a separate groove and does not influence the flameproof gap dimensions. The primary flameproof path must still be the metal-to-metal joint meeting the standard’s gap and length requirements. The O-ring must be for weather protection only and not counted as part of the flameproof function.
A: Yes, but only if the O-ring is confined to a separate groove and does not influence the flameproof gap dimensions. The primary flameproof path must still be the metal-to-metal joint meeting the standard’s gap and length requirements. The O-ring must be for weather protection only and not counted as part of the flameproof function.
Conclusion
CAN/CSA C22.2 No. 60079-1-16 is a critical standard for ensuring safety in hazardous locations in Canada. By specifying rigorous design, testing, and marking requirements for flameproof enclosures, it provides a high level of protection against explosions in gas atmospheres. Engineers and manufacturers must pay close attention to joint design, material selection, and production testing to achieve and maintain compliance. With the adoption of the latest IEC edition, the standard continues to align with international best practices while meeting Canadian regulatory needs. Consulting with a recognized certification body early in the design process is strongly recommended.
© 2026 – This article is provided for informational purposes and does not constitute legal or certification advice. For official compliance, always refer to the latest published edition of CAN/CSA C22.2 No. 60079-1-16 and consult with an accredited certification body.