Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
IEC 62708: Electrical Equipment for Hazardous Areas in the Oil and Gas Industry
Document requirements and best practices for electrical installations in petroleum, petrochemical, and natural gas facilities
IEC 62708, published in 2015, provides comprehensive requirements and recommendations for electrical equipment and installations in hazardous areas within the oil and gas industry. Developed by IEC Technical Committee 18 (Electrical Installations of Ships and of Mobile and Fixed Offshore Units) in collaboration with TC 31 (Equipment for Explosive Atmospheres), this standard bridges the gap between general hazardous area standards and the specific operational realities of upstream, midstream, and downstream petroleum facilities. The scope covers onshore facilities such as refineries, petrochemical plants, natural gas processing plants, and oil and gas production facilities, as well as offshore platforms, FPSO vessels, and floating LNG facilities.
The standard addresses the entire lifecycle of electrical equipment in hazardous areas, from initial concept design through procurement, installation, inspection, maintenance, and eventual decommissioning. This holistic approach is particularly valuable for large capital projects where multiple engineering contractors and equipment suppliers must work to consistent requirements to ensure the overall safety of the installation. The document is structured to align with the IEC 60079 series (Explosive Atmospheres) and IEC 61892 series (Mobile and Fixed Offshore Units), extending their requirements with industry-specific guidance developed from decades of operational experience in the oil and gas sector.
IEC 62708 applies to all voltage levels and covers both fixed and portable electrical equipment. It recognizes the full range of explosion protection techniques including flameproof enclosures (Ex d), increased safety (Ex e), intrinsic safety (Ex i), pressurization (Ex p), encapsulation (Ex m), powder filling (Ex q), oil immersion (Ex o), and non-sparking (Ex nA) protection concepts. The standard provides specific guidance on which protection techniques are most appropriate for different types of equipment and different zone classifications within oil and gas facilities.
Essential Requirements for Equipment Selection and Installation
The standard establishes a systematic framework for equipment selection based on the area classification, equipment protection level (EPL), and the specific gas or vapor group present. For Zone 0 locations — where explosive gas atmospheres are present continuously or for long periods — equipment must be certified to EPL Ga, which provides the highest level of protection such that the equipment cannot become an ignition source even under rare malfunction conditions. Only Ex ia intrinsic safety, Ex s (special protection) with equivalent safety level, or encapsulated systems meeting specific criteria are permitted in these areas. For Zone 1 locations, where explosive atmospheres are likely to occur in normal operation, EPL Gb equipment is required, including Ex d (flameproof), Ex e (increased safety), Ex ib, Ex p (pressurization), and Ex m (encapsulation) protected equipment. Zone 2 requires EPL Gc equipment including Ex nA, Ex nC, and Ex nL protected apparatus.
Cable installation requirements are given particular attention in the standard, reflecting the fact that cable systems represent the most extensive electrical component in any oil and gas facility. The standard specifies minimum armoring requirements for power, control, and instrumentation cables based on the mechanical risks present in different areas of the facility. For offshore installations, all fixed cables must be armored with galvanized steel wire or stainless steel braid, with additional mechanical protection at all termination points. Cable penetrations through rated divisions must maintain the fire integrity of the structure, requiring approved firestop systems tested to IMO Resolution A.754 or equivalent standards. The standard also specifies segregation requirements between power and instrumentation cables to minimize electromagnetic interference and maintain signal integrity in critical safety systems.
| Zone | EPL | Permitted Protection Concepts | Typical Equipment |
|---|---|---|---|
| Zone 0 | Ga | Ex ia, Ex s (equivalent safety) | Level sensors, gas detectors, emergency shutdown transmitters |
| Zone 1 | Gb | Ex d, Ex e, Ex ib, Ex p, Ex m, Ex o, Ex q | Motors (Ex d or Ex n), lighting fixtures, junction boxes (Ex e), solenoid valves |
| Zone 2 | Gc | Ex nA, Ex nC, Ex nL, Ex ec, Ex ic | Standard motors with certification, switchgear, analyzers, HVAC equipment |
| Zone 20/21/22 | Da/Db/Dc | Ex tD, Ex iD, Ex mD, Ex pD | Dust ignition-proof equipment for catalyst handling, solids processing areas |
Grounding and bonding receive extensive treatment in the standard. All metallic cable sheaths, armor, conduit, and equipment enclosures must be bonded to the equipotential grounding system to prevent sparking under fault conditions. The standard requires that the grounding conductor cross-section be sized to carry the full fault current for the duration required to clear the fault, with minimum sizes specified based on the upstream protective device rating. For offshore installations, the standard references the requirements for hull return currents, which must be strictly limited to prevent corrosion of the steel structure and avoid ignition risks in hazardous areas.
A common failure mode in oil and gas electrical installations is the degradation of cable gland and junction box seals due to temperature cycling, UV exposure, and chemical attack. IEC 62708 requires that all cable entries maintain the ingress protection (IP) rating of the equipment enclosure, which for outdoor hazardous area installations must be at least IP56 per IEC 60529. Annual thermographic surveys of all Ex d junction boxes and motor terminal boxes are recommended to detect incipient connection degradation before it leads to excessive temperature rise and potential ignition.
Inspection, Maintenance, and Engineering Design Insights
The standard divides inspection activities into three categories: initial inspection (before putting into service), periodic inspection (at intervals based on the equipment type, protection concept, and environmental conditions), and continuous supervision by competent personnel during operation. The inspection intervals are linked to the equipment protection level, with EPL Ga equipment requiring more frequent inspection (typically every 6-12 months) than EPL Gc equipment (up to 36 months in benign environments). The standard provides detailed checklists for each protection concept, including verification of flameproof joint gaps, integrity of increased safety terminal connections, intrinsic safety parameters, and pressurization system interlocks.
A key innovation of IEC 62708 is the requirement for a documented explosion protection document (EPD) for each installation, similar to the ATEX 137 requirements in European regulation. This document must demonstrate that all explosion risks have been identified and adequately addressed, including the area classification drawings, equipment selection documentation, installation records, inspection and maintenance schedules, and training qualifications of personnel. For existing installations being modified or extended, the EPD must be updated to reflect the current condition of the facility, and a formal management of change procedure must be followed to ensure that modifications do not introduce new ignition risks or compromise existing protection measures.
From an engineering design perspective, several key considerations emerge from the standard. First, the routing of cables in hazardous areas must minimize the length of cable runs through Zone 0 and Zone 1 locations, with transition to non-hazardous areas as soon as practical. Second, the thermal rating of equipment must be carefully evaluated under all operating conditions, including high ambient temperatures common in Middle Eastern and tropical installations where ambient temperatures of 50-55 deg C are not unusual. Third, emergency shutdown (ESD) and fire and gas (F&G) safety system equipment must meet the highest integrity level appropriate for the application, with SIL 2 or SIL 3 certification per IEC 61508 for critical process safety functions. Fourth, the standard emphasizes the importance of competence management for all personnel involved in hazardous area electrical work, requiring documented training and authorization procedures that align with the IEC 60079-17 requirements for inspection personnel and IEC 60079-14 for installation designers.
| Equipment Type | Protection Concept | Normal Environment | Severe Environment |
|---|---|---|---|
| Flameproof (Ex d) | Enclosure integrity, joint gaps | 12 months | 6 months |
| Increased Safety (Ex e) | Terminal tightness, clearance | 18 months | 12 months |
| Intrinsic Safety (Ex i) | Parameter verification, cable integrity | 12 months | 6 months |
| Pressurization (Ex p) | Pressure interlocks, purge flow | 6 months | 3 months |
| Non-sparking (Ex nA) | General visual inspection | 36 months | 18 months |
A well-designed hazardous area electrical installation following IEC 62708 principles can achieve zero ignition incidents over decades of operation. The systematic framework linking zone classification, equipment selection, protection concepts, installation quality, and inspection frequency provides defense-in-depth against potential ignition sources. Global industry statistics show that properly designed and maintained Ex installations have a failure rate of less than 0.01 incidents per installation-year, compared to 0.1-0.5 for installations where basic requirements are neglected.
Q1: What is the relationship between IEC 62708 and the IEC 60079 series?
A: IEC 62708 is an application-specific standard that builds upon the general requirements of the IEC 60079 series. While IEC 60079 defines the protection concepts, equipment construction requirements, and basic installation rules, IEC 62708 provides additional industry-specific guidance for oil and gas applications including offshore platforms, FPSOs, refineries, and petrochemical plants. It extends the general rules with operational knowledge from decades of experience in the petroleum sector and addresses scenarios not fully covered by the base standards, such as mixed hydrocarbon-hydrogen service, high-temperature process areas, and the unique challenges of floating production facilities subject to continuous motion and vibration.
A: IEC 62708 is an application-specific standard that builds upon the general requirements of the IEC 60079 series. While IEC 60079 defines the protection concepts, equipment construction requirements, and basic installation rules, IEC 62708 provides additional industry-specific guidance for oil and gas applications including offshore platforms, FPSOs, refineries, and petrochemical plants. It extends the general rules with operational knowledge from decades of experience in the petroleum sector and addresses scenarios not fully covered by the base standards, such as mixed hydrocarbon-hydrogen service, high-temperature process areas, and the unique challenges of floating production facilities subject to continuous motion and vibration.
Q2: Does IEC 62708 cover equipment for hydrogen sulfide (H2S) service?
A: Yes, the standard specifically addresses the additional challenges posed by sour service environments containing H2S. This includes requirements for hydrogen-induced cracking (HIC) resistant materials for metallic components, enhanced sealing to prevent H2S ingress into equipment enclosures, and specific material selection criteria for wetted parts of electrical equipment in sour gas processing areas. Equipment for H2S service must also meet NACE MR0175/ISO 15156 requirements as referenced by the standard.
A: Yes, the standard specifically addresses the additional challenges posed by sour service environments containing H2S. This includes requirements for hydrogen-induced cracking (HIC) resistant materials for metallic components, enhanced sealing to prevent H2S ingress into equipment enclosures, and specific material selection criteria for wetted parts of electrical equipment in sour gas processing areas. Equipment for H2S service must also meet NACE MR0175/ISO 15156 requirements as referenced by the standard.
Q3: What are the key differences between onshore and offshore requirements in IEC 62708?
A: Offshore installations face more stringent requirements due to the confined space, limited escape routes, higher vibration levels, saltwater corrosion environment, and the criticality of continuous operation. Specific offshore provisions include: mandatory armored cables for all fixed installations, enhanced emergency shutdown system requirements, stricter zoning for enclosed modules, additional corrosion protection for all exposed metallic components, and more frequent inspection intervals (typically 50% of onshore intervals). The standard also requires that all offshore hazardous area equipment be designed for the motion, inclination, and dynamic loading conditions characteristic of floating installations.
A: Offshore installations face more stringent requirements due to the confined space, limited escape routes, higher vibration levels, saltwater corrosion environment, and the criticality of continuous operation. Specific offshore provisions include: mandatory armored cables for all fixed installations, enhanced emergency shutdown system requirements, stricter zoning for enclosed modules, additional corrosion protection for all exposed metallic components, and more frequent inspection intervals (typically 50% of onshore intervals). The standard also requires that all offshore hazardous area equipment be designed for the motion, inclination, and dynamic loading conditions characteristic of floating installations.
Q4: How does IEC 62708 address the competence of personnel working in hazardous areas?
A: The standard dedicates an entire section to competence management, requiring that all personnel involved in the design, installation, inspection, and maintenance of hazardous area electrical equipment have documented training and authorization. Competence levels are defined for five roles: responsible person, technical authority, designer, installer, and inspector. Each role requires specific training modules covering area classification principles, protection concept theory, installation practice, inspection techniques, and management of change procedures. The standard recommends competence reassessment at intervals not exceeding three years.
A: The standard dedicates an entire section to competence management, requiring that all personnel involved in the design, installation, inspection, and maintenance of hazardous area electrical equipment have documented training and authorization. Competence levels are defined for five roles: responsible person, technical authority, designer, installer, and inspector. Each role requires specific training modules covering area classification principles, protection concept theory, installation practice, inspection techniques, and management of change procedures. The standard recommends competence reassessment at intervals not exceeding three years.
