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PD IEC TS 60079 — Explosive Atmospheres Technical Specifications
Explosive Atmospheres — IEC/TS 60079-32-1 / 60079-39 / 60079-40 (BSI UK implementation)
💥 PD IEC TS 60079 is the UK implementation, published by BSI, of several technical specifications (TS) in the IEC 60079 series, prepared by UK Technical Committee EXL/31 (Equipment for explosive atmospheres) and specifically addressing equipment safety and protection in explosive atmospheres. The three parts in this batch are: Part 32-1, guidance on electrostatic hazards; Part 39, intrinsically safe systems with electronically controlled spark duration limitation (the Power-i technology); and Part 40, requirements for process sealing between flammable process fluids and electrical systems. These address three key explosion-protection areas — static electricity, intrinsically safe power supply, and process sealing — and are an important basis for electrical safety design and certification in hazardous areas such as oil, chemical, and pharmaceutical plants.
💡 In explosive atmospheres, electrical equipment can be an ignition source. The IEC 60079 series prevents ignition of explosive gas/dust by electric sparks, static discharge, or high temperature through requirements on equipment construction, electrical parameters, and installation — it is the foundational standard system for explosion-protection electrical safety.
1. Series Overview 📌
IEC 60079 is the comprehensive series on safety of equipment for explosive atmospheres, covering explosion-protection types such as flameproof (d), increased safety (e), intrinsic safety (i), and pressurised (p), as well as equipment classification, zone classification, and installation/maintenance requirements. Within the IEC 60079 framework, in addition to the normative main standards, technical specifications (TS) provide detailed rules on specific technical issues. BSI adopts them as “PD IEC/TS 60079-xxx”, serving explosion-protection certification (e.g., ATEX, IECEx) in the UK and international markets.
The three parts here — 32-1, 39, and 40 — are technical specifications, each protecting explosive atmospheres from a different angle: electrostatic ignition protection, energy limitation of intrinsically safe systems, and process-to-electrical isolation sealing.
2. Series Structure and Part Highlights 📋
| Part | Document Title | IEC Edition | Core Content |
|---|---|---|---|
| Part 32-1 | Electrostatic hazards, guidance | IEC/TS 60079-32-1:2013 (Ed. 1.0) | Protection against electrostatic accumulation and discharge in solids, liquids, and dusts: conductive/dissipative material substitution, earthing, ionisation, humidification, etc. |
| Part 39 | Intrinsically safe systems with electronically controlled spark duration limitation | IEC TS 60079-39:2015 (Ed. 1.0) | Power-i architecture, intrinsically safe source, field devices, wiring, terminator, application classes, and system verification |
| Part 40 | Requirements for process sealing between flammable process fluids and electrical systems | IEC TS 60079-40:2015 (Ed. 1.0) | Single/dual process seal equipment, limited-pressure equipment, pressurised equipment, add-on secondary seals, annunciators, and type verification tests |
All three parts are classified under ICS 29.260.20 (Electrical apparatus for explosive atmospheres) and handled by the same UK technical committee EXL/31. They are mutually complementary and together support explosion-protection safety.
⚠️ It should be noted that technical specifications (TS) are documents at an earlier stage in the standards process, requiring further practical validation. Their technical requirements are detailed, but in some countries or regions they may not yet be mandatory standards. Engineering application should also consider local regulations (e.g., ATEX directives, hazardous-area classification).
3. Key Technical Requirements 🔧
1. Electrostatic Hazard Guidance (Part 32-1)
Static electricity is a common yet hidden ignition source in explosive atmospheres. Part 32-1 systematically gives protection methods for electrostatic hazards in solid materials, liquids, and dusts, mainly including:
- Substituting conductive or dissipative materials for insulating ones: replacing insulating materials that accumulate static with conductive or static-dissipative materials, and reliably earthing conductive/dissipative items;
- Restrictions on insulating materials: limiting the size of chargeable insulating surfaces, using earthed metal meshes, applying insulating coatings on earthed conductive surfaces, and applying conductive/dissipative coatings on insulating materials;
- Other measures: using static dissipative agents, humidification, ionisation/charge neutralisation, etc., to reduce static accumulation;
- Process and equipment design recommendations: specific advice for liquid transfer, powder handling, vessels and piping to prevent electrostatic discharge.
2. Intrinsically Safe Systems with Electronically Controlled Spark Duration Limitation (Part 39)
Traditional intrinsic safety (Ex i) prevents ignition by limiting circuit energy (voltage, current, capacitance, inductance) so that any spark produced under fault conditions cannot ignite the explosive gas. Part 39 introduces the “Power-i” technology: using electronically controlled spark duration limitation to cut off dangerous energy within an extremely short time, thereby significantly increasing available power while maintaining intrinsic safety. Main content includes:
- Power-i architecture: the overall architecture of the intrinsically safe source, field devices, wiring, and terminator;
- Requirements for Power-i devices: separate requirements for the Power-i source, field device, wiring, terminator, and test instruments for Power-i loop checks;
- Application classes: the permissible Power-i application classes;
- System verification: selection of the permissible current class of the Power-i source, verification of a Power-i system, definition of safety-relevant parameters, type tests, and test requirements.
3. Process Sealing Requirements (Part 40)
Where flammable process fluids (e.g., natural gas, hydrocarbon gases) must be isolated from electrical systems (e.g., sensors, transmitters, explosion-proof enclosures), a seal failure could allow flammable fluid into the electrical cavity and ignite it. Part 40 specifies process sealing requirements:
- Equipment classification: dividing equipment into single process seal equipment, dual process seal equipment, equipment with limited pressure at electrical connections, purged or pressurised equipment, and add-on secondary process seals;
- Annunciators: requirements for seal-failure monitoring and alarm;
- Type verifications and tests: test sample, conditioning and test sequence for single process seal equipment (temperature cycling, pressure cycling, leakage test), dual process seal equipment tests, and tests for limited-pressure and pressurised equipment.
🚨 Process sealing is the last barrier preventing flammable fluid entering electrical equipment. After any installation, repair, or replacement of a sensor/transmitter, the seal must be checked per Part 40 to ensure effective isolation between process and electrical sides.
4. Engineering Practice Applications 🛠️
- ⚡ Electrostatic protection: in powder handling, liquid transfer, and plastic/film processing, follow Part 32-1 to select dissipative materials, ensure reliable earthing, and control ambient humidity to reduce electrostatic discharge risk.
- 🔌 Intrinsically safe power supply: for intrinsically safe instruments requiring higher power (e.g., electromagnetic flowmeters, transmitters), evaluate the feasibility of Power-i technology, perform system verification per Part 39, and ensure power class matching.
- 🔧 Process seal management: for electrical instruments that may contact flammable fluids, confirm at selection that they meet the Part 40 process-seal level, and complete type verification and seal checks before commissioning.
- 📋 Explosion-protection certification: combine the IEC 60079 main standards with the IECEx/ATEX certification system, and implement the requirements of these technical specifications into equipment selection, installation, and maintenance procedures.
5. Frequently Asked Questions ❓
❓ Q: What is the difference between a technical specification (TS) and a formal standard?
A: A TS is a document published earlier in the standards process when the technology still needs further validation or the market needs it urgently. Its requirements are detailed but it is usually not a national mandatory standard. Formal standards (e.g., IEC 60079-0, 60079-11) remain the main basis for certification.
A: A TS is a document published earlier in the standards process when the technology still needs further validation or the market needs it urgently. Its requirements are detailed but it is usually not a national mandatory standard. Formal standards (e.g., IEC 60079-0, 60079-11) remain the main basis for certification.
❓ Q: How does Power-i differ from traditional intrinsic safety?
A: Traditional Ex i relies entirely on limiting circuit energy to prevent ignition; Power-i, in addition to energy limiting, uses electronic control of spark duration to cut off before dangerous energy is formed, allowing higher supply power while maintaining intrinsic safety.
A: Traditional Ex i relies entirely on limiting circuit energy to prevent ignition; Power-i, in addition to energy limiting, uses electronic control of spark duration to cut off before dangerous energy is formed, allowing higher supply power while maintaining intrinsic safety.
❓ Q: Why distinguish single and dual process seals?
A: A single-seal device has only one process-to-electrical isolation barrier, so leakage risk is relatively higher. A dual-seal device provides two barriers — even if the first fails, the second protects — so reliability is higher, appropriate for applications where leakage consequences are severe.
A: A single-seal device has only one process-to-electrical isolation barrier, so leakage risk is relatively higher. A dual-seal device provides two barriers — even if the first fails, the second protects — so reliability is higher, appropriate for applications where leakage consequences are severe.
🔍 Q: Where are electrostatic hazards most easily overlooked?
A: In powder/granule conveying, non-conductive liquid piping, plastic film winding, and personnel walking/clothing friction, static accumulation is often not obvious. Assess per Part 32-1 and apply earthing, dissipative materials, and ionisation measures.
A: In powder/granule conveying, non-conductive liquid piping, plastic film winding, and personnel walking/clothing friction, static accumulation is often not obvious. Assess per Part 32-1 and apply earthing, dissipative materials, and ionisation measures.