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PD CLC TR 60079 — Explosive Atmospheres Technical Reports (Part 32-1 Electrostatic Hazards Guidance; Part 33 Special Protection ‘s’)
Explosive Atmospheres — Electrostatic Hazards, Guidance / Equipment Protection by Special Protection ‘s’
⚡ PD CLC/TR 60079 is a group of explosive-atmosphere documents published by the British Standards Institution (BSI) and derived from the European Committee for Electrotechnical Standardization (CENELEC) technical report CLC/TR 60079, corresponding to the IEC 60079 series (equipment for explosive atmospheres). The two parts in this batch, PD CLC/TR 60079-32-1:2015 (electrostatic hazards guidance) and PD CLC/TR 60079-33:2015 (special protection “s”), provide technical bases for equipment and operations in explosive atmospheres from the perspectives of “electrostatic safety” and “special protection type” respectively.
💡 In explosive atmospheres (e.g., petrochemical, oil and gas fields, coal mines, spray booths), flammable gases, vapours or dust form explosive mixtures with air and may explode when an ignition source is present. Electrostatic discharge is one of the most common and least visible ignition sources; “special protection s” is a supplementary protection type in the IEC 60079 system for equipment not suited to the other standard protection types.
1. Overview of the Series 📌
The CLC/TR 60079 series is prepared by CENELEC (the UK participates through Technical Committee EXL/31 and publishes it as a Published Document), with content corresponding to IEC 60079. The two parts in this batch are summarised below:
| Standard | Part Topic | Main Content | Year |
|---|---|---|---|
| PD CLC/TR 60079-32-1:2015 | Electrostatic Hazards | Guidance for identifying, assessing and protecting against electrostatic hazards in explosive atmospheres | 2015 |
| PD CLC/TR 60079-33:2015 | Special Protection ‘s’ | Requirements for equipment protection by special protection ‘s’ in explosive atmospheres | 2015 |
⚠️ PD CLC/TR 60079-32-1:2015 supersedes the withdrawn PD CLC/TR 50404:2003 and PD IEC/TS 60079-32-1:2013; PD CLC/TR 60079-33:2015 supersedes the withdrawn BS IEC 60079-33:2012. Note the version replacement when referencing.
2. Part 32-1: Electrostatic Hazards Guidance ⚡
PD CLC/TR 60079-32-1:2015 provides guidance for identifying, assessing and protecting against electrostatic hazards in explosive atmospheres, applicable to both gas/vapour and dust atmospheres. Its core content covers:
- Electrostatic generation mechanisms: triboelectric charging, contact and separation, flow electrification (e.g., liquid/powder flowing in pipes), induction charging, etc.;
- Ignition mechanisms: whether electrostatic spark, brush discharge, corona discharge, etc., can ignite the explosive mixture;
- Hazard assessment: assessing electrostatic ignition risk under different processes, materials and operating conditions;
- Protection measures: earthing/equipotential bonding, use of static-dissipative materials, flow-rate limitation, inerting, preventing body charging, etc.;
- Personal protection: anti-static clothing, footwear, gloves and wrist straps, and control of body charging.
The guide also references standards for electrostatic performance testing of materials and products (e.g., IEC 61340 series, ISO 8028, ISO 13688), providing specific technical bases for engineering implementation.
🚨 The “three essentials” of electrostatic protection are earthing/equipotential bonding, static dissipation, and avoiding high-speed friction/separation. In flammable-liquid handling, powder conveying and organic-solvent operations, poor earthing or excessive flow rate can instantly trigger an electrostatic spark leading to explosion.
3. Part 33: Special Protection ‘s’ 🛡️
PD CLC/TR 60079-33:2015 specifies requirements for equipment protection by special protection “s” in explosive atmospheres. Special protection “s” applies to electrical equipment that does not fully conform to, or is not suited to, the standard protection types (e.g., flameproof “d”, increased safety “e”, intrinsic safety “i”, pressurisation “p”), preventing the equipment from becoming an ignition source in an explosive atmosphere through additional safety measures.
This part requires:
- Constructional safety: the structure and materials should prevent the generation of sparks, arcs or dangerous temperatures;
- Electrical safety: circuit design, component selection and temperature-rise control should meet requirements;
- Testing and verification: verify by prescribed tests that the equipment does not constitute an ignition source under abnormal and normal conditions;
- Marking: equipment should be marked with protection type “s” and relevant parameters as required.
✅ Special protection “s” provides a compliance route for “non-standard” equipment: it combines multiple safety measures (constructional, electrical, sealing, thermal) so that, even if the equipment does not fully meet a single standard protection type, it reaches the required safety level through integrated protection.
4. Key Technical Requirements 🔧
Combining the two parts, the key technical requirements for explosive-atmosphere safety include:
- Hazardous-area classification: classify explosive hazardous areas per the IEC 60079-10 series and determine equipment selection categories;
- Equipment selection: select the appropriate protection type (d, e, i, p, s, etc.) and temperature class per the zone and gas/dust group;
- Static earthing and equipotential bonding: all metal parts, piping and vessels should be reliably earthed and bonded equipotentially;
- Anti-static materials: use static-dissipative/anti-static materials and control surface resistance;
- Individual protection: operators wear anti-static clothing and footwear to avoid body charging ignitions.
5. Engineering Practice and Applications 🛠️
This series is applied in petrochemical, oil and gas extraction, fine chemicals, powder processing and mining industries, including:
- Hazardous-area electrical equipment selection: selecting compliant explosion-protected equipment in explosive gas/dust atmospheres;
- Electrostatic risk assessment: assessing and protecting against electrostatic risk in loading/unloading, conveying, filling and spraying operations;
- Special equipment certification: designing, testing and certifying equipment not suited to standard protection types under type “s”;
- Work permits and safety management: incorporating electrostatic protection and equipment explosion-protection requirements into work permits and routine safety inspections.
💡 Implementation advice: in hazardous-area electrical design and operational safety management, treat “protection-type selection” and “electrostatic protection” as two parallel priorities; for processes involving flammable liquids and powders, complete an electrostatic risk assessment at the design stage and compile an earthing and anti-static measure checklist.
6. Frequently Asked Questions ❓
❓ Q: Why is static electricity an important ignition source in explosive atmospheres?
A: Although the energy of an electrostatic discharge is small, it is enough to ignite most explosive mixtures formed by flammable gases/vapours and dust with air; static charge often accumulates imperceptibly on equipment, piping and bodies, making it a hidden and dangerous ignition source.
A: Although the energy of an electrostatic discharge is small, it is enough to ignite most explosive mixtures formed by flammable gases/vapours and dust with air; static charge often accumulates imperceptibly on equipment, piping and bodies, making it a hidden and dangerous ignition source.
❓ Q: What is the relationship between Parts 32-1 and 33?
A: Part 32-1 is a general protection guide on “electrostatic hazards”, oriented to processes and operations; Part 33 is a standard for the equipment protection type “special protection s”. The former addresses “process/environment” static risk, the latter addresses “equipment” explosion-protection compliance.
A: Part 32-1 is a general protection guide on “electrostatic hazards”, oriented to processes and operations; Part 33 is a standard for the equipment protection type “special protection s”. The former addresses “process/environment” static risk, the latter addresses “equipment” explosion-protection compliance.
❓ Q: What is “special protection s” and how does it differ from other protection types?
A: “s” is an equipment protection type in the IEC 60079 system that prevents equipment from becoming an ignition source in an explosive atmosphere through integrated additional safety measures (constructional, electrical, sealing, thermal). It applies to equipment not fully conforming to standard protection types (e.g., d, e, i, p).
A: “s” is an equipment protection type in the IEC 60079 system that prevents equipment from becoming an ignition source in an explosive atmosphere through integrated additional safety measures (constructional, electrical, sealing, thermal). It applies to equipment not fully conforming to standard protection types (e.g., d, e, i, p).
❓ Q: What is the most fundamental static-protection measure?
A: The most fundamental is reliable earthing and equipotential bonding so that static charge can be dissipated; next are using static-dissipative/anti-static materials, controlling flow rate and preventing high-speed friction/separation, and operators wearing anti-static clothing and footwear.
A: The most fundamental is reliable earthing and equipotential bonding so that static charge can be dissipated; next are using static-dissipative/anti-static materials, controlling flow rate and preventing high-speed friction/separation, and operators wearing anti-static clothing and footwear.
❓ Q: Are technical reports mandatory?
A: Technical reports (TR) are largely informative and not themselves mandatory; however, their recommended electrostatic-protection and special-protection requirements are often incorporated into engineering specifications, project contracts and regulatory requirements, thereby acquiring practical binding force.
A: Technical reports (TR) are largely informative and not themselves mandatory; however, their recommended electrostatic-protection and special-protection requirements are often incorporated into engineering specifications, project contracts and regulatory requirements, thereby acquiring practical binding force.