What are the safety regulations for SF6 gas handling unit for substation on-site repair?

Safety regulations for SF6 gas handling units during substation on-site repair are governed by international, national, and industry-specific standards to ensure personnel safety, equipment integrity, and environmental protection. Below is a comprehensive breakdown based on key regulations and best practices:

1. Personnel Safety Requirements

Protective Equipment

• Respiratory Protection: Use positive-pressure air respirators (e.g., NIOSH-approved) when handling leaked or decomposed SF6, as it may contain toxic byproducts like HF and SO₂ .

• Personal Protective Gear (PPE): Wear acid-resistant gloves, anti-static overalls, and safety goggles to prevent skin/eye contact with corrosive gases .

• Training and Certification: Operators must complete specialized training on SF6 properties, handling procedures, and emergency protocols (per IEC 62271-4 and DL/T 639) .

Work Environment

• Ventilation: Ensure well-ventilated work areas. For indoor repairs, install SF6/O₂ monitors with alarms (SF6 ≥1000 ppm, O₂ ≤19.5%) and automatic exhaust systems .

• Entry Restrictions: Prohibit unauthorized personnel from the work zone. Avoid solo repairs in confined spaces (e.g., GIS rooms) .

2. Equipment Safety Standards

Handling Unit Specifications

• Explosion-Proof Design: Use units with flame-retardant materials, spark-proof components, and overpressure protection (automatic shutdown at ≥12 MPa) .

• Leakage Prevention: Employ double-seal connections (O-rings + metal gaskets) and fluorine-resistant hoses (pressure rating ≥6 MPa). Conduct helium leak tests annually .

• Vacuum Capability: Units must achieve ≤10 Pa ultimate vacuum to ensure thorough gas extraction and prevent air contamination .

Storage and Transportation

• Cylinder Compliance: Store SF6 in seamless steel cylinders (rated pressure ≥15 MPa) marked "SF6" with hydrostatic testing every 3 years (GB 5099) .

• Transport Safety: Secure cylinders upright during transit, away from heat and flammable materials. Use dedicated trailers for bulk transport .

3. Operational Procedures

Pre-Repair Checks

• Gas Quality Verification: Test new SF6 for purity (≥99.9%), moisture (≤60 μL/L), and decomposition products (SO₂, HF ≤0.5 μL/L) using a portable analyzer .

• Equipment Preparation: Evacuate the substation equipment to ≤133 Pa and maintain for ≥30 minutes before connecting the handling unit .

Gas Recovery and Purification

• Recovery Efficiency: Achieve ≥95% SF6 recovery rate (DL/T 1555-2016). Use compression-cooling (0–5°C) to liquefy gas into storage cylinders .

• Purification Process: Remove moisture (≤30 μL/L), oil (≤5 ppm), and solid particles (≤0.1 μm) via molecular sieves, alkaline filters, and precision filtration .

Re-Injection and Disposal

• Re-Injection Protocol: Refill equipment at ≤0.1 MPa/min to prevent liquefaction. Verify pressure/temperature stability post-injection .

• Waste Disposal: Entrust non-recyclable SF6 to certified facilities for thermal decomposition (1200–1500°C) or chemical treatment (e.g., reaction with AlF₃). Direct emission is strictly prohibited climate.ec.europa.eu.

4. Environmental Compliance

Emission Control

• Regulatory Limits: Adhere to EU F-Gas Regulation (517/2014), which mandates a 67% reduction in F-gas emissions by 2030. In China, follow DL/T 1555-2016 for leak detection and recovery climate.ec.europa.eu.

• Reporting: Submit annual SF6 emission reports to local environmental authorities, including gas usage, recovery, and disposal data .

Waste Management

• Adsorbent Handling: Dispose of spent molecular sieves and alkaline filters in 20% NaOH solution for 12 hours before landfill .

• Contaminated Materials: Clean equipment surfaces with acetone or ethanol to remove decomposition residues .

5. Monitoring and Maintenance

Real-Time Detection

• Fixed Sensors: Install wall-mounted SF6/O₂ detectors in substation rooms with audible/visual alarms and remote data logging (DL/T 1555-2016) .

• Portable Tools: Use handheld leak detectors (detection limit ≤1 ppm) for daily patrols of flange connections and valves .

Preventive Maintenance

• Daily Checks: Inspect hoses, seals, and pressure gauges for wear. Replace defective components immediately .

• Annual Overhaul: Service vacuum pumps, compressors, and filters. Calibrate sensors and verify equipment performance against IEC 62271-4 .

6. Emergency Protocols

• Leak Response: Evacuate personnel, activate exhaust systems, and use recovery units to contain leaks. Avoid entry without PPE until concentrations drop below 1000 ppm .

• Spill Cleanup: Neutralize spilled SF6 decomposition products with baking soda or lime. Dispose of contaminated soil in sealed containers .

• First Aid: If exposed, remove contaminated clothing, rinse skin/eyes with water for 15 minutes, and seek medical attention .

Key Regulatory References

Compliance with these regulations ensures safe, efficient, and environmentally responsible SF6 handling during substation repairs. Prioritize training, equipment maintenance, and real-time monitoring to minimize risks and meet global sustainability goals. Always refer to the latest editions of standards and consult certified experts for complex repairs.