Understanding NEC Article 516: Spray Application, Dipping, Coating, and Printing Processes

NEC Article 516 outlines safety requirements for electrical systems in facilities using flammable or combustible materials for processes like spray application, dipping, coating, and printing. These activities involve hazards from flammable vapors, combustible mists, and residues, requiring proper electrical design to mitigate fire and explosion risks.

Scope of Article 516

This article applies to:

• Spray Application: Applying materials like paint or powder coatings using compressed air, electrostatic methods, or hydraulic systems.
• Dipping and Coating: Submerging objects in flammable or combustible liquids.
• Printing: Using inks or solvents above their flashpoints.

Referenced Standards:

• NFPA 33 for spray applications.
• NFPA 34 for dipping, coating, and printing.

Key Requirements for Spray and Coating Processes

1. Area Classification
   Classified areas depend on the presence and frequency of flammable substances:
   • Class I, Division 1 or Zone 0: Inside containers or spray areas where vapors are present continuously.
   • Class I, Division 2 or Zone 2: Adjacent areas where vapors may occasionally occur.

Examples:

• The interior of spray booths is classified as Class I, Division 1.
• Areas within 3 feet of open containers or spray booths are Class I, Division 2.

2. Wiring and Equipment
   Electrical systems must comply with the Division (Article 501) or Zone (Article 505) classifications.
   • Rigid metal conduit (RMC) or intermediate metal conduit (IMC) is required for classified areas.
   • Portable equipment and luminaires must be suitable for hazardous locations.

3. Ventilation and Sealing
   • Ventilation systems reduce vapor concentrations and may limit the extent of hazardous areas.
   • Sealing requirements prevent vapor migration through electrical raceways.

4. Electrostatic and Powder Coating Equipment
   • Electrostatic systems must de-energize automatically in case of ventilation failure or current leakage.
   • All conductive parts must be grounded to prevent static discharges.

Powder Coating:

• Electrical equipment in powder-coating areas must be suitable for Class II locations.

5. Static Electricity Management
   Grounding and bonding are mandatory for all conductive objects and systems to dissipate static charges. NFPA 77 provides additional guidance.

6. Special Applications
   • Temporary Membrane Enclosures: Spray areas within membrane enclosures are Class I, Division 1, extending 5 feet outward as Division 2.
   • Limited Finishing Workstations: Classified areas extend 3 feet beyond the workstation.

Applications

Industries utilizing Article 516 guidelines include:

• Automotive: Vehicle painting and coating.
• Manufacturing: Applying protective finishes or powder coatings.
• Printing: Large-scale use of solvent-based inks.

Conclusion

NEC Article 516 provides critical guidance for ensuring safety in facilities where flammable or combustible materials are handled during spray application, dipping, coating, and printing processes. Proper area classification, equipment selection, ventilation, and static management are key to mitigating fire and explosion risks.