Spraying, Dipping, Coating And Printing

For years, Article 516 of the National Electrical Code (NEC)— covering spray applications, dipping and coating processes using flammable liquids, combustible liquids and combustible powders—did not seem to change much, if at all. However, there have been substantial changes in the 2014 and 2017 NECs. Definitions were added to 516.2 in the 2014 NEC and then removed or revised in the 2017 NEC. Figures have been added for both editions so users can better understand the requirements.

For electrical contractors, electricians, municipalities and states that have skipped the 2014 NEC changes and are going to adopt the 2017 NEC, there is a major chance of misunderstanding or missing the requirements that were in the 2014 NEC and are no longer highlighted as changes in the 2017 NEC. Careful diagnosis of the differences in Article 516 between the 2014 and the 2017 NEC will help to understand the proper installation methods for spraying, dipping, coating or printing applications.

A new definition of “Flash-Off Area” was introduced in 516.2 as “an open or enclosed area after a spray application process where vapors are released due to exposure to ambient air or a heated atmosphere” based on a definition in NFPA 33, Standard for Spray Applications. The heated air or higher temperature of the ambient air would cause the sprayed liquid to flash into vapor or gas that is more easily ignitable. This definition was deleted in the 2017 NEC.

“Limited Finishing Workstation” was introduced in the 2014 NEC as “an apparatus that is capable of confining the vapors, mists, residues, dusts, or deposits that are generated by a spray application process and that meets the requirements of Section 14.3 of NFPA 33, Standard for Spray Applications Using Flammable or Combustible Materials, but does not meet the requirement for a spray booth or spray room, as herein defined. [33:].”

In the 2017 NEC, the reference to NFPA 33 was inserted into a new informational note in conformance with the NEC Style Manual to not contain any references to another standard within mandatory NEC text. This definition provides coverage of smaller spray areas that do not meet the requirements for larger spray booths or spray rooms. 

The definition of “resin application area” was inserted into 516.2 in the 2014 NEC as “any area in which polyester resins or gelcoats are spray applied.” An example of this is a boat repair facility where resins (fiberglass) are applied to boat hulls (RTRC conduit is an example of a wiring method using resin in its composition), or where gelcoat is applied to a boat hull.

Since “Resin Application area” was not used in Article 516, this definition was deleted for the 2017 NEC. Both “spray area” and “spray booth” definitions had major modifications in the 2014 NEC; however, there were very minor “editorial” corrections between the 2014 and the 2017 NEC, such as changing “may” to “can” in places and “ignitable quantities” to “dangerous quantities” in the definition of spray areas. The definition of “Spray Room” from the 2014 NEC has been considerably shortened in the 2017 NEC by removing examples that may have been better shown as informational notes but have been deleted, making a more user-friendly definition. 

A substantial number of figures have been added for both the 2014 and the 2017 NEC. These figures and the text provide detailed information on installation techniques, such as how luminaires are mounted outside the spray area of a spray room or booth when the luminaires are serviced from outside or inside the booth or room. Many of these figures have been moved around within Article 516 in the 2017 NEC to more adequately locate these figures and the accompanying text by establishing a new Part V for printing, dipping and coating processes with vapor containment and ventilation areas, as well as open dipping and coating processes without vapor containment and without ventilation. The vapor containment areas will require the vapors to be confined within the process equipment. 

A new Part IV to Article 516 has been provided in the 2017 NEC dealing with spray applications in temporary membrane enclosures with a figure showing a large boat located inside the membrane enclosure. During spray painting of large equipment, electrical wiring and utilization equipment used within the classified areas—both inside and outside the membrane enclosures during spray painting must be suitable for the location—all power to the workpiece shall be removed during the painting, and the workpieces must be grounded.

Carefully study the additional changes to Article 516 before using the article.

About the Author

Mark C. Ode

Fire/Life Safety Columnist and Code Contributor

Mark C. Ode is a lead engineering associate for Energy & Power Technologies at Underwriters Laboratories Inc. and can be reached at 919.949.2576 and Mark.C.Ode@ul.com.

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