Mike Dolt Enterprises
Mike Dolt Enterprises
User: gadfly56, Location: New Jersey
Asked on: Thursday, March 24, 2011 at 2:22 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:13 am EDT
Question: We are designing fire protection for a customer storing solvent wet (IPA, 30% w/w) nitrocellulose (NC) in a building with four (4) rooms separated by 3 hr or better rated walls. These areas would appear to be Class I Div 2 for the IPA since the drums are never opened in the storage areas and the only time you have a release is if a drum is accidently opened (falls, gets crushed, top "garroted" off). NFPA guidlines say treat the solvent wet NC as if it were IPA.To save money, it's been suggested to run our raceways above the classified area if we can determine how high the area extends. I've looked at NFPA 497, and it looks like we might be OK at 5 feet above the top of drum storage. Ceiling is at about 20 feet and ventilation is probably poor to nil. Vapor density is 2.1. We'd come down with an EY seal to each rated flame detector. I'm just not 100% confident I want to go in this direction. Can someone point me to other resources? The manufacturer is no help: "follow all local codes and regulations" and "have a nice day" .I'm inclined to tell everyone it's all Class I Div 2, live with it. Other thoughts?
NFPA Resources
NFPA 30: Flammable and Combustible Liquids Code
Provides guidance on the classification of hazardous areas and the design of fire protection systems for flammable liquids.
NFPA 497: Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations
Defines the different classes and divisions of hazardous areas based on the concentration of flammable vapors or gases.
NFPA 70: National Electrical Code (NEC)
Chapter 5, Article 500 covers the installation of electrical equipment in hazardous (classified) locations.
Additional Resources
Factory Mutual (FM) Global
Provides loss prevention data sheets and standards on fire protection for various industries, including hazardous materials storage.
International Code Council (ICC)
Publishes building codes, including the International Fire Code (IFC), which address fire protection requirements for buildings with hazardous materials.
Occupational Safety and Health Administration (OSHA)
Regulates the storage and handling of hazardous materials, including flammable liquids.
Evaluation of Proposed Solution
While running raceways above the classified area may appear to be a cost-saving measure, it is important to carefully consider the potential risks and ensure that the solution meets all applicable codes and regulations.
Vapor Concentration Gradient
The vapor density of IPA is 2.1, indicating that it will tend to accumulate at or near the floor level. Therefore, assuming that the vapors will not extend significantly above the drum storage height may not be accurate.
Ventilation Conditions
Poor to nil ventilation can exacerbate the accumulation of flammable vapors and increase the risk of an explosion. Without adequate ventilation, vapors may spread throughout the room, including areas above the drums.
Code Compliance
NFPA 497 suggests that in rooms with no ventilation, hazardous vapors may extend up to the ceiling. Class I Div 2 areas typically extend 18 inches above the floor and 5 feet laterally from the source. However, if ventilation is poor or nonexistent, the hazardous area may extend further.
Recommendation
Based on the information provided, it is recommended to treat the entire storage area as
Class I Div 2 for the following reasons: The drums contain IPA, a highly flammable liquid. The presence of nitrocellulose, a flammable solid, increases the hazard. Ventilation is poor to nil, which can lead to the accumulation of flammable vapors.* Running raceways above the classified area may not adequately protect against the potential spread of vapors.By treating the entire area as Class I Div 2, you can ensure that all electrical equipment is properly installed and protected to minimize the risk of ignition. Flag for review