Manufacturing facilities that house and handle explosive or flammable materials often have a greater risk involved in their daily operations as well as a need to utilize equipment that is safe for use in these extreme environments. Standard electrical equipment, like a scale, can become a source of ignition, depending on the circumstances, and in such a scenario, could cause serious material damage or even bodily injury. That’s why scale manufacturers must stick to strict regulations when it comes to manufacturing intrinsically safe industrial scales.
The National Electric Code (NEC) was first developed by the Occupational Safety & Health Administration. It’s meant to provide a system of classification based on how materials are handled in a number of different environments. This group also sets the standards for the safe installation of electrical equipment and wiring in industrial facilities. All employees and manufacturers who come into contact with explosive materials must adhere to these regulations if their facility is deemed a hazardous location.
There are three different criteria used in this system:
- Type – Refers to the kind of hazardous material that is handled.
- Condition – Highlights different circumstances where this material could become a hazard.
- Nature – Outlines the flammable characteristics of the material or substance.
NEC Hazardous Location Types
Based on the NEC, there are three different types of hazardous locations:
- Class I Locations
This type of classification encompasses locations where flammable vapors or gases are present in the atmosphere in quantities that create the potential for an explosion, which could then be ignited if any source of ignition is present.
Typical locations that are designated as Class I include spray finishing areas, aircraft hangers, petroleum refineries, utility gas plants, gasoline storage and dispensing areas as well as any facility that stores or handles natural gas or liquefied petroleum gas.
- Class II Locations
Situations where combustible dust is present in a work environment will often classify as a Class II hazardous location. In these instances, combustible materials can often become suspended in air and, if ignited, cause an extremely powerful explosion.
Typical Class II locations include:
- Plants that either manufacture, store or use aluminum or magnesium powders.
- Grain elevators.
- Producers of plastics, fireworks and medications.
- Cocoa and sugar plants.
- Feed and flour mills.
- Producers of starch or candies.
- Class III Locations
Class III hazardous locations include areas where flyings or fibers are present when certain materials are stored, handled or processed. These fibers or flyings are not usually present in the air, but can potentially collect around machinery or on lighting fixtures where a spark, heat or hot metal can cause them to ignite.
Common Class III locations include cotton gins, flax processing plants, textile mills, cottonseed mills and manufacturing plants that pulverize, cut or shape wood and in doing so, create sawdust that can become flammable.
Considerations for Hazardous Location Conditions
The NEC also designates the way that a material exists in each of the location types listed above. Therefore, a Class I, II or III type can be classified as either Division I or Division II.
Division I: Normal
A Division I environment is one where the hazard is expected to exist in the everyday operations of the facility or during frequent maintenance and repair. An example of this type of environment could be areas close to relief valves in a petroleum refinery plant.
Division II: Abnormal
A Division II environment is one where the hazard should be confined to closed systems and containers and only becomes present in the event of an accidental breakage, rupture or unusual equipment malfunction.
For instance, closed storage drums containing flammable materials can be placed in a storage room where the hazardous vapor is not allowed to escape into the atmosphere, but it can become an ignition source if any of the containers were to leak.
The Nature of Hazardous Substances
The last part of the NEC classification system handles the properties of individual substances and places them into various groups. Each group pertains to one of the Classes that were mentioned above.
- Groups A, B, C and D
These four groups only pertain to Class I locations and focus on the ignition temperature of the substance in question, its explosion temperature, as well as other flammable characteristics.
The only substance present in Group A is acetylene, which is a gas that has extremely high explosion temperatures. This material makes up a very small percentage of hazardous locations and therefore, there is little equipment available for this type of location.
Group B also covers a small portion of Class I areas. It includes hydrogen and other materials with similar characteristics. Sometimes, these other materials will be classified as Group C or D if you were to follow certain restrictions set forth in the NEC.
Group C and D are the most commonly used Class I groups and therefore, make up the largest percentage of Class I hazardous locations. Group C includes ether and materials exhibiting similar properties and Group D refers to more common substances such as gasoline, butane, propane and natural gas.
Groups E, F and G
In Class II locations, the different groups are based on the conductivity and ignition temperature of the hazardous substance. Conductivity is especially important in Class II locations where metal dusts are present.
Metal dusts all fall within Group E. This includes magnesium and aluminum dusts as well as others with a similar nature. These dusts can be both explosive and conductive.
Group F areas contain charcoal dust, carbon black, coke and coal dust as well as other similar substances. While only some of these materials are conductive, they are all explosive.
Group G includes flour, starch, grain dusts, cocoa and other similar materials. These materials are not conductive, but are explosive.
Arlyn Intrinsically Safe Scales
As a factory direct manufacturer of industrial scales and their subassemblies, we’re in a unique position that allows us to develop highly specialized equipment that meets the needs of even the most challenging environments. Our Guard Scales are intrinsically safe and approved to be used in the following hazardous environments:
- Class I, Divisions I & II, Groups A-D
- Class II, Divisions I & II, Groups E-G
- Class III, Divisions I & II
Guard B Scales
Our Guard B series of scales are ideal for applications with a capacity between 5 and 150 pounds and feature a resolution of between .001 and .05 pounds.
Guard C Scales
If you’re using drums or cylinders to house hazardous materials, our Guard C cylinder scales are a perfect fit with capacities ranging from 60 to 400 pounds with a resolution from .02 to .1 pounds.
Guard P Scales
For larger applications, our Guard P platform scales are available with a resolution of either .1 or .2 pounds and capacities ranging from 500 to 1,000 pounds.
Guard F Scales
Finally, if your capacities range between 2,500 and 25,000 pounds, our Guard F floor scales are ideal and offer a resolution between a 0.5 and 5 pounds.
Top Notch Customer Service, Intrinsically Safe, Competitive Pricing
As a factory direct scale manufacturer, we’re able to offer competitive pricing on all of our scales. If you’re in need of assistance during the selection process, or are interested in more information about our Guard series of intrinsically safe scales, feel free to contact us today. We look forward to working with you soon.