Facilities that must handle liquid waste often have to use highly specialized scales due to the unsafe nature of the materials being handled. Standard industrial scales may not be able to stand up to these conditions, which is why there are strict standards on how manufacturers must build scales that are deemed to be intrinsically safe.
What is an Intrinsically Safe Scale?
An intrinsically safe scale is simply a scale that will provide accurate weight measurements even in hazardous or explosive environments.
How Do I Know if I Need to Purchase an Intrinsically Safe Scale?
The National Electric Code (NEC), which was first developed by the Occupational Safety & Health Administration created a classification system that catalogs how materials should be handled in various environments. This body also oversees standards for proper installation of electrical equipment and wiring in commercial facilities. Any areas that are in contact with any type of materials that are deemed hazardous or explosive will be classified as hazardous locations and must meet these strict regulations.
The criteria used in this system from the NEC is categorized below:
- Type – Identifies the ‘type’ of hazardous material that’s being handled
- Condition – Identifies different ‘conditions’ in which the hazardous material could become a hazard
- Nature – Details the flammable or explosive characteristics of the hazardous substance
Types of NEC Hazardous Locations
The NEC breaks down hazardous locations into three different types, which are described below:
Class I Locations
These locations include areas where flammable gases or vapors are present in the air in such quantities that could create a potential explosion, which could then ignite if a source were present. Typical Class I locations include aircraft hangers, utility gas plants, areas for gas storage and dispensing and any facility that stores liquefied petroleum or natural gas.
Class II Locations
These locations include areas where combustible dust is present in a work setting. These materials can often become suspended in air, and can cause a serious fire or explosion if ignited.
Examples of Class II locations include:
- Grain elevators
- Plants that come into contact or manufacture magnesium or aluminum powders
- Feed and flour mills
- Medication, fireworks and plastic manufacturers
- Sugar and cocoa production facilities
- Starch or candy producers
Class III Locations
Class III locations include areas where fibers are present when specific materials are stored, or processed. While these fibers are typically not present in the air, they can become lodged in and around machinery, or light fixtures, and if a spark were to occur, they could ignite.
Examples of Class III locations include:
- Flax processing plants
- Cotton gins
- Textile and cottonseed mills
- Any manufacturing facilities that cut, pulverize or shape wood and create sawdust, which can be flammable
Explanation of Hazardous Location Conditions
In addition to the type of hazardous location, the NEC also dictates how a material exists in each of these location types. The NEC breaks down these location types into Division I or Division II.
Division I: Normal
A Division I environment is an area where the specified hazard is expected to exist in normal business operations, or regular maintenance or repair.
Division II: Abnormal
A Division II environment is one where the specified hazard is confined to a certain area, or systems and should only be present in the event of a rupture, breakage or catastrophic accident.
Further Details Regarding the Nature of Hazardous Substances
The third component of the NEC classification system relates to the physical characteristics of certain substances and places them in various groups depending on the severity of their flammable characteristics.
These groups only pertain to Class I locations and relate to the ignition temperature of the substance, as well as any other flammable characteristics.
The only substance in Group A is acetylene, which is a gas that can explode at extremely high temperatures. This material is used in a very small number of hazardous locations, and because of this there’s little equipment available to support this type of location.
Group B also covers a relatively small portion of Class I locations. This group typically includes hydrogen and materials that exhibit similar characteristics.
Group C and D are the most often used Class I groups and in turn make up the largest percentage of Class I locations. Group C includes ether as well as materials with similar properties and Group D refers to common materials such as butane, gasoline, propane and natural gas.
The groupings in Class II locations are categorized by ignition temperature and conductivity. Because many Class II locations may have metal dusts, conductivity is especially important.
Metal dusts all are categorized within Group E. This includes aluminum and magnesium dusts, as well as others of similar nature. These dusts are both explosive and conductive.
Group F areas contain carbon black, coal and coke dust and charcoal dust, and other similar materials. Not all of these materials all conductive, but they all are explosive.
Group G areas contain starch, flour, cocoa, and similar compounds. These materials are explosive, but not conductive.
Arlyn Scales Offers a Wide Array of Intrinsically Safe Scales
Our ArlynGuard B, C, F, and P scales have one or more components that have been tested and approved to be Intrinsically Safe for use in an impressive range of hazardous locations including:
- Intrinsically safe for use in Class I, II, III; Division I; Groups A through G
- Non-incedive for use in Class I; Division II; Groups A through D
- Suitable for use in Class II; Division II; Groups F & G
- Suitable for use in Class III; Division II
Each ArlynGuard scale is equipped with one or more of:
- Model MKE-5-IS(-C) Digital Weight Indicator System
- Load Cell Models 620-300-IS, 620-100-IS, 620-50-IS, 620-25-IS, 620-10-IS, 520-10000L-IS, 520-5000L-IS, 520-5000IS, 520-2500-IS, 520-1250-IS, 320-500-IS and 320-250-IS which are Factory Mutual (FM) Approved components as per Approval Standard 3600, 3610, 3611 and 3810.
If you’re interested in learning more about our variety of Intrinsically Safe Scales, don’t hesitate to reach out to our team today at 800-645-4301 or through our online contact form today. The concepts surrounding intrinsically safe scales can be complicated, but it’s important that you take the necessary steps to ensure you’re keeping your facility and employees safe in the event that hazardous materials are present.