What is "Intrinsically Safe"?
A protection method employed in potentially explosive atmospheres. Certificate IS tools are designed to prevent the release of sufficient energy to cause ignition of flammable material. IS standards apply to all equipment that can create one or more of a range of defined potential explosion sources.
- Electrical sparks
- Electrical arcs
- Hot surfaces
- Static electricity
- Electromagnetic radiation
- Chemical reactions
- Mechanical impact
- Mechanical friction
- Compression ignition
- Acoustic energy
- Ionizing radiation
The Three Key Elements of Combustion are:
- Inflammable material (gases, particles/dust)
- Ignition source
This combination is very common in chemical, petro-chemical, and pharmaceutical industries. Examples of the amount of inflammable material necessary for ignition below show how small of an amount it takes to present a danger to workers.
Lower explosion limit (Volume %)
|Acetylene ||2.3 |
|Ethylene ||2.3 |
|Gasoline ||~0.6 |
|Benzol ||1.2 |
|Natural gas ||4.0(7.0) |
|Heating oil/diesel ||~0.6 |
|Methane ||4.4 |
|Propane ||1.7 |
|Carbon disulphide ||0.6 |
|Hydrogen ||4.0 |
What are the Regulations and Guidelines?
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ATEX (Europe) European Union's 94/9/EC Directive, commonly called ATEX ("Atmospheres Explosibles") Europe's primary regulation for protection systems and equipment intended for use in potentially explosive atmospheres. Indended to serve as total harmonization directive, laying down essential health and safety requirements, and replace existing divergent national and European legislation.
This directive became mandatory on electical and electronic equipment for use in environments subject to explosion hazard sold in the EU on 1 July 2003.
Derivatives of ATEX are being adopted across the world.
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NEC (United States) National Electrical Code (NEC), is the basis for all electrical codes in the United States. Classifications and related product markings for hazardous areas are covered in NEC 500 and 505. Interpretations of NEC 500, a longstanding regulation are utilized throughout the world (outside Europe). NEC 505 is similar to ATEX.
Accreditation Bodies, Examples
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Factory Mutual Factory Mutual Research, Managed by Factory Mutual (FM) Global, has set certification guidelines for equipment used in potentially explosive atmospheres.
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Canadian Standards Association (CSA) Accreditation body for North American regulations based in Toronto Canada.
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ZELM European ATEC accreditation body located in Germany.
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KEMA European ATEX accreditation body located in the Netherlands.
Making Sense of the Product Rating Systems
Each approved intrinsically safe device is rated to ATEX and either NEC or Factory Manual Standards. The corresponding rating system allows you to understand which zones, type of protection, gas groups and temperature classes the instrument is approved for.
Example: Fluke 707ex is ATEX-Compliant II 2 G Ex ia IIC T4
| ||The ATEX examination mark. This sign is required on all devices for use in European hazardous areas. |
|II 2 G ||The classification of zones. "II" designates the tool is approved for all non-mining areas. "2" represents the category of the device, in this case the device is rated for the second most hazardous areas. "G" designates atmosphere, in this case gas, vapors and mist. |
|Ex ||Explosion protection based on European Ex-regulations. |
|ia ||The type of protection from explosion, in this case the energy in a device or connector has been reduced to a safe value. |
|IIC ||Gas Group. "IIC" rating indicates compatibility with the most dangerous gas groups. |
|T4 ||Temperature class is the maximum temperature of a surface that may be. |
| ||Factory Mutual Classification example: Fluke 707ex is FM-classified N.I. Class 1, Div 2, Groups A-D, T4. |
| ||The Factory Mutual Approved mark. |
|N.I. ||Non-incendive apparatus, internal energy is limited so a specified atmosphere cannot be ignited by its use. |
|Class I ||For use with gases, vapors and liquids (not dust, fibers or filings). |
|Div 2 ||Certified for use in Zone 2, explosive atmospheres not normally present, may rarely exist for short duration. |
|Groups A-D ||Rated for use with explosive gasses as defined by groups A-D, including acetylene, hydrogen, acetylene and propane. |