Hazardous Location Definitions
In this article:
- What is a hazardous location?
- Why are hazardous location requirements not well known?
- My site isn't described in the NEC - how is a pipeline site classified?
- What are the requirements of electrical equipment used in a hazardous location?
Hazardous (Classified) Locations are defined in the US National Electric Code (NEC), Articles 500-505, and in other international standards such as the IEC, and describe the requirements of electrical products used in these locations. Decisions on the classification of a particular site depend on several factors, including:
• Whether ignitable concentrations of flammable gases, vapors, or liquids are considered commonly present or uncommon
• The ease of ignition of the material, considering the gas or vapor type and the temperature of ignition
The classification system is summarized below, and compares the NEC Division and Zone methods, where the Zone system is comparable to that found in the IEC. Class I applies to gases, vapors, and liquids, which is broken down into the following areas.
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Division 1 Division 2 |
Zone 0 Zone 1 Zone 2 |
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Division 1 & 2 Groups, with examples A: acetylene B: hydrogen C: ethylene D: propane |
Zone 0, 1, 2 Groups, with examples IIC: acetylene & hydrogen IIB: ethylene IIA: propane |
A number of locations where DEI products are used could fall under an NEC-defined hazardous location. Typically, this would be a Class I, Division 2, Group D site, such as at an outdoor insulated joint, in a pipeline containing natural gas. Other sites may be classified as Class I, Division 1, such as fueling hydrant pits, underground vaults, or inside buildings, where an ignitable concentration is considered typically present. An electrical inspector may be the party that determines the classification of a given site, using the above criteria.
Why are hazardous location requirements not well known?
Admittedly, this area is not well understood by most pipeline operators, electrical inspectors, or federal regulators. Since the National Electric Code deals with electrical installations, most people don't realize that this document also defines hazardous locations.
This education process involves:
• Identification of a site as a hazardous location
• Classification of the site according to the NEC guidelines
• Selection of electrical equipment that meets the NEC requirements
A number of pipeline applications in which electrical products are used are non-traditional, hence electrical inspectors and pipeline operators may not identify that NEC 500-505 covers this installation. For example, an over-voltage protection device used on an insulated joint in a cathodically protected gas pipeline is not in a traditional electric circuit, yet it comes under the NEC hazardous location requirements and should be tested and certified by an independent laboratory for this purpose.
My site isn't described in the NEC - how is a pipeline site classified?
A report by the American Gas Association entitled "Classification of Gas Utility Areas for Electrical Installations," number XF0277, expands on Articles 500-505 of the NEC, to further describe how specific gas pipeline facilities would be classified according to this system. Likewise, the American Petroleum Institute document RP-500 provides guidance to the petroleum industry. These documents help to apply the NEC requirements to equipment installations that are not otherwise obvious as being in a hazardous location.
What are the requirements of electrical equipment used in a hazardous location?
Electrical equipment must be designed and tested to meet the specific requirements of defined hazardous locations. Testing laboratories can verify that devices used for over-voltage protection and grounding meet the appropriate standards. Third party organizations, such as Underwriter's Laboratory (UL), Canadian Standards Association (CSA), and others are certified as a Nationally Recognized Testing Laboratory (NRTL) in the U.S. Similarly, other international organizations are accredited for testing to national or international standards.
For safety and grounding, the DEI Over Voltage Protector (OVP & OVP2), Polarization Cell Replacement (PCR), Solid-State Decoupler (SSD), and Polarization Cell Replacement for Hazardous Locations (PCRH) have been investigated for, and meet the following electrical requirements. The products are UL (United States) and C-UL (Canada) listed for:
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Safety Grounding - "Effective Grounding Path" • Providing an "effective ground-fault current path" as defined in 2002 NFPA 70 (US National Electrical Code - NEC), Article 250.2, and required in 250.4(A)(5) • Similarly, it meets the same per Canadian Standards Association CSA C22.2 No. 0.4-M1982 (reaffirmed 1999), using Canadian Electrical Code Part I, section 10-500, 10-806 as a guide. • Providing DC isolation of objectionable DC ground currents from cathodic protection systems as defined in NFPA 70, Article 250.6(E) • Providing over-voltage protection in accordance with the applicable requirements of ANSI C62.11 |
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Hazardous Location Listings In addition, the OVP and PCRH were certified for use in Class I, Divisions 1 & 2, Groups B, C, D hazardous locations as defined in: • UL 1203: Explosion-proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations The PCR, SSD, and OVP2 have been listed for use in Class I, Division 2, Groups A, B, C, D hazardous locations by UL and C-UL, according to: |
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CE Mark - ATEX Directive The PCR, SSD, and OVP2 have also been tested by the Notified Body UL/Demko for conformity to ATEX directive 94/9/EC, according to the standard EN50021:1999 "Electrical apparatus for potentially explosive atmospheres - Type of protection "n" |
The above products are name-plated for use in hazardous locations, with the UL, C-UL, and/or CE mark and description, as appropriate.
Compliance to the above standards assures that the DEI devices provide electrical over-voltage protection and safety grounding.
The above products are name-plated for use in hazardous locations, with the UL, C-UL, and/or CE mark and description, as appropriate.
