Mechanical equipment in EX-areas - Trainor

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ATEX regulations cover non-electrical (mechanical) equipment.

What does that really mean? Does all mechanical equipment such as manual valves and or larger mechanical components to be installed in a zone 2 or zone 1 have to be Ex-approved and have Ex/ATEX signs? Or by carrying out a risk assessment and implementing the necessary measures (e.g. earth connection, insulation of hot surfaces, etc.) can you use completely normal valves, filters and other components without Ex approval?

(Sorry if the question is not detailed enough. The use of electrical equipment in classified areas is fairly well regulated. But when it comes to mechanical equipment, there may be some uncertainties. How to handle valves and such equipment for use in Ex areas).

This question was originally asked in Norwegian on the trainor.no Forum and has been translated.

In the U.S.A., regulatory bodies have adopted the National Fire Protection Association (NFPA) 70®, National Electric Code® (NEC) to establish a hazardous classification system for electrical equipment. The NFPA 70 NEC uses a system that designates hazardous area by Classification, Division and Group. It has also added a version of the International Electrochemical Commission&#;s, more commonly known as IEC Zone system (more to come on this later) which maintains the NEC wiring and protection methods.

NFPA 70 NEC has established hazardous zones and classifications based on Classes, Divisions and Groups that when combined, define the conditions of a specified production area. This provides the manufacturer with the needed information to source equipment that will operate safely within the designated area. The primary purpose of these designations is to prevent explosions within the equipment and surrounding atmosphere to protect workers.

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The classification of this rating system defines what type of flammable material is present in the area. For example, Class I designates flammable gases and/or vapors are present in the environment. Class II designates that combustible powders can be present, and Class III if used for fibers and flyings that can be easily ignited.

Divisions determine the concentration, or how often the flammable sources are present in the atmosphere. Division 1 is used when these conditions are present under normal operation conditions. Basically, the area of operation has flammable or combustible materials in the atmosphere all or most of the time. Division 2 is used when these conditions are not typically present in the atmosphere, or are unlikely to occur. A typical Classification and Division chart would look something like this:

NFPA 70 NEC Hazardous Locations Classes, Divisions and Groups

Class Division Group I - Flammable gases or vapors may be present

1- Ignitable concentrations exist some of the time or all of the time under normal operation conditions.
2- Ignitable concentrations are not likely to exist under normal operation conditions, but can occur infrequently. 

A -  Acetylene
B - Hydrogen
C - Ethylene
D - Propane
 

II- Combustible dust may be present 1- Ignitable concentrations exist some of the time or all of the time under normal operation conditions.
2- Ignitable concentrations are not likely to exist under normal operation conditions, but can occur infrequently.  E - Metal dust
F - Coal dust
G - Grain Dust III - Ignitable fibers or flying may be present 1- Ignitable concentrations exist some of the time or all of the time under normal operation conditions.
2- Ignitable concentrations are not likely to exist under normal operation conditions, but can occur infrequently.  None Specified

 

The Occupational Safety and Health Administration (OSHA) adopted these hazardous classifications (except the groups) as defined in the 29 Code of Federal Register (CFR) .399. In 29 CFR .307(c)(2)(ii), OSHA requires all equipment used in a hazardous location be marked with the class, division and operating temperature for which it is approved. One interesting thing to note, according to .407(b)(2)(ii)(A), &#;equipment of the non-heat-producing type (such as junction boxes, conduit, and fitting) and equipment of the heat-producing type having a maximum temperature of not more than 100 degrees C (212 degrees F) need not have a marked operating temperature or temperature range&#;.

OSHA will accept equipment as long as it has a specific mark by one of the NRTLs (Nationally Recognized Testing Laboratory) on it. For a list of NRTLs see this link.

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