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Hazardous Area Classifications and

Protections

The intent of this document is to provide a broad

overview of hazardous area classifications and the

types of protection techniques involved. The

information provided in this bulletin is for educational

purposes and should not be used in place of any other

source or governing documents.

Not all approvals are covered in this bulletin. Contact

your Emerson Process Management sales office for

information on approvals not covered in this bulletin.

Contact your Emerson Process Management sales

office for product specific hazardous area approval

information or visit our website at www.Fisher.com.

Hazardous Area

Classifications

When electrical equipment is used in, around, or near

an atmosphere that has flammable gases or vapors,

flammable liquids, combustible dusts, ignitable fibers

or flyings, there is always a possibility or risk that a fire

or explosion might occur. Those areas where the

possibility or risk of fire or explosion might occur due

to an explosive atmosphere and/or mixture is often

called a hazardous (or classified) location/area.

Currently there are two systems used to classify these

hazardous areas; the Class/Division system and the

Zone system. The Class/Division system is used

predominately in the United States and Canada,

whereas the rest of the world generally uses the Zone

system.

Class/Division System

Hazardous locations per the Class/Division system are

classified according to the Class, Division, and Group.

1. Class—The Class defines the general nature (or

properties) of the hazardous material in the

surrounding atmosphere which may or may not be in

sufficient quantities.

a. Class I—Locations in which flammable gases or

vapors may or may not be in sufficient quantities to

produce explosive or ignitable mixtures.

b. Class II—Locations in which combustible dusts

(either in suspension, intermittently, or

periodically) may or may not be in sufficient

quantities to produce explosive or ignitable

mixtures.

c. Class III—Locations in which ignitable fibers may

or may not be in sufficient quantities to produce

explosive or ignitable mixtures.

2. Division—The Division defines the probability of the

hazardous material being able to produce an explosive

or ignitable mixture based upon its presence.

a. Division 1 indicates that the hazardous material

has a high probability of producing an explosive or

ignitable mixture due to it being present

continuously, intermittently, or periodically or from

the equipment itself under normal operating

conditions.

b. Division 2 indicates that the hazardous material

has a low probability of producing an explosive or

ignitable mixture and is present only during

abnormal conditions for a short period of time.

3. Group—The Group defines the type of hazardous

material in the surrounding atmosphere. Groups A, B,

C, and D are for gases (Class I only) while groups E, F,

and G are for dusts and flyings (Class II or III).

a. Group A—Atmospheres containing acetylene.

b. Group B—Atmospheres containing a flammable

gas, flammable liquid-produced vapor, or

combustible liquid-produced vapor whose MESG is

less than 0.45 mm or MIC ratio is less than 0.40.

Hazardous Area Classifications

D103222X012

Product Bulletin

9.2:001

June 2012

Summary of content (8 pages)

PAGE 1
Product Bulletin Hazardous Area Classifications 9.2:001 June 2012 D103222X012 Hazardous Area Classifications and Protections The intent of this document is to provide a broad overview of hazardous area classifications and the types of protection techniques involved. The information provided in this bulletin is for educational purposes and should not be used in place of any other source or governing documents. Not all approvals are covered in this bulletin.
PAGE 2
Product Bulletin Hazardous Area Classifications 9.2:001 June 2012 Typical gases include hydrogen, butadiene, ethylene oxide, propylene oxide, and acrolein. c. Group C—Atmospheres containing a flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor whose MESG is greater than 0.45 mm but less than 0.75 mm or MIC ratio is greater than 0.40 but less than 0.80. Typical gases include ethyl either, ethylene, acetaldehyde, and cyclopropane. d.
PAGE 3
Hazardous Area Classifications Product Bulletin 9.2:001 June 2012 D103222X012 Class/Division system n Explosion-proof—A type of protection that utilizes an enclosure that is capable of withstanding an explosive gas or vapor within it and or preventing the ignition of an explosive gas or vapor that may surround it and that operates at such an external temperature that a surrounding explosive gas or vapor will not be ignited thereby.
PAGE 4
Product Bulletin Hazardous Area Classifications 9.2:001 June 2012 D103222X012 Table 1.
PAGE 5
Hazardous Area Classifications Product Bulletin 9.2:001 June 2012 D103222X012 European Approvals International Approvals Each country belonging to the European Union has established one or more “Notified Bodies” for product approval. Notified Bodies not only approve products for use within their own country, commonly called national certifications/approvals, but also for any other country within the union, known as CENELEC certifications/approvals.
PAGE 6
Product Bulletin Hazardous Area Classifications 9.2:001 June 2012 D103222X012 Figure 1. Typical I.S Installation HAZARDOUS AREA DVC6010 NON-HAZARDOUS AREA I.S. BARRIER Vmax = 30 VDC Imax = 226 mA Pi = 1.4 W Ci = 5 nF Li = 0.55 mH Voc = ? Isc = ? Ca = ? La = ? FIELD COMMUNICATOR Voc = 1.
PAGE 7
Product Bulletin Hazardous Area Classifications 9.2:001 June 2012 D103222X012 Determine Voc and Isc of the barrier. Note that in this example the output of the 475 (Voc(475) and Isc(475)) must also be considered because it can also add energy to the loop besides just the barrier itself. Voc of the barrier plus any additional voltage that could be added to the loop from each device must be subtracted from Vmax for each device.
PAGE 8
Product Bulletin 9.2:001 June 2012 Hazardous Area Classifications D103222X012 Neither Emerson, Emerson Process Management, nor any of their affiliated entities assumes responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use, and maintenance of any product remains solely with the purchaser and end user. Fisher and FIELDVUE are marks owned by one of the companies in the Emerson Process Management business unit of Emerson Electric Co.