PEC CHAPTER 5 SPECIAL OCCUPANCIES Flashcards
Reference Standards of Hazardous Locations
National Fire Protection Association (NFPA)
American Petroleum Institute (API)
Instrumentation Systems and Automation Society (ISA)
Locations have been classified depending on the properties of the flammable vapors, liquid, or gasses, or combustible dusts or fibers that may be present.
HAZARDOUS LOCATIONS
Flammable gases or vapor are present in air which is sufficient to produce explosive or ignitable mixtures.
CLASS I LOCATIONS
a) Ignitable concentrations of flammable gases or vapors can exist.
b) Existence of gas due to frequent repair or maintenance operation or because of leakage.
c) Release of such gasses due to breakdown, failure or faulty operation of equipment.
CLASS I, DIVISION 1
a) Volatile flammable liquids or flammable gases are handled, processed, but in which liquids and gases are confined and can escape only in case of accidental rupture or breakdown, or such abnormal operation.
b) Mechanical ventilations prevent ignitable concentrations of gases or vapors and failure or abnormal operation might become hazardous.
c) Gases or vapors might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air
CLASS I, DIVISION 2
Locations that has presence of combustible dust.
CLASS II LOCATIONS
a) Combustible dust is in the air under normal operating conditions.
b) Where mechanical failure of abnormal operation of machinery or equipment might cause such explosive or ignitable mixtures to be produced.
c) Group E combustible dusts may be present in quantities sufficient to be hazardous.
CLASS II, DIVISION 1
a) Presence of combustible due to abnormal operations
b) Dust accumulations are present in normal operation but are insufficient to be hazardous but infrequent malfunctioning of handling/processing equipment it would be hazardous
CLASS II, DIVISION 2
Locations that has the presence of ignitable fibers or flyings.
CLASS III LOCATIONS
Ignitable fibers are handled, manufacture or used.
CLASS III, DIVISION 1
Ignitable fibers are stored, handled and manufactured
CLASS III, DIVISION 2
MATERIAL GROUPS
MESG
Maximum Experimental Safe Gap
MATERIAL GROUPS
MIC
Minimum Igniting Current Ratio
MATERIAL GROUPS
CLASS I GROUP CLASSIFICATIONS
Acetylene
Group A-
MATERIAL GROUPS
CLASS I GROUP CLASSIFICATIONS
Flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode, MESG value is less than or equal 0.45 mm, MIC ratio is less than or equal to 0.40 mm.
Group B
MATERIAL GROUPS
CLASS I GROUP CLASSIFICATIONS
Flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode, MESG value is greater than 0.45 mm and less than or equal to 0.75 mm, MIC ratio than 0.40 and less than or equal to 0.80.
Group C
MATERIAL GROUPS
CLASS I GROUP CLASSIFICATIONS
Flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode, MESG value > 0.75 mm, MIC ratio > 0.80.
Group D
MATERIAL GROUPS
CLASS II GROUP CLASSIFICATIONS
Atmospheres containing combustible metal dusts, including aluminum, magnesium, and their commercial alloys, or other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards in the use of electrical equipment
Group E
MATERIAL GROUPS
CLASS II GROUP CLASSIFICATIONS
Atmospheres containing combustible carbonaceous dusts that have more than 8 percent total entrapped volatiles. Carbonaceous dust ex. Coal, carbon black, charcoal, and coke dusts.
Group F
MATERIAL GROUPS
CLASS II GROUP CLASSIFICATIONS
Atmospheres containing combustible dusts not included in Group E or F, including flour, grain, wood, plastic, and chemicals.
Group G
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Encloses the parts w/c could ignite the atmosphere by sparking or heating.
Encapsulation “m.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection
- Enclosure can withstand an internal explosion of flammable mixture that has penetrated into the interior, without suffering damage and w/o causing ignition in joints or openings.
Flameproof “d.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Applied to electrical equipment that does not produce arcs in normal service and under specified abnormal conditions, increased security is given against the possibility of excessive temperatures and of the occurrence of arcs and sparks.
Increased Safety “e.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Any spark or thermal effect is incapable of causing ignition of a mixture of flammable or combustible material in air under prescribed test conditions.
Intrinsic Safety “i.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Electrical equipment is immersed in a protective liquid in such a way that an explosive atmosphere that may be above the liquid or outside the enclosure cannot be ignited.
Oil Immersion “o.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Electrical parts capable of igniting an explosive atmosphere are fixed in position and completely surrounded by filling material (glass or quartz powder) to prevent the ignition of an external explosive atmosphere
Powder Filling “q.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Types of Protection:
- Electrical equipment, in normal operation, is not capable of igniting a surrounding explosive gas atmosphere and a fault capable of causing ignition is not likely to occur.
Type of Protection “n.”
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Classification of Locations:
a) Ignitable concentrations of flammable gas/vapors are not likely to occur under normal conditions; but if they do, will exist only for short period
b) Volatile flammable liquids or flammable gases are handled, processed, but in which liquids and gases are confined and can escape only in case of accidental rupture or breakdown, or such abnormal operation.
Class I, Zone 2
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Classification of Locations:
- Ignitable concentrations of flammable gases or vapors are present continuously or for long periods of time
Class I, Zone 0
CLASS I, ZONE 0, 1, AND 2 LOCATIONS
Classification of Locations:
a) Ignitable concentrations of flammable gas/vapors may exist under normal conditions
b) Ignitable concentrations of flammable gas/vapors may exist because of repair/ maintenance
c) Equipment breakdown or faulty operation could result in the release of ignitable concentrations of flammable gas/vapors
Class I, Zone 1
