Hazardous Source List
Hazardous Source List
Hazardous Source List
•Why classification?
-Biological: Bacteria and viruses, insect bite, blood and other body fluid etc.
HAZARD AND HAZARDOUS AREA (2/2)
•API 500
500: Hazardous
a a dous (o
(or cclassified)
ass ed) Area
ea (o
(or Location/Space)*:
oca o /Space)
“A location where fire or explosion hazards may exist due to flammable gases
or vapors, flammable liquids, combustible dust, or ignitable fibers or flyings.”
•These
These terms should be considered interchangeable terms designating a three-dimensional
three dimensional space.
WHY CLASSIFICATION?
•Explosion Protection:
WHY CLASSIFICATION?
•Explosion Protection:
Combustible liquids (Class II and Class III liquids), such as kerosene and
diesel fuel,
f are defined
f as liquids having a closed-cup flash
f point at or above
37.8°C (100°F). Class II liquids are combustible liquids having flash points at or
above 37.8°C (100°F) and below 60°C (140°F).
Class III liquids are combustible liquids having flash points at or above 60°C
60 C
(140°F).
Normally, except near points of release, Class II/III liquids do not produce
vapors of sufficient quantity to be considered for electrical classification
purposes.
*Classes as used here to identify flammable and combustible liquids should not be confused with the classes in the National Electrical Code (NEC) that identify
specific types of flammable or explosive atmospheres.
Note: A specific classification for crude oil is not possible since crude oil is a mixture of hydrocarbons of widely varying composition. Some crude oils may
include volatiles ((e.g.,
g , butane,, propane,
p p , or natural gasoline).
g ) However,, crude oil usuallyy is classified as a Class I flammable liquid,
q , and its flash point
p g
generally
y
is accepted as -6.7 to 32.2°C (20-90°F).
HAZARDOUS SUBSTANCE CLASSIFICATION (2/5)
Highly volatile liquids (HVLs) include liquids such as butane, ethane, ethylene,
propane, propylene, liquefied natural gas, natural gas liquids, and mixtures of
such. Vapor pressures of these liquids exceed 276 kilopascals (40 psia) at
37.8°C (100°F).
Closed cup Flash point of Flammable HVLs is below 37 37.8
8°C
C (100°F)
(100 F).
HAZARDOUS SUBSTANCE CLASSIFICATION (3/5)
-Purpose: 1) Testing,
2) Approval, and
3) Area classification
-Grouping based on NEC Article 505: This gas and vapor sub-division is based
on the maximum experimental safe gap (MESG), minimum igniting current
(MIC), or both.
1) Group I is intended for use in describing atmospheres containing firedamp
(a mixture of gases, composed mostly of methane, found underground,
usually in mines).
2.1) Group IIC. Atmospheres containing acetylene, hydrogen, or gases or
vapors of equivalent hazard.
2.2) Group IIB. Atmospheres containing acetaldehyde, ethylene, or gases or
vapors of equivalent hazard.
2.3) Group IIA. Atmospheres containing acetone, ammonia, ethyl alcohol,
methane,
th propane, or gases or vapors off equivalent
i l th hazard.
d
HAZARDOUS SUBSTANCE CLASSIFICATION (4/5)
-Grouping
Grouping based on NEC Article 500: This gas and vapor subsub-division
division involves
determinations of maximum explosion pressure, maximum safe clearance, and
other characteristics of the atmospheric mixture.
Group A: Atmospheres containing acetylene.
Group B: Atmospheres such as butadiene, ethylene oxide, propylene oxide,
acrolein, or hydrogen (or gases or vapors equivalent in hazard to hydrogen,
such as certain manufactured gases).
Group C: Atmospheres such as cyclopropane,
cyclopropane ethyl ether
ether, ethylene
ethylene, hydrogen
sulfide, or gases or vapors of equivalent hazard.
Group D: Atmospheres such as acetone, alcohol, ammonia, benzene, benzol,
butane, gasoline, hexane, lacquer solvent vapors, methane, naphtha, natural
gas, propane, or gases or vapors of equivalent hazard.
HAZARDOUS SUBSTANCE CLASSIFICATION (5/5)
-Temperature
Temperature Class (T
(T-Rating):
Rating): The temperature rating system is used for
explosion protection of electrical equipment.
T5 mm is
i th
the minimum
i i iignition
iti
temperature of a 5mm layer of
dust.
T12.5 mm is the minimum ignition
temperature of a 12.5mm layer
of dust.
HAZARDOUS AREA CLASSIFICATION (1/8)
Having decided that a location should be classified, and having designated the
gas or vapor as Group IIA, IIB, or IIC (or as Group A, B, C, or D), the next step
is to designate the location as:
Class II locations are those that are hazardous because of the presence of
combustible dust
dust.
Class III locations are those that are hazardous because of the presence of
easily ignitable fibers or flyings, but in which such fibers or flyings are not likely
t be
to b iin suspensioni iin th
the air
i iin quantities
titi sufficient
ffi i t tto produce
d iignitable
it bl
mixtures.
HAZARDOUS AREA CLASSIFICATION (3/8)
Class I- Division 1 / Division 2 (as per API 500)- American style:
API RP 500 Recommended Practice for Classification of Locations for electrical Installation at Petroleum Facilities
Classified as Class I, Division 1 and Division
2.IEC:
IEC 60079-10 Electrical Apparatus for explosive gas atmospheres- Part 10: Classifications of hazardous Area.
IEC 60079
60079-12
12 Classification of Mixtures of Gases or vapors with air according to their maximum experimental Gaps
(MEGs) and minimum ignition currents ratio (MIC).
IEC 60079-20 Electrical Apparatus for explosive gas atmospheres- Part 20: Data for flammable gases and vapors,
relating to the use of electrical apparatus.
3.NFPA:
NFPA 325: Guide to fire Hazard Properties of Flammable Liquids, Gases, and volatile Solids
NFPA 497: Recommended practice for the Classification of Flammable Liquids, Gases or Vapors and of Hazardous
(classified) Locations for Electrical Installations in Chemical Process Areas.
Codes & Standards
4.OISD:
OISD 113: Classification of areas for electrical installations hydrocarbon processing and handling facilities.
5.IS:
IS 5571: Guidance for selection and installation of electrical equipments in hazardous areas. .
IS 5572: Classification of hazardous areas having flammable gases and vapors for electrical installation
Hazardous Area Demarcation (1/4)
Required materials:
2) Plot plan
3) Equipment list
2) Plot Plan:
3) Equipment List:
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