Hazardous Location Guide
North American Markings (Divisions)
Class I
Div 1
ATEX Markings
Groups A, B, C, D
Gas/Dust Group
TYPICAL GAS
A = Acetylene
B = Hydrogen
C = Ethylene
D = Propane
Permitted Class
T4
II (1) GD
Temperature Class
TYPICAL DUST
E = Metal Dust
F = Coal Dust
G = Grain Dust
Class II = Dust
(No group designation)
Hazardous Atmosphere
G = Gas
D = Dust
Equipment
Group
I = Mining
industry
II = Surface
industry
III = Surface
dust
Equipment Category
(..) = Mounted in safe area
No Parentheses = Mounted in hazardous area
North American Markings (Zones)
Class I
Zone 0
Permitted Class
A Ex ia IIC T4 Ga
Conformity to US
Requirements
Class II = Dust
Method of Protection
m = Encapsulation (Zone 0)
ia = Intrinsic safety (Zone 0)
operating conditions
normal conditions and if they
do, only for short periods
Enclosure Protection IP Rating
Protection Against Ingress of Liquids
No protection against live or moving parts
0
1
No protection
Protection against drops of condensed
2
2
3
3
4
4
Protection against liquid drops at
° from vertical
Protection against rain up to
60° from vertical
Protection against splashing from any
direction
Protection against water jets from any
direction under stated conditions
Protection against heavy sea water under
stated conditions
Protection against water immersion under
stated conditions of pressure and time
0
1
(i.e., the hand)
Complete protection against contact
Ingress of dust not in harmful quantities
Complete protection against contact
Protection against ingress of dust
5
6
5
6
7
Brackets
Method of
Protection
m = Encapsulation (Zone 0)
of
apparatus
going into
hazardous
Protection Concept
Symbol
Zones
European Std
Installation Authority
—
—
CENELEC
General
ia = Intrinsic safety (Zone 0)
IIIB = Nonconductive dust
IIIC = Conductive dust
Zone Method
International Std
Canadian Std
United States Std
IEC
Division
—
Division Method
Canadian Std
United States Std
Relevant Safety Std
Basic Electrical
Relevant Safety Std
Pressurization
—
—
Encapsulation
—
—
—
Powder Filled
—
—
—
Increased Safety
—
—
—
Keep the gas away from
Intrinsic Safety
Nonincendive Techniques
limit the temperature
(C,A,R)
op
—
—
—
—
—
—
Keep dust away from hot surfaces
dust from optical radiation
SAFETY INTREGRITY LEVEL (SIL)
NEMA Type Rating and Comparison
IP Code
Ma = Mining “very high”
—
—
8
Rating Type
Gas/Dust Group
IIA = Lowest requirements
IIB = Average requirements
IIC = Highest requirements
apparatus
mounted in
hazardous
area.
Ma = Mining “very high”
Temperature
Class
°C
°C
°C
°C
°C
°C
IIIB = Nonconductive dust
IIIC = Conductive dust
gases or vapors (dust cloud)
Protection Against Ingress of Solids
IIC T4 Ga
Equipment Protection Level
Gas/Dust Group
IIA = Lowest requirements
IIB = Average requirements
IIC = Highest requirements
gases or vapors (dust cloud) are
[Ex ia]
Temperature Class
°C
°C
°C
Equipment
°C
Protection Level
°C
°C
Explosion Protection
gases or vapors (dust cloud) are
present continuously or for
long periods of time
ATEX / IECEx
Protection Description
1
2
3
3R
3S
4
4X
6
6P
7
SIS SAFETY LIFE-CYCLE PHASES
low
9
—
—
10
12/12K
13
Indoor use, protects against entry of dust, dirt, and dripping water. Protects against noncorrosive liquids.
Indoor use, protects against entry of dust, dirt, dripping water, and oil. Protects against noncorrosive liquids.
RISK:
high
PROCESS RISK:
C
TOLERABLE RISK:
Standard Control Equipment
V
oc
I
sc
Ci + C
Li + L
L
Field Instrument
= Internal unprotected capacitance
= Internal unprotected inductance
Entity Comparison
Voc
Isc
Ca
La
a
Key Parts to SIL
RISK REDUCTION
Associated Apparatus
RESIDUAL RISK:
associated with a process.
Typical IS Circuit
Hazardous Area
NECESSARY RISK REDUCTION:
of harm and the severity of that harm.
Comparison based on tests per IEC 60 529. Cannot be used to convert IP code to type rating
Connecting
Cables
medium
RISK ANALYSIS
IP 67
IP 67
—
—
8
V
I
Ci
Li
RESIDUAL RISK VS TOLERABLE RISK
Explanation
SFF
The share of the safe faults or safe failures
PFD
Tproof
The test interval for the entire safety system
HFT
SFF=safe failure fraction HFT=hardware fault tolerance PFD=probability of failure on demand Tproof=test interval
a
SAFETY LIFE CYCLE:
Necessary activities involved in the implementation of
safety instrumented function(s) occurring during a
period of time that starts at the concept phase of a
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