FEDIOL Guide To Good Practice On Safe Operation of Hydrogenation Units (Applicable As From 01 October 2007)
FEDIOL Guide To Good Practice On Safe Operation of Hydrogenation Units (Applicable As From 01 October 2007)
FEDIOL Guide To Good Practice On Safe Operation of Hydrogenation Units (Applicable As From 01 October 2007)
07SAF244
DEFINITIONS ............................................................................................................................................... 3
4.4
4.5
In
In
In
In
In
In
line
line
line
line
line
line
with
with
with
with
with
with
risk
risk
risk
risk
risk
risk
assessment
assessment
assessment
assessment
assessment
assessment
conducted............................................. 20
conducted ................................................................. 20
conducted ................................................................. 20
conducted ................................................................. 20
conducted ................................................................. 20
conducted ................................................................. 20
168, avenue de Tervuren (bte 12) B 1150 Bruxelles Tel (32) 2 771 53 30 Fax (32) 2 771 38 17 Email : fediol@fediol.be http://www.fediol.be
168, avenue de Tervuren (bte 12) B 1150 Bruxelles Tel (32) 2 771 53 30 Fax (32) 2 771 38 17 Email : fediol@fediol.be http://www.fediol.be
1 Definitions
1.
2.
3.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Condensate: any material that has been condensed from the vapor
state to the liquid state.
Condenser: a piece of equipment that lowers the temperature of a
vapor to the point where it changes to a liquid.
Hydrogenation Supervisor: the person in charge of the
hydrogenation process
Hydrogenation Process: The Hydrogenation Process is an exothermic
chemical reaction of hydrogen with unsaturated triglycerides under
influence of temperature, pressure and a catalyst, typically a nickel
compound. It's a batch process taking place in a dead end or loop
reactor. The purpose of hydrogenation is to increase the resistance
of the oil to rancidity and/or changing the melting behavior of the
oil. Physical characteristics will change under the hydrogenation
process where viscosity and melting point will increase as the degree
of saturation increases.
Catalyst : A substance that influences the chemical reaction without
being used in the reaction. At the end of the reaction the catalyst is
still chemically unchanged.
Flame Arrester : a device that prevents the transmission of a flame
through a flammable gas/air mixture by quenching the flame on the
surfaces of an array of small passages through which the flame must
pass. The emerging gases are sufficiently cooled to prevent ignition
on the protected side.
Heat Exchanger : equipment that transfers heat from one vapor or
liquid to another vapor or liquid.
Hydrocarbon : a chemical substance consisting of only hydrogen and
carbon atoms.
Inert Gas : a gas that is noncombustible and nonreactive.
Inerting : a technique by which a combustible mixture is rendered
non-ignitible by adding an inert gas.
Lower Flammable Limit (LFL) : that concentration of a combustible
material in air below which ignition will not occur.
Noncombustible Material : a material that, in the form in which it is
used and under the conditions anticipated, will not ignite, burn,
support combustion, or release flammable vapors when subjected to
fire or heat. Materials that are reported as passing ASTM E 136,
Standard Test Method for Behavior of Materials in a Vertical Tube
Furnace at 750C and in accordance with European Directive
89/106/EEC (the Construction Product Directive with links to
standards for testing and approval), shall be considered
noncombustible materials.
Site Management : the management in charge of all operations of
several units on the same site.
Upper Flammable Limit (UFL) : that concentration of a combustible
material in air above which ignition will not occur.
2.3.4
2.3.5
2.3.6
2.3.7
3.1.1.2
3.1.2 Procurement
3.1.2.1
3.1.3 Contracting
3.1.3.1
3.1.4.2
3.1.4.3
Site Management ensures that all unplanned events in the zoned areas
are investigated and that corrective or preventive measures are taken
to avoid re-occurrence.
3.1.6 Audit
3.1.6.1
Site management has put a plan in place to ensure that all elements as
listed in this document are yearly audited and where required
improvements are made.
3.1.8.2
89/391/EEC
94/9/EC
97/23/EC
98/37/EC or 2006/42/EC
Machine Directive
1999/92/EC
4.2.2
4.2.3
4.2.4
4.2.4.1
2.016
0.06960
0.08342 kg/m3
0.019
100
-252.76C
4.2.4.2
4.2.4.3
4.2.5
4.2.5.1
4.2.5.2
4.2.5.3
4.2.5.4
4.2.5.5
4.2.5.6
4.2.5.7
4.2.5.8
4.2.5.9
4.2.5.10
4.2.5.11
4.2.5.12
4.2.5.13
10
4.3.1.1.2
4.3.1.1.2.1
Location
Outdoors
In detached
building
4.3.1.1.2.2
Quantity of hydrogen
< (MAQ)
>MAQ to
100m3 to
<100m3
<400 m3
A
A
A
A
A
A
In a gas
room
Not in a gas
room
NA
NA
400m3 and
above
A
A
Detached
building
required
NA
11
400m3 +
above
Type of Outdoor
Distance in
Distance in
Distance in
Exposure
meter
meter
meter
(1) Building or structure
(A) Wall(s) adjacent to system constructed of noncombustible or limitcombustible materials
1. noncombustible
0
1.5
1.5
contents or sprinklered
building or structure
2. unsprinklered building
or structure with
combustible content
(a) Adjacent wall(s) with
0
3.0
7.5
fire resistance rating less
than 2 hours
(b) Wall(s) adjacent to
0
1.5
1.5
system constructed of
combustible content
(B) Wall(s) adjacent to
3.0
7.5
15.0
system constructed of
other than
noncombustible or
limited-combustible
materials
(2) Wall openings
(A) Not above any part of
3.0
3.0
3.0
a system
(B) Above any part of a
7.5
7.5
7.5
system
(3) All classes of flammable and combustible liquids above ground
(A) 0-3500 liter
3.0
7.5
7.5
(B) in excess of 3500 liter
7.5
15.0
15.0
(4) All classes of flammable and combustible liquids below ground from
0-3500 liter
(A) Tank
3.0
3.0
3.0
(B) Vent or fill opening of
tank
(5) All classes of
flammable and
combustible liquids
below ground in excess
of 3500 liter
(A) Tank
(B) Vent or fill opening of
tank
7.5
7.5
7.5
6.0
7.5
6.0
7.5
6.0
7.5
12
(6) Flammable gas storage (other than hydrogen), either high- or lowpressure
3.0
7.5
7.5
(A) 0-400m3 capacity
3
(B) in excess of 400m
7.5
15.0
15.0
capacity
15.0
15.0
15.0
(7) Fast-burning solids,
such as ordinary lumber,
excelsior, or paper
(8) Slow-burning solids
7.5
7.5
7.5
such as heavy timber or
coal
7.5
7.5
7.5
(9) Open flames and
welding
15.0
15.0
15.0
(10) Air compressor
intakes or inlets to
ventilating or air-co
equipment
7.5
15.0
15.0
(11) Places of public
assembly
4.5
4.5
4.5
(12) Public sidewalks and
parked vehicles
1.5
1.5
1.5
(13) Line of adjoining
property that is able to
be built upon
(14) Encroachment by
overhead utilities
(A) Horizontal distance
15.0
15.0
15.0
from the vertical plane
below the nearest
overhead wire of an
electric trolley, train, or
bus line
(B) Horizontal distance
1.5
1.5
1.5
from the vertical plane
below the nearest
overhead wire other than
(A)
(C) Piping containing
4.5
4.5
4.5
other hazardous materials
13
4.3.1.1.2.3
4.3.1.1.2.4
4.3.1.1.2.5
4.3.1.1.2.6
4.3.1.1.2.7
4.3.1.2
4.3.1.2.1
4.3.1.2.2
4.3.1.2.3
4.3.1.2.4
4.3.1.2.5
4.3.1.2.6
4.3.1.2.7
The distances in numbers (1), (3) through (9), and (13) inclusive in the
table in 4.3.1.1.2.2 shall not apply where fire barrier walls having a
minimum fire resistance rating of 2 hours are located between the
system and the exposure.
Portions of wall more than 3m (measured horizontally) from any part of
a system shall have a fire resistance rating of at least hour.
When determining the minimum distance between the hydrogen
system and the adjacent fire-rated walls, windows and doors shall be
excluded from the fire rating determination.
Portions of wall less than 3m (measured horizontally) from any part of
a system shall have a fire resistance rating of at least 1 hour.
Unloading connections on delivery equipment shall not be positioned
closer to any of the exposures sited in the table under 4.3.1.1.2.2 than
the distances given for the storage system
Hydrogenation process
The hydrogenation process shall be located in the open or in a building
suitable for the purpose. The building shall be a light construction.
Existing buildings not meeting this requirement will be provided with
areas of light construction.
The zoned areas shall be posted with signs EX (triangular shape yellow
with black surround) around the perimeter warning of the possible
explosion hazard.
The building or structure housing the hydrogenation process shall be of
fire-resistive or noncombustible construction with the ground floor at or
above grade.
An hydrogenation building or open process structure over two stories in
height shall be provided with at least two remotely located means of
egress from each floor, one of which shall be enclosed or separated
from the process by a wall that is blank except for doors.
The enclosure or separating wall shall be of masonry or other
noncombustible construction.
Self-closing, noncombustible doors, normally kept closed, shall be
provided for access to the means of egress.
Indoor Hydrogen System Location.
A separable part of a process containing hydrogen of less than 100
m3 and greater than the MAQ, where located inside buildings, shall
be located in the building so that the system will be as follows:
(1)
In a ventilated area
(2)
Separated from incompatible materials
(3)
7.5 m from open flames and other sources of ignition
(4)
15 m from intakes of ventilation, air-conditioning equipment,
and air compressors
(a)
The distance is permitted to be reduced to 3 m where the
room or area is protected by a listed detection system that shall
shut down the fuel supply in the event of a leak that results in a
concentration that exceeds 25 percent of the LFL.
(b)
Isolation valves used to isolate the fuel supply shall be of a
fail-safe design.
(5)
15 m from other flammable gas storage
14
4.3.1.3
4.3.1.3.1
4.3.1.4
4.3.1.4.1
4.3.1.4.2
4.3.1.5
4.3.1.5.1
4.3.1.5.2
4.3.1.6
4.3.1.6.1
4.3.1.6.2
(6)
Protected against damage
More than one system of 100 m3 or less shall be permitted to be
installed in the same room or area, provided the systems are
separated by at least 15 m or a full-height fire-resistive partition
having a minimum fire resistance rating of 2 hours is located
between the systems.
The separation distance between multiple systems of 100 m3 or
less shall be permitted to be reduced to 7.5 m in buildings where
the space between storage areas is free of combustible materials
and protected with a sprinkler system.
Inerting
Whenever required, the hydrogenation installation (piping,
equipment and reactor) shall be either purged a few times with
nitrogen and/or purged by vacuum followed by pressure
equalization with nitrogen see 4.3.1.5.1
Venting
The hydrogen gas supply is stopped and excess pressure is vented
from the reactor after the hydrogenation reaction and is evacuated
to a safe location either outside, vertically vented to the
atmosphere above roof level, or to a buffer vessel for re-use of
hydrogen.
The hydrogenated oil will be subject to further treatment prior to
discharge to the final product tanks.
Vacuum
Vacuum is used to purge the installation from hydrogen while
pressure is equalized with nitrogen (see paragraph 4.3.1.3.1).
the risk of residual hydrogen gas in the oil in final storage tanks
may be considered to be highly limited.
Safety devices
Excessive temperature in the reactor or loss of cooling water will
close the safety shutoff valve for the hydrogen supply.
Safety valves shall separate the hydrogenation process from
upstream and downstream processes.
15
4.3.2.2
Truck
delivery of
H2
Direct H2
supply
H2 Storage
Hydrogenation
Inert gas
Venting excess
pressure
Vacuum
Inerting
Filtration
Spent catalyst
Product
16
4.3.3.1
4.3.3.1.1
4.3.3.1.2
4.3.3.1.3.
4.3.3.2
4.3.3.2.1
4.3.3.2.2
4.3.3.2.3
4.3.3.2.4
4.3.3.2.5
4.3.3.2.6
4.3.3.2.7
4.3.3.3
4.3.3.3.1
17
(4)
4.3.4.2
4.3.4.2.1
4.3.4.2.2
4.3.4.2.3
4.3.4.2.4
4.3.4.2.5
4.3.4.2.6
4.3.4.3
4.3.4.3.1
4.3.4.3.2
4.3.4.4
4.3.4.4.1
4.3.5.2
18
and sloped roof areas to avoid that hydrogen gets trapped in deadend corners of the roof construction.
If entrapment cannot be avoided, a hydrogen detection system has to
be installed to ensure that in case of the formation of explosive
mixtures no ignition sources will be active in that area, or other
measures have to be implemented to avoid the risk of an explosion.
4.3.6.1.1
4.3.6.1.2
4.3.6.2
4.3.6.3
4.3.6.3.1
4.3.6.3.2
4.3.6.4
4.3.6.4.1
4.3.6.4.2
4.3.6.5
4.3.6.5.1
General
To ensure that ignition through equipment is avoided, there are two
options :
Equipment made available for the first time before June, 30, 2003 should
be assessed using the standard EN 13463-1. The equipment should be
assessed for normal operating conditions when installed in an area
classified as zone 2, and for normal operating conditions and expected
malfunctions when installed in an area classified as zone 1. Equipment
installed in an area classified as zone 0 should be assessed for: normal
operating conditions, expected malfunctions and rare malfunctions.
All equipment made available for the first time after June 30, 2003 should
meet the appropriate minimum requirements as listed in Directive
94/9/EC. This means a Declaration of Conformity with the minimum
requirements of the Directive 94/9/EC should be present for each piece of
equipment.
Hot surfaces
Hot surface temperatures shall not exceed 500C.
Flames and hot gases
Flares or burners from process vents shall be prohibited within areas
classified as zone 0, 1 and 2, but shall be permitted to be installed outside
these areas. Such flares or burners shall be equipped with approved
devices to prevent flashbacks in the vent piping.
To prevent potential explosions caused by fire in the building a
sprinkler/deluge should be considered.
Mechanically generated sparks
In mechanical equipment that has moving parts and where friction,
impact or abrasion can occur, the combination of light metal and steel
should be avoided. The contents of light metal for category 1 equipment
(for use in zone 0,1 and 2) should be not more than 10% in total by mass
of aluminum, magnesium, titanium and zirconium or not more than 7.5%
in total by mass of magnesium, titanium and zirconium.
For category 2 equipment (for use in zone 1 and 2) not more than 7.5%
by mass of magnesium.
For category 3 equipment (for use in zone 2) there are no special
requirements for light metal use.
The use of non-sparking tools and equipment is compulsory when the
installation is operating or when hydrogen can be present.
Power transmission belts shall not be used in any area that is classified as
a zone 0, 1 and 2.
Electrical apparatus (see Annex 3)
Electrical equipment used in hazardous places shall meet the
requirements for at least category 2 equipment in accordance with
Directive 94/9/EC or equivalent when made available for the first time
19
4.3.6.6
4.3.6.7
4.3.6.7.1
4.3.6.7.2
4.3.6.7.3
4.3.6.7.4
4.3.6.7.5
4.3.6.7.6
4.3.6.7.7
4.3.6.8.
4.3.6.8.1
4.3.6.9
4.3.6.10
4.3.6.11
4.3.6.12
4.3.6.13
4.3.6.14
4.3.6.14.1
before June 30, 2003. Equipment made available for the first time after
June 30, 2003 must be selected on the basis of the zoning as per
Directive 1999/92/EC Annex I and comply with Directive 94/9/EC. In
accordance with the explosion protection document the work equipment,
including warning devices, must be designed, operated and maintained
with due regard to safety.
Stray electrical currents, cathodic corrosion protection
4.3.6.1.1.1.1 In line with risk assessment conducted.
Static electricity
Transfer or storage tanks, unloading structures, tank cars, and tank
trucks shall be electrically interconnected with supply piping or containers
during the transfer of hydrogen.
Static protection shall be installed in accordance with accepted good
practice and tested periodically by a competent person.
All tanks, vessels, motors, pipes, conduit, grating, and building frames
within the process shall be electrically bonded together.
Building frames and metal structures shall be grounded and tested
periodically to determine electrical continuity.
All hose, except hose used in water service, shall be electrically bonded to
the supply line and to the tank or vessel where discharge takes place.
All clothing consists of materials which dont give rise to electrostatic
discharges that can ignite explosive atmospheres.
Hydrogen - Electrostatic Ignition Sources
Hydrogen has a low MIE. Safeguards / control measures are required to
eliminate low energy electrostatic discharges capable of igniting
hydrogen. Particular care must be taken to control electrostatic risks
associated with:
personnel; controlled by the use of antistatic footwear and flooring
providing a resistance to earth < 108.
the use of non-conductive (e.g. plastic) components.
Lightning
Where required, an approved lightning protection system, installed in
accordance with the Standard for the Installation of Lightning Protection
Systems, shall be provided for the extraction process.
Electromagnetic fields in the frequency range from 9 kHz to 300
GHz
4.3.6.1.1.2 In line with risk assessment conducted
Electromagnetic radiation in the frequency range from 300 GHz to
3million GHz
4.3.6.1.1.3 In line with risk assessment conducted
Ionizing radiation
4.3.6.1.1.4 In line with risk assessment conducted
Ultrasonic
4.3.6.1.1.5 In line with risk assessment conducted
Adiabatic compression, shock waves, gas flows
4.3.6.1.1.6 In line with risk assessment conducted
Chemical reactions
Catalyst (fresh and spent) conveyors shall be of a design that minimizes
the possibility of ignition of product deposits.
The use of nitrogen gas may be considered to reduce the risk of auto-
20
4.3.6.14.2
ignition of
Insulation
smolders.
Insulation
fats
spent catalyst.
materials soaked with oils and fats may generate hot spots and
Hot surfaces (as such tracings) will accelerate this process.
will be designed as to avoid ingress of / soaking with oils and
4.4.2
4.4.3
4.5.4
4.5.5
4.5.6
21
Zone classification
outside equipment
Area description
Inside hydrogenation process
building
Hydrogen truck unloadinghoses and connections in
tanker bay
Hydrogen truck
connection/disconnection
and discharge
Seals
Zone
Zone
dimensions
Electrical/Mechanical
equipment
category
II 3G
2 m around
II 2G
2 m around
II 2G
II 2G
Within 5 m
around exhaust
point
In area
between 5 and
10 m around
exhaust point
Min. 2 m around
and vertical
column above
depending on
the flow
released
Remarks
* See additional remark
below
Unless otherwise specified
below
In accordance with
equipment supplier
See also 4.3.5.2
II 2G
II 3G
II 2G
./.
* Additional remark: local zones (usually spheric form) should be extended with a vertical cylinder upwards of
at least 5 m high and reaching minimum 3 m above any building or equipment in the direct neighborhood.
22
Zone
Electrical/Mechanical equipment
category
Hydrogen equipment up to
isolation valves
II 2G
II 1G
Pumps
II 2G
(continued)
Remarks
23
Application
Zoning
ATEX (1999/92/EC)
Electrical and mechanical equipment
could provide ignition source not only
through failure.
Equipment classification for suited use in zone /classified areas NFPA 70 also refers
to zone 0,1,2, and 20, 21, 22 as these are IEC :
Zone
NFPA 70 (applies to
electrical only)
0
1
Class I division 1
Class I division 1
Class I division 1 or
Class I Division 2
20
21
Class II Division 1
Class II Division 1
22
Class II Division 1 or
Class II division 2
1999/92/EC refers to
94/9/EC (applies to
electrical and
mechanical)
Group II, category 1G
Group II, category 1G or
Group II, category 2G
Group II, category 1G or
Group II, category 2G or
Group II, category 3G
Group II, category 1D
Group II, category 1D or
Group II, category 2D
Group II, category 1D or
Group II, category 2D or
Group II, category 3D
24
NFPA Zoning
NFPA 497
Class I,
Division 1
Class I,
Division 2
versus ATEX
1999/92/EC
is a location
(1) in which ignitable concentrations of flammable gases or vapors
can exist under normal operating conditions, or
(2) in which ignitable concentrations of such gases or vapors may
exist frequently because of repair or maintenance operations or
because of leakage, or
(3) in which breakdown or faulty operation of equipment or processes
might release ignitable concentrations of flammable gases or
vapors and might also cause simultaneous failure of electrical
equipment in such a way as to directly cause the electrical
equipment to become a source of ignition. [70:500.5(B)(1)]
is a location
(1) in which volatile flammable liquids or flammable gases are
handled, processed, or used, but in which the liquids, vapors, or
gases will normally be confined within closed containers or closed
systems from which they can escape only in case of accidental
rupture or breakdown of such containers or systems or in case of
abnormal operation of equipment, or
(2) in which ignitable concentrations of gases or vapors are normally
prevented by positive mechanical ventilation, and which might
become hazardous through failure or abnormal operation of the
ventilating equipment, or
(3) that is adjacent to a Class I, Division 1 location, and to which
ignitable concentrations of gases or vapors might occasionally be
communicated unless such communication is prevented by
adequate positive-pressure ventilation from a source of clean air
and effective safeguards against ventilation failure are provided.
[70:500.5(B)(2)]
./.
25
NFPA 497
Class I,
Zone 0
is a location
(1) ignitable concentrations of flammable gases or vapors are
present continuously, or
(2) ignitable concentrations of flammable gases or vapors are
present for long periods of time. [70:505.5(B)(1)]
Zone 0
Class I,
Zone 1
is a location
(1) in which ignitable concentrations of flammable gases or
vapors are likely to exist under normal operating conditions;
or
(2) in which ignitable concentrations of flammable gases or
vapors may exist frequently because of repair or maintenance
operations or because of leakage; or
(3) in which equipment is operated or processes are carried on,
of such a nature that equipment breakdown or faulty
operations could result in the release of ignitable
concentrations of flammable gases or vapors and also cause
simultaneous failure of electrical equipment in a mode to
cause the electrical equipment to become a source of ignition;
or
(4) that is adjacent to a Class I, Zone 0 location from which
ignitable concentrations of vapors could be communicated,
unless communication is prevented by adequate positive
pressure ventilation from a source of clean air and effective
safeguards against ventilation failure are provided.
Zone 1
(continued)
1999/92/EC
A place in which an explosive
atmosphere consisting of a mixture
with air of flammable substances
in the form of gas, vapor or mist is
present continuously or for long
periods or frequently
A place in which an explosive
atmosphere consisting of a mixture
with air or flammable substances in
the form of gas, vapor or mist is likely
to occur in normal operation
occasionally
./.
26
NFPA 497
Class I,
Zone 2
is a location
(1) in which ignitable concentrations of flammable gases or vapors are
not likely to occur in normal operation and, if they do occur, will
exist only for a short period; or
(2) in which volatile flammable liquids, flammable gases, or
flammable vapors are handled, processed, or used but in which
the liquids, gases, or vapors normally are confined within closed
containers of closed systems from which they can escape only as a
result of accidental rupture or breakdown of the containers or
system, or as a result of the abnormal operation of the equipment
with which the liquids or gases are handled, processed, or used;
or
(3) in which ignitable concentrations of flammable gases or vapors
normally are prevented by positive mechanical ventilation but
which may become hazardous as a result of failure or abnormal
operation of the ventilation equipment; or
(4) that is adjacent to a Class I, Zone 1 location, from which ignitable
concentrations of flammable gases or vapors could be
communicated, unless such communication is prevented by
adequate positive-pressure ventilation from a source of clean air
and effective safeguards against ventilation failure are provided.
Zone 2
27
(continued)
1999/92/EC
A place in which an explosive
atmosphere consisting of a
mixture with air of flammable
substances in the form of gas,
vapor or mist is not likely to
occur in normal operation but, if
it does occur, will persist for a
short period only.
NFPA 499
Class II,
Division 1
is a location
(1) in which combustible dust is in the air under normal operating
conditions in quantities sufficient to produce explosive or ignitable
mixtures, or
(2) where mechanical failure or abnormal operation of machinery or
equipment might cause such explosive or ignitable mixtures to be
produced, and might also provide a source of ignition through
simultaneous failure of electric equipment, through operation of
protection devices, or from other causes, or
(3) in which combustible dusts of an electrically conductive nature
may be present in hazardous quantities.
Zone
20
Zone
21
Class II,
Division 2
is a location
(1) where combustible dust is not normally in the air in quantities
sufficient to produce explosive or ignitable mixtures, and dust
accumulations are normally insufficient to interfere with the
normal operation of electrical equipment or other apparatus, but
combustible dust may be in suspension in the air as a result of
infrequent malfunctioning of handling or processing equipment
and
(2) where combustible dust accumulations on, in, or in the vicinity of
the electrical equipment may be sufficient to interfere with the
safe dissipation of heat from electrical equipment or may be
ignitable by abnormal operation or failure of electrical equipment.
[70:500.5(C)(2)]
Zone
22
28
1999/92/EC
A place in which an explosive
atmosphere in the form of a
cloud of combustible dust in
air is present continuously, or
for long periods or frequently
Level of
Very high
Cat 1
II
Ignition source
High
Cat 2
N/A
Cat 3
The level of protection required for each of the Group II cat is summarized below :
Level
protection
Very High
of
Category Group II
Performance of protection
High
Normal
There is a clear link between Group II cat and hazardous areas (zones) as defined in ATEX. This relationship is shown in
the table below:
Each category requires sub-division depending on its intended duty.
G = gas, vapor or mist
Gases, Vapors
Zone 0 - category 1 G
Zone 1 category 1 G or 2 G
Zone 2 category 1 G, 2 G or 3 G
./.
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(continued)
It should be noted that where an equipment users ATEX risk assessment determination of safety based on explosion
protection (venting or suppression) reduces risk to an acceptable level, a lower category of equipment can be used.
Temperature classification
Hot surfaces represent potential ignition sources and the maximum surface temperature of equipment should be
considered. A common approach is to use the T class.
When selecting apparatus according to temperature classification, the maximum surface temperature or the T class of
the apparatus should be specified to avoid ignition sources of the potential flammable atmosphere.
T class is normally assigned basis the temperature rise tests assuming ambient temperature not exceeding 40 C.
In other cases revert to the supplier in particular hen equipment is installed inside the insulation.
Temperature classes
T class
T1
T2
T3
T4
T5
T6
T CLASS
T1
APPARATUS GROUP
IIC
(continued)
30
Additional requirements may be required regarding T Class if the ambient temperature exceeds 40C.
ZONE
0
1
2
Any existing electrical equipment within the defined hazardous areas should be surveyed to ensure it meets the
standards outlined below.
ZONE 0
0
1
TYPE OF PROTECTION
Ex i(a)
Ex s
any of the above or
Ex d
Ex i(b)
Ex p
Ex e
Ex s
Ex m
Ex o
Ex q
any of the above or Ex n
Existing non-electrical equipment within the defined hazardous areas must be of good design and construction, properly
installed and well maintained following a formal preventive maintenance program.
31