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CHAPTER 6SELECTION, INSTALLATION AND
WIRING OF Ex CERTIFIEDELECTRICAL EQUIPMENT
Under the Division 1 classification, wire terminations
are considered ignition sources.
6.1 UNDERSTANDING THE DIFFERENCE INZONE VS DIVISION INSTALLATION METHODSTerminations are the key to understanding the differences in
installation methods of Zone and Division rated equipment.
Under the Zone system wire terminations rated as Ex-e,
increased safety, are not considered sources of ignition.
Terminations are tested to ensure that they do not heat up or
vibrate loose and have sizable creepage and clearance
distances to prevent arcing. Under the Division 1 classification,
wire terminations are considered sources of ignition as it is
assumed they could vibrate loose, short out and create an arc.
This results in major differences in the way products are
designed. To illustrate this refer to the push-button control
stations shown below. Both stations contain an explosion-
protected contact block. The one on the left is rated
explosionproof for Division 1 and has an explosionproof metallic
housing. The one on the right is rated flameproof and increased
safety for Zone 1 and has a non-metallic housing. Each contact
block prevents arcs from switch operations inside from igniting
gases within the control station. Why then must the contact
block located in a Division 1 area be housed in an
explosionproof enclosure while the Zone 1 rated control
stations is in a non metallic enclosure?
The Division 1 control station has a metallic enclosure.
The Zone 1 version has a non-metallic enclosure.
Under the Division 1 system, wire terminations areconsidered ignition sources. If volatile gases and air accumulate
inside an explosionproof enclosure and are ignited by the spark
from a wiring fault on the terminals, the enclosure must contain
the explosion. As the hot gases escape the enclosure by passing
across a flat or threaded or serrated joint, they cool so they can
no longer ignite gaseous mixtures in the hazardous area. In a
Division 1 area, the contact block must be housed inside an
explosionproof enclosure rated for the area.
Explosionproof Contact Block in Division 1 Area
Wire terminations are considered sources of ignition for Division 1 products.
An explosionproof enclosure for the contact block is required.
Under the Zone system, wire terminations are not considered
an ignition source if they are rated as Ex-e or increased safety.
If the contact block is rated flameproof with increased safety
terminals, the switch can be housed in an increased safety
housing, e.g. a non metallic enclosure that has a suitable
construction and an IP rating to protect against moisture and
dusts.
Ex-de Contact Block with Increased Safety
Terminals in Zone 1 Area
Ex-e Wire terminations are not considered sources of ignition for Zone 1
products, and Ex-de contacts can be housed in non metallic enclosures
suitable for Zone 1.
Determining which system is safer, less expensive or easier to
install is very difficultsomewhat like comparing the metric and
US systems of measurement. Each application has its own
merits and depends on user preference, as well as how the
areas are classified, and the wiring systems used in the facility.
At the present time North American users have the advantage
of being able to use either type of product in Division 2.
Cooper Crouse-Hinds Ex DigestSelection, Installation and Wiring of Ex Certified Electrical Equipment
Division 1 Vs. Zone 1
Potential Ignition Source?
Not a Source of Ignition
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Equipment listed and marked for use in Class I,Zone 0, 1, or 2 locations shall be permitted in Class I,
Division 2 locations for the same gas and with asuitable temperature rating.
6.2 STANDARDS AND INSTALLATIONPRACTICESEx Electrical equipment certified to U.S., Canadian, CENELEC,
IEC or any other national standards must be installed and
maintained correctly. To ensure that correct installation is
achieved, every industrial country will use a recognized
installation rules or a code of practice.
In North America the installation requirements for Hazardous
Locations is specified in Section 18 of the Canadian Electric
Code and in Article 500 of the National Electric Code. Prior to
1997 most Countries produced their own National Standards for
installation in hazardous areas, which allows the use of Ex
Electrical Equipment certified to CENELEC and other national
standards. In 1997 the IEC Standard, IEC 60079-14 wasadopted as a European standard EN 60079-14. This was a
large step forward toward on worldwide standard for the
installation of electrical equipment in hazardous areas.
6.3 SELECTION OF EX PROTECTEDELECTRICAL EQUIPMENTThere are considerable international differences in the
approach to hazardous area electrical installations. Therefore, it
is important to clearly establish the documented safety rules
that will be applicable to the installation before the selection
process is undertaken. To illustrate this problem, hazardous
area electrical equipment may be manufactured and certified to
comply with the requirements of a Zone classification but may
not be considered suitable for Division 1 Hazardous Locationclassified by the North American (USA and CANADA) Class
and Division concept.
This has become more relaxed with the addition of Article 501-
1 in the NEC which states:
Equipment listed and marked in accordance with Section 505-
10 for use in Class I, Zone 0, 1, or 2 locations shall be permitted
in Class I, Division 2 locations for the same gas and with a
suitable temperature rating.
This has given North American users a wider range of products
to select from. Products which are rated for the IEC Zone
classification system, and are adapted to North American wiringand installation practices can be installed in Division 2.
Cooper Crouse-Hinds has received UL and cUL approvals on all explosion
protected equipment manufactured by Cooper Crouse-Hinds CEAG in
Europe. This product line, called SpecOne, is made out of either metal or
plastic which will accommodate either cable or conduit installation methods.
The SpecOne products include fluorescent lighting, control stations and
panels, power distribution panels, terminal boxes, plugs and receptacles and
disconnect switches.
While there are still many differences between the standards
and installation practices in North America and Europe, not to
mention others in Latin America, Japan, Australia and South
Africa, the gaps are narrowing. The main differences are:
Local safety and fire codes for ordinary locations.
No direct correlation between Class/Divisions and Zone
classification.
Different wiring methods for conduits and cables.
Cable entry hole threads, NPT versus metric openings.
Gas Groupings are different.
Conductor cross sectional areas and current ratings.
Nonacceptance of the Increased Safety concept in Class 1
Division 1 Hazardous Locations. (Connections & terminations
are still considered sources of ignition.)
These differences define the way equipment is selected,
installed and maintained and must be taken account of when
projects are designed.
6.4 BACKGROUND OF WIRINGIn the early 1900s when industry was converting from the use
of natural gas to electrical wiring, it was natural for contractors
to use the gas pipe as a raceway or conduit to run the electrical
conductors. Although this sounded easy, a need developed to
also have junction boxes and elbows to pull and terminate
cables and fixture hangers to assemble the new light fixtures.
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Two entrepreneurs
from Syracuse, N.Y.,
Jesse L. Hinds andHuntington B.
Crouse, made outlet
boxes for the new
conduit wiring
systems. They coined
the term condulet,
which was a
combination of
conduit and outlet box
as seen in an early
advertisement.
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In the 1920s when oil refineries were being constructed, there
was a new need for outlet boxes, fittings and fixtures which
would prevent electrical sparks and heat generating products
from causing explosions. The industry came up with the
concept of Division 1 to define these locations where volatile
gases would be present.
Mr. Crouse and Mr. Hinds engineered and manufactured explosionproofproducts for the oil and gas industry.
In the 1980s Canadian industry readily adopted the use of
TECK cable which is similar to metal clad cable except with an
extra PVC jacket. Now the industries with Hazardous Locations
use a variety of wiring methods ranging from rigid conduit to
various types of cable.
6.5 TYPICAL INSTALLATION CONDUITVS. CABLEThere are primarily 3 different types of wiring systems used:
rigid metal conduits, armored cables, and non-armored cables.
The use of each method is embedded in the electrical
installation culture of the area.
6.5.1 RIGID CONDUITThis system is widely used by specifiers and installers in the
USA and parts of Canada as well as parts of South America,
Middle East and Asia where the NEC is used. This method
ensures the maximum protection of conductors against
mechanical and chemical attack.
There are an equal number of proponents as there are
opponents to the use of rigid conduit. While some maintain that
conduit leads to higher installation costs, others argue the
merits of greater mechanical protection. A recent survey
showed that Canadian users favor TECK cable over rigidconduit. The USA industry is equally divided between favoring
cable over conduit. For example, offshore installations favor
cable over conduit, which is more susceptible to corrosion.
Conduit systemsprovide
mechanical
protection of
wires and
conductors.
6.5.2 TECK CABLEInstead of conduit, cable systems are used more often under
the Zone concept. There are 5 types: TECK, steel wire
armored, steel wire braided, lead sheathed and unarmored.
TECK cable is a variation of the armored cable which is used
primarily in Canada. The TECK cable is a metal clad (mc) cablewith an extra PVC sheath for additional insulation. Special
TECK connectors are used to secure and terminate the cable
into enclosures.
Teck cable has an extra PVC sheath for additional insulation.
6.5.3 ARMORED CABLESArmored cables are widely used in the United Kingdom and
former commonwealth countries and ensures the mechanical
protection and earth continuity. Special cable glands must be
used to guarantee the earth continuity (ground).
6.5.3.1 STEEL WIRE ARMORED (SWA)SWAcable consists of individual PVC-coated conductors within
an aluminum screen surrounded by a PVC coating, then by a
series of steel wires within an exterior PVC coating. The steel
wires are conical in shape and protect the conductors in the
same way as metal-clad cable. SWA is a very high-strength,
durable cable and used in many power applications.
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6.5.3.2 STEEL WIRE BRAIDED (GSWB)GSWB cable consists of individual conductors within an
aluminum screen surrounded by an inner sheath, then by a
steel braid, similar to a basket weave, underneath an outer
sheath. The braid makes this cable more flexible than SWA.
This durable cable is used in many instrumentation applications
or where shielding is required for signal applications.
6.5.3.3 LEAD SHEATH (LWA)
LWA cable consists of individual conductors surrounded by alead sheath for protection from hydrocarbons. A PVC coating
then surrounds the exterior. This cable is popular in the oil
industry and is usually buried in the ground. The lead sheath
protects the conductors from ground spills of oil byproducts.
Crouse-Hinds offers brass,
stainless steel, steel and and non-
metallic cable glands for
any type of cable or thread.
6.5.3.4 NON-ARMORED CABLEThis cable is similar to tray or SO-type cable and normally
contains a ground conductor or earth core. Since the cable is
not considered a source of ignition, under the Zone concept the
cable does not require its own mechanical protection. The
protection is usually provided by open conduit or other cable-
tray type protection called a cage or mounting grid. This
method, which is used in France, Germany, Italy and parts ofAfrica and Asia, can be very flexible, fast and economical. If the
installation is subject to mechanical risks, it is advisable to use
armored cable or an open conduit system. Most exposed
vertical cables are housed in open conduits or pipes to avoid
mechanical abuse.
Cooper Crouse-Hinds non-metallic mounting plate on mounting grid offers a
quick installation method of control stations and switches.
Table 6.1
Typical Cable Systems by World RegionAREA CABLE TYPE THREAD
TYPE
Canada TECK NPT
North America Metal Clad Aluminum NPT
Central Europe Unarmored Cable Metric*Germany
Europe offshore Steel Wire Braid Metric
Ireland, Norway, Steel Wire Armor MetricHolland, Belgium, Unarmored CableSpain
Italy, Belgium Steel Wire Armor Metric
Unarmored Cable & NPT
Middle East Steel Wire Armor MetricUnarmored Cable NPT
Far East Steel Wire Armor MetricUnarmored Cable & NPT
CIS States Steel Wire Armor Metric(Azerbaijan, Unarmored CableKazakhstan)
* Metric threads have replaced Panzer gage (PG) threads
Cooper Crouse-Hinds Ex DigestSelection, Installation and Wiring of Ex Certified Electrical Equipment
(Saudi Arabia & Kuwait)
Steel wire
braided cable
is more flexible
than SWA
Crouse-Hinds NCG non metallic cable glands are offered with
NPT or metric males threads for tray and other flexible cables.
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The use of twist-on connectors, known as wire nuts
or marets, is not allowed in Europe as increased
safety terminals.
The Ex-e push in connectors are a major advantage
for OEMs, and for installation of lighting circuits.
6.6 TERMINATION METHODSTraditionally Ex-e connections are made at increased safety
terminal blocks mounted inside of metal or non-metallic, Ex-e
enclosures. The terminals are rated for creepage and clearance
distances.
6.6.1 TWIST ON CONNECTORSThe most popular method of termination in North America is
with the use of twist-on connectors, also known as wire nuts or
marets. For products approved for use in Europe, twist-on
connectors or wire nuts are not allowed. Some form of terminal
blocks or screw terminals must be used. Twist-on connectors
versus terminal blocks are the main differences between theNorth America and European wiring methods. North American
wiring methods will not be quick to abandon using twist-on
connectors in favor of terminal blocks for branch circuits
especially when both systems are safe when they are installed
properly. Until recently, twist-on type connectors were not rated
as increased safety.
Cooper Crouse-Hinds pioneered the first
Ex-e wire nuts which offer major
advantage for OEMs, and for
installation of lighting circuits.
6.6.2 TERMINAL BOXESThe specifications for terminals according to IEC and
CENELEC standards are very stringent. Certified electrical
terminals for connecting wires in hazardous areas will be tested
with the following requirements:
Insulation resistance to tracking (CTI)
Temperature limitation (thermal stability) Measured Creepage &b clearance distances
Voltage and current ratings
Wire pull out test
Antivibration locking
Thermal end to end resistance
Conductor clamping method (pinch screws are
not permitted)
The connection of wires to terminals is most commonly made
via DIN rail mounted terminals. The underlying design principle
for terminals is a pressure plate contact with the conductor and
an antivibration locking feature to prevent self loosening for the
connected conductors. Other types of reliable certified terminals
include saddle clamps, slotted type clamps (often used for
lighting circuit terminations) and screwless cage clamp
terminals.
6.7 TERMINATING ARMORED CABLE ANDCONDUIT IN NON-METALLIC ENCLOSURESThe armor of steel wire or braided cables must be effectively
connected to the earth/ground system. If a phase to armor
circuit fault occurs there can be thousands of amps flowing.
Therefore the armor must have a low impedance to
earth/ground via the cable gland. The enclosure to which the
armored gland is connected may not be tested to carry fault
currents so internal and or external connections are required.
The biggest dilemma of mixing zone and division installation
methods is the practice of using terminating conduits or
armored cable into non-metallic enclosures. The majorconsiderations are: pull out strength of the conduit from the
enclosure and ensuring a continuous and secure path to
ground. There are 2 different methods commonly used, the
zone rated hub or the integral grounding plate.
Cooper Crouse-Hinds Ex DigestSelection, Installation and Wiring of Ex Certified Electrical Equipment
Under IEC installation
methods it is permitted to
combine two or more
wires in a compression-
type terminal provided
that the terminal is
designed for that purpose,
such as the Cooper
Crouse-Hinds eAZK
enclosures with Ex-e
U-slot terminals.
Ex-e U-Slot terminals,
which accommodate
different sized wires,
are found in Ex-e
terminal boxes (eAZK)
and in some Ex-d light
fixtures
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6.7.1 ZONE RATED HUBSThis hub is specifically designed for Zone applications to be
non-loosening and to have the required IP rating. For through
holes the male threads must have a locking ring which has an
increased safety grounding point and an extra security screw to
ensure against loosening of the locking ring. Either the hub or
the locking ring will have serrated teeth for extra clamping
protection into the non-metallic enclosure. Both of thesefeatures protect the connection from loosening against vibration
and long term use. The hub has an integral silicone rubber o-
ring or gasket to guarantee the require IP rating of the
enclosure. The hubs are machined to accept either NPT or
metric thread form.
The SpecOne Myers
hubs
are rated for
Zone 1 usage.
They are also
available as
metric adapters for
entering
metric threaded
female hubs or
plates.
6.7.2 BRASS BONDING PLATESMany non-metallic enclosures also have integral brass bonding
plates. Because of their nominal thickness these normally have
metric or parallel threaded openings. Each plate must have an
internal and/or external ground point. These plates can be field
drilled or drilled at the factory. If the holes are not used they
must be plugged with a blanking plug certified to Ex-e standards
for the required IP protection.
Ex-e blanking plugs are required to fill in threaded openings for IP
protection as seen on the Cooper Crouse-Hinds GHG 74 Series Ex-e
Enclosures.
For ease of wiring the SpecOne control stations, D2Z distribution panels,
Safety Switches, interlocked 309 receptacles and terminal boxes all have an
brass grounding plates. These have metric female threads for European
armored cable glands. For NPT entries use the Zone 1 Myers metric
adapters which are available in zinc or stainless steel.
6.8 CABLE SEALS
Cable glands have multiple options for material types for Ex-dand Ex-e types of protection. Ex-d cable glands have a brass,
aluminum, steel or stainless steel construction with at least two
seal systems to ensure the flameproof properties and ingress
protection. Ex-e cable glands normally have only one sealing
system for ingress protection and are available in a plastic
construction in addition to brass or stainless steel.
Three types of seal materials are most generally used in cable
glands.
Neoprene, a durable oil-resistant rubber compound with good
weather and ozone resistance. To meet the strict deluge test
requirements of the offshore oil industry, glands employ up to
three neoprene seals. These are used on offshore oilplatforms where they may be submerged for long durations.
Conductive, a neoprene seal with iron filings used to seal lead
sheathed cable.
Silicone, a compound with high fire resistance which holds its
properties well in temperature extremes. This seal may be
used in temperatures as low as -60C to as high as +180 C.
It also does not give off smoke when burning (zero halogen
applications) and is used in tunnels or other similar
applications.
Typical Seals and Application Temperatures
Seal Type Temperature Range
Neoprene (deluge tested) -20 to + 80CConductive -20 to + 80C
Silicone -60 to + 180C
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Typical installation of Zone 1 Myers hubs glands into a Cooper
Crouse-Hinds Ex-e stainless steel enclosure.
6.9 WHEN IS NICKEL PLATING REQUIRED?The inherent corrosion-resistance nature of brass eliminates
the need for plating in most cases. However, brass and
aluminum create a natural galvanic reaction, so nickel plate or
other finishes are required where the brass gland is used with
aluminum enclosures or aluminum cable.
Do not use brass
glands in aluminum
housings, which will
result in corrosion.
Use nickel plated
glands.
6.10 TERMINATING NON-METALLIC EX-eGLANDSIncreased safety non-metallic glands must be certified for
ingress protection, impact resistance and aging resistance.
There are 2 versions, which depend on the use of the glands.
For installations where the cables are secured, the glands have
lower requirements for strain relief. If the cables are not secured
trumpet glands are used. Their main purpose is to provide strain
relief where bending, twisting or pulling is common.
Trumpet glands (on handset)
are used on portable
equipment when support for
the cable is not practical or if
there are extensive tensile or
torsional forces.
Cables should be secured close
to the apparatus.
6.10.1 SELECTION OF NON-METALLICGLANDSCable glands are sold either as separate items mounted on the
apparatus or packaged with the cable. Selecting the proper
gland depends on the following criteria:
Cable type
Hazardous area rating
Seal type
Entry thread
Finish
Cable diameter
Material
Use
The one variable, which usually creates havoc for end users, is
holding the tolerance on the cable diameter especially ifflameproof cable glands are used. If the diameters exceed the
tolerances of the glands, they may not fit or seal properly which
could affect the flameproof integrity of the glands.
Cut-away of trumpet gland
For questions or comments, please contact the author at
Cooper Crouse-Hinds Ex DigestSelection, Installation and Wiring of Ex Certified Electrical Equipment
Lever prevents pull-out or
torsional twisting.
Seal for IP
Protection