Transcript Electrical Equipment for Hazardous Areas

Objectives
At the end of this module you should be able to:
1) Identify “Hazardous Zones” on board a tanker or similar vessel.
2) Predict the possible “Electrical Sources of Ignition” considered to be
“Hazardous”.
3) Identify Explosion Protected Equipment
4) State the significance of equipment with various “Ex” markings
5) Describe essential items to be checked on “Ex-Protected” Equipment.
6) Demonstrate the precautionary measures in the maintenance of explosive
proof lights.
STATUTORY WARNING: SMOKING COULD TAKE YOUR LIFE …
… AND THE LIVES OF OTHERS
The most prominent sign in sight …
The Fire Tetrahedron
Fuel
Gas,
vapours or
powder
Chain
Reaction
Ignition
Source
Thermal or
Electric
Oxidiser
Air or O2
The Dust Explosion Pentagon
Con
finem
n
ersio
Disp
Dust
Explosion
Pentagon
ent
Ig
nit
ion
el
u
F
Oxygen
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Details
The Incipient Flame Sphere
The Incipient Flame Sphere must reach a critical diameter if
combustion is to become a self-propagating explosion.
the
The Incipient Flame Sphere
If the initial spark is not large enough, (i.e. does not possess enough
energy), the combustion zone will not have enough energy to self
propagate. It will just collapse upon itself, and fizzle out.
This means a small spark can occur in a potentially explosive air/gas
mixture, with no danger of an explosion.
The maximum amount of energy of this “safe” spark varies with the
specific air/gas mixture present.
Extract from ABS Rules for Building and Classing Steel Vessels - 2005
Part 4 Vessel Systems and Machinery
Chapter 1 General
Section 1 Classification of Machinery
Quote
1.9.4
Hazardous Area 4-1-1/1.9.4
Areas where flammable or explosive gases, vapors, or dust are normally
present or likely to be present are known as hazardous areas. Hazardous areas
are however more specifically defined for certain machinery installations, storage
spaces and cargo spaces that present such hazard, e.g.:
helicopter refueling facilities, see 4-8-4/27.3.3;
paint stores, see 4-8-4/27.3.3;
cargo oil tanks and other spaces of oil carriers; see 5-1-7/31.5;
ro-ro cargo spaces; see 5-10-4/3.9.2.
Unquote
Classification of Hazardous Materials
(The American System)
Class 1 : Flammable gases or vapours
Class 2 : Combustible dusts
Class 3 : Fibres or flyings (particles normally suspended in air)
Class 1: The following groups are listed in the most dangerous to
the least dangerous ones:
Group A : Acetylenes
Group B : Hydrogen, Hydrogen mixtures
Group C : Ethylene, Ethers, Some Aldehydes
Group D: Alkanes (Butane, Ethane, Methane, Octane, Propane),
Hydrocarbon mixtures (Diesel oil, Kerosene, Petroleum mixtures,
Gasoline), Alcohol, Ketones, Esters, Amines, Alkenes, Benzoids
Class 2 (Combustible Dusts):
Group E : Metallic Dusts (resistivity < 100 kΩ/cm)
Group F, Group G : Non-conductive dusts (agri, plastic, chemical
and textile dusts – resistivity > 100 kΩ/cm).
Hazardous Areas Onboard Ships
When a ship is involved in its normal operational functions there will be some
areas and zones where flammable gases can accumulate in the atmosphere and
present a hazard to the ship, its crew and other personnel who may be onboard.
Such areas are defined as hazardous and classified in terms of the risks involved.
For example, IEC Publication 79-10 defines three such categories:
Zone 0: The flammable mixture is continuously present or present for long
periods.
Zone 1: The flammable mixture is not continuously present, but will be present
during normal operations.
Zone 2: The flammable mixture would not normally be present, but if it is, it would
be present for a short period only.
(Note: Zones 0 and 1 is also known as Division 1 while Zone 2 is known as
Division 2)
Continued…
Hazardous Areas Onboard Ships
The terms ‘gas-dangerous area’ or ‘gas-safe area’ may also be mentioned on
ships. The general ship’s operation manual, or other similar documents, must be
referred to in order to determine the number and extent of the hazardous areas for
any given ship.
Hydrocarbon gases or vapours from crude oil form highly flammable mixtures
with air when they are present in the proportion between 1% and 10%
hydrocarbon with 99% down to 90% normal air.
Below the lower explosive limit (LEL) the mixture is too lean to burn rapidly,
although a lean mixture will burn slowly in the presence of a naked flame or a
spark, as is proved by the operation of explosimeters in this range.
Over-rich mixtures exist when the level of the hydrocarbon exceeds 10%.
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Details
Class I Certified Equipment Comparison Chart
Zone System
Intrinsically safe, Ex i, Ex ia
Division System
Zone 0
All Equipment accepted in Zone 0
Flameproof - Ex d
Pressurized - Ex p
Increased safety - Ex e
Intrinsically safe - Ex ib
Encapsulation - Ex m
Equipment accepted in Zone 0
Equipment accepted in Zone 1
and Class I Division 2
Non sparking - Ex n
Zone 1
Zone 2
Division 1
(100 hrs per
year or 1%
probability)
Class I Div. 1 Equipment
Intrinsically safe Ex i, Ex ia
Equipment Acceptable for
Class I Div. 1 and Div. 2
+
Division 2 (10
Flameproof - Ex d
hrs per year
Pressurized - Ex p
or 0.1%
Intrinsically safe - Ex ib
probability)
Increased safety - Ex e
Non-sparking - Ex n
Encapsulated - Ex m
Note: All Ex Equipment will be explained in subsequent slides
Tanker Installations
Regulations and practices applied to the installation of electrical equipment in
tankers specify the types of safe equipment that can be fitted in the areas where
flammable gas and air mixtures may be present. The degree of risk is not the same
throughout the hazardous areas, which include cargo tanks and the spaces above
them, pump rooms, cofferdams and closed or semi-enclosed spaces with direct
access to a dangerous zone
3 metres from openings
Hazardous Area
2 . 4 metres from openings
Pump Room
Engine Room
Normally Safe Areas
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Details
Cargo Tanks
General Tanker Arrangement showing Hazardous Areas and Normally Safe Areas
Potential Sources of Ignition
Should there be a flammable gas, vapour or dust in the atmosphere,
the following are considered to be potential sources of ignition:
 Sockets And Plugs,
 Open Fuses,
 Light Switches,
 Relays,
 Push Button Contacts,
 Torches,
 Starters,
 Circuit Breakers,
 Electric Bells,
 Components like Capacitors, Inductors and Resistors
Potential Sources of Ignition
When the switch is open the
capacitor charges to ½CV2
energy.
On closing the switch, the energy
is released as a spark.
When the switch is closed
energy is stored in the inductor
= ½LI2.
When the switch is opened this
energy is released as a spark.
R
R
Switch
Hazardous
Area
C
Switch
V
Hazardous
Area
Safe Area
L
V
Safe Area
In resistive circuits when contacts are opened or closed, sparks
can be produced. Voc is the open circuit voltage.
The short circuit current Isc = Voc
R R
Switch
Hazardous
Area
V
Safe Area
Potential Sources of Ignition
Non-Hazardous Side
Hazardous Side
Explosion Possible!
Max 0.1 V produced by the TC
Fault Occurs
Ignition is possible from a fault occurring on the non-hazardous side
Potential Sources of Ignition
There are no special measures taken in ordinary electrical equipment to
encapsulate contacts, which arc as they close or open. Thus the
following are more apparent as sources of ignition:
 The danger from arcing contacts in a starter box or switch is not
obvious because the arc is hidden.
 Sparks from an electric motor, particularly of the commutator-type,
 The momentary glow of a broken light bulb filament,
 Arcing from a broken or damaged power cable
Conventional equipment and cables are suitable for areas that are considered safe.
Continued…
Potential Sources of Ignition
Static electricity is generated within tanks in several ways. Flammable gas
remains in a tank even after it is discharged. This presents a hazard –
particularly during washing – unless appropriate steps are taken. Here, the
product or water mist or steam becomes charged with electricity. This can
occur…
 When filling with clean oil products
 When washing with water jets
 When steaming a tank
 A static charge and spark may also be caused by carbon dioxide or steam
being discharged at a high rate from a nozzle.
!
Keep tank openings closed as much as possible.
!
Do not disconnect tank cleaning hoses from their hydrants until
they have been removed from the tank.
Continued…
Potential Sources of Ignition
There are several ways in which this sufficient charge becomes a hot spark
– capable of igniting a flammable mixture. This might involve the
introduction of metal objects into a tank. Objects which may have caused a
spark include:
 Hand-held metal ullage tapes
 Metal sample cans
 Metal sounding rods
 Ungrounded portable washing machines
!
Do not introduce metal objects into the tank, other than a grounded washing machine.
Click on the icons to see more details on
Static Electricity Each file is unique
Nameplate for Equipment used in Hazardous Areas
BS 5501 Pt 5
d IIB T4
BASEEFA No. Ex 2833010
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Details
Group I is gas encountered in coal mining where methane and
coal dust constitute the risks.
Group II comprises gases such as cellulose vapour, petrol,
benzene, amyl acetate. Group II may be further sub-divided
into:
IIA – propane, which requires higher ignition energy of 180
micro joules;
IIB – ethylene, which requires ignition energy of 69 micro
joules; and
IIC – hydrogen, which requires ignition energy of 29 micro
joules.
Group III is coal and coke gas and ethylene oxide.
Group IV covers excluded gases, i.e., where there is no
flameproof general approval such as acetylene, carbon
disulphide, etc.
Nameplate for Equipment used in Hazardous Areas
BS 5501 Pt 5
d IIB T4
BASEEFA No. Ex 2833010
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Details
Germany
Maximum
Surface
Temperature
(OC)
Europe
(CENELEC)
T1
450
T1
T2
300
T2A
280
T2B
260
T2C
230
T2D
215
T3
200
T3A
180
T3B
165
T3C
160
T4
135
T4A
120
T5
100
T5
T6
85
T6
North
America
(CEC / NEC)
G1: 360 - 400
G2: 240 - 270
G3: 160 - 180
T2
G4: 110 - 125
G5: 80 - 90
T3
T4
Flame-proof (Ex d) Equipment
Cover
Flame Path
Inside
Joint
Inside
Flame Path
Click on the image for animation
Click on the image for animation
Label sometimes found…
Gap
Glass
Inside
Flame Path
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Details
Flame-proof (Ex d) Equipment
Advantages
1. Explosion Containment
2. No Electronics
3. Low Maintenance
4. No Moving Parts
5. High-Powered Equipment
Disadvantages
1. No warning mechanism for containment failure
2. Danger to Equipment After Explosions
3. Possibility of Installation/Maintenance Errors
4. Cost of Protection per ft3 Increases with Enclosure Size
5. Windows are Limited
6. Condensation build-up is common
7. Few sizes to choose from
8. Cumbersome, Limited Access
9. Bulky Designs
10. Causes Harmful Heat Build up
11. Excessive Weight
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Details
Pressurised (Ex p) Equipment
Zone 2 (Non Hazardous Area)
1
2
3
Zone 1 (Hazardous area)
2
4
Zone 2 (NHA)
2
5
6
Over Pressure
0
External Pressure
(1) Protective Gas Inlet (2) Ducting (3) Fan (4) Enclosure (5) Manometer (6) Solenoid Valve
Pressurised (Ex p) Equipment with Leakage Compensation
Enclosure without Rotating Parts
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Details
Pressurised (Ex p) Equipment
Zone 2 (NHA)
1
2
3
Zone 1(Hazardous area)
2
4
Zone 2 (NHA)
2
5
6
Over Pressure
0
External Pressure
B
(1) Protective Gas Inlet (2) Ducting (3) Fan (4) Enclosure (5) Manometer (6) Solenoid Valve
Pressurised (Ex p) Equipment with Leakage Compensation
Rotating Electrical Machine with an Internal fan
Pressurised (Ex p) Equipment
Zone 2 (NHA)
1
2
3
Zone 1(Hazardous area)
2
4
Zone 2 (NHA)
2
5
6
Over Pressure
0
External Pressure
(1) Protective Gas Inlet (2) Ducting (3) Fan (4) Enclosure (5) Manometer (6) Solenoid Valve
Pressurised (Ex p) Equipment with Leakage Compensation
Rotating Electrical Machine with an External Fan
Types of Purge
Type Z Purge
Reduces enclosure from
Div 2 to Non-hazardous
1. Label stating four
volumes of purge gas
needed before power
2. Pressure of 0.1 inch
water
3. Enclosure temperature
<80% of ignition
temperature of gas
4. Purge failure alarm or
indicator (No auto power
off necessary)
5. Warning Nameplate
6. 0.25 inch glass window
Type Y Purge
Reduces enclosure from Div
1 to Div 2
1. Label stating four
volumes of purge gas
needed before power
2. Pressure of 0.1 inch
water
3. Fused based on
enclosure thickness to
ensure enclosure
temperature <80% of
ignition temperature of
gas
4. Purge failure alarm or
indicator (No auto power
off necessary)
5. Warning Nameplate
6. 0.25 inch glass window
7. Equipment mounted
within enclosure must
meet Div 2 (Hermetically
sealed switches, relays
contacts)
Type X Purge
Reduces enclosure from Div
1 to Non Hazardous
1. Timer to allow four
volumes of purge gas
2. Pressure of 0.1 inch
water
3. Fused based on
enclosure thickness to
ensure enclosure
temperature <80% of
ignition temperature of
gas
4. Purge disconnect on
purge loss (pressure or
flow activated).
5. Warning Nameplate
6. 0.25 inch glass window
7. Auto power disconnect
switch on door.
Intrinsic Safety
• Intrinsic safety removes the ignition side from the fire triangle.
• Intrinsically safe wiring and equipment shall not be capable of
releasing sufficient electrical or thermal energy under normal or
abnormal conditions to cause ignition of a specific atmospheric
mixture in its most easily ignitable concentration.
• The Barrier is always located in the safe area.
Requirements for Intrinsically Safe Systems
1. Ensure that there is positive separation between intrinsically and
non intrinsically safe circuits; this prevents the ignition energy from
entering the intrinsically safe circuit.
2. Separate trays, conduits be used for intrinsically safe wiring and be
properly tagged / identified.
3. IS wiring is not to be mixed with other wiring.
4. If conduit is used it must be effectively sealed to prevent gases fro
the hazardous area to reach safe area.
5. ensure that the entity parameters upon which the system is
designed match correctly.
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
What is a simple apparatus?
A simple apparatus does not generate or store more than the
following:
- 1.2 V
- 100 mA
- 20 micro J
- 25 mW
This type of device does not require certification from a third party but
still requires an intrinsically safe barrier.
Examples:
1. Switches – limit, pressure, temperature, float, flow.
2. Push buttons
3. Analogue sensors : Thermocouple, RTD
4. LEDs
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsically Safe (Ex i) Circuit Components
Intrinsic Safety (Ex i) Barriers
1. The intrinsic safety barrier is inserted in the safe area between
the field device and the safe area instrument.
2. The barrier blocks dangerous energy that can be released due
to a fault in the safe area from being transmitted to the
hazardous area. This energy may be from the power supply or
stored in a capacitor, inductor, etc.
3. The dangerous energy is diverted to the ground. Therefore it is
important to ensure a high quality of intrinsic safe ground. As
this grounding is so critical, two separate ground connections
from each barrier are recommended, each with a resistance <
1.0 ohm.
Intrinsic Safety (Ex i) Barriers
Intrinsic Safety (Ex i) Barriers
Intrinsic Safety (Ex i) Barriers
There are two types of intrinsic safety barriers :
1) Zener barrier (2) Active barrier.
1) Zener barrier:
This works on the principle of diverting hazardous energy to the
ground safely before it can reach the hazardous area. Zener diodes
limit the fault voltage to the hazardous area. There are two such
diodes for redundancy. The series resistor limits the current to the
hazardous area.
The zener barrier is a loop which can restrict the current by the
resistor.
At the same time it must allow the loop to function normally by
allowing the required values of current to flow in normal operation to
enable the instrument in the safe area to operate to full range.
Intrinsic Safety (Ex i) Barriers
There are two types of intrinsic safety barriers :
1) Zener barrier (2) Active barrier.
1) Zener barrier:
The series resistor limits the current to the hazardous area.
The zener barrier is a loop which can restrict the current by the
resistor.
At the same time it must allow the loop to function normally by
allowing the required values of current to flow in normal operation to
enable the instrument in the safe area to operate to full range.
Intrinsically Safe (Ex i) Barriers
Intrinsic Safety (Ex i) Barriers
Intrinsically Safe (Ex i) Barriers
Fuse
Transformer
Safety Barrier with up to 3 Zeners for triple redundancy
NON HAZARDOUS AREA
Field Device
HAZARDOUS AREA
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Details
Intrinsic Safety (Ex i) Barriers
2) Active Barrier:
The active barrier uses transformers, opto isolators and relays to
provide the isolation between the safe and unsafe areas.
It does not require an intrinsically safe ground connection.
This is the safest barrier to use if a high quality intrinsically safe
ground connection is not available.
The active barrier can drive a higher power load as compared to a
zener barrier.
Intrinsic Safety (Ex i) Barriers
Intrinsically Safe (Ex i) Barriers
Advantages:
1. A Transformer Isolation Barrier (TIB) contains current limiting
circuitry that limits the short circuit current and the fuse does not
blow unlike the zener barrier.
2. TIBs can be connected in parallel so that one power supply can feed
multiple TIBs.
3. It is designed for specific applications (transmitters, solenoids,
switching inputs, thermocouples), allowing easy system design
4. It does not require an IS ground as the transformer isolates
hazardous area connection from non hazardous area; However for
enhanced safety reasons, grounding is done.
5. Regulated power supply is not required.
6. Any process control signal to remains floating unlike for a zener
barrier where one side is grounded.
7. It can be repaired.
Intrinsically Safe (Ex i) Barriers
TIBs are used when:
1. Installation of a high integrity IS grounding is not available.
2. Regulated power supply is available.
3. The potential of signal noise due to ground loop is un desirable.
4. The cost of replacing the Zener barrier exceeds the cost of TIB.
5. The total loop resistance exceeds the specification.
Intrinsic Safety Barrier and Components’ Certification
1. Any device which does not fall into the category of a simple
apparatus must be certified. This includes transmitters, solenoids,
etc which store energy .
2. A barrier cannot be used to make an uncertified device in the
hazardous area safe. If the field device is uncertified it can have
energy storing components. In the event of a fault this energy can
be released to ignite the flammable gases.
3. The barrier only protects the hazardous area from the energy
released from the safe area’s uncertified devices.
4. An intrinsic safety barrier thus enables a non certified device in the
safe area to be connected to a simple device or a certified device in
the hazardous area and is an energy limiting device.
Certification
1. Why doesn’t a customer just buy a safety product from a vendor,
connect them up and pronounce them as safe?
2. Why does he need an approval agency?
The approval agency does all the safety analysis for the end
user.
The user does not have the responsibility to decide whether the
products are safe or not.
The user does not have the extensive ignition testing facility
used by the certifying agency. The customer may have queries
wrt to the intrinsically safe devices, field devices or combined
devices and he can ask the vendor bout such information .
The vendor has to provide certification papers, drawings etc as
required by the customer.
The vendor has to answer the customers queries wrt use of his
equipment.
Certifying Agencies
1. USA : NEC (National electric code), FMRC (Factory mutual
research corporation)
2. Canada : CSA (Canadian safety association)
3. UK : BASEEFA (British Approvals Service for Electrical Equipment
in Flammable Atmospheres)
4. Other countries have their own agencies as approved by their
government.
Zener Barrier Vs. Isolation Interface
Intrinsically Safe (Ex i) Barriers
The Entity Concept for EXi Equipment
1. The Entity concept specifies the maximum amount of energy an
intrinsic barrier can ever deliver and also the maximum amount of
energy the field device can safely receive.
2. The Entity concept allows interconnection of IS barriers to IS field
devices not specifically tested for such combination.
3. It also allows mixing up of equipment from different
manufacturers without additional approvals.
Entity Equations for Current and Voltage
Entity equations for current and voltage:
1. An IS barrier can safely be used with a field device if it has a
maximum current and voltage less than or equal to that which the
field can safely receive.
2. All these parameters are defined by the approval agency.
3. Entity equations for current and voltage :
I total (barrier) <= I max (field device)
V total (barrier) <= V max (field device)
Entity Parameters
•
•
•
•
•
•
In addition to voltage and current the entity parameters also
include two more terms to ensure that the energy storing
devices in the field do not store up dangerous amounts of
energy.
These terms deal with the capacitance and inductance of the
system.
A barrier has parameters which state the maximum capacitance
and inductance that can be safely be connected to it.
The field device has parameters which state the equivalent
capacitance and inductance of the field device.
Since the wiring has capacitance and inductance this also has
to be considered.
The total capacitance and inductance must not exceed that
permitted by the barrier
Entity Parameters
Entity equations for capacitance and inductance
Capacitance (field device) + Capacitance (field wiring) <= Capacitance
(I.S. Barrier Max)
Inductance (field device) + Inductance (field device) <= Inductance
(I.S. Barrier Max)
Entity Parameters
1.
2.
3.
4.
The field device is approved for the hazardous area if it never
receives more than 35V. The barrier ensures this.
the barrier can never deliver more than 90mA to the hazardous
area under fault condition.
The field device is safe as long as it never receives more than
110mA. The barrier ensures this as well.
Therefore because the voltage and current entity parameters
match up correctly, this circuit is intrinsically safe.
Entity Parameters
1.
2.
3.
4.
5.
The next figure shows a barrier connected between a safe area
terminal and a hazardous area field device.
this barrier can be safely used and also has approval.
The instrument loop operates with normal 24 VDC .
The zener diodes do not conduct until their voltage reaches
25.5VDC.
During a fault the maximum voltage the barrier can deliver to the
hazardous area is 31.2 V.
Entity Parameters
Entity Parameters
Capacitance and inductance as entity parameters
1.
2.
3.
4.
For this circuit which we considered we did not consider the
capacitance and inductance parameters.
All the parameters viz, voltage, current, capacitance, inductance
must match up correctly.
The entity parameters are given by the approval agency and
obtained through the manufacturer.
These are shown in the installation drawing.
Entity Parameters
Cable capacitance and inductance
1.
2.
3.
4.
A cable is an energy storing device.
Cable can store capacitance and inductive energy.
From an intrinsic safety point of view, this cabling has
to be considered .
The attached diagrams show the capacitance and
inductance of cabling as function of length.
Entity Parameters
Choice of cable length
1.
2.
3.
4.
Considering capacitance 5000ft is the largest possible length
allowed.
Considering inductance maximum cable length permitted is
2667 ft.
Thus having known the cable length, the designer can ascertain
other required parameters.
The values use viz 40 pf/ft and 0.3 micro H/ft are high values
chosen and are normally not exceeded.
Entity Parameters
Ignition Curves
Entity Parameters
Cable capacitance
and inductance
Ignition Curves
1.
2.
3.
The following graphs are actual ignition curves for
various gases.
They represent the minimum amount of ignition
energy required to ignite the gas in its most easily
ignitable concentration.
The area under the curve represents energy which is
too small to cause ignition.
Entity Parameters
Entity Parameters
Entity Parameters
Ignition Curves
1.
2.
3.
4.
We have seen some of the many graphs which the
intrinsic safety approval agency uses prior to certifying
a field device for use in hazardous area.
These are the actual ignition graphs for the various
gases.
They represent the minimum amount of ignition
energy required to ignite the gas in its most easily
ignitable concentration.
The area under the curve represents energy which is
too small to cause ignition.
Removal of Safety Barriers
1. Should a safety barrier require removal, from the intrinsically safe
circuit, please follow these guidelines:
2. Disconnect the wiring from the safety barrier’s non-hazardous
terminals prior to disconnecting wires from the intrinsically safe
terminals.
3. Cover bare wire ends with tape or other insulating material,
especially those conductors that are towards the hazardous area.
4. Disconnect the safety barrier from the ground. In most cases this will
also result in removing the barrier from the mounting hardware.
5. Reverse the process to mount a new barrier.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
• Used for isolated signal transfer between safe
and hazardous area.
• Inputs / outputs are galvanically isolated; no
earth is required.
• Certified equivalent to ‘simple apparatus’ no
system certificate is required.
• Extremely low power, avoids affecting
operation of connected equipment.
• Relay coil; AC or DC energised over a wide
voltage range.
• Can be supplied in safe or hazardous
mounting versions.
• DIN rail mounting slim case.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
• Used for isolated signal transfer between safe
and hazardous area.
• Inputs / outputs are galvanically isolated; no
earth is required.
• Certified equivalent to ‘simple apparatus’ no
system certificate is required.
• Extremely low power, avoids affecting
operation of connected equipment.
• Relay coil; AC or DC energised over a wide
voltage range.
• Can be supplied in safe or hazardous
mounting versions.
• DIN rail mounting slim case.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
By using DA 149 intrinsically safe isolating relays, control signals and
other data can be exchanged between items of equipment in
hazardous area and between hazardous and safe area equipment.
Since the relays require very little power they do not affect the
operation of other equipment connected.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
• Each relay is a solid state device consisting of an oscillator and an
intrinsically safe transformer to provide the necessary isolated
coupling to a MOSFET switch.
• For all practical purposes each can be regarded as a coil and a
normally open contact.
• Diodes are connected in series with the hazardous area input / and
or output terminals to make them electrically equivalent to ‘simple
apparatus’, ie, they can be included in any IS lop without any IS
certification.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
Inputs and outputs are galvanically isolated so they do not require any IS
grounding. The only power required is less than 60 µA at 4.0V to
energize the coil by comparison with certified opto isolators or relays
which need at least 10 mA to function, so the relays can be used in
virtually in any loop powered system without affecting the operation.
These relays can be mounted either in the safe area OR in the
hazardous area as required for specific use..
DAA 149 IS relay, Zone 0 to Safe area.
DAB 149 IS relay, Zone 0 to Zone 0; 100 mA fuse.
DAD 149 IS relay, Zone 0 to Zone 0; 50 mA fuse.
DAE 149 IS relay, Safe area to Zone 0; 250 mA fuse.
Intrinsically Safe Relays
DA 149 Series Intrinsically Safe Relay
Intrinsically Safe Relays
Series RLSH Relays
Interface from a Safe Area to a Hazardous Area
Intrinsically Safe Relays
Series RLSH Relays
Interface from a Safe Area to a Hazardous Area
• These relays present volt free contacts to the Safe area in response
to the Hazardous area coils.
• The certified parameters of the Hazardous area coil terminals are
such that they may be used in any IS field loop without further
certification.
Intrinsically Safe Relays
Series ‘RLSH’ intrinsically safe barrier relays
• These are intrinsically safe interfaces which present volt free
contacts to the hazardous area in response to the safe area coils.
Intrinsically Safe Relays
Series ‘RLSH’ intrinsically safe barrier relays
Intrinsically Safe Relays
Series ‘RLSH’ intrinsically safe barrier relays
Intrinsically Safe Relays
Programmable Relays
Intrinsically Safe Relays
Programmable Relays
Intrinsically Safe Relays
Programmable Relays
Other Ex Equipment
Increased Safety (Ex e) Equipment
Non-incendive (Ex n or N) Equipment
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Details
Equipment can also be protected by:
- oil immersion (Ex o),
- using powder, sand or quartz filling (Ex q),
- being encapsulated (Ex m), or
- having a special method of protection (Ex s)
Click here to see a presentation on
The evolution of equipment for harsh and hazardous locations
Wiring Ex Equipment
Wiring Ex Equipment
Wiring Ex Equipment
Maintenance of Ex Equipment
This section contains the following:
Maintenance of Ex Equipment
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Details
Periodic and Continuous Inspection of Ex Equipment
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Details
A movie on maintaining Ex Equipment like lights and motors
The following slides depict methods to maintain a Saab Tank Radar…
 These slides contain movie files that start automatically;
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 Click the left button of your mouse on this
to proceed to the next slide
Maintenance of Ex Equipment
SAAB Tank Radar
Cleaning The Parabolic Antenna
Courtesy: SAAB Marine Electronics
As the IG Pressure Sensor is in the same housing, it will be shown automatically after this video clip
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Cleaning an IG Pressure Sensor
Courtesy: SAAB Marine Electronics
As the IG Pressure Sensor is in the same housing, it will be shown automatically after this video clip
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Replacing an Inert Gas Pressure Sensor
Courtesy: SAAB Marine Electronics
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Cleaning the cone antenna transmitter
Courtesy: SAAB Marine Electronics
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Replacing a Board in the I / O Box
Courtesy: SAAB Marine Electronics
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Replacing the LCI (Interface) Board
Courtesy: SAAB Marine Electronics
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Replacing the LCM (Processor Memory) Board
Courtesy: SAAB Marine Electronics
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Mounting a Transmitter interface
Courtesy: SAAB Marine Electronics
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Removing a Transmitter Interface
Courtesy: SAAB Marine Electronics
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Replacing the LIA (Analog / Digital Power) board
Courtesy: SAAB Marine Electronics
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Replacing a LIZ (Zener Barrier) Board
Courtesy: SAAB Marine Electronics
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Replacing a card in the Work Station
Courtesy: SAAB Marine Electronics
As the Hard Disk is in the same housing, it will be shown automatically after this video clip
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Replacing a hard disk in the Work Station
Courtesy: SAAB Marine Electronics
This ends the maintenance of essential components of the SAAB Tank Radar
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Probable Questions by Examiners
1) Show how “Hazardous Zones” are classified on board a tanker.
2) Predict the possible “Electrical Sources of Ignition” that can be considered to
be “Hazardous”.
3) Identify the “Explosion Protected Equipment” in terms of “Symbol” and “Type of
Protection”.
4) State the significance of equipment marked: Exd; Exe; Exp; Exi; and Exn.
5) Demonstrate the precautionary measures in the maintenance of explosive
proof lights.
6) Describe / demonstrate essential items to be checked on “Ex-Protected”
Apparatus.
May you have a safe voyage
Suggestions to upgrade / correct this module are welcome
Please email any queries or advice to [email protected]