Trolex TX6383 Series User manual

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A T E X
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INTRINSICALLY
SAFE
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FLAMMABLE
GAS SENSOR/TRANSMITTER
INSTALLATION &
OPERATING DATA
contents...
p a g e
1PRINCIPAL OPERATING FEATURES 2
2APPLICATION 3
3DIMENSIONS 4
4TECHNICAL DETAILS 4
5INSTALLATION 6
6CONNECTIONS 11
7CONTROLS AND INDICATORS 14
8CALIBRATION 15
9MAINTENANCE 20
10 APPROVALS AND CERTIFICATION 23
11 FUNCTIONAL SAFETY 25
PETROCHEMICAL
PROCESSING
MINING&
TUNNELLING
OFFSHOREPLATFORMS
MANUFACTURING &
PROCESS PLANTS
STORAGEAREAS&
WAREHOUSING
WATERMANAGEMENT
&SEWAGE
TREATMENT
POWER
GENERATION
GASSTORAGE&
DISTRIBUTION
MARINE & SHIPPING
APPLICATIONS
TELECOMS

FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
M1
GROUPI&II
INTRINSICALLY
SAFE
INSTALLATION & OPERATING DATA
Stationary gas sensors for the detection of a wide range of
flammable gases.
Suitable for use in SIL 1 and SIL 2 applications, in accordance with
any conditions or restrictions
Poison resistant CATALYTIC COMBUSTION sensors.
Pre-calibrated plug-in gas sensing module with a standardised
output signal for convenient replacement and servicing.
Calibration available for a wide range of flammable gases.
LCD readout of gas concentration with OVERRANGE indication.
Convenient push button calibration of ZERO and SPAN.
Signal fix during calibration to prevent false alarms.
Output signal versions:- 4 to 20 mA 0.4 to 2 V
5 to 15 Hz
.
Stainless steel reinforced polycarbonate housing.
Intrinsically safe for use in Group I and Group II hazardous areas.
Special versions with weatherproof plug and socket
connections in place of cable glands.
Optional format with remote mounted gas sensing
module in robust metal housing.
1 PRINCIPAL OPERATING FEATURES
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FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
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INTRINSICALLY
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Fixed gas monitoring for point-source hazards and perimeter
protection in arduous duty and exposed locations.
Safety protection for toxic gas risk occurring in hazardous areas and
general industrial applications.
Petrochemical processing.
Mining and tunnelling.
Offshore platforms.
Manufacturing and process plants.
Storage areas and warehousing.
Water management and sewage treatment.
Power generation.
Gas storage and distribution.
Marine and shipping applications.
Telecommunications.
A choice of output signals for direct interfacing with most
standard industrial monitoring systems.
2 APPLICATION
TRIP AMPLIFIER
for use with
analogue output sensors.
CONFIGURABLE SENSOR CONTROLLER
for monitoring up to
8 analogue output sensors.
COMMANDER DISTRIBUTED I/O SYSTEM
for large scale general plant monitoring systems
and the mining and tunnelling industries.
A range of primary instrumentation and monitoring modules
is available from Trolex to which the sensors can be directly
connected to provide a flexible choice of display and
control functions.
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SAFE
3 DIMENSIONS
ALL DIMENSIONS IN MM
4 TECHNICAL DETAILS
4.1 Specification
Operating Temp. Limits: –10 to +40°C
Storage Temperature: –20 to +60°C
Ambient Pressure Limits: 1013 mbar ± 100 mbar absolute
Humidity: 95% RH non-condensing
Protection Classification: Dust and waterproof to IP66. Gas inlet port to IP54
Housing Material: Reinforced polymer - proof against electrostatic discharge
Nett Weight: 450 g
Cable Entries: M20 x 1.5
Electrical Connections: 4 mm Barrier/clamp terminals
Information Display: Graphic LCD
Impact Limits: 20 joules (Housing)
3.1 TX6383 Flammable Gas Sensor/Transmitter 3.2 TX6383.84 Flammable Gas Sensor/Transmitter
with Remote Gas Sensing Module
110
97
63
26
100 148
64
38
Ø10
Ø6.5
Gas Entry Port
3 Cable Entries to
Suit M20 Glands or
Multi Pole Connector
2 Holes for
M6 Socket
Cap Head
Fixing Screws
External Earth Terminal
110
97
2000 (standard)
148
External Earth Terminal
2 Holes for
M6 Socket
Cap Head
Fixing Screws
2 Fixing Holes for
M6 Socket Cap
Head Screws
124.0
15.0
26.0
GAS SENSING MODULE
Plug-in gas sensing module with signal conditioning. Precalibrated and standardised output signal.
Measuring Range: 0 to 5% v/v CH4. Calibrated for Methane
Alternative sensing ranges available to specification
Linearity: ±1% 0 to 60% FULL SCALE
±5% from 60% up to 100% FULL SCALE
Maximum Drift @ 25°C: ±0.25% v/v per month
Response Time (T90): <20 secs
Sensing Element Life: >5 years in clean atmosphere
Warm Up Time: <5 mins in air or 1% v/v CH4. (To 95% of stated accuracy)
Calibration: Digitally controlled ZERO and SPAN. Pushbutton setting
Signal Fix: The transmitted output signal of the sensor is FIXED at 00.0 during calibration
to prevent false alarms from being initiated
Overrange: If the measured gas concentration exceeds the calibration range of the sensor:
The STATUS indicator will flash
The display value will be CLAMPED
The transmitted output signal will be CLAMPED
Pellistor Protection: The supply to the gas sensing element will be switched off to prevent
oxidisation damage occurring if the gas concentration exceeds safe limits.
The sensor will attempt to switch back on at 5 minute intervals until the
gas concentration has reduced to a safe level
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Output: 0.4 to 2 V dc
Min Load 10 k ohms
Supply 6.5 to 16.5 V dc
Max Current 80 mA
FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
M1
GROUPI&II
INTRINSICALLY
SAFE
INSTALLATION & OPERATING DATA
4 TECHNICAL DETAILS continued
4.2 Electrical Details
20 mA
4
2 V
0.4
15 Hz
5
TX6383.01 GROUP I APPLICATIONS (12 V dc)
20 mA
4
TX6383.02 GROUP II APPLICATIONS (24 V dc)
20 mA
4
TX6383.03 GENERAL PURPOSE APPLICATIONS (24 V dc)
NO
T SUITABLE F OR U SE IN C LASSIFIED HAZARDOUS AREAS.
Output: 5 to 15 Hz
Max Load Opto isolated
. 2 mA max
Supply 6.5 to 16.5 V dc
Max Current 80 mA
Output: 4 to 20 mA
Max Load @ 24 V 240 ohms
Supply Minimum 6.5 V at the sensor
supply terminals (3 and 4)
Max Current 100 mA
Output: 4 to 20 mA
Max Load @ 24 V 240 ohms
Supply 6.5 to 30 V dc
Nominal Current 100 mA
Refer to Section 6
Output: 4 to 20 mA
Max Load @ 12 V 140 ohms
Supply 6.5 to 16.5 V dc
Max Current 24 mA
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INTRINSICALLY
SAFE
(Refer to Test Certificate provided with the sensor).
Does the output signal of the sensor concur with the
input requirement of
the monitoring equipment being used?
Is the correct supply voltage available for the sensor?
Is the type of gas and its anticipated maximum level of
concentration, within the operating parameters of the sensor?
Is the temperature variation range, at the installation, within
the stated temperature range of the sensor?
Is the hazardous area classification correct?
If the hazard is Group II – are the correct safety barriers fitted?
5 INSTALLATION
A
20 mA
4
0.4
V2 V
5Hz
15 Hz
12 V dc 24 V dc
GROUPI GROUPII
5.1 Conformity Check
TX6383.01 FLAMMABLE GAS SENSOR/ TRANSMITTER GROUP I
TX6383.02 FLAMMABLE GAS SENSOR/ TRANSMITTER GROUP II
TX6383.03 FLAMMABLE GAS SENSOR/ TRANSMITTER GENERAL
PURPOSE
TX6383.84.01 FLAMMABLE GAS SENSOR/ TRANSMITTER GROUP I
with Remote Gas Sensing Module
TX6383.84.02 FLAMMABLE GAS SENSOR/ TRANSMITTER GROUP II
with Remote Gas Sensing Module
TX6383.84.03 FLAMMABLE GAS SENSOR/ TRANSMITTER GENERAL
with Remote Gas Sensing Module PURPOSE
TYPE OF GAS
OUTPUT SIGNAL 0.4 to 2 V (11)
4 to 20 mA (12)
5 to 15 Hz output (13)
Refer to Section 4.2
GENERAL
PURPOSE
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STANDARD OPTIONS AVAILABLE
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5 INSTALLATION continued
5.2 Location
Ea ch i ns tall atio n n eeds t o be consid ere d i n i ts own right, wi t h r efere nce to
safety au thoritie s a nd i n c o mplia nce wit h mandatory lo cal safety r e gula tio ns.
The sens or m ust be operated in accord anc e wi t h t he I ns tallatio n and
Operating Da ta to main tain safe ty, r elia bility and t o preserve I ntrinsic Safet y
in tegrity w h ere applicable.
It is important that sensors are located in positions determined in consultation
with those who have specialised knowledge of the plant or installation and of the
principles of gas dispersion. Reference should also be made to those responsible for
the engineering layout and topology of the plant as they will be most familiar
with the nature of the potential dangers and the most likely sources of gas release.
It is also important to recognise that the characteristics of the gas source can be
influenced by many factors; including the relative density or buoyancy of the gas,
the pressure at the point of release, the ambient temperature and the ventilation
of the site.
Sensor coverage cannot be simply expressed in terms of ‘number per unit area’.
Sensors need to be sited where they are capable of monitoring those parts of a
plant where gas may accumulate or when a source of gas release is expected
to occur. This way the earliest possible warning of a gas release can be given to
initiate shutdown functions, alarm functions or safe evacuation of the premises.
5.3 System Integrity
If a gas monitoring system should fail for any reason, it is important that the system is
capable of immediately alerting operational staff to this fact.
The sensor will indicate a system failure or mechanical defect and this information can
be utilised to initiate a warning alarm. It is good practice to provide emergency
facilities to protect against the loss of the mains power supply.
Standby batteries can be incorporated with automatic changeover facilities, so
guaranteeing continued operation of the gas sensing system even in the event of
a plant breakdown as a result of a power supply failure.
Certainly, in critical plants, duplication or triplication of sensors is recommended.
The Trolex TX9042 or TX9044
Programmable Sensor Controller
can be programmed to operate
with sensors in the multiple
voting mode.
5.4 Sensor Management
A very important part of an efficient gas monitoring system is the training of
plant personnel in operation and maintenance of the sensors and the complete
monitoring system. Training facilities can be provided by qualified Trolex
application engineers.
Once a sensor installation is complete, the sensor locations and types should be
formally recorded and a planned test and maintenance procedure instituted.
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Hydrogen
Town Gas
Methane
Ammonia LIGHTER THAN AIR
Acetylene
Carbon Monoxide
Ethylene
Methyl alcohol
Propane
Ethanol
Acetone
Butane
Pentane
Benzene HEAVIER THAN AIR
Hexane
Ethylacetate
Toluene
Petrol
O-Xylene
Octane
FLAMMABLE GAS SENSOR/TRANSMITTER
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5 INSTALLATION continued
5.5 Relative Density
The relative density or buoyancy of the gas or vapour with respect to air is a very
important consideration. This determines its propensity to rise or
fall
when
released into the atmosphere.
Gases or vapours with a buoyancy less than air will tend to rise from the source
of release.
Conversely, gases or vapours heavier than air will tend to fall and accumulate in
concentrations for long periods of time.
This is a particular problem in pits, trenches, machine rooms, etc. Normal air
movements in and around such gas concentrations will have the
inevitable effect of producing zones of highly flammable mixtures.
This knowledge of the characteristics of the gas assists when positioning the gas
sensor.
The behaviour of the gas accumulation will also be affected by the velocity and
location of the gas release and by ambient air movement caused by ventilation
systems or draughts.
Pockets of gas can be trapped in trenches or ceiling cavities, all of which adds to the
unpredictability of critical gas concentrations.
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5 INSTALLATION continued
5.6 Hazardous Areas
Do not disassemble the sensor whilst in the hazardous area or use a sensor
that has a damaged housing in the hazardous area.
5.7 Evacuation
If a dangerous level of gas concentration is detected by the instrument, leave
the area immediately.
5.8 Operating Limits of Catalytic Combustion Sensors
Catalytic combustion gas sensors POSITIVELY detect the presence of flammable
gas. They rely upon the presence of oxygen in the atmosphere and should only
be used for gas concentration up to the Lower Explosive Limit (LEL).
After this point, the output becomes non linear and may erroneously indicate
that the gas concentration is below the LEL. they should not be used in oxygen
enriched or deficient atmospheres.
5.9 Discrimination
Catalytic combustion sensors can detect a wide range of flammable gases but
they cannot discriminate between individual gases. They will respond to most or
all of the flammable components present in the atmosphere without
distinguishing between them.
5.10 Contamination
The response of catalytic combustion gas sensors can be affected by air borne
contaminants which will reduce the sensitivity. Substances such as silicones,
tetraethyl lead, sulphur compounds and phosphate esters can cause permanent
degradation (poisoning). Halogenated carbons may also cause temporary inhibition.
5.11 Interference
If the atmosphere to be monitored contains a gas that dilutes or displaces the
air, this may reduce the response of catalytic sensors. Similarly, steam laden
atmospheres and condensation can reduce the sensitivity.
Air velocity may have a minor effect on the accuracy of the gas sensor.
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5 INSTALLATION continued
5.12 High Concentrations of Flammable Gas
Exposure of low concentration catalytic combustion sensors to concentrations of
flammable gas greater than the LEL can affect the sensitivity and zero stability of
catalytic elements and the calibration should be checked after such an exposure.
If the gas concentration does exceed 100% LEL, the supply voltage to
the catalytic combustion sensing element will be automatically switched
off to prevent damage to the element.
The sensor output signal will be CLAMPED, the display will indicate
OVERRANGE and the STATUS indicator will FLASH.
Refer to Sections
7, 8.5 & 8. 6
5.13 Toxicity
Be aware that most flammable gases and vapours are also toxic at low
concentrations of LEL.
5.14 New Installations
Flammable gas sensors based on pellistor technology require regular zero and
span check and adjustment operations to ensure that they remain accurate.
The pellistor device ages during its lifetime and its baseline and sensitivity
characteristics will change. These operations are normally performed three weekly.
The pellistors baseline tends to move positively throughout its lifetime. In the early stages
of the lifetime, the baseline tends to move positively at a relatively fast rate.
This movement slows down with age. Users may note a small positive reading
from the gas sensor during the first month or so of usage.
The pellistor fitted to the TX6383 will have a baseline change equivalent of upto 2.5%
LEL (0.11% v/v) in its first month of usage, then a further 1.5% LEL
(0.066% v/v) in the second month.
For newly installed equipment, end users should consider performing a zero offset
adjustment every fortnight for the first two months. This will ensure that the offset
movement is kept below 2% LEL (0.088% v/v) during the ‘settling in’ period.
Refer to Section 8
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6.1 0.4 to 2 V Output Signal
A low impedance two-wire voltage
output signal requiring a separate
power supply to the sensor.
This can be derived from a TX9132
Trip Amplifier or TX9042 Programmable
Sensor Controller, when one of those is used
as the monitoring instrument.
This connection configuration works well up to about 10 m
distance between the sensor and the monitoring equipment.
Both the signal and the power supply to the sensor are being
carried in the common 0 V conductor so at some point –
influenced by the length of the cable and the resistance of the
cable cores – the current flowing in the 0 V conductor will impose
an unacceptable voltage error onto the signal.
This effect can be reduced on long distance connections by
increasing the size of the cable cores, or even better, running a
separate 0 V conductor to power the sensor enabling operating
distances up to 1000 m.
1 2 3 45
TX6383
+V Supply
0 V
0.4 to 2 V signal
67 8
0 V Supply
TX9132
1 2 3 45
TX6383
+V Supply
0 V
0.4 to 2 V signal
67 8
TX9132
FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
M1
GROUPI&II
INTRINSICALLY
SAFE
6 CONNECTIONS
TX6383 FLAMMABLE GAS SENSOR/ TRANSMITTER
3 WIRE
4 WIRE
V2 V
0.4
OUTPUT SIGNALOPTIONS
1 2 3 45
Signal
0 V Supply
6 7 8
0 V
+ V
1 2 3 45
TX6383
+V Supply
0 V
4 to 20 mA signal
67 8
TX9131
6.2 4 to 20 mA Output Signal
The sensor may be connected
the
3 or 4 wire connection mode.
The power supply for the sensor may
be sourced from the monitoring equipment
(eg. TX9131 Trip Amplifier or a TX9042
Programmable Sensor Controller) or from
a separate power supply.
3 WIRE 4A20 mA
1 2 3 45
TX6383
+V Supply
0 V
4 to 20 mA signal
67 8
0 V Supply
Monitoring
Device
4 WIRE
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INSTALLATION & OPERATING DATA
APPLICATION GROUP I HAZARDOUS AREAS
APPLICATION GROUP I HAZARDOUS AREAS
GROUP II HAZARDOUS AREAS
GENERAL PURPOSE
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6 CONNECTIONS continued
6.3 5 to 15 Hz Output Signal
A square wave, frequency variable output
that is proportional to the measured value.
The output device is an open collector NPN
transistor.
Output: 5 to 15 Hz
(zero = 5 Hz)
(span = 15 Hz)
Maximum Voltage: 15.4 V
Maximum Current: 2 mA
Minimum Pulse Rise Time: 5 V/ms
1 2 3 4567 8
0 V
5 to 15 Hz signal
+V Supply
A
may be required
at the monitoring
device.
0 V Supply
TX6383
Monitoring
Device
A pull up resistor may be required
at the monitoring device.
6.4 Using Gas Sensors in Hazardous Areas
6.4.1 GROUP I HAZARDOUS AREAS (MINING)
TX6383.01 FLAMMABLE GAS SENSOR/ TRANSMITTER
All options of the TX6383.01sensor (0.4 to 2 V, 4 to 20 mA and
5 to 15 Hz) are certified Intrinsically Safe for use in Group I
hazardous areas (Mining) when used with approved equipment
eg. TX9131 Trip Amplifier or a TX9042 Programmable
Sensor Controller.
THE COMPLETE SYSTEM, BOTH SENSOR AND MONITORING
DEVICE, CAN BE MOUNTED IN THE HAZARDOUS AREA.
The interconnecting cable between the sensor and the
monitoring device must have steel wire armoured
protection or a braided earth screen. The cross sectional
area of the conductors must be a minimum of 1 mm2.
TX9131
HAZARDOUS
SAFE
TX6383.01
Hz
15 Hz
5
6.4.2 GROUP II HAZARDOUS AREAS (24 V dc)
TX6383.02 TOXIC GAS SENSOR/ TRANSMITTER
This version of the sensor (4 to 20 mA) is certified Intrinsically
Safe for use in industrial hazardous areas, when used in
conjunction with safety barriers.
THE SAFETY BARRIERS ARE MOUNTED IN THE SAFE AREA,
ONLY THE SENSOR IS MOUNTED IN THE HAZARDOUS AREA.
The system may be used with either zener safety barriers or
isolation safety barriers.
4 to 20 mA
Signal
HAZARDOUS SAFE
TX6383.02
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6 CONNECTIONS continued
Group II sensor connections using zener safety barriers.
Max. Cable Length: 1 km using 1.5 mm2cable conductors.
If you require any help with the use and connection of hazardous area equipment
please contact the Trolex Technical Department.
Power Safety Barrier: MTL779+
Signal Safety Barrier: MTL787S+
1 2 3 45
Supply
67 8
1
2
4
3
MTL 787S+
MTL 779+ +24 V
0 V
0 V
0 V
+V 1
2
4
3
4 to 20 mA
Signal
HAZARDOUS SAFE
TX6383.02
Group II sensor connections using isolation safety barriers.
Max. Cable Length: 1 km using 1.5 mm2cable conductors.
Power Isolation Barrier:
Pepperl & Fuchs
KFD2–SL2–EX 2B
Signal Isolation Barrier:
Pepperl & Fuchs
KFD2–STC4-EX 1
1 2 3 45
Supply
67 8
1
2
8
7
3
11
12
KFD2–STC4-EX 1
KFD2–SL2–EX 2B +24 V
0 V
0 V
0 V
+V
8
9
7
4
5
1
215
14
4 to 20 mA
Signal
HAZARDOUS SAFE
TX6383.02
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Plug-in Gas
Sensing Module
Cable Entry
Gas Concentration
Display
Earth
Terminal
Gas Entry Port
7 CONTROLS AND INDICATORS
TX6383 FLAMMABLE GAS SENSOR/
GCalibration STATUS indicator
SPAN calibrate pushbutton
ZERO calibrate pushbutton
TX6383.84 FLAMMABLE GAS SENSOR/ TRANSMITTER REMOTE GAS SENSING MODULE.
This version uses the same pre-calibrated gas sensing module as the TX6383.
The module is fitted into a robust metal housing which can be mounted at a
remote location where space is constricted or the operating conditions are
extremely harsh.
Connections: 2 m, flexible cable in a flexible armoured conduit
(other lengths available to specification. Max 10 m).
Protection Classification: Dust and waterproof to IP66. Gas inlet port to IP54.
Housing Material: Brass or Stainless steel.
Maximum Cable Length: Extendible up to 500 m using 1.5 mm2cable conductors.
(General Purpose only)
DISCONNECTING THE REMOTE GAS SENSING MODULE
The connecting cable between the remote gas sensing module
and the Transmitter is normally supplied connected at both ends.
The cable can be disconnected via a plug and socket connector
inside the Transmitter housing for servicing or transportation.
Secure connector to
inside of the enclosure
with a double sided
adhesive foam pad.
(Trim off any excess
before fitting).
Double line
indicates red marker
on ribbon cable.
I
IM MP PO OR RT TA AN NT T! !
The Ribbon Cable
Assembly must lie flat
against the inside rear
of the enclosure &
must be connected to
the feedthrough in
the orientation shown.
View showing
orientation of
ribbon cable.
(All other parts
removed for clarity).
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8 CALIBRATION
The gas sensing module will gradually change its response
characteristics, by a small amount, during normal use.
The output signal is standardised so the module can
be quickly changed when necessary.
Ser vice replacement modules can be
supplied by our Product Support
Department.
Alternatively the gas sensing module
may be re-calibrated when required,
using a Trolex TX6520 Gas Test Kit
equipped with both Air and
Test Gas canisters.
8.1 Prepare to Calibrate
The sensor should be powered for a minimum of 30 minutes
prior to commencing calibration.
Connect the application tube of the gas test kit to the inlet
aperture of the gas sensing module.
The indicator will be GREEN denoting the NORMAL operating
condition.
G
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8.2 Prepare to Calibrate
Press BOTH pushbuttons on the gas
sensing module for about 5 seconds.
Then release.
The indicator will be RED denoting that the
module is now setup ready for:
8 CALIBRATION continued
R
When the Gas Sensing Module is
setup into the CALIBRATE MODE it
will instruct the transmitted output
signal of the sensor to be FIXED at
ZERO SCALE. This will prevent the
possibility of false alarm signals being activated in the
monitoring equipment during the calibration process.
The display will continue to show the measured value of gas
concentration during the calibration process.
The gas sensing module will automatically return to the
normal measuring mode if the pushbuttons are
operated within 60 seconds.
Refer to Section 8.3
Calibrate ZERO
OR
Calibrate
Refer to Section 8.4
FIX
0
G
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8 CALIBRATION continued
8.3 Calibrate ZERO
Apply purge air, at a flow rate of 0.2 to 1 l/min, for 20 seconds
to clear all remnants of gas.
AIR
The CALIBRATE ZERO will NOT function if any level of
gas concentration is detected by the sensing
element – The indicator will NOT flash GREEN.
Press CALIBRATE ZERO until the indicator is flashing GREEN
(about 3 seconds).
Release and the indicator will briefly show RED to denote
ZERO setup.
The Gas Sensing Module will immediately return to the
NORMAL measuring mode.
Switch off the purge air supply.
G
G
R
G
The Gas Sensing Module will automatically return to
the NORMAL measuring mode if NO pushbuttons are
operated within 60 seconds.
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INTRINSICALLY
SAFE
8 CALIBRATION continued
8.4 Calibrate SPAN
Apply test gas, at a flow rate of 0.2 to 1 l/min, until the display
value stabilises.
The Gas Sensing Module will automatically return to
the NORMAL measuring mode if NO pushbuttons are
operated within 50 seconds.
Press CALIBRATE SPAN until the indicator is flashing YELLOW
(3 times).
Press and hold the calibration pushbuttons to SCROLL the
display value UP/DOWN until it concurs with the value of gas
concentration marked on the test gas canister.
Switch off the test gas supply.
5 seconds after SCROLLING has ceased the gas sensing module
will automatically return to the NORMAL measuring mode.
TEST GAS
Y
Y
R
G
R
Re-apply the test gas for a few seconds to verify the response of
the sensor.
DO NOT PRESS CALIBRATE SPAN UNTIL THE DISPLAYED
VALUE HAS FULLY STABILISED.
The CALIBRATE SPAN will NOT function if the level of
gas concentration detected by the sensing
element is less than about 25% FULL SCALE.
The indicator will NOT flash YELLOW.
Release and the indicator will show RED to denote READY.
R
The Gas Sensing Module will automatically return to
the NORMAL measuring mode if NO pushbuttons are
operated within 60 seconds.
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FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
M1
GROUPI&II
INTRINSICALLY
SAFE
8 CALIBRATION continued
8.5 Over Range Indication
Erroneous readings will be given by a pellistor gas sensing
element if it is exposed to gas concentrations that exceed its
normal working range of 0 to 5% v/v CH4.
The increase in gas concentration displaces the oxygen in the
atmosphere so the pellistor becomes progressively less effective,
to the point where its output signal actually starts to
as the gas concentration continues to .
When OVER RANGE is detected, four conditions will be initiated:
The display will indicate OVER RANGE to prevent ambiguous
readings.
The transmitted output signal will be CLAMPED at FULL SCALE
to prevent an ambiguous output signal from being transmitted.
The STATUS indicator will FLASH alternate RED and GREEN.
The pellistor in the gas sensing module will be switched into a
PROTECT state to prevent oxidisation damage.
Pellistor
Signal
Ga s
0/P
v/v
Refer to Section 8.6
Clamp
0
R
G
RESET
Briefly interrupt the power supply to the sensor to RESET the
OVER RANGE condition.
This will only be effective when the gas concentration has
receded and the pellistor in the gas sensing module has reset
itself from the PROTECT state.
Refer to Section 8.6
8.6 Pellistor Protection
Catalytic combustion sensors can be damaged if exposed
to excess concentrations of gas for long periods
.
If the OVER RANGE condition is initiated the gas sensing module
will be switched into the PROTECT state to prevent
oxidisation damage.
The status indicator will flash RED/GREEN to indicate that the
pellistor is the PROTECT state.
The gas sensing module will reset itself to NORMAL operation
after 5 minutes if the gas has cleared. It will continue to attempt
to reset itself at 5 minute intervals until the gas has cleared.
It will now be necessary to RESET the OVER RANGE condition.
R
G
Refer to Section 8.5
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It is good safety practice to carry out regular preventative maintenance to
confirm correct operation. The periodicity for preventative maintenance should
be in line with best practice for the industry where the gas sensor is being used
and take into consideration local operating conditions.
9.1 Output Signal
Check the response of the sensor at pre-determined intervals
by injecting a test gas using a Trolex TX6520.32 Gas Test Kit.
Compare the value of the display with the value marked on the
test gas canister.
Calibrate the TX6383 using the instructions in Section 8.
Insert an approved test meter into the signal line.
Inject a test gas using a Trolex TX6520.32 Gas Test Kit.
Compare the value on the test meter display with the measured
line value.
If the value on the test meter does not match the value on the
display:
Recalibrate and then carry out the proof test again
OR
change the gas sensing module, calibrate and then carry out the
proof test.
9.3 Gas Sensing Modules
The gas sensing modules should be changed at regular intervals to
ensure accuracy of response.
The response of the Pellistor sensor will gradually shift due to normal
device decay. The average life is about 5 years, influenced mostly by
the operating environment and the mean level of
exposure to flammable gas during its lifetime.
The shifting response of the cell should be checked at regular intervals
particularly on new installations.
The modules are conveniently replaceable giving a pre-calibrated
standardised output signal. They can be changed in seconds.
Service replacement modules can be supplied by our Product
Support Department on a regular basis.
Simply insert the new module into the instrument and return the
original for checking and calibration.
FLAMMABLE GAS SENSOR/TRANSMITTER
A T E X
M1
GROUPI&II
INTRINSICALLY
SAFE
9 MAINTENANCE
LOCK
Refer to Section 8
Refer to Section 9.2
AIR
CH4
AIR
CH4
RELEASE
The sensor will transmit an alarm signal if
a replacement gas sensing module is
not fitted within 15 seconds.
CURRENT
OUTPUT
SHOWN
Refer to Section 5.1 4
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