Crowcon TXgard-IS+ Manual

Installation, Operation and Maintenance Instructions
M07214
Issue 8
January 2015
TXgard-IS+
Intrinsically Safe
Toxic and Oxygen Gas Detectors
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Contents
1 INTRODUCTION ....................................................................... 1
Product overview.................................................................. 1
Product description............................................................... 1
2 INSTALLATION.......................................................................... 4
General ................................................................................ 4
Mounting............................................................................. 5
Cabling requirement............................................................. 5
Electrical connections ........................................................... 6
3 OPERATION............................................................................ 10
The operator display panel and keypad............................... 10
Using the TXgard-IS+ menus............................................... 11
4 COMMISSIONING .................................................................. 14
Commissioning procedure: ................................................ 14
Commissioning procedure: ................................................ 20
5 MAINTENANCE...................................................................... 23
Routine maintenance.......................................................... 23
Sensor replacement and servicing of detectors.................... 23
6 FAULT FINDING ...................................................................... 25
Appendices
APPENDIX A.............................................................................. 31
WIRING THE TXGARD-IS+ TO CROWCON CONTROL
EQUIPMENT........................................................................ 31
APPENDIX B.............................................................................. 35
TXGARD-IS+ SPECIFICATION............................................... 35
APPENDIX C.............................................................................. 37
SPARE PARTS AND ACCESSORIES ....................................... 37
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APPENDIX D.............................................................................. 38
MENU SYSTEM................................................................... 38
APPENDIX E .............................................................................. 48
4-20 mA LOOPS ................................................................. 48
APPENDIX F .............................................................................. 50
CABLING REQUIREMENT .................................................... 50
APPENDIX G ............................................................................ 53
SENSOR LIMITATIONS ......................................................... 53
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TXgard-IS+ Introduction
1
1 INTRODUCTION
1.1 Product overview
TXgard-IS+ is an Intrinsically Safe detector for toxic gases or oxygen. It is
suitable for use in Zone 0, 1 or 2, or Division 1/Division 2 hazardous
areas when used with a suitable Zener barrier or galvanic isolator.
TXgard-IS+ is designed to detect a wide range of gases when fitted with
the appropriate electrochemical sensor. Gases include oxygen, carbon
monoxide and hydrogen sulphide. For a full list of supported sensors,
please contact Crowcon.
TXgard-IS+ is a loop-powered instrument providing a 4-20 mA signal
suitable for direct connection to a control panel. Unlike most other 4-20
mA gas detectors featuring operator display panel (LCD) and keypads, it
combines its power and signal in just two wires, so only one barrier is
required. The instruments are supplied with the mA pre-calibrated, so
the mA does not need re-calibration in the field. The keypad and
operator display panel allow access to many powerful features to help
installation and maintenance, such as:
• trueonemancalibration
• signalcurrentcanberampedtoadesiredvaluetohelpset-up
control panels
• congurablefaultandinhibitcurrents
• congurabledisplayoptions
• displayinglinevoltage-noneedtoaccesstestpointsinsideunit
1.2 Product description
TXgard-IS+ comprises of two main parts. The junction box contains the
circuitry, including the PCBs, an operator display panel and keypad. The
sensor is contained in the sensor housing. Figure 1 on page 2.
The sensor comes in a re-usable bayonet sensor housing which is
standard for all gas sensors.
The sensor housing screws into an M20 entry on the junction box.
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Introduction TXgard-IS+
2
All electrical connections to the detector are made through the terminal
blocks on the baseboard J2 and J4 (see and in Figure 1). The
junction box of TXgard-IS+ has one top-entry M20 cable entry for
customer use as standard. Side entry versions and gland adapters are
available (contact Crowcon for details).
The Personality Module , mounted on the baseboard, comes in two
varieties: Toxic and Oxygen. It converts the sensor output into a
standard signal which can be interpreted by the processor. The
Personality Module contains a memory chip with calibration data for
the associated sensor. When replacing a sensor, it is not necessary to
change the Personality Module; you simply rezero (Note: not necessary
for O2 sensor) and recalibrate, and the Personality Module stores the
new calibration constants.
When the detector is powered through a suitable Zener barrier or
galvanic isolator, the system is certified Ex ia IIC T4.
J4
TP1
+
TP2
–
J2







CONNECTION TO
CONTROL PANEL
40-200mV
TEST POINTS
RED
BLU
GRN
M20CABLE ENTRY
BASE BOARD
PERSONALITY
MODULE
SENSOR
HOUSING
Some baseboards may have
J4 in this orientation
Figure 1: TXgard-IS+ fitted with toxic sensor
Important
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TXgard-IS+ Introduction
3
TXgard-IS+ is designed for use in Zone 0, 1 or 2, or Division 1/Division 2
hazardous areas and is certified Ex ia IIC T4 when used with a suitable
Zener barrier or galvanic isolator. Installation must be in accordance
with the recognised standards of the appropriate authority in the
country concerned. TXgard-IS+ should be inspected regularly if used in
a dusty environment. For further information, please contact Crowcon.
Before carrying out any installation work, ensure that local
regulations and site procedures are followed.
Storage Instructions
The sensor used in this detector has a maximum non-powered storage
life of 3 months. Sensors stored within a detector for longer than 3
months prior to commissioning may not last for the full expected
operational life. The warranty period for the sensor begins from the
date of shipment from Crowcon.
Detectors should be stored in a cool and dry environment where
temperatures remain within the 0-20˚C range
TXgardIS+ ATEX, UL and IECEx Intrinsically safe
Abingdon, United Kingdom, OX14 4SD
GAS DETECTOR
TXgard-IS+
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Installation TXgard-IS+
4
2 INSTALLATION
2.1 General
The detector should be mounted where the gas is most likely to be
present. The following points should be noted when locating gas
detectors:
• Todetectgasesthatarelighterthanair,detectorsshouldbe
mounted at high level. Crowcon recommends the use of a
Collector Cone (part no. C01051).
• Todetectgasesthatareheavierthanair,detectorsshouldbe
mounted at low level.
• Todetectgaseswithsimilarweighttoair,forexample,hydrogen
sulphide, mount the detector at normal breathing height.
• Whenlocatingdetectors,considerthepossibledamagecausedby
natural events such as rain or flooding. For detectors mounted
outdoors, Crowcon recommends the use of a spray deflector (part
no. C01338).
• Mountingofoxygendetectorsrequiresknowledgeofthegas
displacing the oxygen. For example, carbon dioxide is heavier than
air and displaces oxygen at low level. Under these circumstances
oxygen detectors should be placed at low level.
• Considereaseofaccessforfunctionaltestingandservicing.
• Considerhowtheescapinggasmaybehaveduetonaturalor
forced air currents. Mount detectors in ventilation ducts if
appropriate.
• Considertheprocessconditions.Gasesthatarenormallyheavier
than air, but are released from a process line that is at a high
temperature and/or under pressure, may rise rather than fall.
Ammonia released from a cooling system may fall rather than rise.
The placement of the sensors should be decided following the advice of
experts with specialist knowledge of gas dispersion, experts with
knowledge of the process plant system and equipment involved, and
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TXgard-IS+ Installation
5
safety and engineering personnel. The agreement reached on the
locations of sensors should be recorded. Crowcon is pleased to
assist in the selection and siting of gas detectors.
2.2 Mounting
TXgard-IS+ should be installed at the location with the detector
pointing down. This ensures that dust or water will not collect on the
sensor and stop gas entering the detector.
TXgard-IS+
5 ppm
4.3mA
CO
OK
124 92
122
38
104
104
Figure 2: TXgard-IS+ dimensions
2.3 Cabling requirement
Cabling to TXgard-IS+ must be in accordance with the recognised
standards of the appropriate authority in the country concerned, and
must also meet the electrical requirements of the detector. Crowcon
recommends the use of 2-core twisted pair cable, but there is no
particular restriction as long as it can supply 8 V at 20 mA to the
instrument terminals. Suitable weatherproof glands must be used.
Cable should be identified as being intrinsically safe by some means, for
example, by having a blue outer sheath. Alternative cabling techniques,
such as steel conduit, may be acceptable provided that appropriate
standards are met.
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Installation TXgard-IS+
6
TXgard-IS+ requires a dc supply of 8-32 V and is loop powered. (If
mounting in a hazardous area, do not use a higher voltage than the
Zener barrier’s rating, usually 28 V). Ensure there is a minimum supply
of 8 V at the detector, taking into account the voltage drop due to
cable resistance and the sense resistance of the control panel to which
it is connected. Table 1 shows maximum cable distances given typical
cable parameters (See Appendix F for more information).
Table 1: Maximum cable distances for typical cables
Cross-sectional
area (mm2)
Typical resistance
(Ωper km)
Maximum
distance (km)
Cable Loop
1.0 18.1 36.2 2.2
1.5 12.1 24.2 3.3
2.5 7.4 14.8 5.4
The acceptable cross-sectional area of cable used is 1.0 to 2.5 mm2.
The table is provided for guidance only. Actual cable parameters for
each application should be used to calculate maximum cable
distance. Assume each termination is 0.5 Ω.
2.4 Electrical connections
All connections to the 4-20 mA loop, and sensor, are made via the
screw terminal connectors mounted on the baseboard in the junction
box. Figure 1 on page 2. For further information on how 4-20 mA
current loops work, see Appendix E. For a worked example of how to
calculate if the cable is suitable, please see Appendix F.
Figure 3 on page 7 , shows the baseboard in detail. The terminals
marked J4 should be connected to the control equipment using the
appropriate + and – terminals. For further details of wiring the
TXgard-IS+ to Crowcon equipment see Appendix A.
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TXgard-IS+ Installation
7
Some baseboards
may have J4 in
this orientation
Figure 3: Baseboard
TXgard-IS+ is a 4-20 mA sink, loop-powered device designed to work in
safe and hazardous zones 0, 1 and 2 areas when used in conjunction
with an appropriate barrier. Figures 4, 5 and 6 summarise the electrical
connections.
SAFE AREA
Figure 4: Electrical connections for safe area
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Installation TXgard-IS+
8
HAZARDOUS AREA
Note: An IS earth connection must be supplied in the safe area,
so as to avoid earth loops and to maintain IS certification.
Figure 5: Electrical connections using Zener barrier
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TXgard-IS+ Installation
9
Figure 6: Electrical connections using galvanic isolator
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Operation TXgard-IS+
10
3 OPERATION
3.1 The operator display panel and keypad
The TXgard-IS+ provides an operator display panel through a Liquid
Crystal Display (See Figure 7). The operator display panel allows you to
communicate with the TXgard-IS+ instrument through a series of text
based menus. Use the operator panel to calibrate the sensor, adjust
signal levels and resolve instrument errors. You may also display
information on serial number, software version and adjusting advanced
settings.
The operator display panel provides continual instrument status on the
gas being sensed, the gas reading and the loop current value. A
flashing ‘OK’ indicates the system is operational (see Figure 8). Press the
down dbutton to display the voltage and temperature (Figure 9 on
page 11), this display will automatically return to the main display
after a few moments.
TXgard-IS+
5 ppm
4.3mA
CO
OK
LCD
Liquidcrystal display
DOWN key
ENTER key
UP key
Figure 7: Operator display panel and keypad
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TXgard-IS+ Operation
11
TXgard-IS+
5 ppm
4.3mA
CO
OK
Gas being detected
eg. CO, H2S, O2
Flashing OK
indicates system is working
UNITS
%or ppm
Loop current
Figure 8: LCD ‘operator display panel’
TXgard-IS+
Power: 21.5V
Temp: 25.0 C
Power V
Temperature
Figure 9: Power and temperature display (after pressing DOWN key)
3.2 Using the TXgard-IS+ menus
Three buttons are provided to select the menu options and respond to
instrument messages, the (UP) and d(DOWN) button moves your
selection through the menu list, a cursor ‘ >’ indicates current selection.
To enter that selection, press the (ENTER) key.
To enter the menu system:
1 Press the button and then the default password, which is the
down button five times.
2 Press the button again to exit the menu system if you decide
not to change the instruments settings.
The operator display panel shows the available menus. The TXgard-IS+
has seven standard menus that allow you to calibrate and configure the
instrument. The menu structure for a TXgard-IS+ Toxic detector is
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Operation TXgard-IS+
12
shown in Figure 10 on page 13, detailed menus can be found in
Appendix D.
NOTE: the menu for the oxygen detector only varies for the ‘Zero/cal
gas’ menu item which is replaced by ‘Cal O2 @ 20.9%’.
To exit the main menu display
1 To exit any menu, use the key to move the cursor to the top of
the menu list where you will find To gas display. If you are in a
submenu you will need to repeat this and move the cursor to the
top of the menu list to return to the gas display. Note: UP = OUT.
Tip
To go directly to the bottom of a menu, press dand simultaneously.
To go directly to the top of a menu, press and simultaneously.
The menu will also return to the gas display after a timeout (default 5 minutes).
Figure 10: Menu structure for TXgard-IS+ toxic detector
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TXgard-IS+ Operation
13
shown in Figure 10 on page 13, detailed menus can be found in
Appendix D.
NOTE: the menu for the oxygen detector only varies for the ‘Zero/cal
gas’ menu item which is replaced by ‘Cal O2 @ 20.9%’.
To exit the main menu display
1 To exit any menu, use the key to move the cursor to the top of
the menu list where you will find To gas display. If you are in a
submenu you will need to repeat this and move the cursor to the
top of the menu list to return to the gas display. Note: UP = OUT.
Tip
To go directly to the bottom of a menu, press dand simultaneously.
To go directly to the top of a menu, press and simultaneously.
The menu will also return to the gas display after a timeout (default 5 minutes).
Figure 10: Menu structure for TXgard-IS+ toxic detector
See Appendix D and Section 4.2 for further information.
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Commissioning TXgard-IS+
14
4 COMMISSIONING
The commissioning procedures for toxic detectors can be found in
section 4.1. To commission oxygen detectors go to section 4.2.
Warning
Before carrying out any work, ensure that local regulations and
site procedures are followed. Ensure that the associated control
panel is inhibited to prevent false alarms.
4.1 Commissioning procedure:
Toxic gas detectors
NOTE: To prevent false alarms during calibration, enable inhibit mode
prior to zeroing or applying gas (see Figure 10 on page 13). The detector
output will then remain at the preset inhibit level (see Appendix D) for
five minutes or until inhibit mode is cleared manually. “Inhibit” will
appear on the normal operating display when inhibit is active, and the
detector will automatically resume gas level output after five minutes.
Step 1:
Connecting the detector to the control panel
1 Apply power to the detector via 2-way connector J4.
Figure 1 on page 2.
The instrument requires a minimum of 8 V dc at connector J4 at
20 mA.
2 Leave the detector to stabilise for at least 2 hours.
NOTE: the detector is factory pre-set to automatically inhibit its
mA output for 30 seconds after power-up to prevent false alarms
while the sensor is settling.
Tip
As long as the instrument is running, you can see the supply voltage
on the display panel, by pushing the dbutton.
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TXgard-IS+ Commissioning
15
Step 2:
Checking the 4-20 mA loop current
This step can be omitted as the TXgard-IS+ is delivered pre-
calibrated, however, if you wish to check the 4-20 mA loop current,
then it can be checked as outlined below. Alternatively the TXgard-IS+
provides a facility to force a known current through the loop. Refer to
the Ramp mA menu item in Appendix D for instructions.
NOTE: there is no need to disconnect a sensor when calibrating mA!
The mA control circuit is completely independent from the gas
measuring circuit!
1 Connect a digital voltmeter (DVM) across test points TP1 and TP2
on the baseboard (Figure 1 on page 2 or Figure 3 on page
7). The loop current flows through a sense resistor between
these test points, so a 4 mA loop current will show as 40 mV on
the DVM, and 20 mA will show as 200 mV.
Step 3:
Zeroing the detector in clean air
Before commencing zeroing the detector, ensure the instrument is in
clean air.
NOTE: Oxygen sensors do not need manual zeroing with the TXgard-
IS+. See section 4.2 for calibration instructions.
1 Enter the menu system by pressing the button.
2 At the password prompt enter the password, by default this is the
down button dfive times.
3 You should now be in the main menu.
Refer to menu structure,
(Figure 10 on page 13)
TXgard-IS+
To gas display
Inhibit mode
>
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Commissioning TXgard-IS+
16
4 Move the cursor down and select the Zero/Cal gas menu item. The
submenu list for zeroing and calibrating the gas appears.
5 Select the Zero gas menu item. The instrument will display a
scrolling text message: ‘Ensure the instrument is in clean
air and the sensor has settled’.
6 Press the button to start zeroing the detector.
The instrument will display the following message
When complete the instrument will report a scrolling text message
‘Zero operation successful’.
7 Press the button to continue, the display will return to the
Zero/cal submenu
8 You may now proceed to calibrate the gas on the detector.
Step 4:
Calibrate gas on the detector
Before commencing calibrating gas on the detector ensure you have
sample gas. For Oxygen sensors go to section 4.2.
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