Crowcon TXgard-IS Plus Assembly instructions

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TXgard
MANUAL
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JUNHO 2013

TXgard-IS+
Intrinsically Safe
Toxic and Oxygen Gas Detectors
Loop Powered Electrochemical and Galvanic Sensor Types Only
Installation, operating and
maintenance instructions, M07214
Issue 7 January 2010

Contents
1 Introduction .................................................................................. 5
Product overview ........................................................................................ 5
Product description ..................................................................................... 5
2 Installation ................................................................................... 8
General ....................................................................................................... 8
Mounting ..................................................................................................... 9
Cabling requirement ................................................................................... 9
Electrical connections ............................................................................... 10
3 Operation ................................................................................... 13
The operator display panel and keypad ................................................... 13
Using the TXgard-IS+ menus ................................................................... 14
4 Commissioning .......................................................................... 16
Commissioning procedure:
Toxic gas detectors .................................................................................. 16
Commissioning procedure:
Oxygen detector ....................................................................................... 21
5 Maintenance .............................................................................. 24
Routine maintenance ................................................................................ 24
Sensor replacement and servicing of detectors ....................................... 24
6 Fault finding ............................................................................... 26
Appendices
Appendix A
Wiring the TXgard-IS+ to Crowcon control equipment ............ 31
Appendix B
TXgard-IS+ specification.......................................................... 35
Appendix C
Spare parts .............................................................................. 37
Appendix D
Menu system............................................................................ 38
Appendix E
4-20 mA Loops......................................................................... 46
Appendix F
Cabling requirement................................................................. 48
Appendix G
Sensor limitations..................................................................... 51
Warranty Statement................................................................. 51

Introduction TXgard-IS+
Issue 7 5
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
•configurable fault and inhibit currents
•configurable 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 1.1” on page 6.
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.
All electrical connections to the detector are made through the terminal
blocks on the baseboard J2 and J4 (see and in “Figure 1.1” on
page 5). The junction box of TXgard-IS+ has one top-entry M20 cable

TXgard-IS+ Introduction
6 Issue 7
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.
Figure 1.1: TXgard-IS+ fitted with toxic sensor
Important
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.
J4
TP1
+
TP2
–
J2







CONNECTION TO
CONTROL PANEL
40-200mV
TEST POINTS
RED
BLU
GRN
M20 CABLE ENTRY
BASE BOARD
PERSONALITY
MODULE
SENSOR
HOUSING
Some baseboards may have
J4 in this orientation

Introduction TXgard-IS+
Issue 7 7
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
GAS DETECTOR
TXgard-IS+

TXgard-IS+ Installation
8 Issue 7
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
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.

Installation TXgard-IS+
Issue 7 9
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.
Figure 2.1: TXgard-IS+ dimmensions
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.
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 2.1" on page 10, shows maximum cable distances
given typical cable parameters (See appendix F for more information).

TXgard-IS+ Installation
10 Issue 7
Table 2.1: Maximum cable distances for typical cables
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
1.1” on page 6. 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 2.2” below, 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".
Figure 2.2: Baseboard
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
Some baseboards
may have J4 in
this orientation

Installation TXgard-IS+
Issue 7 11
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 2.3, 2.4 and 2.5 summarise the electrical
connections.
SAFE AREA
Figure 2.3: Electrical connections for safe area
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 2.4: Electrical connections using Zener barrier

TXgard-IS+ Installation
12 Issue 7
Figure 2.5: Electrical connections using galvanic isolator

Operation TXgard-IS+
Issue 7 13
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 3.1”). 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 3.2"). Press the down 
button to display the voltage and temperature (“Figure 3.3” on page 14),
this display will automatically return to the main display after a few
moments.
Figure 3.1: Operator display panel and keypad
Figure 3.2: LCD ‘operator display panel’
TXgard-IS+
5 ppm
4.3mA
CO
OK
LCD
Liquid crystal display
DOWN key
ENTER key
UP key
TXgard-IS+
5 ppm
4.3mA
CO
OK
Gas being detected
eg. CO, H2S, O2
Flashing OK
indicates system is working
UNITS
%orppm
Loop current

TXgard-IS+ Operation
14 Issue 7
Figure 3.3: 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 (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 shown
in “Figure 3.4” on page 14, 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 and 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).
TXgard-IS+
Power: 21.5V
Temp: 25.0 C
Power V
Temperature

TXgard-IS+ Operation
15 Issue 7
Figure 3.4 Menu structure for TXgard-IS+ toxic detector
See Appendix D and Section 4.2 for further information.
MAIN MENU
To gas display
Inhibit mode
Ramp mA output
Configuration
S/W version
Serial number
Calibrate mA
Clear faults
Zero/cal gas
(cal O2 @ 20.9% gas)
Inhibit mode
Forces instrument to output Inhibit current
Clear faults Clears faults from display and unit
Calibration of zero gas and sensed gas
Zero / Cal gas
To main menu Zero gas Calibrate gas
Submenu
Calibration of 20.9% gas
Cal O2 @ 20.9% gas
To main menu Confirm O2 cal
Submenu Calibration of
4-20mA loop current To main menu Calibrate 4mA Calibrate 20mA
Calibrate mA Submenu
Ramp mA output
Manual ramp of mA output
Configuration
To main menu Limit 4-20mA Set inhibit mA Zero suppress Damping Menu timeout Fatal mA Non-fatal mA Display option Pwr-on inhibit Help screen LCD Contrast
Submenu
Display shows two lines of the menu list at a time, use DOWN key to display other menu items
Serial number Displays serial number
S/W version Displays software version
Toxic detectors
Oxygen detectors
To enter Main Menu press ENTER
key then DOWN key 5 times
NORMAL DISPLAY
To gas display Inhibit mode
TXgard-IS+
0 ppm 4.0mA
CO
OK
-

TXgard-IS+ Commissioning
16 Issue 7
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 3.4). 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 1.1” on page 6.
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.
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
Tip
As long as the instrument is running, you can see the supply
voltage on the display panel, by pushing the button.

Commissioning TXgard-IS+
Issue 7 17
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 1.1” on page 6 or
“Figure 2.2” on page 9). 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 5times.
3 You should now be in the main menu. Refer to menu
structure, (“Figure 3.4” on page 15).
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’.
TXgard-IS+
To gas display
Inhibit mode
>

TXgard-IS+ Commissioning
18 Issue 7
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.
NOTE: Whilst in calibrate mode, the instrument outputs the
Inhibit current.
If you have just completed step 3 (Zeroing) you will still be in
the Zero/Cal Gas submenu, and can skip to 5.
1 Enter the menu system by pressing the button.
2 At the password prompt enter the password, by default this
is the down button 5times.
TXgard-IS+
Zeroing Sensor..
TXgard-IS+
To main menu
Zero gas
>

Commissioning TXgard-IS+
Issue 7 19
3 You should now be in the main menu
4 Select the Zero/Cal gas menu. The submenu list for
zeroing and calibrating the gas appears.
5 Move the cursor down and select the Calibrate gas
menu item
The panel will display a scrolling text message: ‘Apply
calibration gas to instrument ––’.
6 Apply calibration gas (typically half or full scale) to the
detector at a flow rate of 0.5 litre/minute. (Crowcon Flow
Adaptor part No. C03005)
7 Select the button.
Allow gas reading to stabilise.
Tip
Sticky gases which are rapidly absorbed by connecting pipes
(chlorine, nitrogen dioxide and ozone) are applied at 1 litre /
minute.
TXgard-IS+
To gas display
Inhibit mode
>
TXgard-IS+
150 PPM
13.6mA
CO
OK
GAS
0.5 Litre/min
To clean air
or exhaust
pipe
Crowcon
Flow Adaptor

TXgard-IS+ Commissioning
20 Issue 7
Use and buttons to adjust gas reading to calibration
gas value.
Gas value is usually measured in ppm or as %vol (ppb and
%LEL are also available, as appropriate).
8 Select the button to set the calibration value.
The instrument will display the following message:
When complete the instrument will report a scrolling text
message: ‘Calibration successful! Remove gas
from the instrument ––’.
9 Remove the gas from the detector and exit the menu
system.
The instrument is now calibrated.
If the control equipment display requires adjustment, consult the operating
manual for the control display equipment.
Tip
See "Table 4.1" on page 21 for some gases and their typical
range. Please note that detectors can be provided in different
ranges if required.
Contact Crowcon for list of all gases detected.
TXgard-IS+
Calibrating..

Commissioning TXgard-IS+
Issue 7 21
Table 4.1: Typical gas ranges
4.2 Commissioning procedure:
Oxygen detector
Step 1:
Connecting the detector to the control panel
1 Apply power to the detector via 2-way connector J4.
“Figure 1.1” on page 6
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.
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. Alternately
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.
Gas Code Gas Unit Standard Ranges†
O2 Oxygen %vol 0-25
CO Carbon monoxide ppm 0-250
H2S Hydrogen sulphide ppm 0-25
SO2 Sulphur dioxide ppm 0-10 and 0-100
CL2 Chlorine ppm 0-5
†Note: other ranges are available on request
Tip
As long as the instrument is running, you can see the supply
voltage on the LCD, by pushing the button.