Crowcon TXgard-Plus Installation, Operation And Maintenance Manual

Installation, Operation and Maintenance Instructions

M07194

Issue 6
April 2018

TXgard-Plus

Flameproof Toxic and Oxygen Gas Detector

TXgard-Plus Introduction

1

1 Introduction

1.1 Product overview

TXgard-Plus is a ameproof toxic and oxygen gas detector suitable for
use in zone 1 or 2 hazardous areas. It is designed to detect toxic gases
and oxygen using a range of electrochemical sensors. A local display and
magnetically operated switches allow non-intrusive one-man calibration
without a hot work permit. Powered by 24 V dc (nominally) TXgard­Plus provides a 4-20 mA signal (sink or source) proportional to the gas
concentration and can also be tted with optional alarm and fault relays.
For a list of gases that can be detected, please contact Crowcon.

1.2 Product description

TXgard-Plus comprises four parts; 96HD sensor housing, junction box,
amplier and terminal board. Diagram 1 details Txgard-Plus. The overall
assembly is certied Ex db IIC T6 Gb in Europe and Class 1, Zones 1&2
AEx d IIC T6 in the USA.

The 96HD sensor housing is a modular stainless steel assembly that
dismantles to allow plug in sensors to be replaced easily (see Diagram

4). The assembly screws into an M20 entry on the junction box.

The junction box is manufactured from marine grade alloy and is
supplied with 2 x M20 (1/2” NPT for USA) cable entries for customer
use. Alternative cable entries are available from Crowcon.

The amplier plugs into the terminal board, and is held in place by
two captive screws. The amplier provides power to the sensor, local
display and controls, and a 4-20 mA signal proportional to the gas
concentration for connection to a control panel. To remove, turn screws
anti-clockwise and use them to pull amplier out of the enclosure.

All electrical connections are made via the terminal board mounted in
the base of the junction box (see Diagram 2). Optional alarm relays (AL1
& AL2) and one fault relay (FAULT) are mounted on the terminal board
which may be used to drive local warning devices or connect TXgard­Plus to a control panel.

Introduction TXgard-Plus

2

1.3 Status Indication

TXgard-Plus includes a local display and status LED, visible through
the junction box window, see Diagram 1. The display shows the gas
concentration and current mode of operation ie. NORMAL, ZERO or
CAL. The LED shows the current alarm state of the detector. This is
summarised in Table 1.

Operational
state

LED
indication

Relay states* Comment*

Normal
operation

Steady green AL1 - O

AL2 - O
FAULT - On

Gas level < AL1
Current output = 4-20 mA

Normal
operation
(ALARM 1)

Steady red AL1 - On

AL2 - O
FAULT - On

Gas level > AL1 < AL2
Current output = 4-20 mA

Normal
operation
(ALARM 2)

Flashing red AL1 - On

AL2 - On
FAULT - On

Gas level > AL2
Current output = 4-20 mA

Over-range Flashing red AL1 - On

AL2 - On
FAULT - On

Gas level > full scale
Display backlight ashes
Current output = 24 mA

Zero/
calibration
mode

Flashing
green

Conguration
dependent
(see section 2)

Latched until reset via 'MENU'
Current output = 2 mA
4 mA option)

Detector fault Steady

amber

AL1 - O
AL2 - O
FAULT - O

Current output = 0 mA

*See section 2 for AL1 and AL2 standard settings

= Relay version only

Table 1: LED status indicator summary.

TXgard-Plus Introduction

3

Diagram 1: TXgard Plus general arrangement

Introduction TXgard-Plus

4

Diagram 2: Terminal and amplier layouts

TXgard-Plus Detector configuration

5

2. Detector conguration

2.1 Standard conguration

As standard, TXgard-Plus is factory set as follows:

Current source with 0 mA = Fault

2 mA = Inhibit ie. Zero/Cal mode

4-20 mA = Normal operation

24 mA = Over-range clamp

AL1 relay Alarm level 1, see Table 3

Normally de-energised, energising on alarm

Contact normally open (NO), closing on alarm

AL2 relay Alarm level 2, see Table 3

Normally de-energised, energising on alarm

Contact normally open (NO), closing on alarm

FAULT relay Normally energised, de-energised on fault

Contact normally closed (NC), opening on
fault

Alarm/fault relays automatically reset when alarm or fault has cleared.

INHIBIT Normally selected, ie. when CAL/ZERO

selected current output is forced to 2mA and
relays are held in normal/no alarm state.

Table 2: Standard conguration for TXgard-Plus.

Detector configuration TXgard-Plus

6

Table 3 details standard alarm points for the available gases and ranges.

Gas Range* AL1* AL2*

Hydrogen sulphide 0-25 ppm 5 ppm 10 ppm

Carbon monoxide 0-250 ppm 30 ppm 200 ppm

Oxygen 0-25% vv 19% vv 17% vv

*Alternative ranges and alarm set points must be specied when ordering

Table 3: Standard ranges and alarm set points.

Location of links are shown in Diagram 2.

2.2 4-20mA options

To change current source output to sink, set switch to ‘SK’ position. To
change Inhibit from 2 mA to 4 mA, t link to ‘4’ position.

2.3 Relay options

To change AL1 or AL2 relay from NO to NC, t link in the ‘NC’ position.
To change FAULT relay from NC to NO, t link in the “NO” position.

2.4 Inhibit options

To not inhibit 4-20 mA signal and relays, t link to ‘N’ and link to ‘4’.

TXgard-Plus Installation

7

3. Installation

WARNING

TXgard-Plus is designed for use in Zone 1 and 2 hazardous areas
and is certified Ex db IIC T6 Gb (AEx d IIC T6 in USA). Installation
must be in accordance with the recognised standards of the
appropriate authority in the country concerned. For more
information contact Crowcon. Prior to carrying out any work
ensure local regulations and site procedures are followed.

3.1 Location

There are no rules which dictate the siting and location of detectors,
however, considerable guidance is available from BS EN 60079-29­2:2015 ‘Explosive atmospheres. Gas detectors. Selection, installation,
use and maintenance of detectors for ammable gases and oxygen’.
In the USA refer to the National Electrical Code. Similar international
codes of practice may be used where applicable. In addition certain
regulatory bodies publish specications giving minimum gas detection
requirements for specic applications.

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 which are lighter than air, detectors should be
mounted at high level and Crowcon recommend the use of a
collector cone (Part No. C01051).

• To detect heavier than air gases (eg hydrogen sulphide), detectors
should be mounted at low level.

• When locating detectors consider the possible damage caused by
natural events e.g. rain or ooding. For detectors mounted outdoors
Crowcon recommend the use of a Weatherproof Cap (Part No.
C01442).

• 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.

Installation TXgard-Plus

8

• Consider the process conditions (ie whether gas within a process is at
high temperature or high pressure)

Detector placement should be determined following advice of experts
having specialist knowledge of gas dispersion, the plant processing
equipment as well as safety and engineering issues. The agreement
reached on the locations of sensors should be recorded.

3.2 Mounting

The mounting detail of TXgard-Plus is given in Diagram 1. TXgard­Plus should be installed at the designated location with the detector
pointing down. This ensures that dust or water will not collect on the
sinter and stop gas entering the detector.

3.3 Cabling requirement

Cabling to TXgard-Plus must be in accordance with the recognised
standards of the appropriate authority in the country concerned and
meet the electrical requirements of the detector. Crowcon recommend
the use of steel wire armoured (SWA) cable and suitable explosion
proof glands must be used. Alternative cabling techniques, such as steel
conduit, may be acceptable provided appropriate standards are met.

TXgard-Plus requires a dc supply of 12-30 V at up to 100 mA. Ensure
the minimum dc supply of 12 V is observed at the detector, taking into
account the voltage drop due to cable resistance.

For example, a nominal dc supply at the control panel of 24 V has
a guaranteed minimum supply of 20V. The maximum voltage drop
allowed is therefore 8V. TXgard-Plus can demand up to 100 mA and
so the maximum loop resistance allowed is 80 Ohms. A 1.0 mm2 cable
will typically allow cable runs up to 2000m. Table 4 shows maximum
cable distances given typical cable parameters.

TXgard-Plus Installation

9

CSA Resistance (Ohms per km) Max. distance

mm2 (awg) Cable Loop m (ft)

1.0 (17) 18.1 36.2 1000 (3280)

1.5 (15) 12.1 24.2 1500 (4920)

Table 4: Maximum cable distances for typical cables

Acceptable cross sectional area of cable is 0.5 to 1.5 mm2. Table 2
provides guidance only, actual cable parameters for each application
should be used to calculate maximum cable distances.

3.4 Electrical connections

All connections are made via the terminal board mounted in the base
of the junction box (see Diagram 2). The 3 wires from the 96HD are
colour coded and should be terminated in the corresponding colour
coded terminal (terminals 4, 5 & 6). Terminals 1 (0 Vdc), 2 (12-30 Vdc)
and 3 (4-20mA signal) are connected to the control equipment. TXgard
Plus is factory set as a 4-20 mA sink device unless specied otherwise
when ordering (see Section 2 to change conguration). Diagram 3
summarises the electrical connections.

Note: The junction box and cable armour must be earthed at the
detector or control panel to limit the eect of radio frequency
interference and to maintain electrical safety.

Note: The junction box for the TXgard Plus is manufactured from marine­grade alloy, and has a powder-coated nish. Care should be taken during
installation to protect the painted nish, as use in saline environments
could result in paint aking o from damaged junction boxes. This in no
way compromises the performance of the detector, as the marine-grade
alloy junction box is approved for use in oshore environments.

All unused cable entries shall be suitably tted with a suitably certied
blanking elements/stopping plugs. The blanking elements/stopping
plugs shall have a certication coding, temperature class, any service
temperatures (for non-metallic materials) and ingress protection suitable
for use with the equipment.

Installation TXgard-Plus

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All electrical connections to the optional relays are made via the 6-way
terminal block on the terminal board in the base of the junction box (see
Diagram 2). The relay contacts are rated 1 A @ 30 Vdc.

Diagram 3: Electrical connections to TXgard-Plus

TXgard-Plus Operation

11

4. Operation

WARNING

Prior to carrying out any work ensure local regulations and site
procedures are followed. Never attempt to open the detector
or junction box when flammable gas is present. Ensure that the
associated control panel is inhibited so as to prevent false alarms.

4.1 Commissioning Procedure

a Open the junction box of the detector by loosening the tamper proof

grub screw and removing the lid by rotating it anti-clockwise.

b Remove the amplier and check that all electrical connections have

been made and are correct as per Diagram 3.

c Replace the amplier and close the junction box ensuring that all

screws have been re-tted correctly.

d Apply power to the detector. The status LED will show a steady green

indicating normal operation.

e Leave the detector to stabilise for 1-2 hours.

Zeroing the detector (ZERO Mode):

f Place the end of ‘CRO-Mag’ over the ‘MENU’. Green Status LED will

ash. Decimal point above ‘ZERO’ will illuminate. Display backlight
will illuminate. Decimal point above ‘INHIBIT’ may ash if the option
has been internally selected.

g With no ammable gas present at the detector, place the end of the

‘CRO-Mag’ key over the ‘UP’ or ‘DOWN’ arrow pads to make the
display read zero.

Note: Oxygen detectors may be zeroed in fresh air.

Calibrating the detector (CAL Mode):

h Place the end of the ‘CRO-Mag’ over the MENU pad. The decimal

point above the word CAL will illuminate. Other indications remain
unchanged.

i Apply calibration gas to the detector at a ow rate of 0.5 litres/min.

(contact Crowcon for the supply of calibration gas.)

Operation TXgard-Plus

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j Allow the gas reading to stabilise.

k Place the end of the ‘CRO-Mag’ over the ‘UP’ or ‘DOWN’ arrow pads

to make the display read the correct concentration.

l If the control equipment display requires adjustment consult the

operating manual for the equipment.

Returning to normal operation (NORMAL Mode):

n Place the end of ‘CRO-Mag’ over the ‘MENU’ pad. All decimal points

will disappear and the backlight will turn o. The green status LED
will be on steadily (assuming no gas is present at the detector).

o The detector is now operational.

p Verify the control system to which the detector is connected reads

correctly and for detectors tted with the optional relay module;
check that any connected alarms or output functions operate
correctly when the detector is in alarm state.

Note: Always return the detector to NORMAL mode to avoid leaving
the detector in a permanently inhibited state.

4.2 Routine maintenance

The operational life of the sensors depends on the application,
frequency and amount of gas being seen. Under normal conditions
(6 monthly calibration with periodic exposure to CAL gas) the life
expectancy of the detectors are:

• Hydrogen sulphide 18 to 36 months

• Carbon monoxide 18 to 36 months

• Oxygen 24 months

Site practices will dictate the frequency with which detectors are tested.
Crowcon recommend detectors are gas tested at least every 6 months
and re-calibrated as necessary following the steps given in 4.1.

Detectors tted with the optional relay module should be periodically
tested to verify that any connected alarms or output functions operate
correctly when the detector is in alarm state.

TXgard-Plus Operation

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4.3 Sensor replacement/servicing of detectors

WARNING

This work should be carried out by Crowcon or an approved
service centre unless suitable training has been received.

TXgard-Plus uses the 96HD sensor housing which allows the user to
replace the sensors, gaskets and sinter if necessary. An exploded view
of the 96HD sensor housing is given in Diagram 4. The following
procedure may be followed when servicing a TXgard-Plus detector.

a Switch o and isolate power to the detector requiring attention.

b Open the detector Junction box by loosening the tamper proof grub

screw and removing the lid by rotating it anti-clockwise.

c Remove the amplier.

d Disconnect the 3 sensor wires from the terminal board (terminals 4, 5

& 6).

e Unscrew the complete 96HD sensor housing from the junction box.

Note: If a spare 96HD sensor housing complete with new sensor is
available ignore steps f to k and return the old 96HD to Crowcon or an
approved service centre for repair.

f Open the 96HD sensor housing by removing the four Allen head

screws from the Top Cap with a 3mm Allen key.

g Remove the sensor from the Top Cap PCB.

h Fit the replacement sensor checking the part number is correct. This

part number is labelled on the main body of the detector.

i Inspect the gaskets and replace if necessary.

j The sinter assembly will only need to be replaced if it has become

blocked by dust or oil. Such blockage causes the response time
of the detector to be slow and may aect sensitivity. To remove
the sinter a removal tool (Part # M01614) is required. Loctite No
243 must be used on the sinter assembly threads to maintain
certication.

Operation TXgard-Plus

14

Diagram 4: 96HD assembly

k Re-assemble the 96HD housing taking time to ensure that the 3 mm

Allen head screws are securely xed into position.

I Fit the 96HD sensor housing to the junction box ensuring that the

colour coded wires are terminated correctly.

m Replace amplier ensuring the captive screws are fastened securely.

n Switch on power.

TXgard-Plus Operation

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o Close the junction box remembering to fasten the tamper proof grub

screw into position.

p Follow the Commissioning Procedure given in 4.1.

4.4 Changing Alarm Levels (Relay Version Only)

WARNING

This work should be carried out by Crowcon or an approved
service centre unless suitable training has been received. Before
attempting to change alarm levels ensure the detector is in fresh
air and no flammable gas is present.

Alarm levels are factory set as detailed in Table 3. To change either
alarm level:

a Switch o and isolate power to the detector requiring attention.

b Open the junction box of the detector by loosening the tamper proof

grub screw and removing the lid by rotating it anti-clockwise.

c Remove the amplier from the terminal board.

d Ensure that the ‘INHIBIT’ link is set to ‘N’.

e Re-t the amplier to the terminal board ensuring that all screws

have been secured correctly.

f Apply power to the detector and allow the detector to stabilise.

g Place the end of “CRO-Mag’ over the “MENU’ pad. The decimal

point above the word ‘ZERO’ will illuminate, the status LED will ash
green and the display backlight will illuminate.

h With clean air present at the detector, place the end of the ‘CRO-

Mag’ key over the ‘UP’ or ‘DOWN’ arrow pads to make the display
read the desired alarm level.

i Using a long instrument screwdriver, turn the relevant ALARM SET

pot mounted on the terminal board (see Diagrams 1 & 2) to adjust
the alarm level. Tripping of the ALARM 1 level relay is conrmed by
the status LED turning a steady red. Tripping of the ALARM 2 level
relay is conrmed by the Status LED ashing red.

Operation TXgard-Plus

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j Once the alarm level has been set, place end of ‘CRO-Mag’ over the

‘UP’ or ‘DOWN’ arrow pads and reset the display to read zero.

k Place the end of the ‘CRO-Mag’ over the ‘MENU’ pad to return

the detector to normal operation, ie. No decimal points displayed,
backlight o and the Status LED indicating steady green.

l Check that the detector operates correctly by applying test gas as

necessary.

m Switch o and isolate power to the detector.

n Reset jumpers which may have been changed in step ‘d’ above.

o Replace the amplier and close the junction box, ensuring that all

screws have been re-tted correctly.

p Apply power to the detector and allow to stabilise before checking

correct operation.

q Re-calibrate if necessary as per section 4.1.

Notes:

Area Classifications:-

Zone 0: An area classied, as Zone 0 will have ignitable

concentrations of ammable gases, vapours or liquids
present continuously or for long periods of time under
normal operating conditions.

Zone 1: An area classied, as Zone 1 is likely to have ignitable

concentrations of ammable gases, vapours or liquids
present under normal operating conditions.

Zone 2: An area classied, as Zone 2 is not likely to have ignitable

concentrations of ammable gases, vapours or liquids
present under normal operating conditions.

TXgard-Plus Spare parts and accessories

17

5. Spare parts and accessories

Please refer to the Sensor Replacement Label mounted on the outside
of the 96HD housing for the correct replacement part number.

Description Part number

Complete 96HD sensor

housing with sensor

Sensor
only

Hydrogen sulphide (96HD/HS) S01750 E011035
Carbon monoxide (96HD/CO) S01751 E011050
Oxygen (96HD/OX) S01753 E01488/A

M20 to 1/2 inch NPT adaptor M02125

M20 to 3/4 inch NPT adaptor M02281

Gasket 1 M04452

Gasket 2 M04128

Sinter removal tool M01614

Collector Cone C01051

Weatherproof Cap C01442

Replacement ‘CRO-Mag’ C01697

Sinter assembly S01781

Amplier (Toxic version) S01866

Amplier (Oxygen version) S01867

Terminal board S01846

Relay board S01847

Loctite No. 243 Contact Crowcon

Calibration gas Contact Crowcon

Specifications TXgard-Plus

18

6. Specications

Dimensions 200 x 115 x 115 mm (8” x 41/2” x 41/2”)

Weight 2.2 kg (4.8 lbs)

Material 96HD sensor housing: 316 Stainless steel

Junction box: Marine grade alloy

Temperature range -10°C to +55°C (14°F to 131°F)

Humidity range 15-90% RH, non condensing

Ingress protection IP65

Explosion protection Flameproof

Approval codes ATEX: II 2 G Ex db IIC T6 Gb

UL: Class I Zones 1 & 2, AExd IIC T6
Tamb= -20°C to +55°C

Safety Cert No. Sira03ATEX1124

Standards EN60079-0:2012+A11:2013, EN60079-1:2014

UL2279

Zones Certied for use in Zone 1 or Zone 2

areas. (see area classications section)

Gas groups IIA, IIB, IIC

Operating voltage 12-30 Vdc

Operating current Relay version: 100 mA (maximum)

Non-relay version: 50 mA (maximum)

Detector output 4-20 mA source or sink selectable

0 mA = Fault
2 mA = Inhibit (4 mA option)
4-20 mA = Normal gas range
24 mA = Over range

Relays outputs 2 x Alarm relays SPNO (SPNC option)

1 x Fault relay SPNC (SPNO option)

Contact rating 1 A @ 30 Vdc

UK Office
Crowcon Detection Instruments Ltd
172 Brook Drive,
Milton Park,
Abingdon
Oxfordshire
OX14 4SD
Tel: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.crowcon.com

USA Office
Crowcon Detection Instruments Ltd
1455 Jamike Ave, Suite 100
Erlanger
KY 41018
Tel: [phone] or 1 800 527
6926
Fax: [phone]
Email: [e-mail]
Website: www.crowcon.com

Netherlands Office
Crowcon Detection Instruments Ltd
Vlambloem 129
3068JG, Rotterdam
Netherlands
Tel: + 31 10 421 1232
Fax: + 31 10 421 0542
Email: [e-mail]
Website: www.crowcon.com

Singapore Office
Crowcon Detection Instruments Ltd
Block 194, Pandan Loop
#06-20 Pantech Industrial Complex
Singapore 128383
Tel: + 65 6745 2936
Fax: [phone]
Email: [e-mail]
Website: www.crowcon.com

China Office
Crowcon Detection Instruments Ltd
(Beijing)
Unit 316, Area 1, Tower B, Chuangxin
Building
12 Hongda North Road, Beijing
Economic Technological Development
Area
Beijing, China 100176
Tel: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.crowcon.com

© 2018 Crowcon Detection Instruments Ltd.