Crowcon TXgard-IS+ Manuale

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 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+

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.

TP1

TP2

–















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

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+

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

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

124 92

122

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+

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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