Crowcon TXgard-Plus 지침 - 페이지 2

{카테고리_이름} Crowcon TXgard-Plus에 대한 지침을 온라인으로 검색하거나 PDF를 다운로드하세요. Crowcon TXgard-Plus 5 페이지. Flameproof toxic and oxygen gas detector

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OUTPUT

4mA

40-200 mV

CONTACT

REVERSING

LINKS

GND

ISOLATE

LINK

ISOLATE

USED FOR

GND

OXYGEN TXGARD.

FOR TOXIC LINK

OXYGEN

SET TO OTHER

OTHER

CONTROL

EQUIPMENT

96HD

SENSOR

INTERNAL TERMINAL LAYOUT

= ALARM RELAY VERSION ONLY

Diagram 2: Terminal and amplifier layouts

2. DETECTOR CONFIGURATION

2.1 Standard configuration

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

Current source with

0 mA

2 mA

4-20 mA

24 mA

AL1 relay (if fitted)

• Alarm level 1, see Table 3

• Normally de-energised, energising on alarm

• Contact normally open (NO), closing on

alarm

AL2 relay (if fitted)

• Alarm level 2, see Table 3

• Normally de-energised, energising on alarm

• Contact normally open (NO), opening on

alarm

FAULT relay (if fitted)

• Normally energised, de-energising 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 configuration for TXgard-Plus.

REAR VIEW OF

AMPLIFIER

GAS

RANGE

ALARM

OUTPUT OPTIONS

TEST

INHIBIT

N Y

POINT

17 4 2

ALARM 1

ALARM 2

10-30V

4-20mA

= Fault

= Inhibit ie. Zero/Cal mode

= Normal operation

= Over-range clamp

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

Gas

Hydrogen sulphide

Carbon monoxide

Ammonia

Oxygen

Sulphur dioxide

* Alternative ranges and alarm set points must be specified when ordering

RELAY

CONTACTS

Table 3: Standard ranges and alarm set points.

ALARM2

Location of links are shown in Diagram 2.

ALARM1

2.2 4–20 mA options

FAULT

To change current source output to sink, set switch to 'SK' position.

ALARM

To change Inhibit from 2 mA to 4 mA, fit link to '4' position.

SET POTS

2.3 Relay options

To change AL1 or AL2 relay from NO to NC, fit link in the 'NC' position.

To change FAULT relay from NC to NO, fit link in the 'NO' position.

2.4 Inhibit options

To not inhibit 4-20 mA signal and relays, fit link to 'N' and link to '4'.

3. INSTALLATION

WARNING

TXgard-Plus is designed for use in Zone 1 and 2 hazardous areas and

is certified EEx d IIC T6 (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 BS6959:1988 – 'British Standard

Code of Practice for the Selection, Installation, Use and Maintenance of

Apparatus for the Detection and Measurement of Combustible Gases'. In the

USA refer to the National Electrical Code (NEC 1999). Similar international

codes of practice may be used where applicable. In addition certain regulatory

bodies publish specifications giving minimum gas detection requirements for

specific 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 e.g. ammonia, 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 e.g. sulphur dioxide, detectors should be

mounted at low level.

• When locating detectors consider the possible damage caused by natural

events eg. rain or flooding. For detectors mounted outdoors Crowcon

recommend using 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.

• Consider the process conditions. Ammonia is normally lighter than air, but

if released from a process line which is cooled and/or under pressure the

gas may fall rather than rise.

Range*

AL1*

0–25 ppm

10 ppm

0–250 ppm

30 ppm

0–50 ppm

10 ppm

0–25% vv

19% vv

0–10 ppm

2 ppm

AL2*

20 ppm

100 ppm

25 ppm

17% vv

5 ppm