Crowcon Flamgard-4/20 User manual

1. INTRODUCTION
2. INSTALLATION
1.1 Product overview
Flamgard 4/20 is a flameproof flammable gas detector suitable
for use in Zone 1 or 2 hazardous areas. It is designed to detect
flammable gas, present in ambient air, at concentrations not
exceeding the Lower Explosive Limit (LEL) of the target gas for
which it is calibrated. Flamgard 4/20 is powered by 24 V dc
(nominally) and provides a 4-20 mA signal (sink or source)
proportional to the gas concentration. For a list of flammable
gases which Flamgard 4/20 can detect, please contact Crowcon.
1.2 Product description
Flamgard 4/20 comprises three parts; a sensor housing, amplifier and
junction box.
Please note: 96HD sensor and amplifier unit (junction
box) have been certified seperately. 96HD: Sira02ATEX1283X and
Amplifier unit (junction box): Baseefa03ATEX0074.
The 96HD sensor housing is a modular stainless steel
assembly which dismantles to allow plug in pellistor sensors to be
replaced easily. The assembly is certified EEx d IIC T6 and screws into
the junction box.
The amplifier is mounted in the junction box. All electrical
connections to the detector are made via the terminal block on the
amplifier. The amplifier provides power to the pellistor sensor and
converts the gas reading into a 4-20 mA signal for connection to a control
panel.
The junction box is manufactured from galvanised cast iron and
is certified EEx d IIC T6. The junction box is supplied with 1 x M20 cable
entry for customer use. Alternative cable entries are available upon
request. Adaptors for NPTF entries are also available (see Section 4,
Spare Parts and Accessories).
Diagram 1 shows the Flamgard assembly with junction box
cover removed to show the amplifier and wiring details.
WARNING
Flamgard 4/20 is designed for use in Zone 1 and 2 hazardous
areas and is certified EEx d IIC T6. Installation must be in
accordance with the recognised standards of the appropriate
authority in the country concerned. For further information
please contact Crowcon. Prior to carrying out any installation
work ensure local regulations and site procedures are followed.
2.1 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’, 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
flammable gas detectors:
•To detect gases which are lighter than air e.g. methane, 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. butane, detectors should be
mounted at low level.
•When locating detectors consider the possible damage caused by
natural events e.g. rain or flooding. 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.
•Consider the process conditions. Butane is normally heavier than air,
but if released from a process line which is at an elevated
temperature and/or under pressure the gas may rise rather than fall.
The placement of sensors 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. Crowcon would be pleased to assist in the selection and siting
of gas detectors.
2.2 Mounting
The mounting detail of Flamgard 4/20 is given in Diagram 1. Install
Flamgard 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. A Swivel Mounting Bracket (Part No. C01340) is
available to assist in the mounting of the detector if required.
2.3 Cabling requirement
Cabling to Flamgard 4/20 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.
Flamgard 4/20 requires a dc supply of 10-30 V at up to 350 mA.
Ensure the minimum dc supply of 10 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 18V. The maximum voltage drop
allowed is therefore 8V. Flamgard 4/20 can demand up to 350 mA and so
the maximum loop resistance allowed is 22 Ohms. A 1.5 mm2 cable will
typically allow cable runs up to 900 m. Table 1 shows maximum cable
distances given typical cable parameters.
C.S.A. (mm2)Resistance (Ohms per km) Max. Distance (km)
Cable Loop
1.0 18.1 36.2 600
1.5 12.1 24.2 900
2.5 7.4 14.8 1400
Table 1: Maximum cable distances for typical cables
Acceptable cross sectional area of cable is 0.5 to 2.5 mm2. Table 1
provides guidance only, actual cable parameters for each application
should be used to calculate maximum cable distances.
2.4 Electrical connections
All connections are made via the 6 way terminal block mounted on the
amplifier in the junction box. The 3 wires from the 96HD are colour coded
and should be terminated in the corresponding colour coded terminal.
The remaining terminals marked ‘+’,’-’ and ‘Signal’ are connected to the
control equipment. Flamgard 4/20 is factory set as a 4-20 mA source
device unless specified otherwise when ordering. This is set via an
internal switch in the amplifier and may be changed to ‘sink’ on site if
necessary. 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 effect of radio frequency
interference, and to maintain electrical safety.
123
4 5 6
1. INTRODUCTION
2. INSTALLATION
Gas Detection You Can Trust
Gas Detection You Can Trust
instructions
Diagram 1: Flamgard 4/20 assembly Diagram 2: 96HD assembly
Part No C01457
Flamgard-4/20
(formerly EXD90/FL)
Flameproof
Flammable Gas
Detector
4/20
Installation, operating and
maintenance instructions, M07177
Issue 3 03/03
Crowcon Detection Instruments Ltd
2 Blacklands Way
Abingdon Business Park
Abingdon
Oxfordshire OX14 1DY, UK
Tel: [phone]
Fax: [phone]
email: [email protected]
internet: http://www.crowcon.com
1180

3. OPERATION2. INSTALLATION (continued)
NOTES
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.
3.1 Commissioning procedure
The following procedure should be followed carefully, and carried out
only by suitably trained personnel:
a. Open the junction box of the detector by removing the 4 M6 Allen
head screws.
b. Check that all electrical connections have been made and are
correct as per Diagram 3.
c. Apply power to the detector and ensure the minimum supply voltage
of 10 V dc is available at the detector across terminal ‘+’ and ‘-’.
d. Leave the detector to stabilise for 1 -2 hours.
e. Connect a digital volt meter (DVM) to the test points on the amplifier
in the junction box. Note : The test points read 40 mV = 4 mA = 0%
up to 200 mV = 20 mA = 100% LEL gas. There is a current clamp of
25 mA on the 4-20 mA output.
f. With no flammable gas present at the detector adjust the ‘ZERO’ pot
on the amplifier until the DVM reads 40 mV.
g. Apply calibration gas to the detector at a flow rate of 0.5 litres per
minute. Crowcon recommend 50% LEL gas for calibration purposes
(contact Crowcon for the supply of calibration gas).
h. Allow the gas reading to stabilise and adjust the ‘CAL’ pot until the
DVM reads the appropriate reading (120 mV = 50% LEL if used).
i. If the control equipment display requires adjustment consult the
operating manual for the equipment.
a. Switch off and isolate power to the detector requiring attention.
b. Open the junction box by unscrewing the 4 M6 Allen head screws.
c. Disconnect the 3 sensor wires from the terminal block of the
amplifier.
d. Unscrew the complete 96HD sensor housing from the junction box.
e. Open the 96HD sensor housing by removing the four Allen head
screws from the Top Cap with a 3mm Allen Key.
f. Remove the sensor from the Top Cap PCB. Flammable sensors have
an extra black sleeve which may be seperate from the sensor. This
is normal and the sleeve may be re-used.
g. Fit the replacement sensor checking the part number is correct. This
part number is labelled on the main body of the detector. Observe
pin alignment with PCB.
h. Inspect the gaskets and replace if necessary.
i. The sinter assembly will only need to be replaced if it has become
blocked by dust or oil. Such blockages cause the response time of
the detector to be slow and may affect sensitivity. To remove the
sinter a removal tool (Part No. M01614) is required. Loctite No 243
must be used on sinter assembly threads to maintain certification.
j. Re-assemble the 96HD housing taking time to ensure that the four
Allen head screws are securely fixed into position.
k. Fit the 96HD sensor housing to the junction box ensuring that the
colour coded wires are terminated correctly.
l. Remove the amplifier fixing screws and rear lid.
m. Connect a DVM to TP2 on the amplifier PCB.
n. Switch on power and adjust VR3 until DVM reads 0 mV.
o. Re-assemble the amplifier.
p. Follow the Commissioning Procedure given in 3.1 above.
If a spare 96HD sensor housing complete with new sensor is
available, ignore steps (e.) to (j.) and return the old 96HD to Crowcon or
an approved service centre for repair.
j. Close the junction box of the detector ensuring the 4 x M6 Allen head
screws are securely fastened.
k. The detector is now operational.
3.2 Routine maintenance
The operational life of the pellistor sensor depends on the application.
Crowcon expect that such a device will work satisfactorily for up to 5
years in ideal conditions. Site practices will dictate the frequency with
which detectors are tested. Crowcon recommends that detectors be gas
tested at least every 6 months and re-calibrated as necessary. To re-
calibrate a detector follow steps 3.1 (a.), (e.) to (k.) above.
Pellistors can suffer from loss of sensitivity when there is a
presence of poisons or inhibitors such as silicones, sulphides, chlorine,
lead or halogenated hydrocarbons. Crowcon use poison resistant
pellistors to maximise the operational life of Flamgard-4/20. In
applications where such compounds are present continuously we
recommend the use of CIRRUS or NIMBUS, Crowcon’s fixed point
infrared flammable gas detectors, which are immune to such poisons
and inhibitors. Please contact Crowcon for further details.
3.3 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.
Flamgard 4/20 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 2 for reference. The
following procedure may be followed when servicing the detector:
Area Classifications:-
Zone 0: An area classified, as Zone 0 will have ignitable
concentrations of flammable gases, vapours or
liquids present continuously or for long periods of
time under normal operating conditions.
Zone 1: An area classified, as Zone 1 is likely to have
ignitable concentrations of flammable gases,
vapours or liquids present under normal operating
conditions.
Zone 2: An area classified, as Zone 2 is not likely to have
ignitable concentrations of flammable gases,
vapours or liquids present under normal operating
conditions.
Dimensions 190 x 129 x 85 mm (7.3 x 5 x 3.4 inches)
Weight 4.0 kg (8.8 lbs)
Operating voltage 10-30 V dc
Current consumption 140 mA @ 10 V, 50mA @24V
Operating temperature -10-55OC
Humidity 0-99% RH, non condensing
Cable loop resistance 60 Ohm @ 22 V +ve terminal (power)
600 Ohm @ 22 V signal terminal (4-20 mA)
Degree of protection IP66 (when fitted with Weatherproof Cap)
Explosive protection Flameproof
Approval code II 2 G EEx d IIC T6
Safety certification no. Amplifier unit (Junction Box):
Baseefa03ATEX0074
96HD: Sira02ATEX1283X
Standards EN50014, EN50018
Zones Certified for use in Zone 1 or Zone 2 areas.
(see area classifications section)
Gas groups IIA, IIB, IIC
EMC EN50270
Detector output Source or sink selected by internal switch
Description Part Number
M20 to 1/2” NPTF adaptor M02125
M20 to 3/4” NPTF adaptor M02281
Ceiling mounting bracket M01401
Collector cone C01051
Spray deflector C01338
Swivel mounting bracket C01340
96HD sensor housing complete with sensor S01749*1
Replacement sensor S01673*1
Sinter removal tool M01 614
Loctite No. 243
Sinter assembly S01781
Gasket 1 M04452
Gasket 2 M04128
Calibration gas Contact Crowcon
*1 Flamgard 4/20 may be fitted with a range of pellistor sensors depending on the
specific application. The correct spare sensor part number is itemised on the
sensor housing label.
4. SPARE PARTS AND ACCESSORIES 5. SPECIFICATION
7 8 9 10
11 12
Diagram 3: Electrical connections