GDS 2000 User manual

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GDS TECHNOLOGIES LTD |FUSION POINT |ASH LANE |GARFORTH |LEEDS |LS25 2GA |UK www.gds-technologies.co.uk
This document is not contractual and the equipment specification may be modified at any time without prior notice.
GDS2000
MODULAR GAS ALARM
OPERAT NG HANDBOOK
C927
Manual No. PCN002-13
Issue C.v.2

2
CONTENTS
Description ...................................................................................................................1-3
Technical Specification.................................................................................................... 6
nstallation....................................................................................................................7-8
Commissioning.............................................................................................................8-9
Service - Routine Attention.........................................................................................10-11
Table of Lower Explosive Limits ...................................................................................... 13
ILL STRATIONS
Fig
1 Alarm and Facilities Card front panel.................................................................. 14
2 Circuit Board controls layout............................................................................... 15
3 Alarm and Facilities Card terminal connections ................................................... 16
4 Sensor Connections............................................................................................ 17
COPYRIGHT
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form
or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of GDS
Technologies Ltd.
This document is not contractual and the specification may be modified at any time without prior notice.

DESCRIPTION
The GDS 2000 is a modular system designed to operate in conjunction with gas and fire sensors.
Each card and connected sensor may be used as a gas/fire monitor with its own alarm outputs or
coupled together with other units to form a multi-channel system of any required size, having
separate and common alarm outputs.
The design allows for continuous operation in situations of extreme environmental conditions such
as heavy industry, petro-chemical installations and off-shore oil and gas platforms.
COMBUSTIBLE GAS CARD
When connected to a suitable power supply and sensor this unit becomes a single channel monitor
being fully equipped with:-
aMeter - to indicate concentration of gas
bPower ON indicator
cAlarm 1 and alarm 2 indicators (Low and High) - latched or unlatched option.
dFault indicator
eOverrange indicator (Alarm 3 indicator)
fAlarm sounder
gAlarm relays or Alarm signals
hAnalogue output signal 4-20mA - optional 1-5v
iAlarm Accept and Reset switch
jnhibit switch to disable Alarm relays
kAdjustments - see Fig 1
TOXIC GAS/FIRE CARD
Similar to the Combustible Gas Card but having the input circuit configured to function with an
input of 4-20mA from a sensor device. dentified by a ‘T’ after the serial number, and a black plug
restriction access to the calibration potentiometer located on the front panel (Gas Card).
3

COMMON FACILITIES CARD (OPTIONAL)
s used in multi-channel systems to provide alarm outputs which are common to all cards within
the same enclosure, and may be inserted into any slot within the enclosure.
The facilities card collects alarm information from all the connected cards and provides common
alarm functions as follows:
aLow alarm indicator
bLow alarm relay
cHigh alarm indicator
dHigh alarm relay
eOverrange alarm indicators
fOverrange alarm relay
gFault alarm indicators
hFault alarm relay
iCommon alarm sounder
jCommon accept/reset switch (Gas Modules Only)
kPower ON indicator
lModule removed sounder alarm
TERMINAL MOTHER BOARD
Houses the field terminals for the connection of external equipment i.e. sensor, shut-off valves,
mimic panels etc. Also in multi-channel systems is used to connect the various alarm and facilities
cards together.
INSTRUMENT ENCLOSURE
A standard 19“ wide rack houses up to 14 cards, various types of enclosure being available to suit
the users requirements, from single to multiples of 14.
ALARM INDICATORS
Red long-life L.E.D.’s flashing - steady when accepted.
Two levels Low and High adjustable between 10% and 85% F.S. (upper limited may be restricted to
60% F.S.) (Gas Alarm Modules)
FAULT ALARM INDICATORS
Amber long-life L.E.D.
nitiated in the event of a sensor cable fault (short or open circuit).
Constant sounder.
Sounder and indicator latched until fault cleared.
4

OVERRANGE INDICATOR
Red long-life L.E.D.
nitiated when the gas concentration exceeds the trip point. Adjustable between 10% and 100% F.S.
preset to 100% F.S. (Gas Alarm Modules).
Constant sounder.
Overrange indicator may be used to provide a third alarm trip.
ALARM RESET
Alarm circuits when latched may only be reset when the hazard has cleared.
ALARM INHIBIT DELAY
From the application of power a period of 20 seconds applies during which alarm relays and
indicators are held in the normal operating condition (inhibited). This period is indicated by the
Power ON indicator flashing green and red.
ALARM RELAY INHIBIT
Push switch.
Used to inhibit alarm relays during maintenance period.
ndication - Power ON indicator (normally green) changes to red.
PO ER ON INDICATOR
Green long-life L.E.D.
ANALOGUE INPUT
4-20mA
ANALOGUE OUTPUT
4-20mA into 250 ohms max. load.
Optional 1-5V output
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TECHNICAL SPECIFICATION
POWER REQ IREMENTS
DC 24v (nominal) operating range 21 to 32v.
AC 110, 230± 6% 50 Hz.
POWER CONS MPTION
2.5w per module (normal operating condition).
5W per module (full alarm condition).
SENSOR C RRENT
150 to 550mA adjustable constant current drive (no field adjustment required).
SENSOR CABLE
Catalytic - 3 core 1.5mm - screened, M. .C.C., S.W.A – maximum cable loop resistance 20 ohms
Toxic/Oxygen (4~20mA) - 3 core 0.5mm screened, M. .C.C., S.W.A – maximum cable loop
resistance 200 ohms
TERMINALS
Screw type accepting up to 2.5mm cable.
RELAY OUTPUTS
ALARM CARD
Alarm - Low S.P.C.O. N/D
Alarm - High S.P.C.O. N/D
Fault Alarm S.P.C.O. N/E
FACILITIES CARD
Common Alarm - LowS.P.C.O. N/D
Common Alarm - High S.P.C.O. N/D
Fault Alarm S.P.C.O. N/E
Overrange Alarm S.P.C.O. N/D
All contacts rated at 5A/230v AC.
ENVIRONMENTAL
Ambient Operation
Temperature 0-50 degrees centigrade
Storage temperature -20 degrees to + 60 degrees centigrade
Humidity range 0-90% RH
DIMENSIONS
Alarm and Facilities Module - 3U high - 6E wide - 160mm deep.
6

INSTALLATION
The GDS 2000 Series control instrumentation is designed for installation in a safe area only. Siting
of the instrument should be chosen with regard to the following points:
(a) away from sources of local heat and with room for adequate ventilation.
(b) within easy reach and audible distance of operating personnel.
(c) convenient to a separately fused power supply.
(d) incoming sensor cables and outgoing alarm annunciation.
(e) sensor cables to be electrically shielded i.e. M. .C.C., steel wire armoured,
screened cable.
To prevent any effect from earth currents the cable shielding should be grounded at one end only.
The instrumentation should be subjected to a minimum of vibration and shock.
Ascertain the voltage rating of the power supply to which the instrument will be connected.
SITING THE SENSING HEADS -
Gas Sensors
A key feature of the installation is the correct siting of the sensing head. Several considerations
must be taken into account, the most important being the density of the gas.
Density (air = 1)
Acetone ......................................2.0 n-Hexane...............................................3.0
Ammonia....................................0.6 Hydrogen...............................................0.1
Benzene......................................2.8 Methane ................................................0.6
n-Butane.....................................2.0 n-Octane...............................................3.9
Carbon monoxide.......................1.0 n-Pentane ..............................................2.5
Ethane........................................1.0 n-Propane..............................................1.6
Ethyl alcohol ...............................1.6 Town gas .........................................0.4-0.7
n-Heptane ..................................3.5 Xylene....................................................3.7
Under still air conditions, a ‘lighter than air’ gas such as methane leaking from a small orifice at
ground level, will rise in a plume the shape of which approximates an inverted cone. As the gas
rises, it draws air from the surroundings and creates a turbulence. Resulting from this there occurs
rapid dilution and, unless a sensor is positioned within the plume, there will be no initial indication
of a leak.
As gas continues to escape, the diluted concentration rises to ceiling level and begins to layer. n
time the concentration at ceiling level will increase and this, in turn, will displace air downwards.
Dangerous levels will, therefore, tend to occur at ceiling level and the thickness of this layer will
increase with the passage of time.
Ventilation of the room will of course alter the situation significantly, but it should be remembered
that if the ventilator is not at ceiling level, a dangerous concentration can still occur between the
top of the ventilator and the ceiling.
For heavier than air gases such as propane or butane, the formation of dangerous layers occurs at
ground level. These gases tend to behave like water and will run down gradients and pool at the
lowest point.
The number of heads required in individual rooms is determined by the number of possible
hazards in the vicinity.
Gas leakage may occur around valves, flanges and anywhere where gas pipes are jointed. t may
be possible to cover several probable gas leaks in one room by the careful siting of a single head.
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Cable ducts, trenches and manholes are also likely places where a build up of heavy gases may
collect.
When siting a head in such places it is most important to ensure that there is no likelihood of
flooding by water, or excessive dust which may block the sintered disc and prevent gas reaching
the sensor.
When monitoring gases outside, those lighter than air will be quickly dispersed, but gases heavier
than air will tend to form in layers and again cause a dangerous hazard. When siting heads
outside prevailing winds must be taken into consideration and adequate protection given against
wind and rain.
POISONING OF CATALYTIC SENSORS
Catalytic elements used in flammable gas sensors are liable to be rendered inactive due to
‘poisoning’ by certain groups of compounds.
n general contact with any gaseous compound capable of producing an involatile residue upon
heating is to be avoided.
Examples of such substances are:
a. Silicon containing vapours, as emitted by silicone polishes, greases and oils.
b. Petroleum vapours containing tetra-ethyl lead or other organo-metallic compounds.
c. Phosphorus in the form of phosphate esters.
These compounds will permanently affect the detector and if their presence is suspected the
response of the detector should be determined by the calibration procedure.
t is also possible that the reaction of the detector to a flammable gas could be inhibited by
halogen containing gases such as chloroform, carbon tetra chloride and trichloro-ethylene. this
effect is not permanent.
FIRE SENSORS
See separate supplier manual
COMMISSIONING
Gas Sensors
Before applying power to the instrument ensure that all detector heads are connected to the sensor
terminals on the printed circuit board (fig3 & 4) and that each detector head is connected to its
appropriate channel, identified by a small circular, coloured label:
Red = flammable
Yellow = toxic
Blue = oxygen
Green = others
Switch on power to the instrument.
Allow ten minutes for the detector head to stabilize.
8

CALIBRATION
Establish calibration figures with respect to the L.E.L. limit or the T.L.V. limit of the calibration gas
being used.
The following calibration gases are recommended:
Flammable gases - 2.5% methane in air
Toxic gases - T.L.V.
When using this gas ensure adequate ventilation.
f necessary zero each detector channel in clean air (for ambient oxygen monitoring the meter
reading should be adjusted to read 20.8%).
Apply calibration gas to the appropriate head at a flow rate of approximately 1 litre per minute.
When the METER reads a steady value adjust the Calibration Potentiometer to obtain the correct
reading for the calibration gas being used.
Shut off the calibration gas.
CALIBRATION WHEN SING CV TRANSMITTER (4-20mA DEVICE)
Where a sensor CV transmitter has been supplied the setting up procedure as described on page
15 should be followed.
ALARM LEVEL ADJUSTMENT
The alarm level is factory set at the level stated on the instrument test certificate.
To adjust the gas alarm level.
Adjust the Zero Alarm Potentiometer so that the meter indicates the desired alarm level.
Adjust the Alarm Potentiometer until the alarm is initiated. (The Sounder will sound and the
Alarm Lamp will illuminate)
Accept the alarm by pressing the Reset Switch.
Adjust the Zero Potentiometer so that the Meter reads Zero. Reset alarm by pressing the Reset
Switch.
OVERRANGE LEVEL ADJUSTMENT
As for alarm level adjustment procedure.
SENSOR SUPPLY ADJUSTMENTS (CATALYTIC SENSOR)
For ease of setting, measurements are taken across a 1 ohm resistor (located on the alarm card)
which is connected in series with the supply to the detector head. Current required by each type of
sensor is (VQ21-300mA/VQ23DCP-335mA) therefore measuring mV across the 1ohm resistor at
test points TP (see page 12) will provide a mV reading proportional to mA’s supplied. Adjustment
may be carried out using potentiometer 13 (sensor supply adjustment).
Alternatively the sensor voltage may be set at the detector head across terminal P and W (VQ21-
2v/VQ23DCP-2.5v).
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FIRE SENSORS
Before applying power to the instrument, ensure that all detector heads are terminated according
to Fig 4 page 14 (2 wire loop powered) and at the alarm panel in accordance with connecting
detail Fig 3 Page 14.
Switch on power to the instrument. Allow ten minutes for the detector head to stabilize.
For further instruction see fire sensor supplier manual.
STANDBY BATTERY MODULE
Before connecting the system to the supply voltage ensure that the batteries are connected.
The module is designed to supply power to the instrument rack and float charge the 24v DC lead
acid standby batteries.
The no load DC output voltage from the card is set at 27.5v DC, should it be necessary to adjust
this then, having first disconnected the battery, potentiometer No VR1 should be adjusted.
The module has four L.E.D. indicators on the front panel as follows:
1. Mains ON/OFF - Green: When mains on
- Orange: When mains fail
2. Battery high voltage - Red: Output voltage exceeds the set
limit
3. Battery low voltage - Red: During battery discharge voltage
has dropped below 19v.
4. Charge fail - Amber: Mains fail, output voltage high or
charging circuit failure.
NOTE: When the batteries are initially connected to the charger the low battery indicator may
lluminate due to the low charge state of the battery.
SERVICE - ROUTINE ATTENTION
The owner or occupier of the premises should place the supervision of the system in the charge of
a responsible executive whose duty it should be to ensure the day to day operation of the system
and to lay down the procedure for dealing with a gas alarm or fault warning. To ensure reliability
an agreement should be negotiated for regular servicing. When a service contract cannot be
arranged and employee with suitable experience of electrical equipment should be trained to deal
with the more simple servicing and instructed not to attempt to exceed the scope of such training.
Liaison should be established with those responsible for maintenance of the building fabric or
redecoration etc. to ensure that their work does not cause a fault or otherwise interfere with the
operation of the gas alarm installation. Particular attention appertaining to the Detector Head.
The operating instructions should be kept available preferably with the control unit, all faults,
service tests and routine attention given should be recorded.
DA LY: A check should be made that any fault condition which may be indicated is in fact being
attended to and that all other indicators are normal.
WEEKLY: n plants involving a high risk process or having gases which may cause loss of sensitivity
a check on calibration should be carried out.
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