PT2E-1935

2-Wire Gas Detector HeadGD-K88Ai
Operating Manual(PT2-193)

<Contents>
1. Outline of the Product ..............................................................................................................3
1-1. Preface ....................................................................................................................................3
1-2. Purpose of use ........................................................................................................................3
1-3. Definition of DANGER, WARNING, CAUTION, and NOTE ....................................................4
2. Important Notices on Safety ....................................................................................................5
2-1. Danger cases ..........................................................................................................................5
2-2. Warning cases ........................................................................................................................6
2-3. Precautions .............................................................................................................................7
2-4. Operating precautions .............................................................................................................7
2-5. Important information about explosion-proof ..........................................................................8
3. Product Components .............................................................................................................10
3-1. Main unit and standard accessories .....................................................................................10
3-2. Names and functions for each part ....................................................................................... 11
4. How to Use ............................................................................................................................124-1. Before using the detector ......................................................................................................124-2. Precautions for installation sites ...........................................................................................13
4-3. Precautions for system designing .........................................................................................14
4-4. How to install .........................................................................................................................15
4-5. Grounding .............................................................................................................................16
4-6. How to wire ...........................................................................................................................17
4-7. Compatible cables and terminal plate specifications ............................................................17
4-8. System connection example .................................................................................................18
5. How to Operate......................................................................................................................20
5-1. Preparation for start-up .........................................................................................................20
5-2. Basic operating procedures ..................................................................................................20
5-3. How to start the detector (power-on) ....................................................................................21
5-4. Modes ...................................................................................................................................225-5. Description of operation (detection mode) ............................................................................23
5-6. Description of operation (maintenance) ................................................................................26
5-7. How to exit ............................................................................................................................29
6. Maintenance ..........................................................................................................................30
6-1. Maintenance intervals and items ..........................................................................................30
6-2. Replacement parts ................................................................................................................34
7. Storage, Relocation and Disposal .........................................................................................36
7-1. Procedures to store the detector or leave it for a long time ..................................................36
7-2. Procedures to relocate the detector or use it again ..............................................................36
7-3. Disposal of products .............................................................................................................36
8. Troubleshooting .....................................................................................................................37
9. Product Specifications ...........................................................................................................39
9-1. List of specifications ..............................................................................................................39
9-2. Detection principle ................................................................................................................40
10. Definition of Terms ...............................................................................................................40-2-

1 Outline of the Product1-1. Preface

1

Outline of the Product1-1. Preface
Thank you for choosing our 2-wire gas detector head GD-K88Ai.
Please check that the model number of the product you purchased is included in the specifications on thismanual.
This manual explains how to use the detector and its specifications. It contains information required forusing the detector properly. Not only the first-time users but also the users who have already used the
product must read and understand the operating manual to enhance the knowledge and experience before
using the detector.
When the detector is used in combination with an indicator/alarm unit, read also the operating manual of
the indicator/alarm unit.

1-2. Purpose of useThis detector is a fixed type gas detector head which detects combustible and toxic gases.
When the detector detects gas leakage, it outputs a current according to the gas concentration.
The indicator/alarm unit indicates the gas concentration and triggers an alarm if a preset concentrationlevel is exceeded.
The detector is a safety unit, not an analyzer or densitometer which performs quantitative/qualitative
analysis/measurement for gases. Please fully understand the features of the detector before using it,so that it can be used properly.

-3-1 Outline of the Product1-3. Definition of DANGER, WARNING, CAUTION, and NOTE

1-3. Definition of DANGER, WARNING, CAUTION, andNOTE
DANGER

This message indicates that improper handling may cause serious damage on
life, health or assets.

WARNING

This message indicates that improper handling may cause serious damage on
health or assets.

CAUTION

This message indicates that improper handling may cause minor damage on
health or assets.

NOTE

This message indicates advice on handling.

-4-2 Important Notices on Safety

2-1. Danger cases

2

Important Notices on
Safety2-1. Danger cases
DANGER
This detector is the intrinsically safe explosion-proof product with Zener Barrier. However, neverattempt to detect a gas over the lower explosive limit.

-5-2 Important Notices on Safety

2-2. Warning cases

2-2. Warning cases
WARNINGPower supply
Before turning on the detector, always check that the voltage is properly applied.

Need of grounding circuit
Do not cut the grounding circuit inside or outside the detector or disconnect the wire from thegrounding terminal.
In both of the cases, the detector will be in danger.

Defects in protective functions
When seeming defects are found in the protective functions, such as protective grounding, do
not start the detector.
Before starting the detector, check the protective functions for defects.

Grounding Zener Barrier
Arrange A type grounding for Zener Barrier.



Operation in a gas
The detector employs the intrinsically safe explosion-proof structure (Zener Barrier used
separately).
It can be used in a location where a combustible gas, or steam is present; however, it should bedone carefully.
Consult RIKEN KEIKI before operating the detector in such a location.

External connection
Before connecting the detector to the external control circuit, securely connect it to a protective
grounding circuit.

Handling of sensor
Do not disassemble the sensor unit because it contains electrolyte. If contact occurs, rinse thearea immediately with water.

Calibration
When performing calibration for the detector, be careful not to lack calibration gases by loosing
tubes.



Response to gas detection
When a gas is detected, it indicates a potentially dangerous situation. Take proper actions basedon your judgment.

-6-

2 Important Notices on Safety

2-3. Precautions

2-3. Precautions
CAUTION

Do not use a transceiver near the detector.
Radio wave from a transceiver or other radio wave transmitting device near the detector or its
cables may disturb readings.
If a transceiver or other radio wave transmitting device is used, it must be used in a place where
it disturbs nothing.



To restart the detector, wait for five seconds or longer before switching on detector.
Restarting the detector within five seconds may cause errors.



Careful consideration should be given to instrumentation to maintain safety even when atrouble like disconnection of power/signal cable or unexpected malfunction or failure occurs.

This is an electrical appliance. Be careful that it may be affected, in rare cases, by power
supply noises, static electricity and electromagnetic noises. Before using the detector in anenvironment with such noises, provide for protective measures against them.

2-4. Operating precautions
This detector is a gas detector that detects combustible and toxic gases in the air and outputs gas
concentration signals.
The gas detector is a safety unit, not an analyzer or densitometer which performs quantitative/qualitative
analysis/measurement for gases.
Please fully understand the following points before using it, so that it can be used properly.
1.

The detector may be interfered by gases other than the gas to be detected, solvents, vapors etc.
Please note that the gas concentration signal may be fluctuated by interference. In addition, it may befluctuated by environmental (temperature, humidity, etc.) changes in the installation site.

2.

The alarm must be set within a range where the performance of the detector can be ensured.
In facilities compliant with the High Pressure Gas Safety Act, an alarm setting below our standard
alarm setpoint (threshold limit value) may trigger a false alarm.

3.

This is a safety unit, not a control unit.
Use the analog signal output of the detector for an indicator or external recorder.
If these outputs are used to control other units, we shall not be responsible for any malfunctions.

4.

Because the contact point of the gas detector sensor is made of porous polymeric membrane, thewater repellency of the membrane is deteriorated by solvents, thus causing an electrolyte leak from its
inside. Do not use solvents near the detector.
If a solvent is used for unavoidable reasons, attach the recommended filter to the areas such as inletof the gas detector while using the solvent and for one hour after that.

5.

For maintenance of the detector, it must go through a regular maintenance, including replacement andadjustment of the regular replacement parts as specified in the operating manual. In addition, because
this is a safety unit, it is recommended that a regular maintenance and a calibration are performed
every six months in accordance with the regulations.

-7-

2 Important Notices on Safety

2-5. Important information about explosion-proof

2-5. Important information about explosion-proof
The detector is an explosion-proof product.
The following provides information about the explosion-proof structure. Understand the information in thissection thoroughly before using the detector.


Explosion-proof structure and class
The detector employs the following explosion-proof structure and class. Use the detector
according to the operating environment.
Explosion-proof structure
Explosion-proof class
Certificate number
Certification body
Applied standard

:
:
:
:
:

Intrinsically safe explosion-proof structure
Ex ia IIC T4 Ga
TC22665
Technology Institution of Industrial Safety
Recommended Practices for Explosion-Protected Electrical
Installations in General IndustriesJNIOSH-TR-46-1:2015
JNIOSH-TR-46-6:2015

Electrical parameter
Intrinsically safe circuit allowable voltage (Ui)Intrinsically safe circuit allowable current (Ii)
Intrinsically safe circuit allowable power (Pi)Internal capacitance (Ci)Internal inductance (Li)

:
:
:
:
:

28 V
93 mA
0.65 W586 pF
Negligible value

Backup power supply
1.5 VDCOperating temperaturesProtective class of case::

Insulation performance:-20 - +50°C (*1)
IP20 (Water-proof: None/Dust-proof: Up to 12.5 mm foreign solidmaterial protected)
Meet JIS standard (between the power supply and case, 500
VAC, one minute) under the condition that the capacitor
connected to the terminal plate has been removed.

System configuration
Make up the system as shown below.
Hazardous location

Non-hazardous location

Safety maintaining device

Gas detector-8-2 Important Notices on Safety

2-5. Important information about explosion-proof

Important information about explosion-proof (continued)Power supply
Never fail to use the following safety maintaining device (barrier) to maintain explosion-proof
performance.
Ratings to maintain safety
Intrinsically safe circuit maximum voltage (Uo)Intrinsically safe circuit maximum current (Io)Intrinsically safe circuit maximum power (Po)

:
:
:

28 V
93 mA
0.65 W

Performance classification and group
Performance classification
: ia
Group
: IIC
Relations between the intrinsically safe circuit allowable inductance (Lo) and intrinsically safe
circuit external wire inductance (Lc) and between the intrinsically safe circuit allowablecapacitance (Co) and intrinsically safe circuit external wire capacitance (Cc)
Intrinsically safe circuit allowable inductance (Lo) = (Lc) or more
Intrinsically safe circuit allowable capacitance (Co) = 586 pF + (Cc) or moreWiringDetermine the cable type to use and laying distance in consideration of the above parameters tomaintain explosion-proof performance.
Perform wiring so that a current or voltage that disturbs intrinsically safe explosion-proof
performance of the intrinsically safe circuit is not induced to the circuit due to electromagnetic orelectrostatic induction.

Battery
The detector contains a battery for sensor backup. Observe the followings to maintain explosionproof performance.
<Usable battery>Type: AAA alkaline dry battery
Model: LR03Nominal voltage : 1.5 V<Battery Replacement>
Turn off the power of the detector before replacing the battery.
Never fail to use the dedicated battery storage case.



Grounding
Never fail to ground the detector (D type grounding).



OthersConfirm that no combustible gas is present around before opening the door of the unit.
Never disassemble or modify the unit.
Manufacturer:

RIKEN KEIKI Co., Ltd.
2-7-6 Azusawa, Itabashi-ku, Tokyo, 174-8744 Japan
www.rikenkeiki.co.jp*1: The temperature range to maintain explosion-proof performance
The temperature range to maintain gas detection performance is 0 to +40°C. (See
Specifications)-9-3 Product Components

3-1. Main unit and standard accessories

3

Product Components
3-1. Main unit and standard accessories<Main Unit>
48

(1)

24

8

100

(2)
(4)
(5)

200

227

(3)

17

(6)

80

(1)
(2)

LCD display
MODE switch(3)(4)(5)

SET switch
UP/DOWN switch(6)

Nameplate

Display the gas concentration. (Used at maintenance)
Switches the mode from the detection mode to maintenance mode. Or
exits the maintenance mode.
Used to set the mode during the maintenance mode.
Used to select an item for each maintenance mode, increase/decrease areading in zero adjustment or external output test, etc.
Shows ratings, etc.

<Standard Accessories>CF-82 CO sensor filter: Attached when the gas to be detected is CO (carbon monoxide).

- 10 -

3 Product Components

3-2. Names and functions for each part3-2. Names and functions for each part
<Front View of Detector Unit>

(9)
(7)

(10)

(8)

(11)

(12)

(7)
(8)
(9)
(10)
(11)
(12)

Battery box
Power switch
SensorTerminal plate
Grounding terminal
Cable inlet

Houses the battery for sensor backup.
Turns ON/OFF the power of the unit.
Detects a gas.
Connects the power cable.
A terminal (M4) to ground the unit.
An inlet for connected cable.

- 11 -

4 How to Use

4-1. Before using the detector

4

How to Use
4-1. Before using the detector
Not only the first-time users but also the users who have already used the alarm system must follow theoperating precautions.
Ignoring the precautions may damage the alarm system, resulting in inaccurate gas detection.

- 12 -

4 How to Use

4-2. Precautions for installation sites

4-2. Precautions for installation sites



CAUTION
This is a precision device. Because the detector may not provide the specified performance insome places (environments), check the environment in the installation point, and then takeappropriate actions if necessary.
Because the detector plays an important role for safety and disaster prevention, as many unitsof the detector as needed must be installed in appropriate points.
Because points where gases leak and gathering are different depending on the types of gases
and the working areas, please decide carefully on installation points and the number of units to
be installed.

Do not install the detector in a place with vibrations or shocks.
The detector consists of sensitive electronic parts. The detector must be installed in a stable place without
vibrations or shocks and it cannot drop.
Do not install the detector in a place exposed to direct sunlight or sudden changes in the temperature.
When selecting installation points, avoid a place where it is exposed to direct sunlight or radiant heat
(infrared rays emitted from a high-temperature object), and where the temperature changes suddenly.
Condensation may be formed inside the detector, or the detector cannot adjust to sudden changes in thetemperature.
Keep the detector (and its cables) away from noise source devices.
When selecting installation points, avoid a place where high-frequency/high-voltage devices exist.

Do not place the detector next to a noise source device.

Do not run cables in parallel or close to each other.
Do not install the detector in a place where maintenance of the detector cannot be performed or wherehandling the detector involves dangers.
Regular maintenance of the detector must be performed.
Do not install the detector in a place where the machinery must be stopped when maintenance isperformed in its inside, where parts of the machinery must be removed to perform maintenance, or where
the detector cannot be removed because tubes or racks, etc. prevent access to it.
Do not install the detector in a place where maintenance involves dangers, for example, near a highvoltage cable.
Do not install the detector in machinery which is not properly grounded.
Before installing the detector in machinery, the machinery must be grounded properly.
Do not install the detector in a place where interference gases exist around it.
The detector must not be installed in a place where interference gases exist around it.

- 13 -

4 How to Use

4-3. Precautions for system designing

4-3. Precautions for system designing
CAUTION
An unstable power supply and noise may cause malfunctions or false alarms.
The descriptions in this section must be reflected on the designing of a system using the detector.

Using a stable power supply
The external output and alarm contact of the detector may be activated when the power is turned on, whenmomentary blackout occurs, or while the system is being stabilized. In such cases, use a UPS(uninterruptible power system), or take appropriate actions on the receiving side.
The detector must be provided with the following power supply.
Power supply
voltage

15 - 27 VDC (terminal voltage of the main unit)

Allowed time of
momentary
blackout

Approx. 1 msec. (To recover from themomentary blackout for 1 msec. or more,restart the detector.)

OthersExample of actions
To ensure continuous operation andactivation, install a UPS, etc. outside thedetector.
Example of actions
Do not use it with a power supply of large
Use a line filter, etc. to avoid the noise
power load or high-frequency noise.
source if necessary.

Heat radiation designing
When the alarm system is installed in a closed instrumentation panel or the like, attach ventilation fansabove and below the panel.
Introducing protective measures against lightning
If cables are installed outside the factory/plant, or if internal cables are installed in the same duct as thecables coming from outside the factory/plant, "lightning" will cause problems. Because lightning acts as alarge emission source while cables act as a receiving antenna, devices connected to the cables may bedamaged.
Lightning cannot be prevented. Cables installed in a metal conduit or under the ground cannot becompletely protected from inductive lightning surge caused by lightning. Although complete elimination ofdisasters caused by lightning is impossible, the following protective measures can be taken.

Protection
against lightning

Grounding*

Take appropriate measures in accordance with the importance of the facilities andthe environment.
 Provide protection by a lightning arrester (cable arrester).
(Although inductive lightning surge can be transmitted through the cable, it isprevented by installing a lightning arrester before the field devices and central
processing equipment. For information on how to use a lightning arrester, pleasecontact the manufacturer.)
In addition to lightning, there are more sources of surge noise. To protect units fromthese noise sources, the units must be grounded.

The lightning arrester has a circuit to remove a surge voltage which damages field devices, so thatsignals may be attenuated.
Before installing a lightning arrester, verify that it works properly.

- 14 -

4 How to Use

4-4. How to install

4-4. How to install
A certain maintenance space needs to be secured in advance to allow the maintenance personnel to safely
and properly perform maintenance of the gas detector function and performance. Be sure to secure thisspace during construction planning or installation.
235
20

140

404

10

Fixing hole (M5)

Fixing hole (M5)(1) Mount the main unit on the wall.
(2) Insert screws to the upper and lower fixing holes of the main unit and tighten them. (Use M5 screws.)

CAUTION
Check that the main unit is mounted securely on the wall. If not, the main unit may fall off andcause unexpected injury or damage to the unit.
Do not install the detector in a place where maintenance of the detector cannot be performed orwhere handling the detector involves dangers.
Regular maintenance of the detector must be performed.
Do not install the detector in a place where the machinery must be stopped when maintenance isperformed in its inside, where parts of the machinery must be removed to perform maintenance, orwhere the detector cannot be removed because tubes or racks prevent access to it.
Do not install the detector in a place where maintenance involves dangers, for example, near ahigh-voltage cable.

- 15 -

4 How to Use

4-5. Grounding

4-5. Grounding
Connect the detector to your grounding terminal with the internal or external terminal.

WARNING
Before turning on the detector, never fail to connect it to a grounding terminal.

Internal grounding terminal(M4)

External grounding terminal(M4)

For stable operation of the detector and safety, it must be connected to a grounding terminal. Do
not connect the grounding wire to a gas pipe. The grounding must be made as D type grounding(below 100 Ω of grounding resistance).

WARNING
Perform A type grounding when Zener Barrier is connected for explosion-proof specification.

- 16 -

4 How to Use

4-6. How to wire

4-6. How to wire

CAUTIONBe careful not to damage the internal electronic circuit when wiring.
The connected cables must not be installed together with the motor power cables, etc.
When stranded wires are used, prevent wires from contacting each other.

4-7. Compatible cables and terminal plate
specifications<Recommended Cables>
Use CVVS 1. 25 sq 2-core single or stranded wire.
<Specifications of Terminal Plate>
Rated voltage: 250 VAC
Rated current: 20 A

Groundingterminal+－

Power supply and output signal
4 - 20 mA<Supply Voltage>
The supply voltage is normally 24 VDC.
However, the voltage at the terminal plate of the detector becomes lower than the source voltage,
depending on the connected safety maintaining device (barrier), type and length of the cable used.
It may also vary with the signal current value (4 to 20 mA).
When wiring the detector, check the following to make sure that the voltage at the terminal plate isappropriate.
The detector provides stable operation within the power voltage range of 15 to 27 VDC.
< Withstand voltage performance>
The detector has a withstand voltage performance of 500V AC for 1 minute between the power supply andoutput signal terminals and the earth (between containers).

- 17 -

4 How to Use

4-8. System connection example

4-8. System connection example
4-8-1. Example of connecting to indicator, DCS, PLC, etc.
(non-explosion-proof system)
Host system (DCS, PLC)

Non-hazardous location

GD-K88Ai
detector

4-8-2. Example of connecting to Zener Barrier, indicator, DCS,
PLC, etc.
Non-hazardous location
Upper unit (DCS, PLC)

Hazardous location

Zener Barrier

A type grounding
GD-K88Ai
detector- 18 -

4 How to Use

4-8. System connection example

4-8-3. Example of connecting to Zener Barrier and indicator
Non-hazardous location

Hazardous location

EC-5002/EC-592
Short circuit between (3) and (4).

Zener Barrier
(3)
(4)
(5)
(6)

A type grounding
GD-K88Ai
detector

4-8-4. Example of connecting to insulating barrier, indicator,
DCS, PLC, etc.
Non-hazardous location
Upper unit (DCS, PLC)

Hazardous location

Insulating barrier

GD-K88Ai
detector- 19 -

5 How to Operate

5-1. Preparation for start-up

5

How to Operate
5-1. Preparation for start-up
Before connecting a power supply, read and understand the following precautions. Ignoring theseprecautions may cause an electric shock or damage the detector.








Check that the detector is installed properly.
Check that the detector is grounded.
Check that the external wiring is done properly.
Check that the power supply voltage meets the specifications.
The external output may be fluctuated during adjustment. Take an appropriate measure to avoid
the influence on the gas monitoring system.
Make sure to use a fuse with the specified ratings to prevent fire.

5-2. Basic operating procedures
Normally, the detection mode is activated after the power is turned on.
Preparation for start-up

Power-onInitial clear (approx. 25 seconds)

Detection mode

MODE switch (hold down for approx. 3 seconds)
Maintenance mode
• Zero adjustment mode
• Regular maintenance mode

- 20 -

5 How to Operate

5-3. How to start the detector (power-on)

CAUTION
The regular maintenance mode is used by a qualified service engineer.

5-3. How to start the detector (power-on)

Before supplying power to the detector, check that the preparation for start-up is completed.
Turn on the power switch located on the left side of the power terminal plate.
<Initial Clear (approx. 25 seconds)>
System check of the unit
External output: 4.0 mA

Power switch



CAUTION
Do not turn off the detector during the initial clear. The detector is reading the internal memory
during the initial clear.
If the detector is installed newly or the new sensor is replaced, the sensor must be warmed up
for a specified period which is determined depending on the type of the sensor after thedetector is started.
After the warm-up is completed, perform a calibration.

- 21 -

5 How to Operate

5-4. Modes

5-4. Modes
Details on each mode are provided as follows.



CAUTION
Do not change the settings if not necessary. Changing the settings without understanding thespecifications may cause malfunctions.

Mode

Item

Detection mode-

Maintenancemode(User)

Maintenancemode(Regularmaintenance)

LED display
Gas
concentration

Details
Normal state

ROM/SUM display

1-0

Zero adjustment
Setting display
Regularmaintenance modeswitching

1-1
1-2

Display the program version and others.
This is not used by the user.
Perform the zero adjustment.
Display various setting values.

1-3

Switch to the regular maintenance mode.

Test mode

2-0

Zero adjustment
Span adjustment----------

2-1
2-2
2-3

Environmental
setting

2-4

Display

2-5

Switch to factorymode
Switch to user
mode

Perform various tests.
2-0-0 Gas Test
2-0-1 Alarm Test
2-0-2 Fault Test
2-0-3 LCD Test
2-0-4 ---------Perform the zero adjustment.
Perform the span adjustment.
---------Used for various environmental settings.
2-4-0---------2-4-1 INHIBIT Setting
2-4-2 Alarm Setpoint Setting
2-4-3 Alarm Delay Time Setting
2-4-4 Alarm Pattern Setting
2-4-5 Zero Suppression Type Setting
2-4-6 Zero Suppression Value Setting
2-4-7 ---------2-4-8 ---------2-4-9 Zero Follower Selection
2-4-A Maintenance Mode External Output Setting
2-4-B External Output Adjustment
2-4-C Alarm Test External Output Setting
2-4-D Sensor Operation Start Setting
2-4-E ---------2-4-F ---------2-4-G Alarm Limiter Setting
2-4-J Sensitivity Correction Setting
2-4-K Date/Time Setting
2-4-M ---------2-4-N Fault External Output Setting
Display various electrical settings.
This is not used by the user.

2-6

Not used.

2-7

Return to the user mode.

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5 How to Operate

5-5. Description of operation (detection mode)

5-5. Description of operation (detection mode)
5-5-1. Display operation
The operation status of the detector is displayed on the LCD.

Preparation

Power-on
LCD display (Example: Gas to be detected: CO)Initial clear (approx. 25 seconds)

Detection mode
In the detection mode, the sampling gas
concentration is displayed on the LCD.

Normal display (description)

Name of the gas tobe detected

Operation status (Blinking: Normal)

Detected gas concentration
Unit

Gas alarm display

When a gas concentration exceeds the preset alarm
setpoint, the gas alarm display appears and an alarm
message (AL1 or AL2) is displayed in the lower left sideon the display.

- 23 -

5 How to Operate

5-5. Description of operation (detection mode)

Negative value display

The "-0" display is shown when the zero level drops to thenegative (-) side by 10% or more of the full scale.

WARNING
Accurate gas detection cannot be performed with the negative value display.
In this case, perform zero adjustment.

Fault Display

If a fault occurs on the detector, the fault detail is displayed on the
LCD.
(LCD display) (Fault detail)E-9
System abnormalities
E-1
Sensor not connected/Sensor disconnection

NOTE
See "8. Troubleshooting" for remedial actions to fault display.

- 24 -

5 How to Operate

5-5. Description of operation (detection mode)

5-5-2. External output operation4 – 20 mA transmission(1) Signal transmission method : Electric current transmission (non-isolated)(2) Transmission path
: CVVS 2c 1.25 sq(3) Transmission distance: 1000 m or less(4) Connection load resistance : 300 Ω or less(5) Status signal level
1. Detection mode
: 4.0 - 20.0 mA (depends on the gas concentration)
2. Initial clear: 4.0 mA
3. Maintenance mode
: 4.0 mA or lower
4. External output test
: 4.0 - 20.0 mA (varies with the test value)
5. Fault state: 3.5 mA
6. Power off: 0.0 mA
The following figure shows the relation between "gas concentration" and "external output".
External output
20.5 mA
20 mA

4 mA

Maintenance modeGas concentration
Full scale
Zero suppression value
Detection mode
Maintenance mode

CAUTION
The 4 - 20 mA output is adjusted. If readjustment for 4-20mA is needed after installation, it must be
done by a qualified service engineer.

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5 How to Operate

5-6. Description of operation (maintenance)

5-6. Description of operation (maintenance)
5-6-1. Maintenance modeEnter the maintenance mode to perform each adjustment.
Holding down the MODE switch for three seconds in the detection mode enters the maintenance mode.
Holding down the MODE switch for three seconds in the maintenance mode returns to the detection mode.
If the maintenance mode is left unoperated for 10 hours, the detection mode automatically returns.
 4.0 - 20.0 mA: 4.0 mA
Hold down the MODE switch for 3 seconds

Entering the maintenance mode

WARNING
When the maintenance mode is entered while gas detection is performed, the external output
signal (gas concentration signal) becomes 4.0 mA (normal state).

*

The maintenance mode consists of "Daily Maintenance" and "Regular Maintenance", and "Daily
Maintenance (Zero Adjustment)" is normally used.
"Daily Maintenance (Zero Adjustment)"
1-1. Zero Adjustment

Select with ▲/▼ switch

1-3. Regular maintenance mode

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5 How to Operate

5-6. Description of operation (maintenance)

5-6-2. Zero adjustment
This is used to perform the zero adjustment.

NOTE



If the zero calibration failed since the zero point was significantly fluctuated from zero, or by otherreasons, it returns to 1-1 after FAIL is displayed. In this case, the zero adjustment has not been
completed.

(1) Hold down the MODE switch over three seconds to enter the
maintenance mode.
(2) Press the SET switch with the "1-1. Zero Adjustment" menu
displayed.
Introduce a zero adjustment gas. When the reading isstabilized, press the SET switch. The display blinks and zeroadjustment is performed.
(3) Press the SET switch to confirm the setpoint.

WARNING
Do not turn off the power until PASS disappears.

When the process ends normally, the LCD displays PASS
and then goes to"1-1. Zero Adjustment" screen.
(4) Hold down the MODE switch over three seconds to returnto the detection mode.

WARNING
After the adjustment is completed, never fail to press the MODE switch to return to the detectionmode.

CAUTION
If the unit remains in the maintenance mode, it automatically returns to the detection mode in ten
hours.

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5 How to Operate

5-6. Description of operation (maintenance)

5-6-3. External output test
This is used to check the transmission status by outputting a signal equivalent to gas concentration to theexternal device.

WARNING
Before starting the external output test (transmission test), provide a notification to the related
sections so that they can prepare for false alarm.

(1) Hold down the MODE switch over three seconds to enter the
maintenance mode.

(2) Press the SET switch with the "1-3. Regular Maintenance
Mode Switching" menu displayed.

(3) Holding down the SET switch while "----" is displayed enters
the regular maintenance mode.

(4) Press the SET switch while "2-0" is displayed to display "2-01. Alarm Test". Then make a selection with the SET switch.

(5) Increase the reading with the ▲/▼ switch to check thetransmission status.
When the test is completed, hold down the MODE switch overthree seconds to return to "2-0".
(6) While "2-0" is displayed, hold down the MODE switch overthree seconds to return to the detection mode.

- 28 -

5 How to Operate

5-7. How to exit

5-7. How to exit
To turn off the detector, turn off the power switch located on the left side of the power terminal plate. Then,turn off the power supply (24 VDC) to the detector.

WARNING
Before turning off the detector, decide whether the power can be turned off by checking theoperation of the devices connected to the external output of the detector.

- 29 -

6 Maintenance

6-1. Maintenance intervals and items

6

MaintenanceThe detector is an important instrument for safety.
To maintain the performance and reliability of the detector, perform a regular maintenance.
Continuing to use the detector without performing maintenance might cause the sensitivity degradation,
thus resulting in inaccurate detection.

6-1. Maintenance intervals and items

Daily maintenance
Monthly maintenanceRegular maintenance

Maintenance
item

:
:
:

Perform maintenance before beginning to work.
Perform maintenance on the alarm circuit (alarm test) once a month.
Perform maintenance once or more for every six months to maintain theperformance as a safety unit.
Maintenance content

Daily
maintenance

Monthly
maintenanceRegularmaintenanceStatus display
check
Gas
concentration
display
Alarm test*

Check that the status indicates normal○○○
measurement state.
Check that a gas to be detected is not present
around the detector and that the reading indicates a○○○normal value.
Inspects the alarm circuit by using the alarm test－○○
function.
Span adjustment Perform the span adjustment by using the－－○calibration gas.
Gas alarm check Check the gas alarm by using the calibration gas.
－－○*
Check and adjustment are performed at the indicator/alarm unit side. See the operating manual of theindicator/alarm unit for details.
<About Maintenance Services>
We provide services on regular maintenance including span adjustment, other adjustments andmaintenance.
To make the calibration gas, dedicated tools, such as a gas cylinder of the specified concentration andgas sampling bag must be used.
Our qualified service engineers have expertise and knowledge on the dedicated tools used forservices, along with other products. To maintain the safety operation of the unit, please use ourmaintenance service.
Typical maintenance services are listed as follows. Please contact RIKEN KEIKI for more information.

- 30 -

6 Maintenance
Main services
Power supply
check
Status display
check
Concentration
display check*
Alarm test**

6-1. Maintenance intervals and items:

Checks the power supply voltage.

:

Check that the status indicates normal measurement state.

:

Verifies that the concentration display value is zero by using the zero gas.
Performs zero adjustment if the display is incorrect.
Inspects the alarm circuit by using the alarm test function.
 Checks the alarm lamps. (Checks the activation.) Checks the external alarm. (Checks the activation of the external alarm, suchas a buzzer.)
Performs the span adjustment by using the calibration gas.
Checks the gas alarm by using the calibration gas.
 Checks the alarm. (Checks triggering of alarm when the alarm setpoint isreached.) Checks the delay time. (Checks time to delay until the alarm is triggered.) Checks the external alarm. (Checks the activation of external alarms, such asa buzzer and reset signal.)
Checks dust or damage on the surface, cover or internal parts of the unit, andcleans or repairs such parts as needed.
Replaces parts which are cracked or damaged.
Uses the keys to check the operation of functions, parameters, etc.

:

Replaces consumable parts, such as a sensor and filter.

:

Span adjustment
Gas alarm check*::

Cleaning andrepair of the unit
(visual diagnosis)
Unit operation
check
Replacement ofconsumable parts:

Check and adjustment are performed at the indicator/alarm unit side.

- 31 -

6 Maintenance

6-3. Gas calibration method

6-3. Gas calibration method
Perform a calibration in each mode (zero adjustment mode and span adjustment mode) using thecalibration gas.

<Zero Adjustment "2-1">
This is used to perform the zero adjustment.

WARNING
When the zero adjustment is performed in the atmosphere, check the atmosphere for freshness before
beginning the adjustment. If interference gases exist, the adjustment cannot be performed properly,
thus leading to dangers when the gas leaks.

NOTE
Before starting the zero adjustment, provide the detector with the zero adjustment gas and wait until
the indicator is stabilized.

1. Select "2-1" (zero calibration) in the maintenance mode.
2. In the atmospheric air, press the "SET" switch, and confirm that the order in which it is displayed is"CAL".

NOTE
If the zero adjustment failed since the zero point was significantly fluctuated from around zero,It returns to 2-1 after FAIL rather than PASS is displayed. In this case, the zero adjustment has notbeen completed.

- 32 -

6 Maintenance

6-3. Gas calibration method<Span Adjustment "2-2">This is used to perform the span adjustment.

WARNING
Before starting the span adjustment, provide the detector with the calibration gas and wait until thereading is stabilized.

1. Select "2-2" (Span Calibration) in the Maintenance Mode.
2. Set the gas calibration cap in the sensor section.
3. Run calibration gas for the specified time, press "▲/▼" key to adjust the LED display to the gas
concentration, and then press "SET" key to make the display blink. Press "SET" key again to set the gas
concentration. After confirming, make sure that [PASS] is displayed.
4. After the span adjustment, press and hold the "MENU" key to return to the measurement state.

Pump
Needlevalve
Calibration
adapterGassamplingbag

Flow meter
BufferNOTE
If the span adjustment failed since the reading was significantly fluctuated from the introduced gas
concentration, it returns to 2-2 after FAIL rather than PASS is displayed. In this case, the span
adjustment has not been completed.
Check if the correct concentration calibration gas has been provided and check the gas adjustment
tool for a gas leak. If there are mistakes, perform the span adjustment again.
If the span adjustment cannot be performed even when there is no mistake or after recalibration, thegas sensor life might have expired. After turning off the power supply, please contact RIKEN KEIKI.

- 33 -

6 Maintenance

6-2. Replacement parts

6-2. Replacement parts<Replacement of Gas Sensor>
To replace the gas sensor, use the following procedure.
1. Open the door of the main unit, loosen the two anti-removal screws and remove the sensor part.
Do not allow contact between the amplifierboard and the door screw mounting part.
Do not allow the LCD cable to touch the sheet metal.

Loosen the two anti-loss screws.

Sensor

2. Remove the screws from the sensor mounting plate.

3. Disconnect the connectors and remove the sensor from the amplifier board and sensor mounting plate.

4. Replace the sensor.

5. Reassemble the sensor section and reinstall it in the main body using the reverse procedure to theabove.

- 34 -

6 Maintenance

6-2. Replacement parts

NOTE





The gas calibration using the standard gas is required after the sensor is replaced. Please make arequest to RIKEN KEIKI.
If adjustment to the standard gas concentration value fails even with the maximum sensitivity, it
indicates that the gas sensor has come to the end of its life. The gas sensor needs to be replaced.
After replacing the gas sensor, electrical adjustment and calibration using the standard gas arenecessary.

<Replacement of Regular Replacement Parts>
List of recommended regular replacement parts
Part number
4253 9330 10*

Name
Battery Assy

Maintenanceintervals

Replacement
intervals

———

———

Quantity(pieces per
unit)
1Remarks*

Replaced together with the gas sensor. The operation must be checked after replacement by aqualified service engineer.
For the stable operation of the detector and safety, ask a qualified service engineer to take care of
replacement of the parts. Request the operation check from RIKEN KEIKI.

NOTE
In the case where the wireless energization time of the device is a total of more than half a year, thebattery replacement for the sensor may be empty.
If the sensor is not properly backed up, it may lead to a sensor failure, a change in the startup instruction,
or a startup error (E-9).

- 35 -

7 Storage, Relocation and Disposal

7-1. Procedures to store the detector or leave it for a long time7

Storage, Relocation and
Disposal
7-1. Procedures to store the detector or leave it for along time
The detector must be stored under the following environmental conditions.

In a dark place under the normal temperature and humidity away from direct sunlightIn a place where gases, solvents or vapors are not present

7-2. Procedures to relocate the detector or use it
again
When the detector is relocated, select a new place in accordance with "4-2. Precautions for installationsites" and "4-4. How to install".
For information on wiring work, see "4-6. How to wire" and "4-7. Compatible cables and terminal plate
specifications". The unpowered time must be minimized when the detector is relocated.

CAUTION
When using detector again after relocation or long-term storage, never fail to perform a calibration.
For information on readjustment including a calibration, please contact RIKEN KEIKI.

7-3. Disposal of products
When the detector is disposed of, it must be treated properly as an industrial waste in accordance with thelocal regulations.

- 36 -

8 Troubleshooting

8

Troubleshooting
The Troubleshooting does not explain the causes of all the malfunctions which occur on the detector. This
simply helps to find the causes of malfunctions which frequently occur. If the detector shows a symptom
which is not explained in this manual, or still has malfunctions even though remedial actions are taken,
please contact RIKEN KEIKI.
<Abnormalities on Unit>
Symptom/Display FAULT

The power
cannot be turnedon.

Abnormaloperations——

Systemabnormalities
E-9●

Sensorabnormalities
E-1

When powered
ON, the LCD
display may turnOFF for a while(up to 30
seconds).

—

Causes
The wiring is not correct.
The terminal plate isremoved.

Actions
Connect the wiring properly.
Connect the terminal plate properly.

Abnormalities/momentary
blackout of power supply
systemProvide the rated voltage.
Take measures such as checking or adding the
UPS, power supply line filter and insulationtransformer.

Cable abnormalities(open circuit/not
connected/short circuit)

Check the wiring of detector and related devices
around it.

Disturbances by sudden
surge noise, etc.

Turn off and restart the alarm system.
If such a symptom is observed frequently, takeappropriate measures to eliminate the noise.

Abnormalities of ROM,
RAM or EEPROM insidethe detector
The capacity of thebattery for backing up
the sensor is gone.
The sensor is notconnected or improperly
connected.
Faults of the sensor

Please contact RIKEN KEIKI.
Replace the battery.
Check if the sensor cable is securely fastened tothe terminal plate.
Please contact RIKEN KEIKI.
If it shows successfully the measurement mode
display, there is no problem.

—- 37 -

8 Troubleshooting

7-3. Disposal of products<Abnormalities of Readings>*
Take remedial actions to indicator/alarm unit as well See the operating manual of the indicator/alarm
unit for details.
Symptoms
CausesActions
Drifting of sensor
Perform zero adjustment.
output
It is difficult to eliminate interference gases, such as
Presence ofsolvents completely. Please contact RIKEN KEIKI tointerference gas
arrange removal filters.
The reading rises(drops) and does not go
A very small amount of the gas to be detected may beback.
leaking (slow leak). Because ignoring it may cause
Slow leak
dangers, take a remedial measure, i.e., taking actions
the same as those for the gas alarm.
Environmental
Perform zero adjustment.
changes
It is difficult to eliminate interference gases, such as
Presence ofsolvents completely. Please contact RIKEN KEIKI tointerference gas
arrange removal filters.
Turn off and restart the alarm system.
Disturbance by noise
If such a symptom is observed frequently, take
A gas alarm is triggered
appropriate measures to eliminate the noise.
despite of no gas leak
When the environment (temperature, etc.) changes
and no othersuddenly, the detector cannot adjust to it and isabnormalities at theaffected by it.
detection point.
Sudden change in the In some cases, the detector triggers an indication
environment
alarm.
Because the detector cannot be used under sudden
and frequent environmental changes, any preventive
actions to eliminate them should be taken by the user.
Deteriorated sensor
Slow response
Replace the sensor with a new one.
sensitivity
Improper calibration
Use the proper calibration gas.
gas concentration
Span adjustment
impossible
Deteriorated sensor
Replace the sensor with a new one.
sensitivity- 38 -

9 Product Specifications

9

Product Specifications
9-1. List of specifications
Model
Detection principle
Gas to be detected
Concentration display
Detection range
Detection method
Alarm preset point
Alarm accuracy

GD-K88Ai
Electrochemical type
Toxic gases
7-segment LCD (4 digits)
Depends on the gas to be detected
Diffusion method
Depend on Detectable gas
Within ±30% to the alarm setpoint value(under an identical condition)

Alarm-delay time
(under an identical condition)

Gas alarm typeGas alarm indication
Gas alarm action
Trouble alarm・Self diagnosis
Trouble alarm indication
Trouble alarm action
Transmission method
Transmission specifications
Communication schemePower supply
Power consumption
Transmission cable
Transmission distance
Safety maintaining device
Operating temperature
Operating humidity
Structure
Explosion-proof structure
Explosion-proof class
External dimensions
WeightMaterial
Paint
Outer color

60 seconds or less(by providing the gas 1.6 times the alarm
setpoint)
Two-step alarm(H-HH)
A warning message is indicated(AL1/AL2)
Latching or non latching
System failure/Sensor failure
content display
Non latching
2-wire analog transmission + digital transmission (HART
Communication)
4-20mADC (load resistance: 300Ω or less)
HART 7
24VDC±10%
Approx. 0.6W
Shielded cable of CVVS, etc. (1.25 mm2) - 2-core
Up to 1km with CVVS 1.25 mm2(up to 600m between the detector
head and Zener Barrier)
Zener Barrier (MTL7728ac/MTL7728+/MTL7728-) or
insulating barrier (MTL5541/RN221N-J1/KFD2-STC4-Ex1)
0 - +40℃ (non-rapidly-vary)
30 - 70%RH (non-condensing)
Wall mounted type
Intrinsically safe explosion-proof structure, with safety
maintaining device (barrier) used
Ex ia ⅡC T4 Ga
Approx. 100(W)x241(H)x48(D)mm (projection portions excluded)
Approx. 1.0kg
SECC or SS304
Bake-coated with melamine
Munsell 2.5Y9/2- 39 -

10 Definition of Terms

9-2. Detection principle

9-2. Detection principle
An electrochemical type sensor electrolyzes a gas directly while maintaining the interface between
electrode and electrolyte at a constant potential (bias voltage). A gas is electrolyzed by an electrolysis cellto which a certain potential (bias voltage) is applied, and the gas is detected from the electrolytic current
generated at that time.
WE
REF

Potentiostat
circuitOutputCE
WE: Working electrode
CE: Counter electrode10

Definition of Terms
Electrochemical type
Initial clear
Full scale
ppm
Calibration

This is a principle of the sensor installed in the detector head.
See "9-2. Detection principle" for details.
Output from the detector head fluctuates for a while after turning on the power.
This is a function to prevent triggering alarm during that time.
Maximum value of the detection range.
A concentration unit that means part per million of gas to be detected.
Adjusts the readings to the calibration gas concentration value by using thecalibration gas.

- 40 -