Xylem WTW DurOx 325 User manual

OPERATING MANUAL
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DurOx 325
DISSOLVED OXYGEN SENSOR
OPERATING MANUAL

DurOx 325
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Copyright © 2020 Xylem Analytics Germany GmbH
Printed in Germany.

DurOx 325 Contents
3
Contents
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1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4 Measuring / Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2 Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5 Maintenance, cleaning, replacement . . . . . . . . . . . . . . . . . 8
5.1 General maintenance notes . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 Outside cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3 Changing the electrolyte and membrane cap . . . . . . . . . . 9
5.4 Cleaning the electrodes . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5 Checking the sensor for freedom from zero-current . . . . 13
5.6 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 What to do if ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8 Wear parts and accessories . . . . . . . . . . . . . . . . . . . . . . . 17

Contents DurOx 325
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DurOx 325 Overview
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1 Overview
Structure
Recommended
fields of
application
On site measurements in rivers, lakes and wastewater
1Connection head
2Shaft housing
3Temperature sensor and auxiliary electrode
4Ventilation area
5Lead counter electrode (anode)
6Insulator
7Gold working electrode (cathode)
8WP-D membrane cap (filled with electrolyte solution)
9Protective hood
7
6
5
3
1
2
4
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Safety instructions DurOx 325
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2 Safety instructions
This operating manual contains special instructions that must be followed
during the operation of the D.O. sensor.
Always keep this operating manual in the vicinity of the sensor.
Special user
qualifications
The membrane cap of the D.O. sensor is filled with a small amount of an
alkaline electrolyte solution. All maintenance work that requires dealing with
the electrolyte solution must only be carried out by persons who know how to
safely deal with chemicals.
General safety
instructions
The individual chapters of this operating manual use safety labels like the one
below to indicate danger:
CAUTION
indicates instructions that must be followed precisely in order to avoid
slight injuries or damage to the instrument or the environment.
3 Commissioning
Scope of delivery D.O. sensor DurOx 325, filled with electrolyte solution and ready to
operate
Calibration and storage vessel, OxiCal®-D
1 exchange membrane cap, WP-D
Electrolyte solution, ELY/G
Cleaning solution, RL/G
Polishing strip, SF 300
Operating manual
Note
The membrane cap that is mounted on the sensor for delivery serves mainly
as a transport protection. Depending on the duration of the transport and
storage period, it may have a shortened operational lifetime. If the measuring
system cannot be calibrated (error message of the instrument), please
proceed according to section REPLACING THE ELECTROLYTE SOLUTION AND
MEMBRANE CAP.
Preparing the
sensor for
measurement
Connect the sensor to the measuring instrument. The sensor is immediately
ready to measure. It is not necessary to polarize the sensor.

DurOx 325 Measuring / Operation
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4 Measuring / Operation
4.1 Calibration
Note
For calibration, please refer to the operating manual of the measuring
instrument.
4.2 Measuring
Note the required minimum depth of immersion and minimum approach flow
(see chapter 7 TECHNICAL DATA).
The minimum flow can be provided in different ways, e. g.:
The flow of the water to be measured is sufficient (aeration tank, water
pipe, stream)
Slowly pull the sensor through the water by hand (lake, container), or
Use a flow aid, e.g. stirrer.
4.3 Storage
Always store the sensor in the calibration and storage vessel at a
temperature in the range 0 ... +50 °C (32 ... 122 °F). Make sure that the
sponge in the calibration and storage vessel is always moist.
Calibration and
storage vessel,
OxiCal®-D
Moisten the sponge:
Pull out the insert (1).
Take out the sponge (2), wet it, then slightly squeeze it out.
Put in the sponge and install the insert in the calibration and storage
vessel again.
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Maintenance, cleaning, replacement DurOx 325
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5 Maintenance, cleaning, replacement
5.1 General maintenance notes
For your safety Note the following safety instructions when handling electrolyte and cleaning
solutions:
CAUTION
The ELY/G electrolyte solution and RL-G cleaning solution irritate the
eyes and skin. Note the following points when dealing with these
solutions:
During working activities, always wear suitable protective gloves
and protective goggles/face shield.
If it comes into contact with the skin, rinse thoroughly with water and
immediately change contaminated clothing.
If it comes into contact with the eyes, rinse thoroughly with water
and consult a doctor.
Note the safety datasheets.
CAUTION
Before all maintenance activities, disconnect the sensor from the
instrument.
Note
Information on how to order wear parts and maintenance equipment can be
found in chapter 8 WEAR PARTS AND ACCESSORIES.
5.2 Outside cleaning
Cleaning agents
After cleaning, thoroughly rinse with deionized water and recalibrate if
necessary.
Contamination Cleaning procedure
Lime sediments Immerse in acetic acid for 1 minute (volume
share = 10 %)
Fat/oil Clean with warm water that contains
washing-up liquid

DurOx 325 Maintenance, cleaning, replacement
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5.3 Changing the electrolyte and membrane cap
CAUTION
Before starting to work with the sensor, please note the GENERAL
MAINTENANCE INSTRUCTIONS on page 8.
General
information
WTW delivers the sensor ready to operate (see section 3). The electrolyte
solution and membrane cap must only be replaced if:
a calibration error occurs and the membrane is heavily contaminated
the membrane is damaged
the electrolyte solution is exhausted.
Changing the electrolyte and membrane cap
Unscrew the membrane cap.
Caution: Electrolyte solution!
For disposal of the membrane
head and electrolyte solution,
see section 5.6.
Rinse the sensor head with
deionized water.
Carefully rub and dry the
counter electrode with a lint-
free paper towel.
Immerse the sensor head
including the counter
electrode in RL/G cleaning
solution.
Allow to react for 1 to 3
minutes.
Thoroughly rinse the sensor
head with deionized water.
Water the counter electrode in
deionized water for at least
10 minutes.
RL/G
H O
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Carefully shake off the drops
of water.
Fill a new membrane cap with
ELY/G electrolyte solution.
Remove any air bubbles by
carefully tapping the
membrane head. Additionally,
you can prevent air bubbles
by throwing the first filling
away and refilling the
membrane cap.
Thoroughly rinse the sensor
head with electrolyte solution.
Hold the sensor inclined and
screw on the membrane head
fingertight using a paper
towel. Excess electrolyte
solution is forced out of the
ventilation area.
Check the filling:
Inspect the face surface. No
air bubbles may be present
within the dashed circle. Air
bubbles outside this area do
not interfere.
Note
For measurements under high pressure the filling must be
completely free of air bubbles.
Readiness to measure After approx. 30 to 50 minutes, the sensor is ready for operation.
Subsequently calibrate the sensor.
Note
If you want to measure very low oxygen concentrations (< 0.5 %
saturation), we recommend to let the sensor rest overnight and
then calibrate it.
ELY/G
ELY/G
Ventilation area
points upwards
3 mm

DurOx 325 Maintenance, cleaning, replacement
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5.4 Cleaning the electrodes
CAUTION
Before starting to work with the sensor, please note the GENERAL
MAINTENANCE INSTRUCTIONS on page 8.
General
information
Cleaning is only required in cases of slopes too low or too high (sensor
cannot be calibrated) that cannot be resolved by changing the membrane
head and electrolyte solution.
Cleaning the electrodes
Unscrew the membrane cap.
Caution: Electrolyte solution!
For disposal of the membrane
head and electrolyte solution,
see section 5.6.
Rinse the sensor head with
deionized water.
Using the rough side of the
wet SF 300 polishing strip,
polish off any contamination
from the gold working
electrode using light pressure.
Caution: Do not use any
conventional sandpaper or
glass-fiber brushes.
Rinse the sensor head with
deionized water.
Wipe the counter electrode
with a lint-free paper towel
and carefully remove any
loose white deposits.
Immerse the sensor head
including the counter
electrode in RL/G cleaning
solution.
Allow to react for 1 to 3
minutes.
SF 300
RL/G

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Thoroughly rinse the sensor
head with deionized water.
Water the counter electrode in
deionized water for at least
10 minutes.
Carefully shake off the drops
of water.
Fill a new membrane cap with
ELY/G electrolyte solution.
Remove any air bubbles by
carefully tapping the
membrane head. Additionally,
you can prevent air bubbles
by throwing the first filling
away and refilling the
membrane cap.
Rinse the sensor head with
electrolyte solution.
Hold the sensor inclined and
screw on the membrane head
fingertight using a paper
towel. Excess electrolyte
solution is forced out of the
ventilation area.
Check the filling:
Inspect the face surface. No
air bubbles may be present
within the dashed circle. Air
bubbles outside this area do
not interfere.
H O
2
ELY/G
ELY/G
Ventilation area
points upwards
3 mm

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5.5 Checking the sensor for freedom from zero-current
The sensor is zero-current free. Checking the module for freedom from zero-
current is only necessary in the case of malfunctions that cannot be remedied
by exchanging the electrolyte solution and membrane cap or by cleaning the
electrodes.
There are 2 possibilities to check the sensor for freedom from zero-current:
Measurement in a nitrogen atmosphere (recommended method)
Measurement in a sodium sulfite solution according to DIN EN 25814/
ISO 5814.
CAUTION
If you check the sensor according to DIN EN 25814/ISO 5814, do not
leave the sensor in the sodium sulfite solution for more than 2 minutes.
Danger of sensor poisoning!
Test criterion The sensor is OK if the measuring instrument displays < 1 % D.O. saturation
after 2 minutes.
5.6 Disposal
CAUTION
The ELY/G electrolyte solution irritates the eyes and skin. When dealing
with the ELY/G electrolyte solution, observe the following points:
During working activities, always wear suitable protective gloves
and protective goggles/face shield.
If it comes into contact with the skin, rinse thoroughly with water and
immediately change contaminated clothing.
If it comes into contact with the eyes, rinse thoroughly with water
and consult a doctor.
Follow the safety datasheet.
Note
For measurements under high pressure the filling must be
completely free of air bubbles.
Readiness to measure After approx. 30 to 50 minutes, the sensor is ready for operation.
Subsequently calibrate the sensor.
Note
If you want to measure very low oxygen concentrations (< 0.5 %
saturation), we recommend to let the sensor rest overnight and
then calibrate it.

What to do if ... DurOx 325
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Sensor and
membrane cap
For disposal, unscrew the membrane head and rinse the sensor and
membrane head with water. We recommend disposing of the sensor without
the membrane cap as electronic refuse. The membrane head may be
disposed of with the household refuse.
Electrolyte
solution
Disposal according to the safety data sheet.
6 What to do if ...
Error symptom Cause Remedy
The sensor is in the air
and the display shows
0.0 mg/l or 0 % O2
– No connection between
measuring instrument and sensor
– No electrolyte in the membrane
head
– Cable defective
– Check connection between
measuring instrument and sensor
– Replace and refill the membrane
cap (see section 5.3)
– Return the sensor
The sensor cannot be
calibrated
– Contaminated membrane head
– Electrolyte depleted
– Hole in the membrane
– Membrane cap not screwed on
tight enough
– Replace and refill the membrane
cap (see section 5.3)
Subsequently, wait for 30 to
50 min and recalibrate.
– Screw membrane head tighter
The sensor still cannot
be calibrated after
changing the electrolyte
and membrane head
– Contaminated electrodes or
sensor toxification
– Clean the electrodes (see section
5.4)
Incorrect temperature
display
– Temperature sensor defective – Return the sensor
Mechanical damage to
the sensor
– Return the sensor
Meter displays OFL
(display range exceeded)
– Short-circuit between working
electrode and counter electrode
– Clean the electrodes (see section
5.4). If the meter still displays
OFL, return the sensor.

DurOx 325 Technical data
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7 Technical data
General features Measuring principle Membrane covered galvanic sensor
Temperature
compensation
IMT compensation
(calculated by the meter)
Temperature sensor Integrated NTC 30 (30 kat 25 °C / 77 °F)
Dimensions
(in mm)
Weight 310 g (with 2 m cable)
Materials Working electrode Gold
Counter electrode Lead
– Shaft housing
– Connection head
– Membrane head
– Cable screw joint
POM
Membrane FEP
Sensor head Epoxy, PEEK
Insulator PEEK
Thermistor housing VA steel 1.4571
Seals FPM (Viton)
Connection cable Lengths 3 or 6 m
Diameter 6 mm
Smallest allowed
bend radius
Fixed installation: 50 mm
Flexible use: 80 mm
Plug type Socket, 8 pins
Pressure
resistance
Sensor IP 68 (6 bar)
Sensor cable IP 68 (2 bar)
Plug IP 67 (when plugged in)
The DurOx 325 meets the requirements according to article 3(3) of the
97/23/EC directive ("Pressure equipment directive").
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110
17,5

Technical data DurOx 325
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Pin assignment
Measurement
conditions
Measuring ranges at 20 °C
(68 °F)
0 ... 50 mg/l D.O.
0 ... 600 % D.O.saturation
0 ... 1250 mbar D.O. partial pressure
Temperature range 0 ... 40 °C (32 ... 104 °F)
Depth of immersion min. 4 cm
max. 6 m (depending on the cable length)
Operating position Any
Approach flow > 2,5 cm/s with 10 % measurement accuracy
5 cm/s with 5 % measurement accuracy
Storage
conditions
Recommended storing
method
in the calibration and storage vessel,
OxiCal®-ST (moist)
Storage temperature 0 ... 40 °C (32 ... 104 °F)
Characteristics
when delivered
Zero signal < 1 % of the saturation value
Response time of D.O.
measurement at 20 °C
(68 °F)
t90 (90 % of the final value display after) < 25 s
t95 (95 % of the final value display after) < 40 s
t99 (99 % of the final value display after)
< 125 s
Own consumption of
oxygen at 20 °C (68 °F)
0.006 μg·h-1 (mg/l)-1
Drift Approx. 3 % per month in the operating
condition
Response time of
temperature measurement
t99 (99 % of the final value display after) < 60 s
Precision of temperature
measurement
± 0.2 K
Working life min. 6 months with one electrolyte filling
Working electrode
Counter electrode
Auxiliary electrode
Plug (8 Pin)
from the front:
AE
GE
7
5
3
1
8
6
4
2
NTC 1
30 kΩ
NTC 2
30 kΩ
not used
Coding
NTC 2
NTC 1
NTC 1
Shield, NTC 2
4
5
7
38
2
6
1

DurOx 325 Wear parts and accessories
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8 Wear parts and accessories
Note
For further accessories, refer to the WTW catalog or the Internet.
Wear parts and
maintenance
equipment
Description Model Order no.
Set of exchange membrane caps (3 pieces) WP3-D 202 740
Electrolyte solution ELY/G 205 217
Cleaning solution for lead counter electrode RL/G 205 204
Polishing strip SF 300 203 680
Accessory kit, comprising:
– 3 exchange membrane caps, WP-D
– Electrolyte solution ELY/G
– Cleaning solution, RL/G
– Polishing strip, SF 300
ZBK-D 201 578
Accessories Description Model Order no.
Calibration and storage vessel OxiCal®-D 201 579
Protective hood SK-D 201 575

Wear parts and accessories DurOx 325
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What can Xylem do for you?
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meet our world's water needs. Developing new technologies that will improve the way
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efficiently, in their homes, buildings, factories and farms. In more than 150 countries, we
have strong, long-standing relationships with customers who know us for our powerful
combination of leading product brands and applications expertise, backed by a legacy
of innovation.
Xylem Analytics Germany GmbH
Dr.-Karl-Slevogt-Str. 1
82362 Weilheim
Germany
Xylem Analytics Germany
Sales GmbH & Co. KG
WTW
Dr.-Karl-Slevogt-Str. 1
82362 Weilheim
Germany
Tel.:
Fax:
E-Mail
Internet:
[phone]
[phone]
wtw[email protected]
www.WTW.com
Service and Returns:
®
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