JUMO 201040 Bedienungsanleitung
Ammonia-sensitive sensor for measuring
ammonia in aqueous solutions
Type 201040
B 201040.0
Operating instructions
V1.00/EN/00451666
1 Notes ..................................................................................... 4
2 Description ........................................................................... 5
2.1 Areas of application ............................................................................ 5
2.2 Function .............................................................................................. 5
2.3 Operating conditions .......................................................................... 5
2.4 Coolant monitoring ............................................................................. 6
3 Technical data ...................................................................... 7
4 Operating range ................................................................... 8
4.1 Output signal ...................................................................................... 9
4.2 Design ............................................................................................... 10
5 Mounting ............................................................................. 11
5.1 Dimensions ....................................................................................... 11
6 Electrical connection ......................................................... 12
7 Startup ................................................................................ 12
7.1 Taking the temperature dependence of the ammonia sensor into
account when using it in combination with JUMO dTRANS pH 02
or JUMO AQUIS 500 pH .................................................................. 13
7.2 Calibrating the ammonia sensor ....................................................... 14
8 Maintenance ....................................................................... 16
8.1 Refilling/replacing the electrolyte ..................................................... 17
8.2 Storing the sensor in the storage container ..................................... 19
8.3 Removing the electrode from the storage container ........................ 19
9 Accessories ........................................................................ 20
9.1 Quick-change fitting for ammonia sensor ....................................... 20
9.1.1 Replacing the PTFE washer in the quick-change fitting .................... 22
9.2 Maintenance kits .............................................................................. 24
10 Possible errors ................................................................... 24
4
1 Notes
Note:
All necessary settings are described in this operating
manual. If any difficulties should nevertheless arise
during startup, please do not tamper with the sensor
in any way. By doing so, you could endanger your
rights under the instrument warranty! Please contact
the nearest subsidiary or the head office in such a
case.
Please read this operating manual before placing the
instrument in service. Keep the operating manual in a
place which is accessible to all users at all times.
For technical questions
Service hotline:
Phone: +49 661 6003-300 or
+49 661 6003-653
Fax: +49 661 6003-881300 or
+49 661 6003-881653
E-mail: [email protected]
More information can be found in JUMO white paper
631, "Information on measuring ammonia in water".
5
2 Description
2.1 Areas of application
Refrigerating plants (such as indoor ice rinks, cold stores, etc.),
frequently use ammonia as the refrigerant. Ammonia (NH3) is a
toxic, pungent-smelling and colorless gas. These refrigerating
plants are monitored for escaping ammonia (leakage).
To do this, tubes and system parts filled with water are monitored to
determine whether ammonia (NH3) has penetrated (dissolved in the
water). The ammonia-sensitive sensor type 201040 described here
is suitable for this purpose.
2.2 Function
A gas-permeable, hydrophobic PTFE film makes the connection
between the process medium and the sensor electrolyte. A
hydrogen ion-selective electrode is immersed in the electrolyte.
Ammonia escaping through the PTFE film changes the pH value of
the electrolyte. The NH3concentration in the process medium can
be measured in this manner. The electrolyte contains ammonium
(NH4+) ions, with which the sample gas is in chemical equilibrium.
2.3 Operating conditions
The concept of an ammonia leakage monitoring system must
ensure that the escaping coolant reaches the ammonia-sensitive
sensor type 201040 quickly.
The sensor must be installed in a quick-change fitting part no.
00379538. The porous PTFE washer in this quick-change fitting
must not be clogged! If it is, ammonia leakage will be detected too
late or not at all. If necessary the customer should install a filter
upstream from the sensor.
The flow rate of the monitoring circuit must be checked at regular
intervals! A few drops over several hours is sufficient. If the flow rate
Attention:
The ammonia-sensitive sensor type 201040
described here is not suitable for detecting ammonia
in ambient air!
6
is too low the porous PTFE washer must be replaced, see Section
9.1.1 "Replacing the PTFE washer in the quick-change fitting",
page 22.
2.4 Coolant monitoring
The following components are required for coolant monitoring:
- Ammonia-sensitive sensor, type 201040/65-22-120/000,
part no. 00440655 (JUMO type sheet 201040)
or
Ammonia-sensitive sensor for low-temperature applications,
type 201040/65-22-120/854, part no. 00440655
(JUMO type sheet 201040)
- PP manual quick-change fitting, type 202820/107-66/87,
part no. 00379538 (JUMO type sheet 202820)
- JUMO AQUIS 500 pH transmitter/controller,
type 202560/20-888-000-310-000-23/000, part no. 00480050
(JUMO type sheet 202560)
or
JUMO dTRANS pH 02 transmitter/controller,
type 202551/01-8-01-4-0-00-23, part no. 00560379
(JUMO type sheet 202560)
- Low-noise coaxial cable 1.5 m long, part no. 00085154
(JUMO type sheet 202990)
or
Attention:
The process medium must not contain any
substances that could damage the membrane (such
as oils, greases, particles of dirt or surfactants).
The porous PTFE washer in the quick-change fitting
20/00379538 that matches the sensor must not be
clogged!
A measurement taken in a mixture of ice and water is
not diagnostically conclusive!
7
Low-noise coaxial cable 5 m long, part no. 00307298
or
Low-noise coaxial cable 10 m long, part no. 00082649
3 Technical data
Measuring range: 0.01 to 9999 ppm (= mg/l) NH3
Temperature range:
Standard version 0 to +50°C
Extra code 854 (low temperature) -8 to +50°C
pH range: 7.5 to 14
Fitting length: 120 mm
Diameter: 12 mm
Connection: Pg 13.5 screw-on head
Medium pressure
Sensor in quick-change fitting
Part no. 00379538 installed 2 to 3 bar (max. 6 bar)
Sensor free 1 bar abs. (atmospheric
pressure)
Suitable transmitter: JUMO AQUIS 500 pH or
JUMO dTRANS pH 02
Note:
Use of an impedance converter (type 202995/00-91,
part no. 00300455, JUMO type sheet 202995) is
recommended at low temperatures as the electrical
resistance of the ammonia sensor's glass membrane
increases sharply.
8
4 Operating range
(1) Only NH4+ions (ammonium) are present
(2) The ratio of NH4+ions (ammonium) and
NH3(ammonia) is 1:1
(3) Only NH3(ammonia) is present
Note:
The presence of ammonia in the process medium is
heavily dependent on its pH value (see above
diagram).
In the acidic range, there will be a predominance of
ammonium (NH4+) ions that are not detected by the
sensor!
At approx. 9.3 pH, the concentration ratio of ammonia
(NH3) and ammonium (NH4+) is about 1:1.
It is only in the heavily alkaline range that ammonia is
predominant.
9
4.1 Output signal
The electrochemical process in the thin electrolyte layer upstream
from the glass membrane proceeds as per the following equation:
Hydrogen ions are taken out of the electrolyte, moving the pH value
up to higher values.
The correlation between ammonia concentration [NH3] and voltage
U, is given by the Nernst equation:
In the ideal case, the value of slope S is 58.16 mV/decade (at 20°C).
U0is the cell zero point.
The dependence levels off as the ammonia concentration falls, that
is, there is a lower detection limit. The following diagram shows a
typical characteristic line.
NH + H O NH
32 4
+-
+ OH
U = U - S *log [NH ]
03
(1)
10
4.2 Design
Reference system lead (1) is immersed in the electrolyte and
provides a fixed reference potential for measurement as an Ag/AgCl
electrode, with the chloride ions contained in the electrolyte.
If the sample solution contains ammonia (NH3), for example, the
gas diffuses through the gas-permeable PTFE film (6) until the
partial pressure of the ammonia is the same on both sides of the
film (6). As the partial pressure changes, so does the pH value in the
thin layer of liquid upstream from the glass membrane (5). This
process is recorded by the hydrogen ion-sensitive glass membrane
(5). As the partial pressure depends on the concentration of
ammonia in the sample solution, the pH value can be used to
determine the ammonia concentration in the solution.
(1) Reference system lead
(2) Electrolyte
(3) Internal buffer
(4) Internal lead (Ag/AgCl)
(5) Glass membrane (hydrogen ion-
(6) Gas-permeable PTFE film
(Ag/AgCl)
selective) with a thin electrolyte layer
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