Potassium Content
Measurement
LB 444 K-40
ID No. 55884BA2
Rev. Nr.: 00
01/10 347LB 444 K-40
I
Operating Manual Potassium Meter
LB 444 K-40
Contents
1 GENERAL INFORMATION ..................................................... 1
2 OVERVIEW........................................................................... 2
3 SYSTEM DESCRIPTION......................................................... 4
4 INSTALLATION OF THE DETECTORS..................................... 5
4.1 Selection of the Measuring Site .............................................................. 5
4.2 Installation of the Detector LB 5430 on a Bunker................................... 6
4.3 Installation of the Detector LB 5402 in a Bunker.................................... 7
4.4 Measurement in a Pipe ........................................................................... 7
4.5 Measurement on a Conveyor Belt ........................................................... 9
4.6 Installation of the Evaluation Electronics ............................................. 10
4.7 Installation of the Detector .................................................................. 10
4.7.1 Installation in a Container .............................................................. 10
5 CONNECTIONS................................................................... 11
5.1.1 Evaluation Unit LB 444 K-40........................................................... 11
5.2 Evaluation Unit LB 444 K-40 ................................................................. 13
5.2.1 General Description....................................................................... 13
5.2.2 Display........................................................................................ 13
5.2.3 Keypad Function ........................................................................... 13
5.2.4 Softkeys...................................................................................... 14
5.2.5 Menu Structure............................................................................. 14
5.2.6 Menu Potassium Content Measurement ............................................ 15
6 SOFTWARE FUNCTIONS AND SYSTEM CONFIGURATION ... 19
6.1 General Data......................................................................................... 19
6.2 Operating Mode .................................................................................... 20
6.3 Parameter............................................................................................. 21
6.4 Product Data......................................................................................... 23
6.5 Calibrate............................................................................................... 24
6.6 Live Display .......................................................................................... 26
6.7 Service Menu ........................................................................................ 26
7 GETTING STARTED............................................................. 27
7.1 Quick Installation Overview.................................................................. 27
7.2 Getting Started..................................................................................... 28
7.2.1 Basic Settings............................................................................... 28
7.2.2 Calibration ................................................................................... 29
7.2.3 Checking the Calibration ................................................................ 31
7.3 Live Display .......................................................................................... 31
7.4 Correcting the Results: Addition and Multiplication .............................. 32
7.4.1 Additive Constant.......................................................................... 32
7.4.2 Multiplication Factor ...................................................................... 32
7.5 Automatic Measuring Time Switchover................................................. 33
7.6 Batch Measurement.............................................................................. 34
7.7 Radiating Interference Detection.......................................................... 35
7.8 Error Messages ..................................................................................... 36
7.8.1 Acknowledging Error Messages ....................................................... 36
01/10 347LB 444 K-40
II
7.8.2 Error Messages during Operation .................................................... 36
7.8.3 Error Messages during Calibration ................................................... 36
7.8.4 Error Messages during Measurement ............................................... 37
7.9 System Start/Stop................................................................................ 39
8 TECHNICAL DATA ...............................................................40
8.1 Evaluation Unit LB 444 K-40................................................................. 40
8.2 Detectors.............................................................................................. 41
9 SERVICE INSTRUCTIONS....................................................42
9.1 General Safety Precautions................................................................... 42
9.2 Evaluation Unit LB 444 K-40................................................................. 42
10 SERVICE.............................................................................44
10.1 Service Menu Overview ........................................................................ 44
10.2 Service Menu ........................................................................................ 46
10.2.1 Plateau Check .............................................................................. 47
10.3 Detector ............................................................................................... 50
10.3.1 Checking the Crystal-Multiplier Assembly ......................................... 50
10.3.2 Testing and replacement of the photomultipliers in the detector LB 543051
10.4 Replacing the Evaluation Unit LB 444 K-40........................................... 52
10.5 Setup Protocol...................................................................................... 53
11 DIMENSIONAL DRAWINGS.................................................55
11.1 LB 5402 ................................................................................................ 55
11.2 LB 5430 ................................................................................................ 55
11.3 LB 444 K-40.......................................................................................... 56
01/10 347LB 444 K-40
III
Operating Manual
Potassium Meter
LB 444 K-40
Issue
No. Date Comments
1 01.01.10 First edition
01/10 347LB 444 K-40
1
1 General Information
Safety Summary
Electrical Shock Hazard
Disconnect power to ensure that contact with energized part is avoided during installation
and servicing.
Specific Warnings
Never change the installation or the parameter settings without a full knowledge of the
relevant part of this manual, the connected controller and the process, if it is controlled
by this measuring device.
01/10 347LB 444 K-40
2
2 Overview
The Potassium Meter LB 444 K-40 is designed for measurements of the concentration of
potassium in bulk materials, suspensions and solutions.
The concentration of potassium in bulk materials or liquid solutions is measured by
detecting gamma radiation of the natural isotope K-40. This isotope is contained in
natural potassium in a constant percentage (0.0119%). As the isotope K-40 decays, it
emits gamma radiation with an energy of 1.46 MeV.
The detector LB 5430 detects radiation using an organic scintillator (PVT), the detector
LB 5402 using a NaI crystal. The radiation triggers tiny flashes of light in the scintillator
which are converted into electrical pulses by the photomultiplier. The count rate of this
radiation is a direct measure for the potassium concentration. In addition, the scintillation
detector responds to radiation emitted from the environment, for example, the walls and
the floor which are covered with a layer of potassium.
Further radiation is generated by incident cosmic rays at the location of the detector.
Background radiation remains more or less constant for each installation within a plant,
provided the location is not changed. To keep the statistical error of the measured result
as small as possible, the scintillation detector, fixed at the outside of a bunker or below a
belt conveyor, is shielded against background radiation by an additional lead shielding.
If the scintillation detector is inserted into bulk material, solutions or suspensions inside a
protection tube, the material itself is acting as a shielding against the background
radiation.
Potassium can be found predominantly in the form of KCl. However, to this day the unit K2O is
still used in many companies. The evaluation unit LB 444 K40 allows the calibration and
measurement in both units. Important: the calibration and measurement have must be
performed in the same unit. The following details for “K20” also apply for “KCI”.
There is a linear relationship between the count rate measured by the scintillation
detector and the potassium concentration.
This relationship can be expressed as follows:
K = a (N - N0) (1)
where:
N
0 = count rate measured by the scintillation detector if the bulk material or the
liquid contains 0% K2O.
“N” = count rate detected by the scintillation detector at a concentration “K” of K2O.
“K” = concentration of K2O.
“a” = reciprocal value of the count rate per % K2O.*
* This value can also be understood as the slope of the linear function. The term a x N0
is the background expressed as a percentage of K2O.
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3
The hardware and software of the LB 444 K-40 system makes it easy to adapt the
system to rather different measuring geometries and measuring tasks. Therefore, the
settings and parameters of the measuring instrument have to be defined with care for
the respective measuring task when taking the system into operation. Important
parameters may not be changed later, in order not to compromise the reliable operation
of the system. The system should be taken into operation and settings changed only by
persons who know how to work with the instrument. Therefore, all users should read
these operating instructions carefully. We recommend documenting all settings in a setup
protocol.
Before starting any work, please read this operating manual carefully!
01/10 347LB 444 K-40
4
3 System Description
The system is comprised of the following components:
Figure 1: Measuring system with LB 5430 detector
a) Detector LB 5430 for installation on the outside of the container or
b) LB 5402 for installation in a protective pipe inside the container
c) Connection cable
d) Evaluation unit LB 444 K-40
A 19” rack can be supplied for installation of up to 4 devices or a protective housing for
two devices for installation of the evaluation unit.
The device LB 444 K-40 with a software that has been expanded for potassium
content measurements is used as evaluation unit. The functions of the density
measurement are still available. This operating manual describes only those
functions that are relevant to the potassium content measurement.
01/10 347LB 444 K-40
5
4 Installation of the Detectors
4.1 Selection of the Measuring Site
Assuming a homogeneous mixture of potassium in the material to be measured, the
number of K-40 isotopes increases with increasing amount of material. This means that
the count rate of the detector rises when the amount of material in front of the detector
rises, although the material contains a constant percentage of the K-40 isotope.
The radiation is partially absorbed between its point of origin and the detector.
Consequently, material that is farther away from the detector does not contribute much
to the result. If the material thickness in front of the detector is increased, or the
detector is surrounded by material, the count rate will reach a saturation value and does
not rise anymore even if the thickness of the material layer still increases. This material
thickness is called saturation thickness which is expressed as follows:
d = 100/ρ cm,
where ρ is the density of the bulk material in g/cm3.
Example: For a potassium sample with a bulk weight of 1.2 g/cm3 the saturation
thickness necessary for the measurement would be 100 cm /1.2 = 83 cm.
This means, for a surface probe, the inner diameter of a bunker should be
about 83 cm; a dip probe should be inserted in the center of a bunker having
an inner diameter of at least 166 cm.
These conditions ensure that the measured value is independent of bulk density
variations.
If this conditions cannot be fulfilled, one has to
calculate if the errors that occur as a result of a
smaller volume and a possible change of the bulk
weight or the density are still acceptable.
The goal of a continuous measurement of the K20
content is to cover the detection device with the total
amount of material to be measured, i.e. the position
of the scintillation detector has to be selected such
that the surrounding material thickness is not much
thicker than the saturation thickness.
If this is not the case the material being further away
from the detector than the saturation thickness would
not contribute to the measurement and therefore its
potassium content would not be taken into account
(see Figure 2).
Provided the product to be measured shows a
homogeneous structure, no measurement errors will
occur.
Figure 2: Saturation layer
S = saturation layer thickness
1 = measured material layer
1
2
S
S
S
01/10 347LB 444 K-40
6
2 = material not covered by the measurement
4.2 Installation of the Detector LB 5430 on a Bunker
The LB 5430 detector is installed on the outside wall of a bunker. Typically, it is fixed to
the flange of the detector.
Figure 3: Detector LB 5430
Depending on the version, the detector weights approx. 60 – 70 kg. Please take this
weight into account in your planning.
All screws and mounting parts have to be secured such that they cannot come loose
during operation, so that the detector cannot fall down.
The detector must not be subject to heavy mechanical vibrations. If extreme vibrations
are likely to occur at the installation site, the detector has to be mounted on a damping
and shock absorbing arrangement.
Care must be taken that no potassium containing material may be deposited between the
surface probe and the outside wall. This would result in measurement errors.
The ambient temperature at the installation site of the detector must not exceed 50°C. If
the bunker wall is hot (>50°C), you may insert a suitable insulating plate having a
thickness of approx. 20 mm between the container wall and the detector or use a
detector with water cooling.
01/10 347LB 444 K-40
7
4.3 Installation of the Detector LB 5402 in a Bunker
The detector is installed into a protective pipe, front side closed, and inserted into a
bunker. The distance of the material surface in front of the detector head sensitive to
radiation (position of the scintillation crystal) should on all sides correspond to the
calculated saturation thickness.
If hot liquids are used a cooling water jacket for
the probe is necessary.
The detector temperature must never
exceed 50°C.
No crystallization must occur on the protective
pipe. If necessary, the protective pipe has to be
provided with a thermal insulation and possibly
with a heating jacket.
Crystallizations would significantly falsify the
measured results, since the potassium
concentration in the crystallized layer is
typically higher than in the liquid solution.
S = saturation layer thickness
1 = measured material layer
2 = material not covered by the measurement
Figure 4: Measurement in a container
4.4 Measurement in a Pipe
When measuring in a pipe, the saturation layer thickness is usually not achieved or at
least not achieved in all directions. In the case of large pipes, the saturation layer
thickness is usually achieved in the longitudinal direction of the pipeline, However,
transverse to the pipeline axis, the saturation layer is not always achieved. This can have
an effect on the measurement result, which is larger:
a) the smaller the pipe is
b) the stronger the density varies in the pipeline, (see Figure 6).
The measurement of the saturation thickness is also affected by the diameter of the pipe,
the pipe material and the wall thickness of the pipe.
A correction of the influence is possible in some cases by an additional density
measurement.
This will require an extended period of time for the recording of
a) Density values
b) Displayed K2O values and
c) the appropriate, K2O values determined in the laboratory.
01/10 347LB 444 K-40
8
A correction function can then be calculated from these values.
Figure 5: Measurement in a pipeline
Potassium measurement. Saturation thickness for different densites resp.
bulk densities
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500 600 700 800 900 1000
Layer thickness in mm
cps in %
Density =1,0
Density =1,2
Density =1,4
Figure 6: Influence of thickness and
density
Installation:
01/10 347LB 444 K-40
9
The detector should be mounted in a horizontal pipeline at the top or side. This will
prevent that the measurement is influenced by any deposits on the ground of the
pipeline.
4.5 Measurement on a Conveyor Belt
Normally, the required saturation thickness cannot be reached on a conveyor belt, so the
measured result will be influenced by changes of the bulk weight and/or changes of the
material layer thickness.
However, if it is ensured that
• variations of the bulk weight in the material cannot occur (uniform grain size)
• the height of the material layer is kept constant by leveling device.
a measurement can also be carried out on a conveyor belt. However, the measurement
error is larger than with measurements in a bunker.
01/10 347LB 444 K-40
10
4.6 Installation of the Evaluation Electronics
The evaluation unit (protection type IP 20) can be installed in a 19” rack. This rack then
has to be installed into a suitable measurement cabinet.
The wall housing can be fixed directly to a wall using screws. For outdoor installation, you
may have to install a sunshield to protect the evaluation unit against solar heating.
4.7 Installation of the Detector
Use a water cooling jacket to protect the detector against temperatures > 50°C.
Cables have to be protected against temperatures > 70°C.
Measuring system installed outdoors have to be protected from rain and direct sunshine
by a canopy. The cable entry must not be exposed to temperatures exceeding 70°C. The
cable gland and the cable entry must be aligned such that no water can flow along the
cable into the connection box.
The detector installation site must not be subject to heavy vibrations as this could
damage the detector.
Samples have to be taken for calibration of the measurement. A sampling point has to be
foreseen in the direct vicinity of the measuring site.
4.7.1 Installation in a Container
If the detector is installed in a protective pipe inside the
container, the protective pipe has to be sealed to prevent
the penetration of dust and humidity. The detector
includes two suspension eyes. Wire ropes can be attached
to these suspension eyes. It is not permitted to suspend
the detector on the cable.
The cable should form a loop to allow possibly penetrating
water to drip off.
Figure 7: Installation of de-
tector in a protective pipe
Suspension
eyes Loop
01/10 347LB 444 K-40
11
5 Connections
The power supply of the detector and the transfer of the measured values and important
information to the evaluation unit LB 444 K-40 takes place via a two-wire screened cable.
The possible cable length is dependent on the cross-section of the connection cable used.
The cable entry at the detector
permits a cable diameter of 6-10
mm.
5.1.1 Evaluation Unit LB 444 K-40
c a
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
Relay 2
Relay 3
Relay 1
Mains
2(-) 1 (+)
Probe
RS 485
0/4 - 20 mA
LB 444
Voltage
selection
Fuses
Dig. IN 1
Dig. IN 2
Dig. IN 3
4
6
8
Distanzpart
1
2
Connect cable on the
rear panel of the
evaluation unit as shown
in the wiring diagram in
the appendix to this
manual.
Figure 8: Terminal connection evaluation unit (rear panel)
Connect the device only to the appropriate line voltage.
All safety previsions regarding the power distributor have to be observed.
The evaluation units do not include a separate mains switch. A separate
safeguarding and easily accessible shut-down have to be foreseen.
The device must not be installed in explosive hazardous areas.
Refer to the wiring diagram in the appendix to this manual regarding the connections.
cross-section in mm² Max. cable length in m
1 1000
1.5 1500
2.5 2500
01/10 347LB 444 K-40
12
Detector (2a/2c)
Relay 2 (12a/12c)
The relay can be set for the following functions:
Min. – Alarm, Max. – Alarm, Detector temperature,
Relay 3 (4a/14c)
Functions:
Min. – Alarm, Max. – Alarm, Detector temperature,
Relay 1 (16a/16c)
The relay is used to indicate errors. The contact opens in case of error.
External product selection
Digital input 1 (18a/18c)
Digital input 2 (20a/20c)
Calibration data of up to 4 different products can be defined in the evaluation unit LB 444
K-40. These data sets can be selected via digital inputs.
External Start/Stop Signal (22a/22c)
Option to interrupt measurement for the following special applications:
- Start/Stop in batch mode
- Stop of continuous measurement, e.g. to suppress unexpected malfunctions
0/4-20mA (26a+/26c-)
Isolated current output for measured value, max. load 500 Ω.
Current input (28a-/28c+)
Product temperature for temperature compensation (usually not needed for potassium
content measurements).
Power supply (30a/30c)
Power supply 115V/230V AC or 24 V AC/DC depending on power supply unit (see
label on instrument rear pane!).
Fuses
To replace fuses, you have to open the fuse holder with a screw-driver. Observe fuse
type and rating!
Before turning on the power supply, carefully check all connections once more to rule out
any damage to the instruments.
RS 232
Port for data transfer from evaluation unit to printer or PC (front panel of evaluation
unit).
01/10 347LB 444 K-40
13
5.2 Evaluation Unit LB 444 K-40
5.2.1 General Description
The evaluation electronics is
designed as a 19” module in
the format 3 HE, 21 TE. It
includes the microprocessor-
controlled evaluation electro-
nics and the power supply
for the required operating
voltage. A 32 bit microproc-
essor is used for signal
processing.
enter
clear run
BERTHOLD
LB 444 - 1 V 1.0
Density -Meter more
enter enter
enter
clear run
LCD display
Softkeys
Function keys
Figure 9: Operating elements of the evaluation unit
The instrument is operated via six foil keys:
Three keys work as softkeys which allow user-guided definition of all instrument settings
and input of the required parameters.
Three more keys serve as function keys.
The front panel includes a RS 232 interface port. Data can be transferred to a PC using a
terminal program.
The terminal strip on the instrument rear panel includes all terminals for power supply,
for the detector, and for the analog and digital output signals. The current output is
isolated. The built-in relays for max.-min.-indication and for error messages include an
isolated contact.
System malfunctions are signaled by error messages.
Calibration data is stored in a FLASH memory and saved, so they will not be lost in case
of power failure.
5.2.2 Display
The instrument’s illuminated display comprises four lines. The first three lines show the
menu titles, the currently selected parameters or the current measurement value. The
bottom line shows the current function of the respective softkey button. If a measure-
ment is running, the “run” status is displayed.
5.2.3 Keypad Function
The Potassium Meter is operated via the softkeys and function keys described below.
With these keys you can select the operating level you want within a menu structure in
order to select a function or enter parameters.
01/10 347LB 444 K-40
14
5.2.4 Softkeys
Softkeys are used to select different menu groups and operating levels within the menu
structure. Depending on the current position in the menu structure, functions are
assigned to these keys, as shown on the display above the respective key.
5.2.5 Menu Structure
The menu structure is illustrated on the following pages. Push <more> to select the
various menu groups. From there you get to the respective menu by pushing <sk1> or
<sk2>. Within the menu, push <more> to go to the individual windows and at the end
of the menu push <done> to return to the menu group.
sk1 and
sk2 Go to the indicated menu
more Go to next display or menu group
done Shows the end of the menu and
takes you back to the menu group
^^^
T
ext: scrolls through the various
selection options
Numerical values: increments the
number marked by the cursor by 1
Moves the cursor to the left and at
the end of the input field again to the
start position
+ and - Scrolls forward / back in a result list
or in the live display
Figure 10: Softkey functions
sk1: General Data
sk2: Operating Mode
sk1 sk2 more
Relay 2
Minimum 50%
Hysteresis 5%
<-<-<- ^^^ mo re
Time constant
Value 20s
^^^ <-<-<- more
HV (500): 20/s
HV (560): 123/s
HV (560): 620/s
+ - exit
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