aboniGmbH
für Mess- & Automatisierungstechnik
FAQ’s
Date: 2017-01-05
Which measuring method is used?
The HydroTracer determines the water content of the sample with a chemical method. The
introduced sample is heated in the reactor, water is converted into hydrogen and the hydrogen
content is detected by a sensor. This patented measuring method specifically measures the
water content, other volatile ingredients are not detected.
Is the device suitable for all plastics?
Yes, for all engineering plastics in the field of injection molding. No false measurements are
known to us. An exception is PVC - here the thermal stability has to be considered.
Comparison HydroTracer – Thermogravimetric Balance
The thermogravimetric moisture analyzer consists of a scale with an overhead heating lamp.
The sample is heated on the scale, the weight loss is postulated as water content. This simple
method is practical for the determination of high water contents, e.g. in foodstuffs, when the
proportion of water is very high compared to other contained volatiles.
Disadvantages: No water is determined, but a weight loss. The cause of the weight loss cannot
be determined. This can be water or caused by other volatile substances such as plasticizers,
paraffin’s, fire inhibitors, etc.
A frequent sales argument for thermogravimetry is the hypothesis that at a low heating
temperature (for example, 110 ° C.) the proportion of the other volatiles can be neglected. On
the other hand, at these temperatures in the presence of atmospheric moisture, the water
only partially escapes from a hygroscopic test material until a state of equilibrium with the
water content of the air is reached.
A further disadvantage is the heating lamp: Contrary to the statements of the manufacturers,
it is not possible to heat a plastic granulate evenly by means of heat radiation. The surface will
absorb more heat than the core. This accelerates the thermal degradation of the plastic (and
therefore the weight loss). This is clearly visible in the case of translucent material on the basis
of the discolouration.
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Measuring Accuracy (%)
The measuring range is between 0 mg and 35 mg of water.
The measurement accuracy is 0.1 mg in a range from 0 mg to 5 mg of water,
0.2 mg in a range of 5.1 and 15 mg of water and 0.3 mg in a range of 15.1 and 30 mg of
water.
Conversion of the absolute average measurement error of the HydroTracer
To determine the relative water content of the sample material, the water mass of the
sample is divided by the weight of the sample.
Example 1:
A water content of 1 mg is determined during a measurement, the sample mass was 1 g. The
average error (standard deviation) according to the calibration certificate is 0.1 mg. The
relative water content is thus: 1 mg / 1000 mg = 0.001 = 0.1% = 1000 ppm. Neglecting the
weighing error, the average error of the relative water content is 0.1% x (± 0.1 mg / 1 mg)
= ± 0.01% and ± 100 ppm, respectively
Example 2:
A water content of 1 mg is determined during a measurement and the sample mass is 20 g.
The average error (standard deviation) according to the calibration certificate is 0.1 mg. The
relative water content is thus: 1 mg / 20000 mg = 0.00005 = 0.005% = 50 ppm. Neglecting
the weighing error, the average error of the relative water content is 0.005% x (± 0.1 mg / 1
mg) = ± 0.0005% and ± 5 ppm, respectively
These examples illustrate the great importance of the sample quantity to the accuracy of the
measurement result.
Density of the sample material
Why the material density is required in the menu?
The water in the reactor is converted into gaseous hydrogen. The concentration of hydrogen
depends on the reactor volume. The sample volume in the reactor reduces the reactor volume
or the volume of enclosed gases air and hydrogen. The sample volume is required to calculate
the exact concentration of hydrogen. The sample volume is calculated by dividing the weight
divided by the density. The input of an incorrect density value (error > 0.3 g / cm³) affects
the result only for very large weights (> 20-30 g). In practice this is hardly detectable. So if
you want to test a thermoplastic material with an unknown density, use a density of 1 g / cm³.
IMPORTANT: It is the value of the raw density of the material, not the lower bulk density.
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Is the used reagent toxic?
Some remarks concerning calcium hydride
Calcium hydride is reported as dangerous goods in the material safety data sheet. This
classification refers to large amounts, so that the recommended precautions to exposure
are valid over any length of time with any great amount (e.g. filling in a silo or the like).
About the toxicity of calcium:
Calcium hydride reacts with water immediately to calcium hydroxide (slaked lime) and
hydrogen. In this reaction, heat is released. In minor amounts, which are used in the
measurement with the HydroTracer, damage by heat development is virtually impossible. In
an aqueous solution of calcium hydroxide reacts alkaline (pH up to about 11). The
resulting solution is an irritant and skin contact should be avoided. From the overall experience
it is known as calcium lime mortar. In the food industry, calcium lime is added as an acidity
regulator for foods and in the EU as a food additive called E 526 approved without maximum
limit (quantum satis) generally for food. The resulting hydrogen is produced also as a
metabolite in the human body and is non-toxic.
About the explosion capacity of calcium hydride:
Hydrogen is produced by the reaction of calcium hydride with water. In air hydrogen is
explosive at concentrations of 4% (detonating gas reaction). Since only small amounts of the
reagent used (maximum of 75g per bottle) it is practically impossible to create a flammable
mixture with air in a room. The very high volatility of the hydrogen gas prevents locally higher
concentrations formed in the air.
Disposal of the used reagent:
The reagent used in the HydroTracer is still largely reactive after the measurement. By
exposure to air, it can react slowly with atmospheric moisture to calcium hydroxide
(approximately 1-2 hours). Subsequently calcium hydroxide reacts with the carbon dioxide of
the air to calcium carbonate (limestone) and can then be disposed of with household waste.
Conclusion:
When dealing with calcium, it is crucial that the amount used is minimized. Ingestion inhalation
and contact with the mucous membranes should be avoided to prevent irritation. The minor
potential of harm is also caused by the small amounts (about 0.1 g) which are advised in the
manual. The chemical hazard corresponds to that of slaked lime.
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Calibration
A calibration is included in the initial delivery. The measurement accuracy can be checked by
the customer, but we recommend the maintenance and calibration by aboni.
Explanation of the calibration certificate for the moisture analyzer HydroTracer
Type FMX, FLV
The calibration is based on a method described in ISO 15512 PLASTICS - DETERMINATION
OF WATER CONTENT.
A defined amount of an analytical salt is heated to 150 ° C. in the closed reactor, thereby
ensuring complete evaporation of the entrapped water. The salt used is sodium molybdate
dihydrate, the crystal water content of it is 14.89 mass%.
The salt is weighed with an analytical balance, the resolution of the scale is 0.01 mg, the
accuracy +/- 0.03 mg, so the accuracy of the water weighed is 0.03 mg x 0.1489 = 0.005 mg.
The traceability of this method is based on a tested scale with which the calibration salt is
weighed.
The average results must be within a tolerance range.
The allowed values are:
0.1 mg in a range of from 0 mg to 10 mg of water,
0.2 mg in a range of 10.1 and 20 mg of water and
0.3 mg in a range of 20.1 and 30 mg of water.
The absolute limit of 0.1 mg for a sample weight of 10 g is equal to the relative limit of 0.001%
= 10 ppm.
The absolute limit of 0.1 mg for a sample weight of 20 g is equal to the relative limit of
0.0005% = 5 ppm.
The recommended time until the next calibration is
1 year with continuous use,
2 years with regular use,
2-3 years for occasional use.
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Maintenance of the HydroTracer
During the measurement some volatile constituents are released from the sample material,
e.g. paraffin or plasticizer. Depending on the condensation point and the measuring
temperature, these substances are separated off at the cooler locations of the reactor and
should be removed.
Therefore it may be necessary to clean the
reactor when the significant deposits are
visible to the naked eye.
Important: Check the O-Ring regularly for
deposits!
To do this, switch off the power, open the
reactor and take out reagent tray and
sample tray.
Use a paper tissue, wetted with pure alcohol
(moist but not dripping) and wipe over the
soiled spots. Especially the reactor- surface
opposite to the sample tray can be cleaned
this way.
The pipes are cleaned best with a test-tube
brush (see picture). Put in the sample tray to
avoid contamination of the heating plate.
Afterwards, check the O-ring. No dirt
particles may remain on the sealing.
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If the reagent was dispersed involuntary in the whole reactor, it is also recommended to clean
the reactor. If the powder is only below the reagent tray in some quantities, just pull out the
cables, open the reactor, take out reagent tray and sample tray, turn the instrument on the
top and let the powder fall out.
After the cleaning a dry run should be performed.
Dry Run
When should a dry measurement be carried out?
We recommend this action if,
-
the HydroTracer has not been used for a period of several days
was not stored completely closed
the HydroTracer has been cleaned before
the measuring range was exceeded during a measurement
How do I perform a dry measurement?
The procedure is analogous to an actual measurement, with the difference that no sample
material is filled in. For material density and weight, please enter 1 and set the heating
temperature to 210°C.
What should I do if the sample tray is tight?
If the HydroTracer is not yet on standby temperature or still switched off, it is often very
difficult or impossible to detach the sample tray from the counterpart. Switch on the
HydroTracer and/or wait about 10 - 15 minutes, so that the reactor can heat up.
CAUTION: Do not forcibly loosen the sample tray. This can lead to mechanical defects in the
reactor or closure system.
Storage
How the HydroTracer should be stored if I do not want to carry out further measurements?
After finishing your last measurement, remove the sample material and the used reagent. Add
a little fresh reagent to the reagent bed and close the HydroTracer completely. This measure
ensures that the reactor space always remains dry.
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System requirements
What are the minimum requirements to run the control software of the HydroTracer on a
PC?
The current control program of the HydroTracer runs under Windows XP (check in individual
cases), Windows 7, Windows 8, Windows 8.1 and Windows 10.
RAM size should be 1 GB or more. A USB-port to connect the HydroTracer is necessary.
Export of measurement results
The measurement data of every test is stored twice: Once as a line in a table in ".txt" format
and as a container file in ".zip" format. This file contains the measurement report as ".html"
file including diagrams. The report may be used as proof of the materials condition against
third parties.