The EUROX® measurement system for extractive measurements on tin baths can detect smallest amounts of oxygen and determine several characteristic values like the dew point temperature. The gas to be investigated is heated up and catalytically decomposed. After reaction the oxygen content is measured at equilibrium and converted.
Up to 8 measuring points along the tin bath can be observed and analysed with one EUROX® TB-System.
EUROX® TB-System includes a solenoid valve unit for switching between the connected measuring points and a measuring unit including an OM-4 multifunctional unit for evaluation, controlling and visualisation. The measuring system can be connected with the PLC, so controlling and visualisation can also be done via PLC.
Visualisation of EUROX® TB-System is done via visualisation unit of OM-4 and via PLC. Evaluation is also done via OM-4 multifunctional unit.
Adapted to the application and number of observed measuring points, all evaluated values are presented.
The following evaluations can be offered:
Dew point measuring in tin bath
The dewpoint temperature – based on an equilibrium of oxygen, hydrogen and water steam in the tin bath atmosphere – is calculated after measuring the oxygen content in the atmosphere.
Oxygen partial pressure measuring in tin bath
Also a HORN created key figure of the atmosphere based on the tin, oxygen and tin oxide is defined. This gives the controller a quick and scientifically sound statement about the overall state of the atmosphere and its effect on the tin bath.
Oxidation-State
The oxygen partial pressure in the tin bath atmosphere is measured and related to temperature dependent tin/tin-oxide equilibrium curves. This indicates the degree of oxidation of the tin bath surface.
The oxidation – state is defined as 1 on the tetravalent tin / tin oxide equilibrium curve. When the measured oxygen partial pressure is higher than the tetravalent equilibrium curve, then also the oxidation state is higher than 1.
Hydro-State
Hydrogen in the atmosphere does not only reduce the oxygen in the atmosphere, it can also reduce tin oxide to tin and water. The quotient water to hydrogen is a measure of the potential of this reaction.
The water content in the atmosphere can be calculated and related to the H 2 content. So the Hydro
– State is defined. This indicates a reasonable range of the H 2 content, but also gives an indication about the water content in the tin bath and thus also about the dissolved water content in the liquid tin.
If the measured quotient is equal to the temperature dependent maximum, the state is by definition equal to one. If it is less, then it is less than 1.
Comparison
All three characteristic values are compared according to their measurement location. If the dew point at the beginning of the tin bath indicates an air ingress, the oxidation - state shows that no significant oxidation of the tin bath takes place due to the high temperature in this area.
At the other end of the tin bath, however, the degree of oxidation is increased, which is mainly due to the low temperature.
However, the fact that the hydro-state is far below 1 in the entire tin bath shows that the protection of the liquid tin is given and could even be reduced somewhat, which would have a positive effect on the operating costs.
To avoid oxidation of the liquid tin in tin baths of float plants what would cause glass defects it is important to analyse and control the atmosphere in the tin bath. With the EUROX® TB-system up to 8 selected measuring points per measuring system along the tin bath can be monitored with just one sensor.
EUROX® sensors measure even at very low oxygen partial pressure. The gas to be investigated is heated up and catalytically decomposed. After reaction the oxygen content is measured at equilibrium and converted.
