H2 /T Monitoring during the
Degassing Process in Al Melt
What is AlproH M?
AlproH M is a portable quick- measuring system for the determination of dissolved hydrogen content in molten aluminum alloys.
The system comprises of a Probe, an Analyzer (includes connecting line), and an optional Probe stand. The probe can use indefinitely until it breaks a part.
A patented PARK-RAPP probe, housed at the tip of the probe, provides an EMF output which depends purely on the hydrogen partial pressure (pH2) and temperature in the melt. The sensor is housed in a robust, impact-resistant probe constructed from special high temperature alloy and graphite, which ensures that the AlproH Palm is able to withstand the harsh environments in the Al foundry.
The sensor and temperature outputs are fed into the analyzer, which when combined with the alloy interaction parameters, gives the dissolved hydrogen concentration in units of ml/100g Al.
How it works
▲ AlproH Plam test
The technology is based on a novel solid electrochemical hydrogen sensor, so called Park-Rapp probe, which, at an elevated temperature, is able to measure hydrogen content with reference to oxygen in the air through the adoption of proton conductor/oxygen ion conductor hetero- junction electrolytes. The principle behind how it can be used to measure hydrogen concentration is described below:
An impervious section of Park-Rapp probe (yellow and grey tube) is coated with Pt electrodes on both faces. The inside of the sensor (reference electrode) is exposed to the oxygen-containing air and the other side (working electrode) is to the hydrogen gas in the melt. For this arrangement, the measured EMF of the sensor, E is expressed as
E = E0 + 9.921x10-5 T log[H2]
, i.e. it depends logarithmically on the hydrogen partial pressure at the working electrode immersed in the melt. Here Eo, and T are sensor constant, and absolute temperature, respectively.
The schematic diagram below shows how a voltage is generated across the solid hetero-junction electrolyte exposed to a given hydrogen partial pressure (pH2)
Thus the hydrogen concentration can be calculated from the measured EMF. To work out the dissolved hydrogen content in the melt, the relation between the gas partial pressure of hydrogen and its solubility for Al melt must be known. From Sievert’s law, the dissolved hydrogen content in Al melt for a given hydrogen partial pressure, S is expressed as
where S has units of ml/100gAl and T, f are absolute temperature H and alloy interaction parameter, respectively
Probe
The probe has long life time. It can be used until it breaks. But we recommend to calibrate it once in a three months or 100 times use. If it is malfunctioning by some reasons, analyzer recognizes it immediately to give a error-notice to the user.
The probe(20cm long) is equipped with a handle (40cm long) which is then electrically connected to the analyzer. Thermocouple installed in the handle acts as a reference electrode as well as temperature sensing for the WE of the sensor.
Specifications
| Measuring Range | 0.05-0.99 ml/100gAl |
| Accuracy | ±0.05 ml/100gAl or ±15% (whichever is greater) |
| Reproducibility | <0.01 ml/100gAl or ± 10% (whichever is greater) |
| Measuring Time | <5 min |
| Max. depth of Immersion | 250mm |
| Sensor Operating Temp. | 660-700 ℃ |
| Size | 120x244x46 mm |
| Weight | 600g |
Probe Stand
For the convenience and safety purposes, we recommend to use probe stand when the AlproH Palm-measurement is made by inserting the probe into the hot melt. It is made to grasp the probe firmly with grip which can move up-and-down by pull and push action. It also provides with a cooling pad which enables the temperature of the heated probe to drop rapidly after taking out the probe from the melt.
Because the probe stand is made of Al alloys, it is light in weight and easy to deploy.
Fast, Accurate, Easy to handle and Long Life
Due to the use of patented air reference electrochemical sensor along with special measuring algorithm, the probe gives a fast reading in <5 minutes and a solid firm structure can be possible to make it immune to any mechanical and physical problems.
