Video: Rapidox 2100-FGA

Video transcript

What forming gas is, why this analyser reads its moisture through oxygen, and how to install the sensor, calibrate it and read it. Forming gas, usually 5% hydrogen in nitrogen, protects metal in the furnace. What spoils the work is water: at furnace temperature it splits, and the oxygen stains and scales the parts. That is why atmospheres are specified by dewpoint. This analyser goes to the cause. A zirconia sensor measures the oxygen directly,

down to 10 to the minus 30 parts per 1000000. With the hydrogen content entered, it solves the equilibrium and gives the dewpoint. 10 to the minus 30 parts per 1000000 up to 30%, a response under 4 seconds, one percent of reading, and more than 17500 hours of sensor life. Above 660 degrees, the calculation takes the temperature from the type K thermocouple, so its tip must sit in the forming gas, right beside the sensor. On the front: the display with oxygen, dewpoint and hydrogen, the five-pin sensor socket,

the auxiliary socket for a pressure or vacuum transmitter, and the keypad. At the back: oxygen and auxiliary outputs, two alarm relays, the thermocouple input, the serial port and the mains inlet. The sensor screws into an M 18 port in the furnace wall, with its rear in fresh air, on a cable of up to 25 metres. The thermocouple goes beside it, and the optional pressure sensor at the same point. Or the gas is brought to the sensor in a manifold: half a litre to a litre per minute,

with a metre of outlet tube so room air cannot mix back in. Stainless, high pressure and vacuum versions exist. At switch-on it heats and cleans the sensor, in about a minute. Allow half an hour to settle, and check the hydrogen content first: the dewpoint is only as right as that number. Hydrogen mode is for pure hydrogen, vacuum mode reads the sensor as a vacuum gauge, and with a pressure sensor, auto correction keeps oxygen and dewpoint independent of pressure.

Calibration follows 5 points, from fresh air down to 10 parts per 1000000. Three are set in the factory; the two in between can be recalibrated with your own gases. Each point uses a gas of known oxygen, flowing at a litre a minute near ambient pressure. Enter the value, wait for a steady reading, and hold enter for two seconds. The R squared value shows the quality. Auto cleaning burns off soot at every start,

and the pre-calibrated sensor can be swapped on site. Two things it must never see: SF₆, which destroys zirconia, and flammable mixtures such as hydrogen in air. For the plant: voltage and current outputs for oxygen and dewpoint, with a logarithmic scale available, two alarm relays that can even watch the dewpoint, and Modbus RTU. The supplied software mirrors the display, configures everything remotely and logs every channel. In a furnace run, oxygen and dewpoint move together, exactly as the analyser assumes.

Heat treatment of metals, annealing, sintering and brazing, protective atmospheres and research: on the bench, in a 19 inch panel, or in an IP 65 wall housing. Gas analysis, from Amperis.