Measuring moisture in blanketing gases
To prevent oxidation of the metal product, inert blanketing gases are required during the heat treatment of steel. At heat-treating temperatures, moisture and oxygen will react with the metal to form an undesirable metal-oxide coating on the steel. The blanketing gas purges the oven of ambient air, thereby removing the moisture and oxygen found in it. Occasionally, the blanketing gas itself will contain an unacceptable concentration of moisture. When this problem occurs, the blanketing gas will fail to perform its needed function, resulting in a loss of product quality.
Monitoring the moisture concentration of the blanketing gas entering the furnace provides a very useful quality control parameter and a safeguard against poor-quality blanketing gas. Common blanketing gases are nitrogen, argon, and hydrogen. They are fed to the ovens at moderate pressures, so a quartz crystal-based analyzer is a good option for moisture analysis.
Moisture content measurement
The sample gas for the analyzer is taken from the blanketing gas line just before it enters the heat-treatment ovens and the moisture content is monitored accurately, directly, and continuously. Quality control parameters based upon concentration are more reliable than dew point parameters, which were pressure dependent and the high accuracy of a quartz crystal analyzer enables a tightening of the moisture allowance specification in the blanketing gas, resulting in greater operator confidence in both the gas supply and the analyzer.
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