Emerson Process Management has enhanced its Rosemount Analytical Oxymitter™ to provide accurate oxygen (O2) measurements during the annealing of cold rolled metal products. Annealing is the process of heating metal products to a point when the crystalline structure is returned to normal, allowing the rework of stresses and imperfections that may have occurred during rolling. Product quality may be greatly compromised if oxidation occurs during annealing – therefore the most accurate oxygen measurements are essential.

Various types of furnaces may be used to raise the metal temperature to the level necessary for annealing, including electric and direct fired. The Oxymitter operates accurately at temperatures up to 1300˚ F (700˚ C), allowing it to be inserted directly into the furnace atmosphere.

By receiving accurate measurements from the Oxymitter, operators are able to maintain the necessary preset oxygen levels (usually 0.05 percent to 0.1 percent) to avoid oxidation. Electric furnaces maintain oxygen levels by varying nitrogen (N2) injection rates, while direct fired furnaces accomplish the same goal by adjusting the fuel-to-air ratio.

The Oxymitter yields an accuracy level of ± 0.05 percent, reducing the risk of oxidation and maintaining product quality. Other benefits of utilizing the Oxymitter for oxygen measurements during the annealing process include:

• Low maintenance costs – With the transmitter inserted directly into the furnace, there is no sampling system to maintain.
• Easy installation – Signal-conditioning electronics are incorporated into the design.
• Remote diagnostics – HART® protocol allows calibrations and diagnostics to be performed remotely, without entering the furnace atmosphere.

The HART® protocol also provides a link into Emerson's PlantWeb® digital plant architecture. Instrument technicians can interface with the Oxymitter from the operator console in the control room or any location where the transmitter's signal wires terminate. This functionality results in superior control performance, optimization of plant assets, increased plant availability and reduced maintenance cost.