A maker of smoke-stack sampling equipment for power and process industries needed some help meeting the U.S. Environmental and Protection Agency’s rules.

Under the Clean Air Act, the EPA requires all coal-fired electric generating plants to monitor and report mercury emissions from their stacks. Coal-fired plants are the single largest source of mercury emissions in the country. To meet the requirements, accurate measurement devices are a necessity.

The amount of monitoring needed at a particular source plant is a function of its current output levels. In some cases, high levels of mercury emissions require continuous monitoring. Accurate measurement is most critically affected by one thing: the amount of moisture content in the gas. It is imperative to keep the sampling draw on the stack gas above the dewpoint to prevent condensation and measurement variance. NIST–traceable calibration standards from the National Institute of Standards and Technology are used for maximum accuracy, and readings are taken based on a dry-standard cubic-meter basis for the gas sample.

A power plant specified single-end tubular heaters from Pittsburgh-based Chromalox to keep the stack-probe gas temperature sampling tube dry and the measurement error-free. The design also extended probe life by protecting against corrosion that could be caused by condensation. For continuous monitoring operation environments, using heaters like those from Chromalox could make the difference between the ability to ratify compliance data without interruption and having a gap in data recording due to a failure that could result in costly fines to the site owner.

For more information on Chromalox heat and control products, go to www.chromalox.com.