Back to basics

What are Keys to Steam Purity Monitoring?

By William Harfst


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Welcome to our GWi | Ultrapure archive of more than 2,200 articles. This month’s article is by William Harfst and was originally published in January 1997 as a part of our Back to Basics series. Mr. Harfst examines steam purity and ways to monitor it in power plant and in industrial plants using boilers.

Maintaining the integrity, reliability, and efficiency of steam turbines, super heaters, and heat exchangers requires a source of high-purity steam. Steam of inferior quality can result in costly downtime caused by corrosion, solids deposition, and fouling of this equipment. Fortunately, these problems can be prevented by routine measurement and monitoring of steam quality.

Steam Contaminants

Boiler water contains dissolved and suspended impurities. These solids are introduced into the boiler from the feedwater, or added via the chemical feed system. As steam is generated, it separates from the bulk of the boiler water where it exits through the main steam header. Under these conditions, the steam is pure (that is, it does not contain any of the dissolved or suspended solids present in the boiler water. In actual practice, however, steam separation is not 100% efficient. Some of the boiler water becomes entrained or carries over with the steam, resulting in its contamination with boiler water impurities. 

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