When a major fossil fuel power plant in Texas prepared for a schedule plant outage, they also prepared for the heavy cost of protecting their turbines. For two to four weeks during the shutdown, the turbines and their stators and windings would be left wide open for maintenance, continuously exposed to the high heat, humidity and dust of Texas air.
Turbines can be massive, but they are also finely engineered and tooled machines that are vulnerable to environmental damage. Ferrous metals, such as iron and steel, as well as glass and ceramic components, are highly susceptible to both gross and microscopic corrosion. Microscopic oxidation and corrosion cause damage, which can develop quickly and go undetected. Both gross and microscopic corrosion can cause millions of dollars of damage to the turbine and lay the plant up for months. So, protecting the turbine, stators and windings from humidity and moisture during maintenance is critical - and expensive.
For years, the standard practice was to blanket turbines with a continuous flow of nitrogen from external tanks or nitrogen generators. Nitrogen, inert and extremely dry, provides excellent protection. However, providing the volume of nitrogen required to blanket a large turbine for weeks on end is extremely expensive, and working around high concentrations of nitrogen requires safety precautions. Another alternative, coating the turbine and components with corrosion inhibitors or grease, is less effective and requires additional days of downtime for coating and cleanup. A team of Aggreko engineers and technicians working at the site proposed a new and potentially simpler, more efficient and cost-effective approach: dehumidify the air.
