Chemical Cleaning of Generator Stator Windings
(Room G105, Auditorium Centre, First Floor)
10 Jun 15
4:00 PM
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5:30 PM
Tracks:
Theme: Grid Support with Data & Generators
Large turbo generators employ direct water cooling through hollow conductors to transfer heat away from within the stator bars. Various circumstances can lead to plugging of these hollow conductors when existing copper oxides are being mobilized.
Hollow conductor plugging results in reduced cooling capacity, which in turn can lead to various problems. These range from reduced insulation lifetime over downrates to catastrophic failure. While finding the root cause should be the first priority, restoring the system to full cooling capacity often takes precedence if plant is being limited by the plugging, or if complete plugging of some hollow conductors is imminent.
There are two methods to restore full cooling capacity which each have their time and place: Mechanical and chemical cleaning methods. Sometimes both are necessary for successful removal of oxide plugging. Both methods are described in some detail, along with their areas of application.
Mechanical cleaning methods often require bespoke tools and highly customized methods. In other words, they usually involve a certain degree of improvisation.
Chemical cleaning comprises acid cleaning methods derived from boiler cleaning, or methods employing complexants. The latter include state-of-the-art, specialized processes, and while it was shown that some acids employed in acid cleaning are highly aggressive on system materials, such as copper.