Fouling of steam turbine blades and vanes is a common problem. A complete and thorough cleaning would require stoppage and opening up the turbine, which may mean shutting down a profitable process. Online cleaning is possible that doesn’t require dismantling although the results are not guaranteed.
Below are excerpts from a case study, “Successful Online and Offline Cleaning of Steam Turbines With and Without Disassembly” by Bladimir Gomez Supervisor of PDVSA and Barry Snider of Small Hammer Inc. at the 43rd Turbomachinery Symposium held in Houston in 2013.
At a facility, the steam turbines driving critical compressors were losing power and speed. The governor/steam valve was unable to maintain desired rpm. Unit production reduced and revenue loss was occuring. The cause of the problem was fouling of turbine rotor blades and static guide vanes. The fouling was water soluble chemicals [NaCl, NaOH] bound with insoluble oxides [Fe, Si, Al] > 50 ppb
Fouling typically occurs in stages prior to saturation. Below are some pros and cons of cleaning methods:
Offline mechanical cleaning with aluminum oxide
Offline slow-roll soak and flush with hot water
Online Manipulation of Saturation Point
Online Water Injection into Steam at Turbine Inlet
• No disassembly
• Medium risk managing axial thrust
• No downtime for cleaning but
• Requires modifications of facilities (downtime)
• Results not guaranteed
Slow-roll soak cleaning procedure
Solid deposits of both soluble and insoluble material can be safely and effectively removed from turbine blades and guide vanes. There are removal methods available that do not require disassembly of the turbine. The key mechanism for removing the solids without disassembly of the machinery is to dissolve the soluble material thus releasing the insoluble material. This may be done by:
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