St. Lucie cleans turbines with water-jetting technique
Florida Power & Light Co.?s (FP&L) St. Lucie power plant, a two-unit, 1,700-MW nuclear electric generating facility, selected Applied Radiological Control Inc. (ARC) for its turbine component cleaning project in preparation for non-destructive examination. The decision was made after extensive evaluation of cleaning principles and methods, non-destructive examination of metal substrates and a full-scale demonstration of ARC?s ultra high pressure (UHP) water-jetting process.
OA key advantage of UHP cleaning is that the lower casing, fixed blades and seal areas can be cleaned in place, which results in significant time and labor savings,O said Ronnie Ball, St. Lucie mechanical maintenance department head. OAlso, the potential for component damage due to multiple lifts is mitigated by using the overhead crane exclusively for the initial disassembly and final reassembly lifts. We achieved even greater savings because the secondary clean-up of grit, dust and residual abrasive contamination was completely avoided.O
Abrasive blasting creates large quantities of solid waste for disposal and can erode substrates or compromise the structural integrity of the material. The mixture of spent blast media and material usually requires special disposal or recycling procedures, as well as secondary cleaning. The UHP process uses high-velocity water jet streams at pressures up to 40,000 psi, with multi-orificed water jets positioned at various angles, rotating up to 3,000 rpm for maximum cleaning efficiency. For enhanced cleaning capability, a proprietary abrasive can be used in the water jet.
Since there were no radiological concerns, ARC cleaned the components in the open, with welding curtains protecting other crews from back-spray and mist. No sizable containment was required. After non-destructive examination of the two LP rotors revealed indications of potential problem areas, a walnut shell blasting method was unsuccessfully used to remove a heavy layer of protective cosmoline from two spare LP rotors. Cosmoline, used to protect turbine rotors during long storage periods, was then removed using UHP before installation. OWith ARC?s help, Florida Power & Light was able to complete the outage in 35 days,O said B.R. Nichols, FP&L project supervisor. OI would recommend water blasting over standard grit blasting. It saves set-up time, transporting turbine components to a blast tent area and clean-up time after the work is complete.O
Highlights of the project included:
Y Two original LP rotors were cleaned within 30 hours.
Y Cosmoline was removed from both replacement rotors within 28 hours.
Y In-place cleaning of the lower casing, fixed blades and seal areas was successful.
Y Component cleaning included horizontal joints, blade rings and stationary blading.
Y The project was performed within the schedule and budget, in less than 1,000 man-hours.