|
Contract Number:
|
Design Number:
|
| Library File Number: | Submitted Date: 11/20/2012 |
|
SR/Terminal/Vessel: M/V Kittitas |
Region: WSF |
| Contract Title: M/V Kittitas, Failure of the Controllable Pitch Propeller Telescoping Oil Tube, On October 16, 2010 | |
|
EXPERIENCE: Describe the particular situation or event. On Saturday, October 16, 2010 at approximately 2:30 p.m. on a voyage from Mukilteo, WA to Clinton, WA, the M/V Kittitas experienced a failure of the Controllable Pitch Propeller (CPP) on the #1 end of the vessel. The vessel was able to land at the Clinton Terminal without incident and unloaded its passengers and vehicles. The vessel was removed from service and the U.S. Coast Guard was notified. On October 17, M/V Kittitas was towed to Todd Pacific Shipyard in Seattle, WA. The vessel was subsequently required to be dry docked. The vessel’s #1 end CPP and its associated oil tubing were removed for inspection. During the course of removal and inspection of the CPP and the oil tubing it was discovered that the outer oil tube was completely fractured at approximately seventy five inches from the forward end of the CPP assembly. During the emergency dry docking of the vessel in November of 2010 a new outer oil tube section was fabricated with improved design modifications and installed on the vessel. The vessel was returned to service on December 1, 2010. The cost to repair the M/V Kittitas in material and labor was $660,041 and 23 days of service were lost. |
|
|
LESSON: Describe what knowledge was gained from the experience. The fractured outer oil tubing was removed and the failed sections of tubing were sent to a lab for a full metallurgical analysis. The analysis determined that the oil tube failed due to high-cycle/low-stress fatigue. The lab concluded that there were three distinct fatigue failure origins (at the 0, 90, and 270 degree positions relative) in the oil tubing. Each of these fatigue cracks had initiated at the toe of the fillet weld that attaches the “spiders” to the tube (Spiders are small rectangular pieces of metal that are welded to outside diameter of the oil tubes and function as a riding or bearing surface for both inner and outer oil tubes as they move axially within the intermediate and tail shaft bores when the blades are pitched.) The initial fatigue cracks were caused by improper temperature control during the original welding and manufacturing of the outer oil tubes. The three fatigue cracks expanded circumferentially until they coalesced into a secondary fatigue crack that ultimately caused the oil tubing to completely fail and separate. The analysis, along with maintenance records obtained from archives, determined that the failed section of oil tubing had been in operation for at least 17 years. Additionally, there is a very real possibility that the oil tubes may have been in service as long as 20 years, when the M/V Kittitas was upgraded from an Issaquah 100 Class ferry to Issaquah 130 Class ferry in 1992. |
|
|
RECOMMENDATION: Describe how the knowledge gained can be used. Over time, insignificant errors may have a higher rate of failure. Keeping good records of construction may be helpful in diagnosing these failures |
|
|
Project Delivery Method: Design-Build Design-Build Phase: Operations |
Categories: Engine |
|
Share this Lesson |
|
|
For assistance with Lessons Learned, or if you have questions or comments, |
