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Contract Number:
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Design Number:
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| Library File Number: | Submitted Date: 11/20/2012 |
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SR/Terminal/Vessel: M/V Yakima |
Region: WSF |
| Contract Title: M/V Yakima, Thrust Bearing Damage, October 7, 2011 and January 6, 2012 | |
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EXPERIENCE: Describe the particular situation or event. The reduction in service in the San Juan Islands from October 7-17, 2011 was caused by the removal of the MV Yakima from service due to the failure of the No. 1 end thrust and journal bearings. Through the investigation process it was found that on September 26, 2011 excessive vibration was noticed on number 1 end while that end was being used as the bow. Efforts were made to reduce the vibration and the vessel remained in service until divers could be scheduled to make an underwater inspection. The vessel was given an early tie-up on the evening of September 27, 2011 to perform this dive survey. During the underwater inspection the divers discovered that the lower pintle nut access plate on the rudder which is normally welded to the rudder itself had been partially torn away from its welds. The ruptured pintle nut cover was affecting the flow of water to the propeller, causing turbulence in the water flow as it passed by the rudder. At the time of the inspection, the divers were not prepared to affect a repair or remove any steel under the water. The removal of the ruptured metal had to be delayed. The divers were rescheduled and on October 1, 2011 at which time the ruptured plate was removed. Subsequently, the vibration was eliminated. Shortly after the removal of the ruptured access plate, the vessel received the oil analysis report findings that there was possible oil contamination in the thrust and journal bearings. The failed pintle nut access plate on the No. 1 end rudder resulted in excessive vibration of the propeller shaft and associated thrust bearing. This excessive vibration caused severe scoring of the Babbitt on the pulling shoes of the thrust bearing. Because the thrust bearing shares a common housing and lubrication system with the journal bearing, the failed Babbitt material of the pulling shoes resulted in cross-contamination of the journal bearing lubrication oil. The cross-contamination, in turn, caused damage to the lower half of the journal bearing. The pintle nut access plate that failed was removed and the vessel was returned to service on October 17, 2011 . |
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LESSON: Describe what knowledge was gained from the experience. The thrust bearing and journal bearing are located in a single housing. The thrust bearing and journal bearings are splash lubricated; as the shaft turns, oil is carried around the bearing by the rotating shaft eliminating the need for a lubricating pump. There is a lube oil cooling pump within the system; this pump is independent of the bearing lubrication system and is only used for bearing lube oil cooling. The lube oil cooling circuit has an inline filter, but due to its independent system, the filter would not prevent Babbitt material from circulating from the thrust shoes to the journal bearing. Since both bearings are internal to the same housing, cross-contamination of all surfaces is inevitable when the bearing Babbitt fails and migrates. |
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RECOMMENDATION: Describe how the knowledge gained can be used. Excessive vibration caused the initial failure which was compounded by shared housing/lubrication system. When inspecting vibration on similar vessels, check also the condition of the thrust and journal bearings. |
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Project Delivery Method: Design-Build Design-Build Phase: Operations |
Categories: Engine |
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