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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 Sealth |
Region: WSF |
| Contract Title: M/V Sealth, Shaft Bearing Failure, February 3, 2010 | |
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EXPERIENCE: Describe the particular situation or event. On Tuesday January 5, 2010 at 2:40pm while the MV Sealth was westbound to Friday Harbor the engine room crew of the MV Sealth received a call from the ship's captain indicating that he had been seeing an anomaly in the ship's shaft tachometer in the pilot house. At this time the engine room crew noticed that the No.2 engine room had begun to fill with smoke. The Assistant Engineer entered the engine room to investigate the source of the smoke and found that bearing E2-1 was on fire. He quickly extinguished the fire. The Chief Engineer secured the No. 2 Main Engine and disconnected the output shaft clutch. Chief Engineer and Assistant Engineer did an initial survey of the bearing and found that bearing E2-1 had suffered a catastrophic failure. The vessel continued on to Friday Harbor operating with the No. 1 main engine supplying power to both ends and then offloaded passengers. The vessel was then removed from service and sent back to the Anacortes Terminal. Repairs where completed to the broken shaft and failed bearing on January 13, 2010. On January 14, 2010 sea trails where conducted in Elliot Bay to determine the effectiveness of the repair. Upon the completion of the sea trials, the Sealth was returned to the San Juan Island ferry routes on January 15, 2010. |
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LESSON: Describe what knowledge was gained from the experience. The investigation found that the E2-1 bearing failed as an unintended consequence of the alteration of the E2-1 bearing housing. The alteration was an effort to keep the bearing outer race from spinning in its housing. Severe heating of the shaft locally under the inner race of the failing bearing, and subsequent loss of strength, was concluded to have been the major contributor to failure of the shaft. |
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RECOMMENDATION: Describe how the knowledge gained can be used. Restricting the motion of a double spherical roller bearing by clamping its outer race is not advisable. This type of bearing is primarily intended for radial loads, and has limited capacity for thrust loads. Therefore, the outer race of this type bearing must be loose enough in its housing bore to slide freely under axial loads. The outer race of this type of bearing is prone to rotate in its housing because of this looseness, particularly when exposed to serious vibrations that are typical of diesel applications. Where outer race rotation is evident, it is recommended to check the bearing housing for significant vibration levels, such as: a) If there are strong 1/rev vibrations which could be caused by dynamic unbalance of the flywheel and Geislinger coupling combination, and is correctable by in-place balancing. b) If there are strong engine firing frequency vibrations which could be caused by loose engine mount bolts, and are correctable by are-torque of the foundation bolts. c) If neither of these checks indicates an unusual condition, it may be that this particular bearing, so close to the engine, is just prone to suffer outer race rotation and needs periodic replacement. |
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Project Delivery Method: Design-Build Design-Build Phase: Operations |
Categories: Engine |
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