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Contract Number:
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Design Number:
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| Library File Number: | Submitted Date: 11/26/2012 |
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SR/Terminal/Vessel: M/V Tacoma |
Region: WSF |
| Contract Title: M/V Tacoma Investigation of Crankshaft Damage #1 Main Diesel Engine, December 8, 2011 | |
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EXPERIENCE: Describe the particular situation or event. On December 8th 2011, at approximately 0620, the #1 main engine on the M/V Tacoma developed a "knock" emanating from the base of the engine. At the time that the "knock" was detected the vessel was in the final stage of approach/vessel landing at the Bainbridge Island Ferry Terminal. Due to maneuvering, the engine continued in operation for approximately three minutes, so that the vessel could safely complete the landing. Once the vessel was secured at the Bainbridge Island terminal, the engine was shut down. The initial inspection made by the vessel's engine crew revealed that the connecting rod bearing for the #2 and #10 cylinder shaft failed, this failure subsequently caused significant damage to the corresponding crank pin journal. The damage rendered the engine inoperable. However, because the Mark II class vessels are designed with redundancy in propulsion machinery, the MV Tacoma was able to continue to operate on the sailing schedule without delay or disruption to service. The MV Tacoma was taken out of service on March 15, 2012 and moved to the Eagle Harbor Maintenance Facility to load the new crankshaft and power assemblies. On March 19, 2012, the M/V Tacoma was shifted to dry-dock at Vigor Shipyard in Seattle where the repairs were completed by Eagle Harbor machinists. |
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LESSON: Describe what knowledge was gained from the experience. During start-up of an EMD engine, the oil pressure builds quickly and then drops. After a short period of time, the oil pressure slowly builds to normal operating pressure. This initial drop in oil pressure is due to the main lube oil pump quickly depleting the lube oil strainer housing in which it draws from. The lube oil strainer housing contains two separate compartments. The lube oil scavenging pump draws oil from the engine sump through one of the two compartments of the strainer housing. The scavenging pump then forces oil through an oil filter and oil cooler before re-entering the second compartment of the strainer housing. From there, the main oil pump draws from the second compartment and supplies oil to the engine. The scavenging pump supplies a higher volume of oil than the main oil pump can draw when the engine is running. The excess oil overflows from the strainer housing back to the oil sump. While the engine is shut down, the oil is allowed to drain by gravity from the cooler through the strainer overflow, back to the engine sump. The drop in oil pressure at start-up is due to the time that it takes for the oil cooler to be filled by the scavenging pump. Under normal start-up and use of an EMD (1 start per day), this momentary loss of oil supply at start does not have a substantial adverse effect on the engine. It has been determined that when this action is repeated 10-12 times per day, the service life of the bearings is shortened. |
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RECOMMENDATION: Describe how the knowledge gained can be used. Following discussions between the Port Engineer and the Staff Chief Engineers on the Jumbo Mark II class, standing orders were implemented requiring a minimum five-minute pre-lube for the main engines prior to starting, except in emergencies. This modified operation far exceeds the pre-lube requirement published in the engine maintenance manual. Valley Power Systems has submitted the following additional recommendations: • Pre-lube engines for 3-5 minutes prior to each engine start, and continue operation of the pre-lube pump until the engine has achieved full, consistent oil pressure of at least 21 psi at the oil pressure sensor while at idle speed • Consolidate multiple starts to one designated engine per vessel • Implement a "10 second start" accessory rack plumbing, and pump/controls package to improve pre-lube and pick-up of engine-driven pump oil supply on engine expected to be required for fast startup and ramp to rated speed • Implement an annual upper rod bearing inspection program on start and stop engines to ensure bearings are replaced prior to ultimate failure |
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Project Delivery Method: Design-Build Design-Build Phase: Operations |
Categories: Engine |
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