The Nationwide Transportation Security Board of the USA (NTSB) revealed “Safer Seas Digest 2023”, which incorporates plenty of incidents which can be of curiosity to IMCA members. IMCA stories considered one of them.
What occurred?
An offshore provide vessel was conducting sea trials after a protracted interval of upkeep, when its no. 3 foremost diesel generator engine suffered a mechanical failure that resulted in a hearth within the engine room. The crew extinguished the hearth earlier than it may unfold all through the vessel. There have been no accidents nor air pollution reported, however harm to the vessel amounted to round $1.1 million.
Throughout the upkeep interval, service technicians recognized a standard-sized connecting rod bearing on the no. 3 foremost engine that didn’t meet the service firm’s specs and, in accordance with their coverage, changed all of the connecting rod bearings with standard-sized bearings. Additionally they eliminated and inspected the no. 6 foremost bearing, which, unbeknownst to them, was undersized with a smaller internal diameter.
As a result of not one of the connecting rod bearings they changed had been machined, the technicians used standard-sized bearings to exchange the no. 6 foremost bearing, because it was the service firm’s expectation that each foremost bearing journals and connecting rod bearing journals could be machined on the similar time. There was no document of the primary bearing’s half quantity within the service technician’s notes; due to this fact, the technician seemingly didn’t determine and document the half quantity. The service firm’s commonplace follow was to exchange any eliminated bearings with new bearings, so a brand new standard-sized bearing was ordered and put in.
After upkeep was accomplished, sea trials had been scheduled to check and make sure the correct operation of the vessel’s engines, propulsion programs, and automated energy administration system. Throughout the exams, with the 2 stern thrusters about 75% load, and the no. 3 foremost engine about 30% load, the engineering crew within the ECR heard a “giant bang” and noticed smoke within the engine room. No. 3 foremost engine skilled a catastrophic mechanical failure. The no. 6 foremost bearing’s incorrect measurement allowed lube oil to leak from the bigger clearances of the bearing within the no. 3 foremost engine, thus reducing the lube oil provide stress to the adjoining nos. 9 and 10 connecting rod journal bearings. The lack of lube oil provide stress resulted in a fast temperature enhance of the connecting bearings and subsequent fracturing of the bearing cap bolts on the nos. 9 and 10 connecting rods. Consequently, a number of engine elements broke free whereas the engine was working. These elements had been strewn concerning the crankcase, blew open the inspection cowl and a part of the engine block, and allowed scorching oil and fuel to begin a hearth within the engine room.
The crew’s response to the hearth was well timed and efficient. They shortly stopped the working engines, remoted all gas provides, shut down engine room air flow programs, and closed the area’s air dampers and watertight doorways to successfully starve the hearth of gas and oxygen, thereby stopping its unfold. After the captain known as for assist, tugboats shortly returned to the vessel to help it because the crew fought the hearth. Moreover, the crew activated the vessel’s mounted CO2 fireplace extinguishing system, which successfully diminished and smothered the hearth.
What was the (possible) trigger?
Investigation revealed that the possible explanation for the mechanical failure of the no. 3 foremost engine and ensuing fireplace was the substitute of a crankshaft foremost bearing with an incorrectly sized bearing throughout a earlier engine overhaul. Engine service technicians didn’t accurately determine the eliminated bearing’s half quantity, which resulted within the lack of lube oil stress in adjoining connecting rod bearings.
Lesson
When upkeep is carried out, appropriate substitute of equipment elements is important to making sure protected and dependable vessel operation. Vessel crews and gear producer technicians ought to fastidiously determine and doc half numbers of all elements faraway from shipboard gear. Monitoring programs are an efficient type of record-keeping that can be utilized to make sure correct substitute half choice for reinstallation.
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