Project
Neptunus successfully carried out a breakdown major overhaul and crankshaft replacement of a NIIGATA 8L-28HLX main engine with approximately 31,589 running hours.
Prior to dismantling, the engine was found seized and difficult to rotate. Heat marks were observed on crank pin No. 8 and main journal No. 9, indicating a possible bearing or lubrication-related failure. Since the engine was already seized, operating parameters could not be recorded before dismantling.
The overhaul included detailed inspection, cleaning, calibration, component renewal, crankshaft replacement, reassembly, alignment, chockfasting, pre-commissioning, and sea trials. Major activities included renewal of the crankshaft, main bearings, connecting rod bearings, cylinder head valves, valve guides, valve seats, piston rings, connecting rod components, fuel injection pump components, fuel injectors, air starting valves, pump components, vibration damper components, intermediate shaft bearing, and associated seals and gaskets.
All cylinder heads were cleaned and inspected, with Dye Penetrant testing and hydro pressure testing carried out. The engine block underwent Magnetic Particle Inspection, while piston crowns and connecting rods were subjected to DP testing.
Cylinder liners were removed, cleaned, honed, and calibrated. Main bearing line boring and surfacing of the main bearing caps were carried out. Main bearing cap No. 9 was renewed, followed by line boring and alignment checks.
The existing crankshaft was removed and replaced with a new crankshaft assembly in accordance with OEM recommendations. Crankshaft deflection, thrust clearance, main journal dimensions, crank pin dimensions, bearing clearances, camshaft clearances, piston ring clearances, valve clearances, gear backlash, and intermediate shaft alignment were checked and recorded.
The engine foundation and plummer bearing arrangement were also attended, including chockfasting, bearing renewal, intermediate shaft run-out checks, and laser alignment.
Following reassembly, comprehensive pre-commissioning checks were carried out. A sea trial was conducted up to 750 RPM, with engine parameters monitored throughout the trial. The engine performance and recorded parameters were found satisfactory, with no leakages observed.Neptunus successfully completed the breakdown major overhaul and crankshaft replacement of a NIIGATA 8L-28HLX main engine with approximately 31,589 running hours.
The engine was found seized and difficult to rotate before dismantling, with heat marks observed on crank pin No. 8 and main journal No. 9. The overhaul therefore included detailed inspection and renewal of critical engine components, along with crankshaft replacement.
Major activities included renewal of the crankshaft, main bearings, connecting rod bearings, cylinder head valves, valve guides, valve seats, piston rings, connecting rod components, fuel injection pump components, fuel injectors, air starting valves, pump components, vibration damper components, intermediate shaft bearing, and associated seals and gaskets.
Critical inspection and calibration activities included cylinder head DP and hydro testing, engine block MPI, piston crown and connecting rod DP testing, crankshaft deflection measurement, main journal and crank pin measurement, main bearing line boring, piston pin measurement, piston ring and groove clearances, rocker arm clearances, camshaft clearances, gear backlash, intermediate shaft run-out, and laser alignment.
The engine foundation and plummer bearing arrangement were attended through chockfasting, bearing renewal, foundation bolt tightening, and alignment checks. Following reassembly and pre-commissioning, the engine successfully underwent a sea trial up to 750 RPM. Engine performance and operating parameters were found satisfactory, with no leakages observed.
A freshwater temperature-regulating valve malfunction identified during the trial was rectified, after which the engine temperature returned to normal and remained within permissible limits.
Following successful testing, the engine was handed over with recommendations for close monitoring during the first 100 operating hours, post-overhaul lube oil analysis, filter inspection, bearing temperature monitoring, and rechecking of main bearings No. 1, No. 5, and No. 9 after 1,000 running hours.Leave a Reply
