L48/60CR

## 30,000-hour Major Overhaul Workflow (per anonymized service report) Typical scope: 2 weeks per engine, all 9 cylinders or selected cylinders by inspection. Performed at yard or in-port with engine cooled and isolated. ### 1. Cylinder Heads - Dismantle from engine, transport to workshop - Recondition Valve Seats and Valve Spindles by special machine - Inspect Valve Guides, Springs, Injector Sleeves; clean - Disassemble Valve Rotators (intake + exhaust); replace worn parts; reassemble - Pressure-test each head (must show no leakage) - Reassemble with **new O-rings and Seal Rings** - Install in place; tighten per MAN-ES manual specs ### 2. Rocker Arm Casings - Dismantle, clean, visual inspection - Install with **new seal rings**; tighten to specified torque - Readjust Valve Clearance per manual; lock ### 3. Piston Connecting Rods - Dismantle pistons, disassemble, clean - Check Piston Groove Height (must be within wear limit) - Penetration test on Piston Skirts (no abnormality acceptable) - Inspect Piston Pins (Gudgeon Pins) - Inspect Conrod Small End Bushes — scratches indicate LO contamination - Reassemble with **new piston rings** (Top, Sec, Oil) - Tighten Con-rod Small End nuts per manual - Verify Bolt Elongation ΔI within specified range ### 4. Cylinder Liners - Clean; measure diameter (must be within wear limits) - Hone internal surface to restore running geometry - Replace **Top Land Rings** with reconditioned spare parts ### 5. Crankpin Journals & Bearings - Open up requested bearings (typical: 1-2 bearings per overhaul as sample inspection) - Inspect crankpin journal at TDC + BDC positions - Polish bearing if scratches found (LO contamination signature) - Reassemble with bolt elongation check within range ### 6. Main Bearings - Open up sample main bearing - Inspect Main Journal - Polish bearing if scratches found - Verify **Crankshaft Deflection** at all units - Verify **Axial Clearance** - Reassemble; bolt elongation check ### 7. Camshafts - 9 sections incl. bearings — clean and inspect each - Document scratches/seizures (especially on intake cams + rollers) - Verify Camshaft Bearing Clearance within wear limit - Polish minor scratches; replace seized components ### 8. Control Drives - Open Control Drive Case cover; visual inspection - Verify Camshaft Drive Gearwheel + Intermediate Gearwheel + Crankshaft Gearwheel surfaces - Check gear backlash (must be within range) - Verify lubrication injection nozzle clear with priming pump running ### 9. VVT Control (Variable Valve Timing) - Test with hydraulic pump running - Verify VVT Cylinder + Shaft activate sensitively in manual mode ### 10. Fuel Injection Valves - Dismantle requested valves, disassemble, clean, inspect - **Replace Nozzles + Pressure Springs as standard** - Adjust Opening Pressure on test rig - Reassemble with **new O-rings and Seal Rings** - Clean Fuel Injection Pipes; install with new sealing rings - Scrap entire valve if nut corrosion found ### 11. Engine Test - Fill cooling water; verify no leakage - Clean oil sump thoroughly - Start priming pump; verify LO flow at all main bearings, crankpin bearings, pistons, camshaft, rocker arms - Start engine at rated speed (~500 RPM) - Open crankcase covers for inspection at 5/10/30 minutes idle - Verify CR-system pressure values, lube oil pressures + temperatures within normal range ## Post-overhaul recommended re-checks (after 500 running hours) - Conrod Nuts (re-torque check) - Big End Nuts (re-torque check) - Valve Clearance (readjust if needed) - Crankshaft Deflection (verify alignment held) ## Critical operating recommendation **Lube Oil Purifier must remain in continuous operation.** Most documented failure modes (bearing scratches, cam seizure) trace directly to LO contamination. Idle purifier = accelerated wear.