5S50ME-GI8.5
The MAN 5S50ME-GI8.5 is a five‑cylinder, low‑speed 2‑stroke dual‑fuel main engine delivering up to 8 900 kW at 127 rpm, capable of running on HFO/MDO or LNG with instant fuel switching.
Engine Specifications
Inspector Detail
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Designation decoded
5 stands for 5 cylinders, S for Super-Long-Stroke, 50 for 500 mm bore, ME-GI for electronically controlled two-stroke engine with high-pressure gas injection (LNG), 8.5 for Mark 8.5. MEP 21.0 bar.
Background
The S50ME-GI8.5 is a dual-fuel engine of the ME-GI series, optimized for LNG operation (Liquefied Natural Gas). ME-GI uses high-pressure gas injection at approx. 300 bar within the diesel cycle — eliminating any knock risk. Mark 8.5 as an older generation. MEP 21.0 bar indicates high specific loading. Typical use in LNG carriers that use boil-off gas as fuel.
Calculated metrics
Inspector checklist
- Cylinder liners: S/B 4.0 at MEP 21.0 bar — high mechanical and thermal load, watch cold corrosion wear risk in LNG operation
- Piston rings: Accelerated wear at high MEP, different lubrication conditions in gas operation
- Cylinder lubrication: BN adjustment essential in LNG operation — gas produces no sulfuric acid
- Gas injection valves: High pressure (300 bar) — tightness safety-critical, inspect at every piston withdrawal
- High-pressure gas compressor: Condition, tightness, vibration — most critical component in the FGSS
- Gas supply system: Evaporator, pressure control, safety valves
- Gas detectors: Calibration — methane lighter than air, collects at the top
- ME control: FIVA valves, HPS/HCU, EICU
- Gas/diesel changeover: Test automatic and manual procedure
- Safety logic: Gas trip, shutdown, ventilation sequence
- Pilot fuel control: Minimum pilot quantity for ignition
- Scavenge air box: Very clean in LNG operation
- Turbocharger: Significantly less fouling with gas
- Exhaust temperature: Lower in LNG operation than diesel
- Double-wall piping system for gas: Check integrity
- Monitor ventilation of the annular space
- Cylinder head gaskets for blow-by
Logbook reference values
| Parameter | Expected | Deviation means |
|---|---|---|
| Exhaust temperature by cylinder | 310–370 °C (LNG); 350–420 °C (diesel) | Spread >15 °C → check gas/pilot injection |
| Gas injection pressure | 280–320 bar (high pressure) | Deviation → check HP compressor or injection valve |
| MEP | ~21.0 bar | Deviation → analyze combustion/injection |
| Pmax | ±2 bar cylinder balance | Deviation → check control system and pilot quantity |
| Pilot fuel share | 3–8% of total energy | Too low → ignition problems; too high → inefficient gas injection |
Common Failure Modes
Expert tips
- 💡 ME-GI with 300 bar gas injection: The HP compressor is the most critical component — redundancy and condition are top priority
- 💡 MEP 21.0 bar on Mark 8.5: High specific loading — the operating limits have little buffer, take deviations seriously
- 💡 In LNG operation: Methane is lighter than air — gas detectors near the ceiling of the engine room are decisive (unlike ethane with ME-GA)
Related components
Classification & regulatory
IMO Tier II/III-capable. IGC Code for LNG carriers. SOLAS gas requirements. MARPOL — LNG operation reduces SOx to near zero, CO2 by approx. 25% vs. HFO.
Reference content for inspector orientation. Always verify against manufacturer's manual, latest service letters and class society requirements.
Other Cylinder Configurations 36
Components & Design
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Technical Data
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