6S70ME-C10.5-GI

Common issues

• Gas injection valve (GIV) wear, leakage, or sticking due to high operating pressures and temperatures, or gas quality variations.
• Pilot fuel (HFO) injection system issues (e.g., nozzle clogging, wear) due to infrequent use or poor fuel quality when primarily operating on LNG.
• Cylinder liner wear and scuffing, particularly at the top dead center, influenced by varying fuel types (HFO/LNG) and cylinder oil selection/feed rate optimization.
• Exhaust valve burning or sticking, often exacerbated by high thermal loads and potential deposits from HFO combustion or incomplete gas combustion.
• Turbocharger fouling (compressor and turbine sides) leading to reduced efficiency and surging, especially with prolonged HFO operation or poor combustion.
• Scavenge port fouling and carbon build-up, impacting scavenging efficiency and potentially leading to scavenge fires.
• High-pressure gas pump/compressor (if part of the engine system) reliability issues, including seal failures or bearing wear.
• Control system (ME-GI specific) sensor failures, software glitches, or actuator malfunctions affecting fuel timing and combustion stability.

Inspection checklist

• Visual Inspection for Leaks: Thoroughly check all HFO, gas, lube oil, and cooling water lines, especially high-pressure gas lines (double-wall integrity) and connections, for any signs of leakage. Pay close attention to gas valve blocks and fuel pumps.
• Scavenge Space Inspection: Open scavenge ports and inspect for carbon deposits, oil ingress from piston rod glands, liner condition (scuffing, corrosion), and piston ring pack integrity. Check scavenge fire flaps for free movement.
• Cylinder Unit Condition Monitoring: Review cylinder condition reports (liner wear measurements, piston ring condition via indicator cocks or scavenge ports). Monitor exhaust gas temperatures (EGTs) for cylinder balance and potential exhaust valve issues. Check for cold corrosion signs on liners when operating on gas.
• Fuel System Integrity (HFO & Gas): Inspect HFO fuel pumps, filters, and piping. For the gas system, verify gas valve block condition, check for proper operation of gas detection systems, and ensure ventilation is adequate. Verify pilot fuel system functionality.
• Turbocharger Inspection: Check compressor and turbine blades for fouling, erosion, or damage. Inspect turbocharger bearings for play and lubrication. Monitor turbocharger speeds and pressures.
• Engine Control System (ECS) Diagnostics: Connect to the ECS to check for active or historical alarms, fault codes, and critical sensor readings (e.g., knock sensors, fuel pressures, temperatures). Verify software versions and parameters.
• Crankcase Inspection: Conduct a visual inspection of the crankcase for abnormal conditions, oil mist, or signs of bearing distress. Check main and crosshead bearing clearances if due for inspection.
• Safety Devices & Alarms: Verify the functionality of critical safety devices including overspeed trip, low lube oil pressure trip, high cooling water temperature trip, and engine room gas detection system (for GI engines).

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Cylinder liner (1-2 units)
• Piston crown and skirt assembly (1-2 units)
• Complete exhaust valve (spindle, seat, cage) (1-2 units)
• Gas Injection Valve (GIV) complete (1-2 sets)
• Pilot Fuel Valve (HFO) complete (1-2 sets)
• Full set of piston rings for at least one cylinder
• Turbocharger bearing cartridges or complete rotor assembly (1 set/unit)
• High-pressure fuel pump (HFO) elements/plungers (1 set)
• Main and crosshead bearing shells (1 set for one position)
• Assorted O-rings, gaskets, and seals, especially for fuel and gas systems
• Critical control system PCBs and sensors (e.g., knock sensors, pressure/temperature transmitters)

Safety

• Gas Leakage & Explosion Risk: High-pressure LNG poses a significant fire and explosion hazard. Ensure gas detection systems are fully operational, ventilation is adequate, and double-wall piping for gas lines is intact and monitored.
• High-Pressure Fuel/Gas Jet Fires: Leaks from high-pressure HFO or gas injection systems can result in dangerous jet fires. Emphasize proper maintenance, torqueing, and immediate reporting of any leaks.
• Hot Surfaces: Exhaust manifold, turbocharger, and other engine components operate at very high temperatures, posing burn risks. Ensure insulation is intact and personnel are aware.
• Rotating Machinery: The large rotating mass of the crankshaft, flywheel, and turbocharger presents entanglement and impact hazards. Strict lockout/tagout procedures are essential during maintenance.
• Confined Spaces: Inspections within the crankcase or scavenge space require adherence to confined space entry procedures, including gas testing and standby personnel.

Class survey

For a Doosan 6S70ME-C10.5-GI, class surveyors will typically focus on: 1. Documentation Review: Comprehensive check of logbooks, maintenance records (especially for gas system components), oil analysis reports, performance data, and class certificates. 2. Safety Systems: Witness testing of overspeed trip, low lube oil pressure trip, high cooling water temperature trip, emergency stops, and critically, the engine room gas detection and ventilation systems. 3. Crankcase Inspection: Visual inspection for abnormal conditions, oil mist detectors, and spot checks of main/crosshead bearing clearances if scheduled. 4. Scavenge Space Inspection: Visual inspection for carbon deposits, piston rod gland condition, fire flap integrity, and signs of scavenge fires. 5. Cylinder Unit Inspection: Opening of cylinder covers (or inspection via scavenge ports) to assess liner wear, piston crown condition, and exhaust valve condition. Focus on signs of cold corrosion or scuffing. 6. Fuel System (HFO & Gas): Verification of HFO fuel pump and injector condition. For the gas system, integrity of high-pressure gas lines (double-wall), gas valve blocks, and purging arrangements. Operational checks of gas supply and safety valves. 7. Engine Control System (ECS): Review of alarm history, fault codes, and verification of critical parameters. Discussion on operational modes (HFO/LNG) and changeover procedures. 8. Turbocharger & Exhaust System: Inspection of turbocharger for fouling/damage, and exhaust manifold for leaks or hot spots. 9. Performance Data: Review of historical performance trends (EGTs, scavenge pressure, fuel consumption, power output) to identify any deviations.

Estimated lifetime: 100,000 - 150,000 running hours before major overhaul (e.g., crankshaft out, full engine strip-down), with regular component replacement and maintenance. The engine structure itself can last 20-25+ years.