H35/40DF

Common issues

• Gas valve malfunction (sticking, leakage, timing issues)
• Pilot injector fouling and carbon build-up, leading to poor combustion
• Combustion sensor faults (e.g., pressure, temperature, flame detection) impacting engine control
• Turbocharger fouling (compressor and turbine sides) reducing efficiency and increasing exhaust temperatures
• Exhaust valve burning and seat wear, particularly with varying fuel quality or load changes
• Fuel gas system leaks (flanges, seals, double-wall piping integrity)
• Engine Control System (ECS) glitches or software issues related to dual-fuel mode switching
• Cylinder liner scuffing or excessive wear due to suboptimal combustion or lubrication

Inspection checklist

• Fuel Gas System Integrity: Visually inspect all gas piping, flanges, and components for leaks (use leak detection spray/sniffers). Check pressure and temperature transducers for accuracy. Verify ventilation in gas-dangerous zones.
• Pilot Fuel System: Inspect pilot injectors for external leakage, carbon deposits, and proper spray pattern (if possible). Check fuel pressure and filter condition.
• Gas Admission Valves: Check for proper actuation, sealing, and timing. Inspect for carbon build-up or signs of leakage into the manifold. Verify cooling if applicable.
• Cylinder Units: Perform borescope inspection of cylinder heads, piston crowns, and exhaust valves for signs of burning, cracking, or excessive carbon. Check liner wear data against limits.
• Turbocharger: Inspect compressor and turbine blades for fouling, erosion, or damage. Check axial and radial bearing clearances. Monitor bearing temperatures.
• Engine Control System (ECS): Verify alarm and safety functions. Check sensor readings against expected values. Test mode switching (gas to diesel and vice versa) and emergency shutdown (ESD) functions.
• Lube Oil System: Check oil level, pressure, and temperature. Take samples for analysis. Inspect filters and coolers for cleanliness and leaks.
• Cooling Water System: Check temperatures, pressures, and expansion tank levels. Inspect for leaks and ensure proper coolant treatment.
• Exhaust Gas System: Check for leaks at manifold joints and bellows. Monitor exhaust gas temperatures (EGTs) per cylinder for consistency.

Service intervals

Typical wear limits

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

Critical spares

• Gas admission valve complete unit (at least one per cylinder bank)
• Pilot fuel injector complete unit
• Combustion sensor (pressure/temperature) for at least one cylinder
• Turbocharger cartridge or complete bearing set
• Exhaust valve spindle and seat ring
• Complete set of piston rings for one cylinder
• Fuel gas filter elements (various stages)
• Lube oil filter elements
• Assortment of O-rings and gaskets for fuel gas system and cylinder heads

Safety

• Flammable Gas Leaks: High risk of explosion or fire from LNG/gas leaks, especially in enclosed engine rooms or gas valve units. Ensure robust leak detection and ventilation.
• Cryogenic Hazards: LNG is stored and supplied at extremely low temperatures (-162°C). Direct contact can cause severe frostbite. Proper PPE and handling procedures are critical.
• High Pressure Systems: Fuel gas is supplied at high pressure (e.g., 5-10 bar for low-pressure DF, much higher for high-pressure DF), posing a risk of injury from leaks or component failure.
• Asphyxiation Risk: Gas leaks can displace oxygen in confined spaces, leading to asphyxiation. Ensure adequate ventilation and gas detection.
• Emergency Shutdown (ESD) Malfunction: Failure of the ESD system to properly isolate fuel gas in an emergency (e.g., fire, gas leak) can lead to catastrophic events. Regular testing is vital.

Class survey

For the HiMSEN H35/40DF, class surveyors place significant emphasis on the integrity and functionality of the entire Fuel Gas Supply System (FGSS). This includes thorough inspection of all gas piping, valves, insulation, and ventilation in gas-safe and gas-dangerous zones, verifying double-wall piping integrity and leak detection systems. Functional testing of all Emergency Shutdown (ESD) levels (engine, FGSS, ventilation, fire dampers) from all control points is mandatory. Engine performance in both gas and diesel modes, including monitoring of critical parameters and safety devices (overspeed, low lube oil pressure, high cooling water temp), will be checked. Scrutiny of planned maintenance system (PMS) records, defect reports, and spare parts inventory, especially for gas-related components, is paramount. Calibration certificates and functional testing of gas detectors in the engine room, gas valve unit (GVU) rooms, and double-wall piping spaces are essential. Review of combustion analysis data and sensor calibration records is critical for safe and efficient dual-fuel operation. Fire safety systems in gas-dangerous areas, including fire dampers and fire boundaries, will also be closely examined.

Estimated lifetime: 60,000 - 80,000 hours before major overhaul (e.g., main bearing renewal, crankshaft inspection). Design life often exceeds 100,000 - 120,000 hours with diligent maintenance.