6H35/40G

Common issues

• Excessive valve clearance leading to high-temperature erosion of valve seats, particularly exhaust valves, requiring periodic adjustment.
• Ignition system failures (spark plug fouling/wear, ignition coil breakdown) affecting combustion stability and power output, common in lean-burn gas engines.
• Gas admission valve leakage or malfunction, leading to incomplete combustion, increased emissions, or potential backfiring.
• Increased cylinder liner wear due to dry gas operation and potential issues with cylinder lubrication, requiring careful monitoring.
• Turbocharger fouling or bearing wear, impacting engine efficiency, exhaust gas temperatures, and overall performance.
• Pilot fuel injection system issues (clogging, wear of nozzles) affecting ignition reliability and engine starting.
• Crankcase oil contamination or degradation due to combustion byproducts or gas blow-by, necessitating frequent oil analysis.

Inspection checklist

• Valve Clearance Check & Adjustment: Verify clearances are within manufacturer specifications (e.g., every 2000-4000 running hours) to prevent valve seat erosion.
• Spark Plug Inspection & Replacement: Check for fouling, electrode wear, and correct gap; replace as per schedule (e.g., every 2000-4000 hours or based on condition).
• Gas Admission Valve Function & Leakage Test: Check for proper opening/closing, signs of external or internal leakage, and actuator condition.
• Cylinder Liner Wear Measurement: Periodically measure liner diameter for ovality and taper, especially at the top dead center (TDC) region.
• Turbocharger Inspection: Check rotor for axial/radial play, compressor/turbine blades for fouling, damage, and bearing condition.
• Crankshaft Deflection Measurement: To assess main bearing alignment and wear, typically performed during major overhauls or significant maintenance.
• Pilot Fuel Injection System Inspection: Inspect nozzles for carbon buildup or damage, check injection timing and pressure.
• Oil Mist Detector (OMD) Function Test: Ensure proper operation and calibration for crankcase safety.
• Cooling Water System Integrity: Check for leaks, proper pressure, temperature stability, and inspect heat exchangers for fouling.

Service intervals

Typical wear limits

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

Critical spares

• Spark plugs (full set + spares)
• Ignition coils
• Gas admission valve repair kits / complete valves
• Pilot fuel injection nozzles
• Cylinder head gaskets and O-rings
• Turbocharger bearing cartridge / repair kit
• Main and connecting rod bearing shells (at least one set for emergency)
• Various O-rings and seals for gas lines and engine components

Safety

• Gas Leakage: High risk of fire and explosion from LNG/Natural Gas leaks in the engine room or gas supply lines. Ensure proper ventilation, gas detection systems, and emergency shut-off procedures are strictly followed.
• High Voltage Ignition System: Danger of electric shock during inspection or maintenance of spark plugs and ignition coils. Always de-energize the system and follow LOTO procedures before working.
• Crankcase Explosions: While less common in lean-burn gas engines, accumulation of oil mist and hot spots can still lead to explosions. Ensure Oil Mist Detector (OMD) and crankcase relief valves are fully functional.
• Emergency Shutdown System (ESD): Critical for gas engines; ensure all ESD functions (gas shut-off, engine stop) are regularly tested and fully operational to prevent catastrophic failures.
• Hot Surfaces & Rotating Machinery: Standard engine room hazards, but gas engines can have specific hot spots related to exhaust and ignition systems. Always use appropriate PPE and caution.

Class survey

For this HiMSEN 6H35/40G gas engine, class surveyors typically focus on: 1. Gas System Integrity: Verification of gas piping, valves, leak detection, ventilation, and safety shut-off systems (e.g., Gas Valve Unit - GVU) to ensure compliance with IGF Code. 2. Emergency Shutdown (ESD) Functionality: Thorough testing of all engine and gas system ESDs, including overspeed, low oil pressure, high temperature, and manual stops. 3. Crankshaft Deflection: Mandatory measurement to assess main bearing condition and alignment, crucial for engine longevity. 4. Safety Devices: Verification of overspeed trip, low lube oil pressure, high cooling water temperature, and other critical alarms/trips. 5. Maintenance Records: Comprehensive review of engine logbooks, maintenance schedules, and records of repairs/overhauls to ensure adherence to manufacturer and class requirements. 6. Crankcase Safety: Inspection of oil mist detector (OMD) and crankcase relief valves for proper function. 7. Emissions Compliance: Review of NOx technical file and verification of emissions monitoring equipment (if applicable) to ensure environmental regulations are met.

Estimated lifetime: 100,000+ running hours with proper maintenance and scheduled overhauls; major overhaul typically at 24,000-36,000 hours.