Main Engine 4-Stroke · Main Engines (4-Stroke)
The Wärtsilä 31DF is a 4-stroke dual-fuel medium-speed engine that operates on the Otto cycle in gas mode. Manufactured by Wärtsilä, this engine is available in 6L, 8L, 10V, 12V, 14V, and 16V configurations, offering a power range from 2,610 kW to 10,440 kW. It is designed for dual-fuel operation, capable of running on LNG (Dual-Fuel) in conjunction with HFO, MGO, Methanol, and Ammonia (future). The Wärtsilä 31DF features two-stage turbocharging with intercooling, common rail direct injection, and a trunk piston design with DF gas admission and pre-chamber ignition. This engine achieves an SFOC of 165 g/kWh in gas mode and meets IMO Tier III emission standards. The Wärtsilä 31DF is suitable for various applications, including gearboxes, CPPs, and generators.
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What our service work and the manufacturer documentation say about keeping this model running.
Spark plug: 2,000-4,000 hrs. Gas valve: 6,000-8,000 hrs. Piston: 18,000-24,000 hrs. Standard 4-stroke intervals for remaining components.
| Spark plug (pre-chamber) replacement | 2,000-4,000 hrs |
|---|---|
| Gas admission valve overhaul/replacement | 6,000-8,000 hrs |
| Piston overhaul/withdrawal | 18,000-24,000 hrs |
| Standard 4-Stroke intervals | For remaining components (e.g., main/con-rod bearings, turbocharger overhaul, fuel injectors), refer to manufacturer's specific PMS schedule, typically ranging from 6,000 to 24,000 hrs. |
| Cylinder Liner Wear | Max. 0.6 - 0.8 mm total wear or 0.1 mm/1000 hrs, whichever is less, at the top ring reversal point. |
|---|---|
| Piston Ring Groove Wear | Max. 0.15 - 0.2 mm increase in axial clearance from new specification. |
| Crankshaft Deflection | Max. 0.05 - 0.10 mm between adjacent main bearings (depending on engine size and manufacturer's specific limits). |
| Main/Connecting Rod Bearing Clearances | Max. 0.15 - 0.25 mm increase from new specification. |
| Pre-chamber Spark Plug Gap | Max. 0.8 - 1.0 mm (new typically 0.3 - 0.5 mm) before replacement due to erosion. |
| Turbocharger Bearing Clearances | As per manufacturer's specified axial and radial limits, typically checked during overhaul. |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Class surveyors will rigorously check compliance with the IGF Code for gas-fueled ships. Key focus areas include: verification of the gas fuel supply system's integrity (piping, valves, ventilation, gas detection systems), functional testing of all gas safety systems (Emergency Shut-Down, gas detection alarms, ventilation interlocks), witnessing fuel changeover procedures (Gas-Diesel, Diesel-Gas) to ensure stability and safety, inspection of engine components as per the vessel's approved Planned Maintenance System (PMS) and class requirements (e.g., piston withdrawal, bearing inspections), review of engine performance data, alarm logs, and maintenance records, and verification of IMO Tier III compliance in gas mode through documentation and operational checks.
Estimated lifetime: 80,000 - 120,000 hours before major overhaul (e.g., crankshaft inspection, reconditioning, or replacement of major components).
Wärtsilä global. Spark plugs: an Bord vorhalten (10+ Sätze).
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