Two Wärtsila 18V32DF engines will be installed in the FPSO (floating, production, storage and offloading) vessel "Petrojarl I". The two engines, each developing 3720 kW at 720 rev/min, will be supplied as complete generating sets. They will burn wellhead gas. The vessel will operate under Norwegian jurisdiction where a carbon dioxide tax is levied on power production in the offshore sector. Efficiency of the power plant has a significant impact on the operation costs of the oil fields. Since the operator's requirements also include low NOx emissions, the Wärtsila 32DF engine emerged as the first choice for this installation.
The Wärtsila 32DF engine has been introduced to marine applications to meet the requirements of a new safety class for installations with a gas pressure of less than 10 bar in a single-pipe arrangement. Class approval in principal for this safety concept is now in hand and a class-approved control system based on the Wärtsila WECS 8000 electronic control system has been introduced on the 32DF marine engine. WECS 8000 control system provides control of the air-gas ratio, and the quantity and timing of the pilot fuel injection to keep every cylinder at the correct operating point between the knock and misfiring limits.
The pilot fuel system is a common-rail system with one engine-mounted high-pressure pump supplying diesel oil to the injection valves at a constant pressure of 900 bar. The gas fuel is supplied to the engine at a pressure of less than four bar.
To reach low NOx emissions, it is essential that the quantity of injected diesel oil fuel is very small. 32DF engines therefore use a "micro-pilot" injection with less than one per cent of the fuel energy requirement at nominal load. As a result, the NOx emissions of a Wärtsila 32DF engine are about one-tenth those of the standard diesel version.