Wärtsilä X72 (New)

• Extended rating field offers optimum propeller speed for different applications
• Low fuel consumption thanks to advantages stroke-bore parameters
• Proven Wärtsilä electronically controlled common-rail concept for high performance
• Reliability through proven main parameters
• Five years operation between overhauls
• Stable operation down to 12% nominal engine speed for easier manoeuvring

Dimensions and weights

• All dimensions are in millimetres and are not binding.
• The engine weight is net in metric tonnes (t), without oil and water, and is not binding

Fuel consumption

• All brake specific fuel consumptions (BSFC) are quoted for fuel of lower calorific value 42.7 MJ/kg, and for ISO standard reference conditions(ISO 15550 and 3046).
• All given BSFC figures for Wärtsilä engines are given with a tolerance of +5% across 40–100% of engine load.

Wärtsilä RT-flex engines have a lower part-load fuel consumption than the corresponding Wärtsilä RTA engines. Wärtsilä RT-flex engines are also available with Delta Tuning and the RT-flex82C and RT-flex96C also with Low-Load Tuning for even lower part-load fuel consumptions (see chart). Low-Load Tuning will also be introduced to the other RT-flex engines in the portfolio. Delta Tuning and Low-Load Tuning both take advantage of the complete flexibility in engine setting provided by the RT-flex common-rail system to optimize fuel injection pressures and timing at all loads. Delta Tuning focuses on reducing BSFC in the operating range below 90% engine load. Low-Load Tuning further reduces BSFC in the operating range below 75% engine load by means of a modified turbocharging system layout in combination with appropriately adjusted RT-flex system parameters.

Rating points for Wärtsilä low-speed engines

The engine layout fields for Wärtsilä lowspeed engines are defined by the power/ speed rating points R1, R2, R3 and R4 (see diagram to the right). In certain engines, the layout field is extended to the points R1+ and R2+. R1, or R1+ instead if applicable, is the nominal maximum continuous rating (MCR). Any power and speed within the respective engine layout field may be selected as the Contract-MCR (CMCR) point for an engine.

ISO standard reference conditions

• Total barometric pressure at R1: 1.0 bar
• Suction air temperature: 25 °C
• Relative humidity: 30%
• Scavenge air cooling water temperature: 25 °C

IMO NOx emissions

All Wärtsilä low-speed engines comply with the NOx limits specified in Annex VI of the MARPOL 73/78 convention. The latest versions of these engine types are available either complying with the amended regulations under IMO Tier II, or complying with the existing IMO Tier I regulations. Previous versions of these engine types comply only with existing IMO Tier I regulations.
Compliance with the IMO Tier II NOx emissions limits involves a small increase in fuel consumption compared with the BSFC with the Tier I limits. Wärtsilä RT-flex electronically-controlled common-rail low-speed engines will comply with the Tier II NOx emissions limits with a smaller increase in fuel consumption than Wärtsilä RTA low-speed engines.
Provisions for compliance with IMO Tier III NOx emissions limits will be announced at a later date but in ample time for the implementation date.

Cylinder Lubrication

The Pulse Lubricating System with electronic control of lubrication timing has been further developed.
It is available for all Wärtsilä W-X, RT-flex low-speed engines and for selected RTA engines.
The guide feed rate for new engines equipped with Pulse Jet cylinder lubrication system is 0.6g/kWh. Engines with different Lubricating Systems might require a higher feed rate. This allows important savings in engine operating costs.

Wärtsilä RT-flex common-rail system

With the RT-flex common-rail system, fuel oil, servo oil and control oil are delivered at regulated pressures to rail pipes arranged along the side of the cylinders. Electronic control units then regulate delivery from these rail pipes for fuel injection and exhaust valve operation.
In this way, the Wärtsilä RT-flex engines have complete flexibility in fuel injection timing, rate, pressure and volume, as well as in exhaust valve operation. This provides engine operational benefits that cannot be obtained with mechanically-controlled systems.