main engine · propulsion system

MAN B&W 7S65ME C8.6

The MAN B&W 7S65ME-C8.6 is a low-speed, two-stroke crosshead diesel engine built for the main propulsion of medium and large merchant ships such as tankers and bulk carriers. Like the rest of MAN Energy Solutions' celebrated ME series, its designation is descriptive: the 7 is the number of cylinders, the S marks it as a super-long-stroke engine, the 65 is the cylinder bore in centimetres, and ME signifies that the engine is electronically controlled. The super-long-stroke S design reflects the industry's drive for fuel efficiency. By combining a long piston stroke with a moderate bore, these engines run at low revolutions and develop high torque, which lets them turn a large, slow, efficient propeller directly on the shaft with no reduction gearbox. Slow propeller speeds improve propulsive efficiency, and the engines are optimised to burn heavy fuel oil economically over the long passages typical of the trades they serve, which is why two-stroke crosshead engines of this kind power the great majority of large ocean-going ships. The electronic control that defines the ME series replaces the traditional camshaft with a computer-controlled, hydraulically actuated system that governs fuel injection and exhaust valve operation. This allows injection timing and profile to be adjusted continuously for the best fuel economy and emissions across the load range, gives smoother slow-speed running for manoeuvring, and provides extensive monitoring. As a crosshead engine it has a diaphragm separating the cylinders from the crankcase, permitting separate cylinder and system lubrication suited to heavy fuel operation, and it is built to run continuously for long periods with planned maintenance of its running gear, injection equipment and turbocharging. Engines such as the 7S65ME-C are typical of the modern main engine: large, efficient, electronically managed and designed for the reliability that a deep-sea ship depends on for years of service.