The MAN B&W 12S90ME-C Mark 9.2 type diesel engine set the world record in October of 2014 for the largest engine ever built. It’s not only physically the largest, but the diesel manufacturer’s low-speed two-stroke diesel engine is one of the most powerful, rated at 98,000 hp.
The MAN B&W 12S90ME-C Mark 9.2 uses electronically controlled hydraulic/mechanical actuators for the fuel injection and exhaust valves. It’s fuel pressure booster is a plunger powered by a hydraulic piston. An electronically controlled proportional valve sends pressurized oil to drive the hydraulic piston. Each cylinder, also, has its own hydraulically activated fuel oil pressure booster. Fuel injection is performed with a valve that is electronically controlled by the the Engine Control System (ECS).
Exhaust valves are opened by a two-stage valve actuator with oil from an electronically controlled proportional valve and closed with an “air spring.” With electronic control of the valves, the valve timing is infinitely adjustable. All ME-C engines, including the massive 12S90ME-C Mark 9.2 are dual fuel engines (CNG or diesel) using high-pressure injection.
Cylinder Frame, Liners, and Cover
The 12S90ME-C Mark 9.2 has a cast block with access doors on its lower side allowing technicians to enter and clean the scavenge air space (the huge open space in the engine block), inspect scavenge ports and piston rings. The scavenge air receiver, turbocharger, air cooler box, and gallery brackets are all mounted to the engine block.
The piston rod stuffing box (a space surrounding the upper rod of the two piston rods) is provided with sealing rings for scavenge air and with oil scraper rings to prevent crankcase oil from coming into the scavenge air space. Drains from the scavenge air space and the piston rod stuffing box are located at the bottom of the engine block.
Cylinder liners are alloyed cast iron and suspended in the cylinder frame with a low-situated flange and have scavenge ports and holes for cylinder lubrication. The top of the cylinder liner is fitted with a cooling jacket. The cylinder liners offer temperature sensors as standard.
The engine features a forged steel, single-piece cover (the equivalent of a head) that has passages for cooling water. It, also, has a central hole for the exhaust valve, as well as holes for the fuel valves and starting air valve.
Fuel Valves and Starting Air Valve
The 12S90ME-C Mark 9.2 is equipped with three fuel valves, a starting air valve and an indicator cock. Fuel valves are controlled by the high-pressure fuel oil (a crude type of diesel not used for standard highway vehicle engines) created by the fuel oil pressure booster and the valves are closed by a spring. When the engine is stopped, circulation of fuel oil is continued through the valve and high pressure pipes via an automatic vent slide.
The vent slide, also, prevents the compression chamber from being filled up with fuel oil in the event that the valve spindle sticks. Oil from the vent slide and other drains is led away in a closed system. The fuel oil high-pressure pipes are double-walled with conical support.
The starting air distributor is mechanically driven and the starting valve is opened by air and is closed by a spring. These functions, as well as slow turning before engine start-up, are all controlled by ECS.
The exhaust valve consists of a valve housing with a flame hardened seat and a valve spindle with a spindle guide. The valve housing is made of cast iron and the housing has a water-cooled bottom piece of steel. The exhaust valve is mounted to the cylinder cover, and is opened hydraulically by the electronic valve activation system and closed by an air spring.
The exhaust valve operates by having the valve spindle slowly rotate, driven by the exhaust gas acting on a vane wheel fixed to the spindle. Sealing of the exhaust valve spindle guide is provided by an oil bath in the bottom of the air cylinder, above the sealing ring. This oil bath lubricates the exhaust valve spindle guide and sealing ring as well.
Hydraulic Cylinder Unit
The hydraulic cylinder unit (HCU), one per cylinder, consists of a base plate on which a distributor block is mounted. The distributor block is fitted with one or more accumulators to ensure that the necessary hydraulic oil peak flow is available during the fuel injection sequence. The distributor block serves as a mechanical support for the hydraulically activated fuel pressure booster and the hydraulically activated exhaust valve actuator.
Bedplate and Main Bearing
When installed in the ship, the engine’s bedplate was assembled with the thrust bearing in the aft (rear) end of the engine. The 12S90ME-C Mark 9.2 bedplate is made with welded, high longitudinal girders, welded cross girders, and cast steel bearing supports. The bedplate was built without a taper for engines mounted on epoxy chocks.
Its steel plate oil pan is welded to the bed plate, and collects the return oil. The oil outlets are vertical and have gratings. The main bearings are thin-walled steel shells with metal liners, and the bottom shells can be removed for service or replacement when the crankshaft is lifted.
A welded frame box with relief valves for each cylinder is on one side, while the other side has a hinged door for each cylinder. Crosshead guides are welded in to the frame box, which is bolted to the bedplate.
Crankshaft and Thrust Bearing
For MAN engines with nine cylinders or more, such as the 12-cylinder 12S90ME-C Mark 9.2, the crankshaft comes in two parts. The rear of the crankshaft has a thrust bearing collar, a flange for the tuning wheel and for the coupling bolts to an intermediate shaft. The crankshaft’s front end has a collar for the vibration damper and a flange for a tuning wheel, and operates two-part piston rods.
The thrust bearing is located in the rear of the engine. It consists of a thrust collar on the crankshaft, a bearing support and segments of steel lined with white metal. Type 60 and larger with nine cylinders or more, such as the 12S90ME-C Mark 9.2 come with a 360 degree thrust bearing, while the 240 degree unit is used in all other engines. MAN Diesel’s flexible thrust cam design is used for the thrust collar on a range of engine types, and the thrust shaft is an integrated part of the crankshaft that is lubricated by the engine’s lubricating oil system.
Scavenge Air Cooler and Auxiliary Blower
A mono-block-design scavenge air cooler that uses sea water cooling is fitted to each turbocharger. The scavenge air cooler is designed so that the difference between the scavenge air temperature and the water inlet temperature can be kept at about 53 degrees F.
The engine also features scavenge air blowers integrated in the scavenge air cooler. The suction side of the blowers are connected to the scavenge air space after the air cooler. Between the air cooler and the scavenge air receiver, non-return valves automatically close when the auxiliary blowers supply the air. The auxiliary blowers begin consecutive operation before starting the engine to make sure there is enough scavenge air pressure for a safe start-up.
Exhaust System and Turbos
Exhaust gases go from the exhaust valves to the exhaust gas receiver, where the pressure from the individual cylinders is equalized and then the total volume of exhaust gas is fed to the turbochargers. After the exhaust is used to power the turbochargers, it exits through an external exhaust pipe system. Compensators are used between the exhaust valves and the receiver, and between the receiver and the turbochargers. The exhaust gas receiver and exhaust pipes are provided with insulation, covered by galvanized steel plating.
The 12S90ME-C Mark 9.2 can be set up with MAN, ABB, or MHI turbochargers. MAN TCA and ABB A100-L turbochargers with variable-nozzle technology that helps reduce fuel consumption at part load by controlling the scavenge air pressure are an option.
The engine is provided with gallery brackets, stanchions, railings and platforms, and the brackets are placed for the best possible overhauling and inspection conditions. Some of the engine’s main pipes hang from the gallery brackets and the gallery platform on top of one side of the engine is provided with overhauling holes for the pistons. The engine is, also, prepped for top bracing on the exhaust side.
The MAN B&W 12S90ME-C Mark 9.2 diesel engine is currently the world’s largest engine. The sheer size of the engine dwarfs men working on it. Its dimensions are almost unbelievable. Completely assembled, the engine stands nearly 57 feet high–that’s the equivalent of a building five stories tall. The 12-cylinder beast tips the scales at 4,160,000 pounds. Depending upon the choice of turbochargers for the gigantic two-stroke diesel, one turbo alone can weigh anywhere from 3,900 to 7,716 pounds and a crane is used to remove them for service or replacement.
The crankshaft for the 12S90ME-C Mark 9.2 diesel engine is immense, especially when you compare it to the crankshaft of a typical diesel pickup truck, commercial truck, or even that of MAN’s 6,000 hp four-stroke 9L32/40 diesel powerplant. The crankshaft for the gigantic 12-cylinder two-stroke weighs 930,000 pounds, and is almost 76 feet long.
Some of the engine’s capacities are enormous as well. For instance, engine oil is not measured in gallons, but by weight. The MAN B&W 12S90ME-C Mark 9.2 holds approximately 35,250 pounds of oil between the engine system, hydraulic system and oil pan. Between the jacket cooling system and the scavenge air cooling system, it holds close to 25,380 pounds of water.
The second record set for MAN came when its 12S90ME-C Mark 9.2 was ordered by China Shipping Group (CSG) and installed in the world’s largest container ship, the 19,000-TEU Newbuilding. A TEU (twenty-foot equivalent unit) is a unit of cargo measurement describing the capacity of container ships and container terminals, and based on the volume of a standard 20-foot-long intermodal container, the kind you see used on and transferred between ships, trains and trucks.
Photographs and illustrations courtesy MAN Diesel and Turbo.