WÄRTSILÄ 46DF, Product Manual

Page: 54 / 242

All crankshafts can be equipped with a torsional vibration damper at the free end of the engine,
if required by the application. Full output is available also from the free end of the engine
through a power-take-off (PTO).
The main bearing and crankpin bearing temperatures are continuously monitored.
4.2.3 Connecting rod
The connecting rods are of three-piece design, which makes it possible to pull a piston without
opening the big end bearing. Extensive research and development has been made to develop
a connecting rod in which the combustion forces are distributed to a maximum area of the
big end bearing.
The connecting rod of alloy steel is forged and has a fully machined shank. The lower end is
split horizontally to allow removal of piston and connecting rod through the cylinder liner. All
connecting rod bolts are hydraulically tightened. The gudgeon pin bearing is solid aluminium
bronze.
Oil is led to the gudgeon pin bearing and piston through a bore in the connecting rod.
4.2.4 Main bearings and big end bearings
The main bearings and the big end bearings have steel backs and thin layers for good resistance
against fatigue and corrosion. Both tri-metal and bi-metal bearings are used.
4.2.5 Cylinder liner
The centrifugally cast cylinder liner has a high and rigid collar preventing deformations due to
the cylinder pressure and pretension forces. A distortion-free liner bore in combination with
wear resistant materials and good lubrication provide optimum running conditions for the
piston and piston rings. The liner material is a special grey cast iron alloy developed for excellent
wear resistance and high strength.
Accurate temperature control is achieved with precisely positioned longitudinal cooling water
bores.
An anti-polishing ring removes deposits from piston top land, which eliminates increased
lubricating oil consumption due to bore polishing and liner wear.
4.2.6 Piston
The piston is of two-piece design with nodular cast iron skirt and steel crown. Wärtsilä patented
skirt lubrication minimizes frictional losses and ensure appropriate lubrication of both the
piston skirt and piston rings under all operating conditions.
4.2.7 Piston rings
The piston ring set consists of two compression rings and one spring-loaded conformable oil
scraper ring. All piston rings have a wear resistant coating.Two compression rings and one
oil scraper ring in combination with pressure lubricated piston skirt give low friction and high
seizure resistance. Both compression ring grooves are hardened for good wear resistance.
4.2.8 Cylinder head
A rigid box/cone-like design ensures even circumferential contact pressure and permits high
cylinder pressure. Only four hydraulically tightened cylinder head studs simplify the maintenance
and leaves more room for optimisation of the inlet and outlet port flow characteristics.
The exhaust valve seats are water cooled. Closed seat rings without water pocket between
the seat and the cylinder head ensure long lifetime for valves and seats. Both inlet and exhaust
valves are equipped with valve rotators.
4-2 DBAD209883
Wärtsilä 46DF Product Guide 4. Description of the Engine