The crankshaft is fully balanced to counteract bearing loads from eccentric masses by fitting counterweights
in every crank web. This results in an even and thick oil film for all bearings. If necessary, the crankshaft is
provided with a torsional vibration damper.
4.2.3 Connection 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 hy-
draulically tightened. The gudgeon pin bearing is made of tri-metal.
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 are of tri-metal design with steel back, lead-bronze lining and
a soft running layer. The bearings are covered all over with Sn-flash of 0.5-1 µm thickness for corrosion
protection. Even minor form deviations become visible on the bearing surface in the running in phase. This
has no negative influence on the bearing function.
4.2.5 Cylinder liner
The cylinder liners are centrifugally cast of a special grey cast iron alloy developed for good wear resistance
and high strength. Cooling water is distributed around upper part of the liners with water distribution rings.
The lower part of liner is dry. To eliminate the risk of bore polishing the liner is equipped with an anti-polishing
ring.
4.2.6 Piston
The piston is of composite design with nodular cast iron skirt and steel crown. The piston skirt is pressure
lubricated, which ensures a well-controlled lubrication oil flow to the cylinder liner during all operating
conditions. Oil is fed through the connecting rod to the cooling spaces of the piston. The piston cooling
operates according to the cocktail shaker principle. The piston ring grooves in the piston top are hardened
for better wear resistance.
4.2.7 Piston rings
The piston ring set consists of two directional compression rings and one spring-loaded conformable oil
scraper ring. All rings are chromium-plated and located in the piston crown.
4.2.8 Cylinder head
The cylinder head is made of grey cast iron, the main design criteria being high reliability and easy mainten-
ance. The mechanical load is absorbed by a strong intermediate deck, which together with the upper deck
and the side walls form a box section in the four corners of which the hydraulically tightened cylinder head
bolts are situated.
The cylinder head features two inlet and two exhaust valves per cylinder. All valves are equipped with valve
rotators. No valve cages are used, which results in very good flow dynamics. The basic criterion for the
exhaust valve design is correct temperature by carefully controlled water cooling of the exhaust valve seat.
The thermally loaded flame plate is cooled efficiently by cooling water led from the periphery radially towards
the centre of the head. The bridges between the valves cooling channels are drilled to provide the best
possible heat transfer.
4.2.9 Camshaft and valve mechanism
There is one campiece for each cylinder with separate bearing pieces in between. The cam and bearing
pieces are held together with flange connections. This solution allows removing of the camshaft pieces
sideways. The drop forged completely hardened camshaft pieces have fixed cams. The camshaft bearing
housings are integrated in the engine block casting and are thus completely closed. The bearings are installed
and removed by means of a hydraulic tool. The camshaft covers, one for each cylinder, seal against the
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Product Guide Wärtsilä 34DF - 3/2012
Product Guide
4. Description of the Engine
