WÄRTSILÄ WARTSILA 26, Product Manual

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Depending on the outcome of the torsional vibration calculation, vibration dampers will be fit
at the free end of the engine. If required full output can be taken from either end of the engine.
4.2.3 Connecting rod
The connecting rod is of forged alloy steel. All connecting rod studs are hydraulically tightened.
The connecting rod has a horizontal split at the crankpin bearing. The advantages of this type
of connecting rod are:
● Shorter length
● High rigidity (stiffness)
●
Low mass (results in smaller bearing load)
For overhaul the piston and connecting rod are removed together with the cylinder liner as
one unit. The oil supply for the piston cooling, gudgeon pin bush and piston skirt lubrication
takes place through a single drilling in the connecting rod.
4.2.4 Main bearings and big end bearings
The main bearings and the crankpin bearings are of the bi–metal type with a steel backing
and a soft running layer with excellent corrosion resistance.
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. They are of wet type, sealed against the engine block by
means of a gasket at the upper part and by O-rings at the lower part. To eliminate the risk of
bore polishing the liner is equipped with an anti-polishing ring.
Cooling around the liner is divided into two parts: the greater volume in the lower part for
uniform cooling water distribution and a smaller volume at the top of the jacket to facilitate an
efficient cooling due to a high flow velocity.
4.2.6 Piston
The piston is of composite design with nodular cast iron skirt and steel crown. The piston skirt
and cylinder liner are lubricated by a unique lubricating system utilizing lubricating nozzles in
the piston skirt. This system ensures excellent running behaviour and constant low lubrication
oil consumption 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.
The two compression rings are asymmetrically profiled.
4.2.8 Cylinder head
The cylinder head is made of spheroidal or grey lamellar cast iron. The thermally loaded flame
plate is cooled efficiently by cooling water led from the periphery radially towards the centre
of the head. Cooling channels are drilled in the bridges between valves, to provide the best
possible heat transfer.
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 exhaust valve seats are directly water-cooled.
All valves are equipped with valve rotators.
4-2 Wärtsilä 26 Product Guide - a9 - 7 September 2016
Wärtsilä 26 Product Guide 4. Description of the Engine