4. Description of the Engine
4.1 Definitions
Fig 4-1 Engine definitions (V93C0028)
4.2 Main components and systems
4.2.1 Engine block
The engine block, made of nodular cast iron, is cast in one piece for all cylinder numbers and
it supports the underslung crankshaft. The block has been given a stiff and durable design to
absorb internal forces and the engine can therefore also be resiliently mounted not requiring
any intermediate foundations. It incorporates water and charge air main and side channels.
Also camshaft bearing housings are incorporated in the engine block. The engines are equipped
with crankcase explosion relief valve with flame arrester.
The main bearing caps, made of nodular cast iron, are fixed with two hydraulically tensioned
screws from below. They are guided sideways and vertically by the engine block. Hydraulically
tensioned horizontal side screws at the lower guiding provide a very rigid crankshaft bearing
assembly.
A hydraulic jack, supported in the oil sump, offers the possibility to lower and lift the main
bearing caps, e.g. when inspecting the bearings. Lubricating oil is led to the bearings through
this jack.
The oil sump, a light welded design, is mounted on the engine block from below. The oil sump
is available in two alternative designs, wet or dry sump, depending on the type of application.
The wet oil sump includes a suction pipe to the lubricating oil pump. For wet sump there is a
main distributing pipe for lubricating oil, suction pipes and return connections for the separator.
For the dry sump there is a main distributing oil pipe for lubricating oil and drains at either end
to a separate system oil tank.
The engine holding down bolts are hydraulically tightened in order to facilitate the engine
installation to both rigid and resilient foundation.
4.2.2 Crankshaft
Crankshaft line is built up from several pieces: crankshaft, counter weights, split camshaft
gear wheel and pumpdrive arrangement.
DBAE248994 4-1
4. Description of the EngineWärtsilä 31DF Product Guide
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