Wartsila ?31DF Series Product Manual page 184

15. Foundation
type of resin and the requirements of the classification society. It is recommended to select
a resin type that is approved by the relevant classification society for a total surface pressure
of 5 N/mm
During normal conditions, the support face of the engine feet has a maximum temperature of
about 75°C, which should be considered when selecting the type of resin.
The bolts must be made as tensile bolts with a reduced shank diameter to ensure a sufficient
elongation since the bolt force is limited by the permissible surface pressure on the resin. For
a given bolt diameter the permissible bolt tension is limited either by the strength of the bolt
material (max. stress 80% of the yield strength), or by the maximum permissible surface
pressure on the resin.
15.2.1.2 Steel chocks
The top plates of the foundation girders are to be inclined outwards with regard to the centre
line of the engine. The inclination of the supporting surface should be 1/100 and it should be
machined so that a contact surface of at least 75% is obtained against the chocks.
Recommended chock dimensions are 250 x 200 mm and the chocks must have an inclination
of 1:100, inwards with regard to the engine centre line. The cut-out in the chocks for the
clearance bolts shall be 44 mm (M42 bolts), while the hole in the chocks for the fitted bolts
shall be drilled and reamed to the correct size (Ø43H7) when the engine is finally aligned to
the reduction gear.
The design of the holding down bolts is shown the foundation drawings. The bolts are designed
as tensile bolts with a reduced shank diameter to achieve a large elongation, which improves
the safety against loosening of the nuts.
15.2.1.3 Steel chocks with adjustable height
As an alternative to resin chocks or conventional steel chocks it is also permitted to install the
engine on adjustable steel chocks. The chock height is adjustable between 45 mm and 65
mm for the approved type of chock. There must be a chock of adequate size at the position
of each holding down bolt.
15-2
2
. (A typical conservative value is Ptot 3.5 N/mm
Wärtsilä 31DF Product Guide
2
).
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