Volvo D11 series, Руководство по установке

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Power take-off
92
Torsional vibration
The diesel engine, plus its driven equipment (driven
from either front or rear) is made up of rotating
masses connected by a series of shafts. This forms a
torsional mass-elastic system, which will vibrate at its
own natural frequency when acted upon by an excit-
ing torque.
A resonant condition will occur when the frequency of
the exciting torque is equal to the natural frequency
of the system, or one of its harmonics.
This condition will result in high vibratory stress,
which can lead to damage of the crankshaft or any
driven shafting. It is therefore necessary to ensure
that the characteristics of the total system, i.e. en-
gine and driven machinery (including front end PTO
if fitted) are such that excessive torsional vibration
stresses will not occur.
As a general guide, all axially driven inertia should be
as low as possible in order to minimise the effects of
vibratory torque. Driven equipment which introduces
damping into the system will have a beneficial effect
on the torsional vibration characteristics.
The use of a flexible coupling in the system will have
a similar beneficial effect, and coupling manufactur-
ers are usually able to give guidance in this respect.
D5/D7 Moment of inertia
On D5/D7 it is important not to exceed allowed mo-
ment of inertia for additional component mounted on
front of the crank shaft.
Allowed max moment of inertia
Engine 900 rpm 2300rpm
D5A T 0.53 kgm
2
0.24 kgm
2
D5A TA 0.5 kgm 2 0.22 kgm 2
D7A T 0.64 kgm 2 0.64 kgm 2
D7A TA 0.54 kgm
2
0.44 kgm
2
D7C TA 0.26 kgm
2
0.9 kgm
2
Below you can find a guidline for the moment of iner-
tia for some additional equipment.
Pulley for 40A extra alternator 0.54 kgm
2
3-belt pulley 0.0334 kgm
2
Pulley on stub shaft* 0.040 kgm
2
*
estimated weight 8 kg
Power output from front end of
crankshaft
Power can be taken out, for in-line duty, from the front
end of the crankshaft. The limit for this power is the
bolted joint between the damper/pulley and polygon
hub. In the
Sales Guide Marine Propulsion Diesel
Engines you will find the max. permissible torque for
our engine range. There are however a number of
things that have to be considered before the installa-
tion.
Alignment of the engine
It is of utmost importance to align the engine to the
unit which is to be driven.
The stress on the crankshaft, engine mounts, drive
shaft and coupling might otherwise be big enough to
cause interruptions in the operation. Check to make
sure that the drive shaft is straight prior to beginning
alignment work.
Imbalance in the driven unit and in the drive shaft
and the coupling can cause noise and vibrations.
This is why these components have to be balanced.
The alignment is facilitated if adjustment screws are
installed on the engine feet.
After alignment, the distance between the frame and
each bracket is measured.
Then steel shims with the correct measurement are
installed.
Crankshaft end thrust
If anything is fitted to the engine that imposes an ax-
ial end loading on the crankshaft, it must be ensured
that the end loading of the crankshaft does not ex-
ceed the maximum allowable values for the particular
engine type.
The manufacturer should be contacted for details of
the operating end thrust of their equipment if this in-
formation is not known.