Marine Installation Manual 2022-03 6-18
6 Engine Dynamics
6.4 Torsional vibration
X62DF-S2.0
Figure 6-15 Vibration dampers (spring type and viscous type)
6.4.2 PTO / PTI systems effect on torsional vibration
A propulsion plant may include a main engine-driven generator (PTO, power
take-off), a shaft-line connected electric motor (PTI, power take-in), or both.
These elements are connected to the engine or shafting by clutches, gears, shafts
and/or elastic couplings (see Figure 4-68,  4-114 for the different arrange-
ments).
Installations with PTO or PTI require special attention in the early stages of a
project. These systems may cause torsional vibrations and alignment challenges.
Risk of unstable
engine speed
For many PTO / PTI systems that use elastic couplings, the lowest torsional nat-
ural frequency can be problematic if it is below approximately 1.5 Hz. Here, there
is a risk of engine speed instability where the engine constantly adjusts its speed
to compensate the rotating vibration; this must be considered and compensated
for in the engine speed control system.
Installation of MFD
In addition, such PTO /PTI systems are very sensitive to misfiring as varying
firing loads can cause inadmissible torsional vibrations. To protect the elastic
couplings and gears from any misfiring, a misfiring detection device (MFD) must
be installed. This indicates either partial or total misfiring, allowing for appro-
priate countermeasures (e.g. speed reduction, de-clutching of PTO /PTI branch)
to be applied automatically, protecting the PTO /PTI components.
For additional consideration about PTO / PTI application refer to section 4.13,
 4-113, and for support regarding system layout, please contact WinGD.
SM-0095
Cover
Inertia ring
Casing
Silicone fluid
Springs
Intermediate parts
Lube oil supply
Viscous type
Spring type
To Next Page
Loading...
Need help?
General