A torsional vibration calculation of an installation is performed in order to predict the behaviour of the installation, with regards to Torsional vibration, in the steady state condition.

For this, Techno Fysica uses the Transfer Matrix Method developed by Holzer. Other methods, such as the finite element method, are also possible, but since the Holzer method is well proven and accepted by the classification societies, this makes it the preferred method for standard installations.

With the computer model, the natural frequencies of the complete system are calculated. The next step is to predict the response of the system to sources of vibration. This requires knowledge of the combustion forces (engine orders) as well as other sources of excitation such as propeller excitation, excitation by cardan shafts, etcetera.

Using the excitation forces as mentioned, and damping supplied by elastic couplings, vibration dampers, and propeller damping, the alternating torques are calculated.

In principle, the calculation predicts the presence of so called critical speeds. By this is meant: speeds where resonances are excited. Some people are of the opinion that no resonances should occur within the operating speed range of an installation. This is usually not possible, or can only be achieved by very complex and carefully tuned installations. However, it is absolutely not necessary to avoid having resonances within the operating speed range. It is however important to know if the resonances are well dampened, and that overloading of components such as gears, dampers and elastic couplings is avoided, and that fatigue of shafts will not occur. A good calculation, and a sound evaluation of the calculation results is all that is required.

However, the delivery times for the calculations made by the engine manufacturers are usually not among the fastest, which may cause problems with delivery times for components such as gears, elastic couplings and propellers.

Also, and especially, in the case of damage of vibration hinder it may be necessary to produce a calculation within a short time span.

Techno Fysica can, if the necessary data is available, deliver within very short time. In some instances even within a day. This makes it possible to avoid problems with delivery times of components.

If you are in need of a torsional vibrations, download this PDF-document for the required data.