TORSIOGRAPHY / TENZOMETRY

TORSIOGRAPHY / TENZOMETRY

The occurrence of torsional vibration resonances at certain revolutions of the internal combustion engine is a common problem that can lead to breakdown of shaft elements. Therefore, carrying out theoretical calculations with the determination of resonant frequencies is an important component of the modernization of the circuits of propulsive systems: replacing the internal combustion engine, screws and shafts, gearboxes, elastic couplings.
TORSIOGRAPHY / TENZOMETRY

Torsional vibrations of shaft lines

What we work with and Our capabilities in solving the problems of resonances of torsional vibrations of shaft lines on marine and river vessels. 
The occurrence of torsional vibration resonances at certain revolutions of the internal combustion engine is a common problem that can lead to breakdown of shaft elements. Therefore, carrying out theoretical calculations with the determination of resonant frequencies is an important issue of both the new ships in projecting and of the modernization of the schemes of propulsive systems: replacing internal combustion engine, propeller and shafts, gearboxes, elastic couplings.
It is important to understand the difference between the resonances of "shaft-conducting" and "motor" forms. In the first case, these are resonances in the elements of the shaft line, in the second — in the elements of engine (crankshaft). At the same time, any malfunction caused by torsional vibrations can lead to the failure of the entire system.

The accumulated experience and the advanced equipment at our disposal allow us to evaluate the torsional vibrations of the "shaft-conducting" forms of any system.

The theoretical calculations of torsional vibrations carried out are confirmed by data obtained by torsiography and/or tenzometry.

Reports are done in accordance with current requirements and are submitted to proper Class Office.

Torsional vibration dampers are installed on internal combustion engines in order to reduce the stresses arising from "motor" forms.

The resource of their working condition is limited and ranges from 10 to 30 thousand hours. The wear of the silicone damper is accompanied by a decrease in the efficiency of its operation at the resonance frequency, which is fraught with a breakdown of the crankshaft and an accident of the ship's power plant.

To avoid this, it is recommended to carry out work to determine the general condition and residual life of the elements. Our laboratory specialists carry out this evaluations in accordance with Class requirements.

Due to significant loads, the damper is subject to wear and, therefore, needs regular inspection and preventive replacement in case of unsatisfactory condition.

Since the cost of new elements is high, and the scale of the consequences of their incorrect operation is difficult to predict, the expediency of work to determine the residual working life of the torsional vibration damper is obvious from a commercial point of view.

In addition to determining the residual life of the dampers in operation, the laboratory of our group is engaged in the selection of dampers with certain characteristics for new internal combustion engines.

When evaluating the working condition of a damper, it is often a choice between torsiography and silicone analysis of dampers. The latter is carried out in strict accordance with the manufacturer's instructions. However, torsiography is preferable due to the difficulty of complying with factory recommendations for sampling and the necessary disassembly of the internal combustion engine in some cases.

Regular sampling reduces the efficiency of the damper — it is necessary to top up the silicone liquid in the volume of the sample taken. The method cannot be used for operational control, since the analysis of silicone liquid should be performed in a chemical laboratory with special equipment. An example is the internal combustion engine of the German manufacturer SKL, where sampling for one damper can be carried out no more than twice.

Removal of dynamic load data by torsiography and strain measurement (longitudinal, torsional and bending vibrations) in different navigation conditions of ships with the preparation of accounting documents.

Assessment of the correctness of the theoretical calculations of oscillations by the method of control measurements of dynamic loads.

Measurement of the amplitude of vibrations and evaluation of the residual life of dampers.

Analysis of polymethylsiloxane liquids (silicone oils, organosilicon liquids, polymers) for torsional vibration dampers with determination of the following characteristics: density, flash point, kinematic/conditional/dynamic viscosity, mass fraction of mechanical impurities and water.

Competency of laboratory

Vibroacoustic measurements and tests for shafting

  • Measurement of dynamic loads of shaft lines:
    1. torsional vibrations;
    2. axial vibrations;
    3. bending vibrations.
    Torsiography and tenzometry measurements are carried out in different navigational conditions.
  • Theoretical calculations of torsional, axial and bending vibrations of shafting.
  • Measurement of the vibration of main and auxiliary machinery, processing equipment, hull and superstructure; functional vibration diagnostics
  • Measurement of oscillation amplitudes of vibration dampers
  • Serviceability period and residual service resource evaluation of silicone dampers
  • Temperature measurement and evaluation of service durability of flexible couplings based on tests
  • Determination of the residual life of highly elastic couplings
  • Processing the results of measurements performed and preparing reporting documents in accordance with Class rules requirements.

    Analysis of polymethylsiloxane liquids - silicones

    • Organosilicon liquids
    • Silicone oils
    • Polymers

    The analysis is carried out to determine a number of characteristics: kinematic/conditional/dynamic viscosity, mass fraction of mechanical impurities and water, flash point, density.



    • propulsion systems and engines of propulsion units with power starting from 75 kW;
    • engines of auxiliary diesel generators with power from 110 kW.

    Purposes for torsiography:

    • To check the correctness of theoretical torsion calculations
    • Torsion damper performance assessment
    • Diagnostics of shafting elements (elastic connections, propeller, connections of propulsion complex elements)
    • Diagnostics of gearboxes
    • Adjustment of fuel equipment, etc.

    In accordance with Class rules, calculations must be submitted:

    • when new propulsion system or new DG Set with flexible element is under projecting;
    • with the following changes in the shaft line on a vessel or unit:

      installation of the main engine of a different brand; installation, removal or replacement of the elastic coupling with an element with other characteristics; installation, removal or replacement of the gearbox with an element with other characteristics; installation of a propeller of a different size or of a different material; cutting of blades of an existing propeller (if the new moment of inertia differs from the previous one for more than 10%); changing the diameter or shaft lengths for more than 2% or an elastic change for more than 5%;
    • when replacing a diesel engine, generator, or elastic coupling of another brand with a diesel generator set.