G&O Vibration Compensator
Vibration Problems? Why deal with the symptoms, when we can eliminate the source!
Gertsen & Olufsen Vibration Compensators are world leaders in eliminating unwanted vibrations and improving the performance and comfort of ships and power plants. The company specialises in the development, production, installation and sale of electrically driven moment compensators.
A Gertsen & Olufsen vibration compensator is designed to do the exact opposite of the inducer (engine or propeller) by delivering a cyclic and opposing counterforce in a specific direction at a specific time. Main engines, propellers and hulls are all having very low natural frequencies; our systems have a corresponding operational frequency bandwidth from 1to 25Hz depending of the type of compensator in question.
The system creates an opposing sinusoidal varying force and phase angle that simply outbalances the source of vibration. Two sets of counter rotating irregular masses are driven by an electric servo drive ensuring a cyclic counterforce. The two counterweights can be individually adjusted to any required counterforce – once the necessary force has been determined it will be locked in that specific position. The servo drive is synchronized with the main engine ensuring that the correct and opposing phase angle is maintained.
There are two types of compensators: The horizontal- and the vertical type of compensators. The compensators are delivered in different sizes comprising the varying size of forces required.
A complete Gertsen & Olufsen vibration compensator system comprises three main components:
The synchronising unit controls frequency and phase angle of the compensator unit, based on the measured inputs from the encoder unit.
The Compensator ensures synchronising with the main engine by means of
small mass-moments of flyweights and high torque of the servomotor.
The main engine RPM detection system detects the main engine rpm
(3.000 pulses per engine revolution) and the top dead centre (TDC) of
main engine cylinder no.: 1.
In the following we will give you a general overview of different type of vibrations induced by either main engine or propeller and some practical application examples of how to solve the problems. Generally we are working with the following different fields of vibrations;
External Unbalanced Moments
External unbalances are caused by the inertia of the rotating unbalanced masses of the engine - The most common external unbalanced moment is the 2nd order moment acting in vertical direction only and with a frequency corresponding to two cycles per engine revolution.
Guide Force H-Moments
The purpose of the cross heads of a two stroke slow speed diesel engine is to convert oscillation forces into rotation forces. The transverse reaction forces that occur when the engine crossheads are acting on the engine upper structure cause this guide force moment. Engines with 4-7 cylinders are having a guide force H-moment, which is identified as a transverse rocking movement of the engine top.
Guide Force X-moment
The purpose of the cross heads of a two stroke slow speed diesel engine is to convert oscillation forces into rotation forces. The transverse reaction forces that occur when the engine crossheads are acting on the engine upper structure causes this guide force moment. Engines with 7-14 cylinders are having a guide force X-moment, which is identified as a horizontal twisting movement of the engine top.
Hull Beam & Propeller Vibration
In cases where it is not possible to outbalance the source of a vibration, the second best choice is to outbalance the local vibration (symptom) where it occurs. The advantage of a lever arm between the inducing source and the compensator is utilized and consequently a relatively small imbalance is required to outbalance the local vibration.
Download reference list here
Main engine RPM detection system