Contact Details
Gertsen & Olufsen AS
Savsvinget 4
DK-2970 Hørsholm
Denmark
Tel: +45 4576 3600
Fax: +45 4516 4199
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Gertsen & Olufsen (Noise & Vibration)
G&O Vibration Compensators
G&O Vibration Compensators are world leaders in eliminating unwanted vibrations and improving the performance of ships, offshore installations and power plants. The backbone of our unique product range is a number of worldwide patents and more than 15 years of constant product development, enabling us to offer our customers the best solutions within the field of vibration damping.
The Product
Why deal with the symptoms - when we can eliminate the source! Guide force moments, unbalanced moments, axial thrust- and hull beam vibrations are all unavoidable characteristics linked to the low-speed two-stroke diesel engine. Most vibration problems are reduced by adequate conventional countermeasures such as stays and dampers. However, these only reduce the symptoms, they do not eliminate the source of the vibrations. An electrically driven moment Compensator is consequently the best and most economical countermeasure available as the source of vibration is eliminated because the system simply outbalances the source of vibration.
Applications
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 four different fields of vibrations as follows:
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. The problem is most frequent on 4 to 6 cylinder engines and in most cases these engines are delivered with a built in mechanical 2nd order moment damper. The location of the vessels zero hull nodes can enhance the 2nd order reaction forces causing hull vibrations
Guide Force Moments:
The transverse reaction forces that occur when the engine crossheads are acting on the engine upper structure, when converting linear movements to rotating movements causes this guide force moment - these moments are exciting engine vibrations moving the engine in transverse direction. Conventional countermeasures such as hydraulic top-stays or hull reinforcement will have limited impact on this type of moments, as they tend to either transfer the vibrations to other parts of the vessel or change the natural hull frequency of the vessel. Engines with 4-7 cylinders are having a guide force H-moment, which is identified as a transverse rocking movement of the engine top. Engines with 8-12 cylinders are having a guide force X-moment - which is identified as a twisting movement of the engine
Axial Vibrations:
During combustion the engine crankshaft deflects in axial direction of the engine (horizontal/longitudinal) - In rare cases the zero hull node is "interfering" and creating reaction forces in the thrust bearing, which can cause vibrations in the superstructure. The problem is most frequent on 5 cylinder engines and in most cases these engines are delivered with a built in axial damper. The frequency of an axial vibration corresponds to the number of cylinders multiplied by the engine revolution..
Hull Beam and Propeller Thrust Vibrations:
Removing the source of vibrations could in some cases be too complicated or even impossible, and in such cases outbalancing the symptoms is a second to none choice. Local induced hull beam vibrations can be outbalanced by placing a compensator where the actual vibration occurs, by referring to the frequency of the inducing source e.g. with a propeller it is possible to create a synchronised counterforce and thereby eliminating the symptom.
More than 200 G&O Vibration Compensators have been successfully installed. A reference list can be obtained from Gertsen & Olufsen.
