Damper Condition Monitoring

Which of these conditions does your sample look like?



New silicone fluid is a clear / colourless fluid.



Fluid colourless to light shades of yellow / brown, and free from particles. Usually indicates no internal damage. Fluid viscosity will determine suitability of damper for further service periods.


Requires Service

Fluid dark brown or black in colour, usually with particles in the fluid. As a general rule, dampers with fluid in this condition have suffered internal mechanical damage and have restricted remaining service life.


Emergency Condition

A damper with gelled / solidified fluid is unsuitable for service and it should be removed from service as soon as possible as it is no longer protecting the crankshaft from torsional vibration.



Most diesel engines are fitted with one or two viscous shear type torsional vibration dampers attached to the crankshaft, at the opposite end to the flywheel.

Why Are Dampers Fitted?

The crankshaft damper is fitted to control the torsional vibrations developing in the crankshaft induced by the combustion process in the engine. The viscous damper, by reducing oscillations in the crankshaft to a low amplitude, keeps the material stresses arising from these vibrations within permissible design limits and prevents premature failures of the driven equipment due to fatigue.

How does the AAM Viscous Damper Work?

The viscous damper absorbs torsional vibration energy by the shearing effect of a highly viscous silicone fluid in the small gaps between the inertia ring and the damper casing. This is achieved by shearing a thin film of silicone fluid surrounding the inertia ring mass (seismic mass). As the fluid undergoes the shearing action it creates a reaction force to counter the torsional vibration.

The shearing of the fluid generates heat which is dissipated through the external surfaces of the damper. The silicone fluid within the damper casing will, after constant heat absorption during its service life, reduce in viscosity value.

How is the Performance of the Damper Monitored?

The internal condition and operating efficiency of the Holset viscous damper is monitored by periodically extracting small samples of silicone fluid for laboratory analysis.

Condition monitoring of the damper is an essential preventative maintenance practice. It ensures that the torsional vibration system of the vessel, generator or pump continues to function as per the design calculations, thus preventing early life failures due to metal fatigue.

AAM will advise subsequent sampling intervals via the analysis report. Special sampling kits complete with instructions are available from AAM or an appointed service representative.