Friday, February 3, 2023
Maritime Propulsion

Posted by July 15, 2015

Couplings Cure Gensets’ Destructive Vibration

  • Image: Renold Hi-Tec
  • Image: Renold Hi-Tec
  • Image: Renold Hi-Tec
  • Image: Renold Hi-Tec
Rubber-in-compression couplings help protect gas- and diesel-driven generator sets from torsional vibration and the possible catastrophic effects of resonance occurring if this were to coincide with the natural frequency of the system, says couplings manufacturer Renold Hi-Tec.
 
The company explains torsional vibration is an inherent feature of any internal combustion engine as pulses, or peaks in torque, occur as the pistons are driven on their power strokes when the fuel and air mixture ignites. Each pulse, or peak in torque, results in an imperceptible twisting of the drive shaft, and when large amounts of power are involved the forces involved can be enormous.
 
All physical systems have a natural frequency at which they vibrate – a bit like the sound of a ringing bell. If external forces are applied to a system that coincide with its natural frequency, then amplification, known as resonance, will occur. Resonance can be very destructive, as was seen in the collapse of the Tacoma Narrows Bridge, U.S. in 1940, when the frequency of the wind gusts coincided with the natural frequency of the bridge.
 
Renold Hi-Tec notes that if the torsional vibration on a diesel- or gas-engine driven generator set coincides with the natural frequency of the system, the results could be catastrophic in the same way, or at the very least will reduce component lifetime and significantly increase the level of maintenance and operating costs.
 
Rubber-in-compression couplings eliminate these problems as the rubber blocks within the coupling are selected to dampen vibration and move the natural frequency away from the operating speeds of the engine, the manufacturer says. The couplings provide drive through rubber blocks, which are compressed, and hence the term rubber in compression.
 
This type of flexible coupling is maintenance free, intrinsically failsafe and a better option than rubber-in-shear type flexible couplings that are prone to early fatigue failure on diesel- and gas-driven systems, according to Renold Hi-Tec. Capable of operating at temperatures up to 200 degrees C, the company's rubber-in-compression couplings also offer misalignment capabilities and blind assembly options if required.
United States