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Safety, Engineering Practice

Sensing vibrations

Condition monitoring and vibration analysis

All onboard machinery generates vibrations. But when these vibrations reach certain levels, they can quickly cause major—and expensive—problems. By closely monitoring machine conditions, ship engineers are able to identify faults and take the appropriate action to resolve them.

High levels of vibration in a ship’s machinery often indicate a problem. Whether they in the vessel’s propulsion shaft, gearbox, or propeller, vibrations show that components are reacting to internal or external forces. Possible causes include shaft or coupling misalignment, unstable foundations, or worn out bearings. If left unchecked, such problems will dramatically shorten the lifespan of components and could lead to machinery damage and failures.

High levels of vibration indicate problems and can significantly reduce component lifespan.

Frequency versus amplitude

Fortunately, modern condition monitoring technology can help identify problems and determine their root cause. Different mechanical defects generate different types of vibration—analyzing the signal enables you to figure out what is causing the machine to vibrate and take any necessary action.

When performing condition analysis, experts examine two different parts of the signal: its frequency and its amplitude. Frequency is the number of times an event occurs within a certain time period. In the context of ship components, certain types of faults typically occur at certain frequencies. This means that by establishing the vibration’s frequency, technicians get a clearer picture of the problem causing it.

Amplitude, on the other hand, is the size of the signal. It varies depending on the type of machine and is compared with the vibration level of a new machine in good condition. Measuring amplitude helps to assess the severity of the fault: the higher the amplitude, the greater the problem.

Taking remedial action

Using condition monitoring technology and software, experts can analyze vibration data and determine the root cause. They then convey detailed insights on the machine’s true condition to service technicians, who decide on the best course of action. This enables them to carry out maintenance and repairs with confidence.

 

Standard measurement methods used by SKF include:

  • Overall vibration analysis
  • Phase analysis
  • Acceleration enveloping
  • SEE technology (for detection of acoustic emissions)
  • High frequency detection
  • Other sensor resonant technologies

 

Keeping vibrations within safe levels increases the safety of the vessel, protects the lifespan of components, and helps to prevent machinery breakdowns. For this reason, detailed analysis and condition monitoring are absolutely vital to a ship’s reliability.

Steady as she goes

Excessive vibration is one of the most common problems onboard vessels. Proper shaft alignment and secure machinery foundations can help to prevent it. Adjustable chocks for mounting heavy machinery provide an effective solution.

Find out more

 

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