Vibration Measurements on Yacht
AdMeS has undertaken measurements, vibration and noise analysis in the mechanical parts and in the interior of a yacht, in order to assess the comfort of passengers. The measurements showed results which were exceeding the ISO limits. Consequently, a detailed technical report was prepared, analysing the findings and the suggested actions in order to solve the detected problems. A partner company performed all the necessary actions on specific points in the engine room area. After their completion, new measurements of vibration and noise were taken, resulting in decreased values in all the vessel compartments, making the results to comply with passengers’ comfort as defined in the ABS Comfort On Yachts * directive.
*Guidelines of ABS Classification Society (Guide for Comfort On Yachts), and are executed in accordance with the international standard ISO 20283-5:2016 (Mechanical vibration — Measurement of vibration on ships — Part 5: Guidelines for measurement, evaluation and reporting of vibration with regard to habitability on passenger and merchant ships).
Findings
Some of the findings on the left machine of the yacht are listed below:
- After the elastic fastenings were placed on the support beams, new measurements were taken on 04/07/2018 and they showed that the phenomena are not maintained with the oscillation width at 1.833rpm being reduced from the value of 11.064mm / sec to 5.28mm / sec.
- There is a tooth load on the gear mesh of the low speed shaft with the intermediate shaft. The increased load is due to the low speed shaft. The phenomenon is intense and monitoring is recommended.
- During the check for the resonance frequency, increased vibrations in the frequency range 50-150Hz were observed. During the re-check which was carried out on 04/07/2018, measuring at the same points, it is noted that the amplitude of the vibration has decreased by about 5 units (mm / sec).
Measurements on Deck:
From the measurements taken at certain points of the yacht before and after the placement of the elastic fastenings to the turbo supports, there is a reduction in vibration intensity at RMS within limits for passenger comfort. The measurement points are as follows:
- At the main deck lounge
- At the main deck bar
- At the main deck dining room
- At the outer lounge of the upper deck
- At the wheelhouse
Suggestions
Taking into account the measurement period (summer months) and the conditions, the instructions given to the yacht repair company (following measurements made on 08/05/2018) were the addition of elastic links between the supports holding the exhaust ducts and the tracking the gears of the craft to increase shavings.
Following the above actions, a re-check was carried out at all points (on the engine room) and then on all the vessel (on all three decks) to confirm the reduction of vibrations.
It is reported that the post-repair change was felt by the yacht’s wheelhouse and the entire outer deck.
Below are the findings, after the repair completion:
Left Engine
In particular, the observations / damages per machine are as follows:
1. Balance in the left axial system. The intensity of the phenomenon is not worrying.
2. Heavy shaft tooth gear load. This phenomenon stems from the axle’s gross velocity.
3. High vibration amplitude in the turbo and cooling bed racks.
Right Engine
In particular, the observations / damages per machine are as follows:
1. High vibration amplitude in the turbo and cooling tank support beams.
Comments
Indicative charts are presented regarding the reduction of vibrations in the main spaces of the vessel and the two gear units, before and after the repair of the yacht,as below:
Gearbox Clutch
