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www.marinelink.com 23? Bent shafts ? Unbalance of rotating components ? Main engine mis Þ re problems ? Mechanical looseness ? Deterioration of rolling-element bearings within transmissions and thrust bearings? Gear wear ? Rubbing? Structural resonance ? Machinery soft-foot conditions The vibration analyst will then create a report with Þ ndings and recommenda- tions. The data collected can pinpoint the cause of faults way before expensive stays at a shipyard are scheduled. Expe-rienced analysts, such as those with Ad- vanced Mechanical Enterprises/AME, use three key criteria to assess vibration on vessels:1. Crew Comfort Level Vibration levels are within the guide- lines established for human comfort and well-being (habitability). In ana-lyzing Passenger Comfort Level vibra-tion; AME uses the applicable ?Comfort Class? guidelines established by the ma-jor marine classiÞ cation societies. 2. Machinery ConditionVibration that does not cause any re- duction in the life of the machine or any damage to nearby equipment and surroundings. In analyzing Machinery Condition; AME uses a combination of the following methods when performing data analysis:a. Trend recorded vibration data on critical points on the machine periodi-cally over the years.b. Compare vibration levels of identi-cal machines. If three machines have similar vibration spectra and the fourth machine exhibits higher levels at the same conditions, it is an easy matter to determine which machine is having problems.c. Have the manufacturer evaluate vi-bration data.d. Use a vibration severity monograph based on the accumulated experience of similar machines. In this regard; ISO Standard 10816 ?Mechanical vibration ? Evaluation of machine vibration by measurements on non-rotating parts? is referenced.3. Structural Vibrations Vibration that can appear in other ar- eas of the vessel which are not in the accommodation areas which may be in resonance or near-resonance. In this case, considerable dynamic magniÞ -cation can result in inadequate fatigue strength. Many factors can inß uence fa- tigue strength such as:a. Material.b. Structural details (stress concentrations).c. Vibration mode. d. Welding processes applied. e. Production methods.f. Environment (corrosion).Mechanical issues can burn a hole in your wallet, but what other harm can it cause? Even a minor misalignment (often a cause of vibration), can cause extra load and added stress on compo-nents, which increases the heat output from prime movers, making the machine with misalignment draw more current. This causes increased fuel consumption, thus increasing your carbon emissions. If aligned correctly, a noted 1-3% reduc- tion in energy usage can be attained, not to mention a reduction in your vibration. ?When it comes to machinery health, consistency is what counts with any maintenance plan,? said Merhige. ?Vi- bration analysis is a cost effective ser- vice that can be scheduled on a regular basis. And, most importantly, it increases your bottom line.?MR #10 (18-25).indd 23MR #10 (18-25).indd 2310/3/2013 10:01:35 AM10/3/2013 10:01:35 AM
