VIBR

Class notation covering the vibration performance of a vessel

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Purpose

The harmful vibration of machinery components and equipment has not generally been addressed in building specifications or in the class rules. The aim of the vibration class is to avoid vibration-induced breakdowns by ensuring that the vibration levels are within defined limits. Vessels complying with the limits set by this notation have a reduced risk of failure in machinery, components, equipment and structures caused by excessive vibrations. The VIBR notation is offered to both new vessels at the design stage and ships in operation.

Benefits

With the Vibration Class Notation included in the building specification, a clear definition of measurement procedures and vibration limits is assured. Thus disputes regarding the interpretation of levels and measuring procedures are avoided. The owner may experience the following benefits:

  • The risk of expensive operational disruption and possible off-hire is reduced by avoiding vibrationinduced damage to the machinery, equipment and structure

  • The vibration limits, as well as equipment and positions to be checked, are well defined

  • The documentation of vibration levels may be used as basis for later measurements in connection with docking and re-building.

Features

The vibration class limits are based on international standards and DNV’s experience of measurements world wide. These requirements come in addition to the requirements for machinery components as described in the main class DNV Rules. For each individual vessel, riskbased methods are applied to reveal critical components. The VIBR notation ensures that a proactive, systematic risk-based plan for the survey, measurement and evaluation of main components in respect of vibration limits has been applied.

Process

s towards the VIBR notation:

  • the Owner/Yard requests the notation

  • DNV arranges and carries out HAZID in order to identify critical positions

  • the positions to be measured are defined in the PROTOCOL

  • the survey and measurements are carried out on board according to the PROTOCOL

  • If compliance is OK, the VIBR notation is issued