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Revised version of Class Note 30.9 - Sloshing analysis of LNG membrane tanks


Class Note 30.9 has since its first release in 2006 been a unique reference for sloshing assessment of membrane type LNG tanks. Like no other document it provides in-depth description and guidance on how to perform the assessment.

Items covered are:

  • Sloshing fundamentals
  • Assessment basis and principles
  • Sloshing impact load assessment
  • Sloshing load assessment for pump tower structures
  • Structural resistance and strength assessment of load bearing insulation
  • Strength assessment of the inner hull structure supporting the insulation
  • Strength assessment of in tank pump tower and tower supports

The original version of the Class Note was ahead of its time in many ways, and pointed the way for much of the development seen in sloshing assessment methodologies in the years following its release, mainly in the period from 2007 - 2010. Although still relevant in many respects, there was a need to revise the document to bring it in line with the current assessment practice followed by DNV GL and the main players in the industry.

The revised version of the document contains the following main changes:

  • Introduction of the concept of risk based sloshing strength assessment: The sloshing load is determined as a function of the consequence of a structural failure
  • Updated guidance on sloshing load assessment to represent the current practice followed by DNV GL. The key item is the use of long term statistical description as basis for determination of the sloshing impact design load.
  • Implementation of the results of the latest research on model testing conditions and scaling of model test results to full scale.
  • New simplified and user friendly assessment methodology for the inner hull supporting the containment system
  • Improved readability and user friendliness through improved document structure

The revised Class Note 30.9 enters into force from August 2014. Copies of the document can be downloaded from DNV Exchange or you can send an e-mail to Tom Klungseth to request a copy.

If you have any questions about the document or its contents, please contact tom.klungseth.oestvold@dnvgl.com.