DNV GL has revised Class Note 30.9 which, since its first release in 2006, has been a unique reference for sloshing assessment of membrane type LNG tanks.
Items covered include:
- 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 led 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 entered into force in August 2014. Copies of the document can be downloaded from DNV Exchange.
Adapted from press release by Katie Woodward
Read the article online at: https://www.lngindustry.com/lng-shipping/05092014/dnv-gl-revises-lng-sloshing-guidelines-1352/