DNV-liquefied gas carriers with type A and B prismatic tanks

Classification Society DNV has published a "class guideline" document with updates on liquefied gas carriers with independent prismatic tanks of type A and B.

This document was published on 1 May 2023 and it supersedes the August 2021 edition.

In May 2023, the following changes were made:

General:

The document was updated and restructured to align with the standard DNV format.

Clarification of material for hull outfitting:

Section 2.4 clarified the material requirements for the supporting structure attached to the outer surface of the secondary barrier.

Update of finite element (FE) procedure:

Section 4.2.3 updated the modeling of a wooden block, replacing the spring element with a compression-only truss element. Gaps in the analysis were also addressed and described.
Section 4.4 updated the simplified procedure to an iterative method.
Section 5.2 improved the fine mesh analysis procedure based on the updated procedure.
Section 6.1.3 clarified the modeling approach for fatigue analysis.
Removed Appendix A.

Load case tables:

Friction for anti-floatation supports:

Section 4.4 updated the friction coefficient to be used for anti-floatation support from maximum to minimum.

Acceptance criteria table for cargo hold FE analysis:

Table 5 in Section 4 was changed to align the acceptance criteria for static conditions with DNV-RU-SHIP Pt.5 Ch.7 Sec.20. The criteria changed from 70% to 80% of AC-II criteria.

Rule load application instead of using direct loads:

Section 6.1.1 added an option to use rule fatigue loads instead of direct loads, providing an alternative approach.

These changes were made to enhance clarity, update procedures, and align with established standards in the document.