Filling Limits for Liquefied Gas Cargo Tanks (eBook)

Published Date

January 1990

Filling Limits for Liquefied Gas Cargo Tanks (eBook)

(Excludes any applicable taxes)

This paper discusses why an IACS-SIGTTO study recommends deletion of section 8.3, "Additional pressure relieving system for liquid level control," from the Gas Carrier Codes. (12pp)

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At its 14th session in December 1984, the IMO Bulk Chemicals Sub-Committee invited the International Association of Classification Societies (IACS) and the Society of International Gas Tanker and Terminal Operators Ltd (SIGTTO) "to submit proposals for filling limits of cargo tanks in the light of recent experience and new developments in technology". IACS and SIGTTO submitted their proposals, together with the scientific case on which the proposals were based, to the IMO in June 1990 for consideration at the 20th session of the Bulk Chemicals Sub-Committee in October 1990.

This paper briefly describes the background to the present filling limit rules, the scientific work undertaken in the light of recent experience and new developments in technology, the proposals for loading limits for cargo tanks and considerations for the simplification of the requirements for cargo tank vent systems.

The Paper discusses: - The avoidance of cargo tank rupture as the primary safety objective. The cargo tank wall between the 75% and 100% fill levels will receive the highest heat flux in the worst credible fire engulfment incident studied. Filling the tank to a 98% loading reduces tank wall temperatures and minimise the risk of tank rupture.
- The avoidance of venting cargo through tank pressure relief valves as a secondary safety objective.
- Pressure relief valves sizing in accordance with present Gas Carrier Code requirements to protect tanks from over-pressure under worst credible fire exposure, even with completely liquid filled conditions at the time of relief actuation.
- Why filling tanks to near 98% loading limits under present Gas Carrier Code requirements will probably vent two-phase, liquid-vapour mixture when subjected to severe fire exposure.

The Joint IACS-SIGTTO study recommends deletion of section 8.3, "Additional pressure relieving system for liquid level control," from the Gas Carrier Codes as an unnecessary complication of the cargo tank vent system requirements which may increase the risk of tank rupture above the liquid level.

Paper Delivered by:
WS Wayne (Shell)
M Böckenhauer (Germanischer Lloyd AG)

Prepared for:
Gastech Amsterdam 1990

For over 45 years, the Gastech Exhibition & Conference has been at the forefront of the international gas and LNG market. This world-renowned event is regarded as the most significant meeting place for gas and LNG professionals, where the global industry gathers to do business.

Gastech hosts major IOCs, NOC’s, global utility companies, EPC contractors, shipbuilders, pipeline companies, manufacturers, distributors, technology and service providers, all who play an active role in the global energy value chain.


Title: Filling Limits for Liquefied Gas Cargo Tanks (eBook)
Product Code: 4433g060
Published Date: January 1990

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