Guidance for the Prevention of Roll over on LNG Ships
Year: 2012 Language: english Author: SIGTTO Genre: Handbook Publisher: Witherby Publishing Group Ltd Series: First Edition ISBN: 978-1-85609-558-7 Format: PDF Quality: Scanned pages Number of pages: 14 Description: "Rollover" refers to the rapid release of LNG vapour that can occur as a result of the spontaneous mixing of layers of different densities of LNG in a storage or cargo tank. A pre-condition for rollover is that stratification has occurred, ie the existence in the tank of two separate layers of LNG of different density. The possibility of a sudden release of large amounts of vapour and the potential over-pressurisation of the tank resulting in possible damage or failure is recognised by the major design codes. EN 1473 - "The design of onshore LNG terminals" and NFPA 59A - "Standard for the Production, Storage and Handling of LNG" both require this phenomenon to be taken into consideration when sizing relief devices. Whilst the relief valves may prevent damage to the tank, LNG vapour is not only flammable and heavier than air on release, but a valuable commodity and a potent greenhouse gas and therefore venting should be avoided whenever possible.
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Guidance for the Prevention of Roll over on LNG Ships
Language: english
Author: SIGTTO
Genre: Handbook
Publisher: Witherby Publishing Group Ltd
Series: First Edition
ISBN: 978-1-85609-558-7
Format: PDF
Quality: Scanned pages
Number of pages: 14
Description: "Rollover" refers to the rapid release of LNG vapour
that can occur as a result of the spontaneous mixing
of layers of different densities of LNG in a storage
or cargo tank. A pre-condition for rollover is that
stratification has occurred, ie the existence in the tank
of two separate layers of LNG of different density.
The possibility of a sudden release of large amounts
of vapour and the potential over-pressurisation of
the tank resulting in possible damage or failure is
recognised by the major design codes. EN 1473 -
"The design of onshore LNG terminals" and NFPA
59A - "Standard for the Production, Storage and
Handling of LNG" both require this phenomenon to
be taken into consideration when sizing relief devices.
Whilst the relief valves may prevent damage to the
tank, LNG vapour is not only flammable and heavier
than air on release, but a valuable commodity and a
potent greenhouse gas and therefore venting should
be avoided whenever possible.
Gas rollover.pdf
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