7% Ni Steeel for LNG Storage Tanks

[ronfrend]

Does anyone know if 7% Ni steel is now approved under API620 or AME VIII for LNG storage tanks? I know this has been used in Japan and the Middle East with huge cost savings but if I'm building a tank in North America I don't know if it's allowed.

Ron Frend

http://www.predicon.net

 

[MJCronin]

I think a little background information may help here .....

Storage of LNG is generally in large-volume above-ground low-pressure (less than 5 psig design) tanks. These tanks are double-walled, with a carbon steel or concrete outer shell and a nickel-steel inner tank. Design of the inner taank is typically done in accordance with the rules of API-620 and ASME VIII.

There have also been successes in configuring these tanks with an post-tensioned concrete outer shell instead of a CS shell

Currently, in the USA, 9% Ni steel has been the most commonly selected material for the inner shell of LNG Storage tank and has been in use for over 50 years

https://www.gti.energy/wp-content/uploads/2018/12/Materials-3-Patrick_Toussaint-LNG17-Poster.pdf

"9% Nickel steel plate is the most common material used to construct the cryogenic containment system of onshore LNG storage tanks. As along its toughness at cryogenic temperatures, it also possesses both high strength and economical advantages, it can be considered as an interesting choice for newer concepts"

This is a very useful document for understanding LNG tank design details:

http://large.stanford.edu/publications/power/references/docs/add10896.pdf

This is a very useful paper for understanding the low-temperature issues for LNG storage using 7% Nickle steel:

https://www.mdpi.com/2075-4701/6/11/285/pdf

Another good site for advantages of the 7% Nickel steel:

https://www.nipponsteel.com/en/news/20140619_100.html

Addressing your question, the API-650, 620 codes and the ASME-VIII codes do not direct the user into a specific choice based on desired service. The codes simply list various materials that are automatically approved with the rules of the code.

IMHO, the cheaper 7% nickel steels seem to be relatively new on the US scene (since 2014) and I doubt if they are addressed by the slow moving API Code People







MJCronin
Sr. Process Engineer