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Material Selection for LNG Storage Tank

Material Selection for LNG Storage Tank

(OP)
Hi Experts,


If natural gas is liquefied (methane CH4) at -260F and the transport pressure is 4 psi, should the mdmt be -260F and design pressure be higher than 4 psi?

-MrTank

ôI have not failed. I've just found 10,000 ways that won't work.ö
-Thomas A. Edison

RE: Material Selection for LNG Storage Tank

The MDMT is normally specified as either -320 F or -325 F, the approximate temp. of liquid nitrogen at which impact testing is done for welding procedures and some materials.

RE: Material Selection for LNG Storage Tank

(OP)
Thanks. What about the pressure? I assume it will be designed under API 620 as API 650 maxed out at 2.5 psi internal.

-MrTank

ôI have not failed. I've just found 10,000 ways that won't work.ö
-Thomas A. Edison

RE: Material Selection for LNG Storage Tank

MrTank,

API 620 will be required as API 650 does not permit refrigerated service. It would be prudent to rate the vessel for enough overpressure to permit proper relief valve operation.

RE: Material Selection for LNG Storage Tank

I would be inclined to get somebody a lot more familiar with that kind of service involved in the design and/or specification. Not a good area to experiment.
If it's a fairly small tank, it might be just as easy to use ASME.

RE: Material Selection for LNG Storage Tank

Understand that the pressure at the bottom course of a 100+ ft high, tank shell will be considerably greater than 4 psi.

RE: Material Selection for LNG Storage Tank

(OP)
Thank you for your input guys. This is not a job but rather it is just for my own curiosity. In case I get asked, I already know what to answer based on your feedback. So feel free to answer.

Weldstan,

Yes I understand the concept of pressure head. Thanks.

JStepehen,

I have no problem hiring an experienced engineer if a job like this is thrown my way but I would like to understand as much as I can before I do.

-MrTank

ôI have not failed. I've just found 10,000 ways that won't work.ö
-Thomas A. Edison

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