I found a direct comparison paper here: http://www.scribd.com/doc/32688077/Comparison-A36-amp-SS400

Weldability and one has no Mn content. They aren't exactly the same, but they are very close.

Alphard,

You should be aware of the fact that API-650 does not have a group of acceptable materials for usage in tanks installed "anywhere".

API-650 puts materials into various groups and allows usage of these groups based on the Design Metal Temperature of the proposed tank location.

The competent tank designer selects materials based on cost, strength, corrosion, ease of fabrication AND having the material in a permissable group based on the DMT of the site .

By the way, thank you for a clear, welll worded and understandable question in English. This seems to be an increasing rarity on this middle-eastern forum.

Are you new to API-650 tank design ?

Are there any senior engineers availble to you for questions?

Does your boss have an MBA ?

KeepItSimpleStupid- I found it and I guess it can be a good reference, but wondering where it comes from (i.e. how reliable it is?) but I'm using the details herein. Anyway, thanks!

MJCronin- I've been following your comments for several times before- always meaningful! I got my English while studying in Iowa before. I'm very sorry in my question- it supposed to read "....since i am NOT a designer"!!!

Back to the topic, I will check the DMT aspect and looks like I will have to do some study about tank design since I have been more in PMT and construction before. I hate the situation now since our FEED and EPC contractors both kinda screw up the technical issues and it tails down to me to verify their designs (...and I am not a designer!!!!).

Cost- not my job (anyway internet research suggests that A283 is cheaper); Strength- checked and A36 is "stronger"; Corrosion- we have CP, painting/coating for external and internal with CA= 3mm all; Ease of fabrication- A36 is better for formability (higher elasticity) and weldability (lower CE); "Having the material in a permissable group based on the DMT of the site"- I have to check this aspect since I have never been a designer (just in case if you want to comment further, our DMT is -5degC to 90degC).

... and my boss doesn't have an MBA.

Thanks all!