X70 vs. 516-g70n (normalized) for pressure vessel

[Lampropeltis]

I would like an opinion (or better) on whether or not 516-70n (normalized) is a suitable material replacement for API5LX70 (X70) for construction of a pressure vessel - giving consideration to modulus, ksi, etc of both materials (I believe they are similar enough).

vessel design criteria is as follows: 36" OD x 40'long @1500 psi @120*F no corrosion allowance.
I just cant find enough good data on the 516-70n to justify the substitution.

The 516-70 would be purchased in plate form, then rolled and welded, whereas the x70 would be purchased as pipe from the mill and have heads or endcaps welded.

Thanks for any help or suggestions that can be offered. And just FYI - the reason for the switch is material lead time. the x70 takes a lot longer to acquire than the 516-70. If anyone has any other material suggestions, they are gladly welcome.

 

[blacksmith37]

The X70 ( and any other pipe) will be made from plate, rolled and welded , DSAW. So the difference is whether or not you want to have control of the long seam weld; and you could make it by some weld process other that DSAW.
You might be able to find centrifugal cast 36" diameter. And if money and time are no problem; ring forged/rolled (try Kobe/Japan).

 

[SJones]

You do realise that the '70' is yield strength for one and tensile strength for the other? Weldability could also be a world apart. If you accept that you could use X42 on a yield strength basis, then you should be able to get a joint or two from a stockist. 36-inch X70 is not a real commodity item. If you do need the strength to keep wall thickness down, try X60 from a stockist. What 'data' are you looking for exactly?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[blacksmith37]

I am so embarrased by my missing the "70". Especially since I was on ASTM A1 committee and later on API 5 ;I'll have to ask my doctor for a senility test.

 

[21121956]

Hello everybody:

Lampropeltis, first of all you need to have clear, among other things what will be the use of this pipe (the fluid or sustance it will be conveying), the changes in temperature of that fluid that can provoke expansion/contraction of itself, etc.

In general terms, the chemical composition of these materials is:

ASTM A516-70: C, Mn, P, S, Si.
API 5LX70: C, Mn, P, S, Si, Nb, Ti, Ni, Al, B, Ca, Cr, Mo, Cu, V, Pb, Co.

Normally the steel A516-70 is used when high mechanical strenght is a decisive factor and the temperature of the fluid is from low to moderated.

The steel pipe API 5LX70 is generally intended to be used for the transportation of gas and/or fuel oils.

El que no puede andar, se sienta.

 

[metengr]

My first question is if this is indeed a so-called pressure vessel what is the code of construction??? If it is ASME B&PV Code, Section VIII, the PI 5LX70 material is not permitted.

 

[Lampropeltis]

The tanks will contain air only, and will NEED to be ASME code stamped. We have both a U and U2 certification - Not sure if that makes a difference. Max test temp is about 120*F.

I was basically looking for material with similar properties to the x70, that WOULD be allowable under section 8. I thought the 516-70N had similar properties to the x-70.

What we DONT want is to end up with a 2" thick shell on these vessels if we can avoid it.

If I can provide additional info, I will be glad to. Thanks for the help so far.

 

[stanweld]

SA-302 Grades B, C & D have an 80 ksi minimum specified Tensile strength and are somewhat more typical of X70. Also look into SA-724 which has grades up to 95 ksi minimum specified ultimate tensile strength.

 

[Lampropeltis]

Awesome, thanks all. I will throw those materials into our software and see what pops out.
Are those fairly available plate materials?

 

[stanweld]

In my experience, it has not been a problem; however, you may depending on quantity ordered and your location.

 

[Guest102023]

Overlooking possible Code prohibition, I suspect you will not save much after you solve all the issues, only some which are technical.