Pipeline wall thickness for full vacuum

[lhwingking]

Hello,

There is a 36" 6km long crude oil pipeline. Thickness is 9.5mm with 3mm corrosion allowance.

How do I verify if this thickness is sufficient for full vacuum condition?

Thanks,


Never forget what you are. The rest of the world won't. Wear it like an armor and it can never hurt you.

 

[XL83NL]

As per your applicable design code.

 

[LittleInch]

Do an extrenal 1 bar pressure calc. Look at any subsea design code.

It will be ok.

Remember - More details = better answers
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[KevinNZ]

See what your piping code refers to. it maybe ASME BPV VIII Div 1 UG-28 to 30

 

[lhwingking]

Thank you LittleInch.

XL83NL and KevinNZ,

Design code is ASME B31.4. It does not lead me to ASME BPV VIII Div1 UG 28. Only ASME B31.3 does. But my pipeline is not as per ASME B31.3. Even if I follow ASME VIII Div1 UG 28, what will be the value of L in L/D?

Thanks for your responses.

Never forget what you are. The rest of the world won't. Wear it like an armor and it can never hurt you.

 

[DSB123]

L is the length between stiffeners. In your case L = 6000m

 

[lhwingking]

Yes I tried with L = 6000m. It's failing.

But should I really follow Section VIII here?

Thanks.



Never forget what you are. The rest of the world won't. Wear it like an armor and it can never hurt you.

 

[LittleInch]

Try DNV OS F-101 - it's free to download from DNV, section 5 D400.

you need to calculate a fair number of items, but it's a recognized pipeline code.

If you're taking the min wt as 6.5mm, that's a D/t of 150 - pretty thin.

I think that's a bit excessive though, both as a CA and to remove the entire wt from the pipe calc.

You may well be in trouble at that sort of thickness.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

Why not refer to para 402.4 of B31.4 as it seems the appropriate section for your design code?

 

[LittleInch]

The issue isn't circumferential stress, it's buckling which is different.

31.4 states in a number of places that the pipe shall be designed with a margin of safety over buckling, but doesn't tell you how to do it....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[lhwingking]

@LittleInch, Yes sir exactly. I will try DNV OS-F-101. Though the pipeline thickness is 9.5mm, it's inclusive of 3mm corrosion allowance and a negative mill tolerance of 12.5%. So, I think the check has to be done for 5.3mm

Never forget what you are. The rest of the world won't. Wear it like an armor and it can never hurt you.

 

[LittleInch]

This little table

http://lss.fnal.gov/archive/test-tm/1000/fermilab-tm-1378.pdf

multiplied to 36" gives a value of around 7mm.

Also this doesn't take into account any other forces, moments or axial stress, all of which could impact the final number.

apparently API RP 1111 has a formulae as well. Tried that and got a collapse pressure for 6mm pipe of 18 psi, but allowable is 0.7 of that so 13.2 psi.

http://fianagusta.blogspot.co.uk/2012/02/pipe-wall-thickness-design.html

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.