Longitudinal Weld High Pressure Pipe

[MegaStructures]

What strength reductions are required for a longitudinal weld joint made in the field on a high pressure pipe? 100% radio graphic testing to be performed, material is 304 stainless.

 

[XL83NL]

Further details required.
Designed & built to ASME B31.3, base Code chapters (i.e. I through VI), assuming Normal Fluid Service?

Huub

 

[MegaStructures]

Designed to ASME B31.3, pipe will support "occasional" loads.

 

[XL83NL]

As you havent addressed the rest of my questions, I assume this will be for base Code chapters, Normal Fluid Service.

Which sections of the code have you checked so far to verify what could possibly affect any possible strength reductions? Im happy to help you but @ eng-tips, we're not free-of-charge consulting engineer who will do your homework.

Alos, making a long seam in to field? Why is that? And the pipe bears no pressure, just occasional loads?

Huub

 

[MJCronin]

Which piping code is being followed for you pipeline ?

How high is "high pressure"?

What materials have you chosen ?

MJCronin
Sr. Process Engineer

 

[MegaStructures]

I wanted to get an idea if there was something I was not checking, but let me be a little clearer about my main question. ASME B31.3. Table A-1B gives strength reduction factors for longitudinal weld joints in pipes, but it is not clear whether the value is applicable for field welded joints, or manufactured seams. Is there an additional consideration if the longitudinal joint is made in the field? The seam will be fairly short, a fitting will be made by cutting pipe in half and rejoining to accommodate special field conditions, circumferential joint cannot be made as typical. Material is 304 stainless. Pressure is 100 psi

 

[LittleInch]

Use table 302.3.4

It's a bit odd, but if you radio / NDT the daylights out of it then I don't see why you need to apply any de-rating factor.

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

 

[EdStainless]

You are not making a pipe or a fitting, it would not meet those specs so those ratings don't apply.
This is a fabrication, think of it as a tank that happens to be inline, and the same size.
So follow those rules and you should be fine.

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P.E. Metallurgy

 

[MegaStructures]

LittleInch

I have looked at this table as well, but it's not clear if it accounts for welds made in the field, or only manufactured seams.

EdStainless

Are you suggesting to use a different ASME code other than B31.3, or a different section of B31.3, rather than 302.3.4?

 

[EdStainless]

Unless there is a section of 31.3 that covers such a fabrication.
You will not be able to claim that this piece meets the pipe specification so you will need something else.

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P.E. Metallurgy

 

[MegaStructures]

So perhaps something like ASME BPVC Boiler and Pressure Vessel Code may be more appropriate?

 

[XL83NL]

If it’s piping you can’t just switch to VIII-1 if that better suits your design approach.
This sounds more like a 304.7.2 approach, although a piping code doesnt seem to fit a pipeline design really. However cutting pipe in half and just rejoining makes that the original starting point is still pipe rather than selfmade pipe from e.g. plate.

Can you elaborate a bit more on the application, you mentioned a fitting is made by cutting pipe in two halfs in the long direction.

Where is this installation located?

Huub

 

[MegaStructures]

From a mechanics of materials standpoint, I don't understand why a strength decrease would be required. The filler metal to be used will be stronger than the base material and the stainless is not heat-treated, so no strength reduction should be required. The only way I could see that a reduction is warranted is for imperfections in the weld, which wouldn't be accepted in the 100% radiographic test. I'm not as familiar with ASME as I am structural codes, but I just do not see why ASME would not allow this condition or would require lower strength to be considered. The joint should be stronger than the original pipe.

The existing high-pressure pipe is being retrofitted to change direction. There is an obstruction blocking one side of the splice point, so a circumferential weld is not possible. No, the pipe cannot be connected in another spot that is not obstructed.

 

[EdStainless]

In ASME welded pipe/tube takes a 15% de-rate, regardless of how much it has been cold worked, tested, and heat treated. It is just one of those things.
There are a couple of code cases for special application that allow you to use 100% for tubing if you do two different pressure/leak tests (air and hydro) and two different electromagnetic tests (ET and UT).

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P.E. Metallurgy

 

[MegaStructures]

I'm ok with a 15% de-rate, but some think that this fitting just can't be made and won't be allowed per ASME and I just cannot see how that would be the case. A metal pipe with an internal pressure behaves in a predictable way with, or without, a welded joint.
My knowledge gap is particularly with the ASME code and I would like to

1) make sure I am not overlooking a critical piece of the design
and
2) Find a clear "safety factor" to be applied per ASME for this custom made fitting.

I don't have the code in front of me, but I will check 304.7.2 and see if there are factors that will apply in that section. Otherwise, I'm tempted to believe 302.3.4 applies

 

[LittleInch]

Can we all please use the correct designation here. "ASME" on its own means nothing other than the organisation. As we're in a piping forum this could be ASME VIII, ASME B 31.3, B31.4 B 31.8 etc etc.

It's not hard to be precise and we are engineers here.

I'm assuming ed means ASME VIII and mega structures means ASMe B 31.3

Personally I can't see a difference in whether the longitudinal seam is welded in a factory, on site or on the moon. The pipe doesn't care.

The only thing I wouldn't be wild about is if the pipe was cut along the previous weld seam as well as the other side. So if you're design to ASME B 31.3 then table 302.3.4. is your best guide. sure it's not exact, but how else do you make a decision? Use the engineering judgement that the code requires you to use.

"(3) The Code generally specifies a simplified
approach for many of its requirements. A designer
may choose to use a more rigorous analysis to develop
design and construction requirements. When the designer
decides to take this approach, the designer shall provide to
the owner details and calculations demonstrating that
design, construction, examination, and testing are consistent
with the design criteria of this Code. These details
shall be adequate for the owner to verify the validity
and shall be approved by the owner. The details shall
be documented in the engineering design."



However we don't really know what diameter, thickness or pressure we're talking about here which can colour the discussion.

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