DUPLEX GAS PIPELINE THICKNESS CALCULATION 3

[GabrieleB]

I have to calculate the thickness for a gas pipeline made in UNS S31803 (duplex). Design code shall be B31.8. Where I can take derating data for this material. Is it possible to consider data from ASME II sect.D? Or I can consider the derating pitcure on the DNV OS F101? Which is the preferrable approach?

Thanks for your help

 

[BigInch]

If it is not an approved material, you can't use it in B31.8 except under the "Unknown Pipe Material" provisions.

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[GabrieleB]

Ok so which approach will you use if you have to design a gas pipeline made on the common S31803 duplex material? I think there should be a common acceptance way to do this calculation.

 

[vpl]

GabrieleB

This is from the Introduction Section of B31.8:

Materials are listed in the Stress Tables only when
sufficient usage in piping within the scope of the Code
has been shown. Materials may be covered by a Case.
Requests for listing shall include evidence of satisfactory
usage and specific data to permit establishment of allowable
stresses or pressure rating, maximum and minimum
temperature limits, and other restrictions. Additional
criteria can be found in the guidelines for addition of
new materials in the ASME Boiler and Pressure Vessel
Code, Section II and Section VIII, Division 1,
Appendix B. [To develop usage and gain experience,
unlisted materials may be used in accordance with para.
811.2(b).]

So, IMO, IF you are designing to B31.8 AND you want to use the [presumably] unlisted S31803 duplex material THEN you follow B31.8 paragraph 811 (I hesitate to just say 811.2(b) as there is pertinent information in the rest of para 811.)



Patricia Lougheed

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[BigInch]

Patricia, you seem to have picked up a different version of B31.8 than I have (-2007), or at least one with some different paragraph numbers from somewhere.

I can quote these,

811.22 Important items of a type for which standards
or specifications are referenced in this Code, such
as pipe, valves, and flanges, but that do not conform to
standards or specifications referenced in this Code [para.
811.1(b)] shall be qualified as described in para. 811.221, (my note: It seems to be an "and" that goes here)
811.222, or 811.24.

811.221 A material conforming to a written specification
that does not vary substantially from a referenced
standard or specification and that meets the
minimum requirements of this Code with respect to
quality of materials and workmanship may be used.
This paragraph shall not be construed to permit deviations
that would tend to affect weldability or ductility
adversely. If the deviations tend to reduce strength, full
allowance for the reduction shall be provided for in the
design.

811.222 When petitioning the Section Committee
for approval, the following requirements shall be
met. If possible, the material shall be identified with a
comparable material, and it should be stated that the
material will comply with that specification, except as
noted. Complete information as to chemical composition
and physical properties shall be supplied to the
Section Committee, and their approval shall be obtained
before this material is used.

811.23 Relatively unimportant items .....

811.24 Items of a type for which no standards or
specifications are referenced in this Code [para. 811.1(d)]
and proprietary items [para. 811.1(e)] may be qualified
by the user provided
(a) user conducts an investigation and tests (if
needed) that demonstrate that the item of material or
equipment is suitable and safe for the proposed service
(e.g., clad or duplex stainless steel pipe); or
(b) the manufacturer affirms the safety of the item
recommended for that service (e.g., gas compressors and
pressure relief devices).

With the difficulties I see indicated in bold text, and not being totally sure if the last (b) clause is intended to include pipe.

I know of no operators that are so adventureous to push these clauses for one reason or another, so I wouldn't recommend that you do it either. I can only see increased potential delays for your project, if not things that may be worse. Can't you find anything to use that is already in the list?

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[vpl]

Big Inch -- The version I have available (through IHS) is 2010. I confess I didn't read all of 811, just enough to suggest that this probably wasn't the best path to follow. I totally agree with your comment about finding some other material that's already covered.

Of course, there also exists the possibility of designing to some other standard, if the client agrees.



Patricia Lougheed

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[BigInch]

Right..time flies when you're having fun. So it's me with the outdated copy again??? Should have known you'd have the latest ver. I've been trying to get IHS access at my desk for the last month, but haven't even gotten around to getting "Business Procedures" installed ... whatever that might be.

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[GabrieleB]

I think that this discussion was too much focused about paragraph of B31.8. It's clear that ASME B31.8 is antiquoted, beacuse give only reference to the last decade materials like carbon steel and so on.
Everybody knows that S31803 is very common nowdays and it's very strange that ASME B31.8 consider that material non-standard in the 2010 version!!!

I don't think I am working on the first gas pipeline in the world made of duplex. So I think that somebody have already made calculatioin and design consideration without any additional wasting time tests.
It is also obvious that when you have to develop a project you can't lost months to permorm tests on materials like S31803 that everibody knows and thousand and thousans articles was written and tests were performed.


So I need a common pratical calculation solution with no tests and no abstract discussion on the absurd theoretical paragraph of ASME B31.8.

Sorry if I was rude, and my best apologies for this, but I think that some very glorious standards like B31.8 should be updated every now and then and not only minor corrections in 10 years!! Thanks for your support anyway ;-)!!

 

[BigInch]

10 years is nothing in the face of the major gas transmission companies. We're normally talking in "Pope years" for them. You see it's not the fact that they dislike technological improvements, its just a different ball game entirely when you find you line blows out 300 miles away from the nearest repair contractor's facility. Its not just like going out and patching up some bit of pipe in the plant. They need to be sure that the stuff they're using WILL last for at least the next 50 years. Its not like they're just buying 1000 meters of the stuff either. They're buying 1000 miles of it. 10 years of history in some refinery isn't really history at all. Somebody convinced them to use spiral pipe one time too. Some of them are still removing it from service.

So, if you're going to do gas pipelines, the sooner you get used to it, the better. My best advice is to follow the code, if you like collecting regular paycheques.


We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[stanweld]

GabrieleB:
If your line is a used for gas gathering and is not subject to 49CFR 192, B31.3 may be used. Dupelex stainless steel was used in North Slope gathering systems designed per B31.3 years ago.

 

[vpl]

GabrieleB

You're the person trying to do the design. Railing against the ASME standard gets you nowhere. Both BigInch and I have outlined the process in B31.8 for you to use the material you want. That's the only way you can use your beloved duplex and still meet the standard. We're not going to tell you that either of your approaches are acceptable, because they aren't.

As I see it, your options are
1) Follow B31.8 and use a material permitted by the standard.
2) Follow B31.8 and the provisions in Section 811 for unapproved materials to show that your choice of material is acceptable.
3) Convince your client that a different specification is more appropriate. For example, if you are in Europe, there might be an EN standard that applies. Here's a Wikipedia article that purportedly gives a list of EN standards:

http://en.wikipedia.org/wiki/List_of_EN_standards

4) Go rogue, use the material you want, and ignore the B31.8 standard. If you do this, be prepared to accept the consequences. Just to be perfectly clear, I DO NOT ADVOCATE THIS OPTION.

Patricia Lougheed

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[BigInch]

stanweld was that the same pipe that leaked in 2006?

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[MortenA]

we have lot of duplex pipeline (and even super duplex) for gas and multiphase service in the North Sea. If its offshore Europe, DNV is more commonly used. But then again, if US oil/gas in anything like i see on the semi "reality-TV shows" i have seen on TV its a bit ore "hey-ho Silver" than here and maybe a reåair shop is more urgently needed? (just kidding)

Best regards

Morten

 

[BigInch]

You can keep your (super)duplex. Maybe it will outlast the production platforms too and you can use it for fiber optic cables.

Its Gabriel trying to use B31.8 in Norway that's creating the problem.

We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer

 

[stanweld]

BigInch,
I do not believe that was the leaker. The 2205 gathering line was installed around 1990 for the Kuparak [unsure of spelling] field. I was involved in the original Engineering and mandating that automatic orbital welding be performed in the field.