code break between 31.4 and 31.3 3

[brpillai]

I have a small 8" branch line from a 24" API 5L X 60, 9.53 wt pipeline at the block valve station for the valve by pass. The pipeline is over 100 km long, having 4 similar block valve stations. as the length is very short, I want to use 8"piping material, as I do not want to buy few meters of API5L X60 of API 5L PSL2 line pipe. as there valve is underground, the branch is also underground and if I want to change to 31.3, I can not add a flange, below ground.

I would like your view whether I can have a code break at a weld joint, and whether any code allows this code break to be at a weld joint, as shown in the sketch.

Thanks in advance

 

[BigInch]

THERE IS NO CODE BREAK. All pipe shown in that entire picture should be a B31.4 design.

Apparently you think that B31.4 is only for design of underground portion of pipelines. That is not correct. B31.4 even includes product piping within pump stations. Read B31.4 Scope.

If it was gas transportation pipeling using B31.8, B31.8 would also include the whole picture. B31.8 also includes gas piping within compressor stations as well.

While not ideal, you can use flanges underground. Grease and protect the flange with a "flange protector".

 

[BigInch]

Additional comments.

You should use plug valves, or any other valve type capable of regulating flow. Ball valves are not ideal, as they are for on/off service.

If that were a gas pipeline valve station using B31.8, the whole assembly would use a maximum design factor of 0.60, lower if within a compressor station 0.50 or within high density "city" area classification 0.40.

Make sure that you use XXS walll as a minimum wall thickness in your 8" risers and bypass. I can probably find some spactacular photos of a valve bypass assembly (within a meter station) that was totally destroyed because someone used "pressure stress only" wall thickness for design of a riser and relief valve stack. The first time that the station activated, the blowdown thrust force through the relief valve (probably started oscilation which) caused it to bend completely over, after which the assembly went into liftoff phase and knocked down another relief valve stack nearby. Also why you want to use some kind of valve capable of good flow regulation.

 

[LittleInch]

Agree with BI - you really don't need to change code, but if you want to then yes, you can do it at a weld. It is much better than buried flange, that's for sure.

All you need to do is get the tee made in F60 and make sure the thickness of the branch matches the thickness of your AG 8" pipework. You will probably need a specific F60 to A105 weld procedure as the strengths are different which might not be cheap so a few lengths of X60 8" pipe and elbows might be worth it after all.

Without getting into the double isolation issue, your design only has single isolation when connecting anything to the blind flanges. Many system incorporate another valve between the bypass line tee and the blind flange so you always have double isolation from both sides when removing the blind flange.

You quote 31.4 so I assume this liquid so BI's apocalyptic scenario might not be valid..., However risers like this are notorious for suffering corrosion and stress caused by the main pipeline moving a bit and should have plenty of "meat" on them, at least until you get A/G.

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

 

[BigInch]

So if you use B31.3 on that, you must hydrotest that pipe to higher pressure... how many other things will be different. Material difference, inspection differences. API 1104 won't apply to B31.3 Different inspectors? Your construction contractor will make a lot of money.

 

[LittleInch]

True, hadn't thought about that, but you could make up all the pipework for the bypass in a shop (4 off), hydro at higher pressure then cut off the end and weld the final tie-in on site and bolt up the rest.

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

 

[BigInch]

That's how you'd do it anyway, no?

 

[LittleInch]

Probably, but it would make it easier if you really wanted to make it 31.3 to build and test separately. Still agree with you that there is no reason to create a break in code - getting hold of the pipes and fittings shouldn't be a big issue.

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

 

[zdas04]

BigInch,
How would you feel about the picture you were talking about appearing in my book? I have a great picture of a PSV on a separator bending over from the reaction force, but the resolution is too low for my publisher to accept. If you are willing, please e-mail it to me

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

And me.

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

 

[BigInch]

I'll try to find it. It's in one of those NTSB accident reports (Majove Pipeline Company), so it must be in the public domain by now. It was quite a mess.

 

[brpillai]

@BigInch , @littleinch, Thank you very much for your suggestions. This is liquid tarnsportation pipeline.

I summarise my understanding as below:

1. Code break can be at weld joint. I can use
2. All the valve station piping can be ASME B 31.4, Flange can be underground, though not preferred.
3. If I use piping material, that portion to be tested at higher pressure, this can be done at a shop seperately.
4. Need a specific F60 for Barred Tee to pipe A105 weld procedure as the strengths are different.
5. My intention was to use piping material as X60 line pipe might be difficult for small quantity of about 3 pipe length only.
6. I inderstand if I use A105, only more expensive weld procedure will result, whic can be avoded by using A105, Am I right in this.

Thanks for your valuable suggestions.

 

[BigInch]

1. Code break can be at weld joint. I can use
I WOULD NOT ALLOW A CODE BREAK to be made, because pipelines are simply outside the scope of B31.3. This assembly is clearly a part of a pipeline, as described in B31.4, full stop. If you insist on making that bit compliant with B31.3, you can do that as an additional engineering design exercise after you have designed it to B31.4, without putting a code break note on the drawing. There are many clauses in B31.4 that address future operations, maintenance, testing and inspection requirements for the life of the system and, with your B31.3 piping, someone in the future might claim that none of those clauses apply to your B31.3 components, even though it is installed in a pipeline system.

2. All the valve station piping can be ASME B 31.4,
Yes, it must be so.

2A Flange can be underground, though not preferred.
Yes. Did you see what a flange protector is?
3. If I use piping material, that portion to be tested at higher pressure, this can be done at a shop seperately.
Yes, you always have the option to make certain sub-assemblies in a shop, as long as they can be transported to site and attached into the main pipeline and be installed in accordance with inspection, testing and QA requirements.
4. Need a specific F60 for Barred Tee to pipe A105 weld procedure as the strengths are different.
I don't see what material the main pipeline is made of.
Optionally, why not use high strength F60 flange?
5. My intention was to use piping material as X60 line pipe might be difficult for small quantity of about 3 pipe length only.
Short bits of X60 pipe is not difficult to find near oil producing regions, but that depends where you are constructing this.
6. I inderstand if I use A105, only more expensive weld procedure will result, whic can be avoded by using A105, Am I right in this.
Why not use high strength F60 flange?

It is NOT impossible to weld A105 to X60, but it is far easier if there is an intermediate X52 transition pipe, but that complicates the design and construction. I would think it is preferable to avoid different weld procedures and needlessly complicate the design and simply use all X60, F60 materials.

 

[LittleInch]

I agree with all above, but didn't follow item 6,

A105 is a forging/fitting material spec, A106 is pipe

You can still use 8" A105 pipe designed to B 31.4 (31.4 allows A106 or A333 see page 39, table 423.1-1), only issue is the F60 to A105 weld on the tee. It means you can use standard grade A105/216 flanges.

If what you have is thicker than what B 31.4 requires, there is no issue here and then the whole thing is one code. Result.

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

 

[weldstan]

If the Jurisdiction mandates B31.4, you may not use B31.3 in your particular design. And as LI states you can design and test the A106/A105 materials to B31.4 so there is no real reason to use B31.3. You should also be able to purchase small quantities of 8" X60 seamless or ERW pipe.

 

[brpillai]

Thank you BigInch, LittleInch weldstan for your expert and valuable suggestions.

 

[BigInch]

The pictures of the failed relief stack mentioned above can be seen in the incident report,

http://www.phmsa.dot.gov/staticfile...ports/El Paso-Mojave GT 2012-5-2 Redacted.pdf

 

[brpillai]

Thanks to all for the clarifications.