Piping Material Grade Query

[Anirudh_96]

Hello, I'm designing a pipeline connecting to a 28" pig trap via a 28" x 20" Reducing tee via a Weldneck Flange and a spool of 20" pipe. Pressure class of the piping is 600#. We've received a Piping Material Specification from our client that specifies the materials as :

Pipe - API 5L Gr. X65 PSL2, SMYS - 65000 psi
Flange - ASTM A105N (600#, WNRF) , SMYS - 36000 psi
Tee - ASTM A860 Gr. WPHY, SMYS - 65000 psi

Thickness of all three items is 1/2".

I'm still fairly new to materials but I'm concerned if these materials can be used together given the large difference in yield strength. I'd also like to know if there are any concerns on welding as well.


Thanks in advance!

 

[akpipelineengr]

What is the design code?

Assuming design pressure is 1480 psig, 0.500" wall thickness is thin in the low yield flange material, but how thin will depend on your design code.

 

[LittleInch]

Your flange needs to be A694 F65.
Your won't find it in B16.5 so you need to use MSS SP- 44 for the pipeline flange.

And you need a barred tee.

A 28 " pipeline eh? Can't say I've even seen that size used.

 

[Anirudh_96]

What is the design code?

Assuming design pressure is 1480 psig, 0.500" wall thickness is thin in the low yield flange material, but how thin will depend on your design code.

Design code is ASME B31.4 and yes the wall thickness is another thing I'm worried about.

 

[Anirudh_96]

Your flange needs to be A694 F65.
Your won't find it in B16.5 so you need to use MSS SP- 44 for the pipeline flange.

And you need a barred tee.

A 28 " pipeline eh? Can't say I've even seen that size used.

Yep, that's exactly what I generally use but I've got a client PMS that says I need to use a A105N flange.

FYI, The pipeline's 20", but the Pig trap major barrel its connecting to is 28", hence the 28" x 20" barred tee. I forgot to mention that in my original query.

 

[goutam_freelance]

Thickness of all three items is 1/2".

Which thickness are you talking about regarding flange? 1/2 in flange thickness is grossly in error. For 24 in 600 lb rating flange, the minimum flange thickness (C) is 4 in, as per B 16.5. However, please check the latest code.

 

[Anirudh_96]

Which thickness are you talking about regarding flange? 1/2 in flange thickness is grossly in error. For 24 in 600 lb rating flange, the minimum flange thickness (C) is 4 in, as per B 16.5. However, please check the latest code.

1/2" is the flange bore thickness - equivalent to Sch XS

 

[Krausen]

Which thickness are you talking about regarding flange? 1/2 in flange thickness is grossly in error. For 24 in 600 lb rating flange, the minimum flange thickness (C) is 4 in, as per B 16.5. However, please check the latest code.

He's talking about the thickness of the weldneck end

 

[goutam_freelance]

Assuming P=1480 psi, D=28 in, E=1, S=0.72x65000x1=46800 psi,
Min thickness t=(PD/2S)=0.443 in. for pipes

Considering a manufacturing tolerance of 12.5%, the minimum thickness should be 0.443/0.875=0.506 in.

On top of this, you need to add corrosion allowance A as per industry practice.

So, the 1/2 in thickness as shown may be insufficient. Especially for the weld neck flange.

 

[LittleInch]

Yep, that's exactly what I generally use but I've got a client PMS that says I need to use a A105N flange.

FYI, The pipeline's 20", but the Pig trap major barrel its connecting to is 28", hence the 28" x 20" barred tee. I forgot to mention that in my original query.

Then you need to tell your client that they need to create a new PMS for pipeline flanges which mate to X65 line pipe. Piping / plant people never understand pipelines and try and force you into using incorrect systems. You need to stand firm and tell them pipelines are not piping, work to different codes and standards and that's how it works all over the world.

I really don't understand your set-up here - can you sketch it out? Pig traps consist of major barrel, minor barrel and the reducer to connect between the two. A 20 x 28" is rather odd as you normally go two pipe sizes up so a 20 x 24 would be more normal. I really don't understand what this tee is doing?

A reducing tee to me is a main run of 28" and "reduced" branch line of 20" off the tee.

There's quite a few things here which I don't really understand / doesn't make sense and would be good to sort out.

 

[weldstan]

It appears that your client is rooted in the distant past when A105 flanges were commonly used for X60 and lower strength grades because of availability. Ask the client for a waver and provide the reasons thereof.

 

[akpipelineengr]

Considering a manufacturing tolerance of 12.5%, the minimum thickness should be 0.443/0.875=0.506 in.

B31.4 does not consider the manufacturing tolerance separate from design factor. 0.443" would be the Code minimum wall thickness, exclusive of any corrosion allowance.

Refer to para. 403.2.1:
"In setting design factor, due consideration has been given to and allowance has been made for the underthickness tolerance and maximum allowable depth of imperfections provided for in the specifications approved by the Code."

 

[Anirudh_96]

LittleInch and weldstan,

You guys were right on the money on both your assumptions. I managed to convince the client to let us take care of the PMS. (It is more work for me but at least I won't be struck with a 30 year old PMS with outdated information.)

I have attached a screenshot of our arrangement below. (Everything in yellow is the new scope. The rest is the existing arrangement). Here's some background on the project - We're basically rerouting a pipeline to feed to a different terminal due to a change in the custody transfer agreement between our client and a 3rd party. A small part of this involves the modification of an existing pig trap - the idea is to weld the new 28"x20" Tee to the major barrel with a pup piece and connect the new 20" pipeline to the Tee.

 

[LittleInch]

I'm glad you've got that fixed.

That errrr arrangement is one of the strangest I've ever seen and I've been out to the FSU.

So your 28" major barrel has a flanged end?

So there is no flow through your new line when any pigging occurs?? I'm working on the basis here that this is flow out of the pig trap, but it doesn't really make much difference. So I assume the pigging is very infrequent....

But if its a flanged end then I guess you're just connecting somewhere easy?
Still a bit weird.

 

[Anirudh_96]

The client used the word “Unconventional” but downright weird is what it is . Apparently the flanged end on the major barrel is a temporary solution until the pig trap door they’ve ordered comes in.

We’re still about 10% into FEED. I’m still waiting on confirmation on the pigging. Apparently they want to leverage (read: Hijack) the pipeline to the downstream of the pig trap to save some costs. This means that I’ve got a bunch of crappy site markups with these sort of arrangements at 3 different sites.

Makes me want to pull my hair out but hey, nobody said brownfield modifications were easy.

 

[LittleInch]

Hmmm, still weird.

Most company I know gave up flowing trough the trap against a quick opening door on a regular / normal basis decades ago as the risk of leakage was too high or if it did start leaking then you needed to shutdown to repair it.

So is the flow being split between the normal way in and this new connection?

 

[Anirudh_96]

No, the normal way is going to be idled for the time being. Flow is only going to be through the new line.

 

[LittleInch]

Why don't you just hot tap that line at the bottom?

Or even cold tap it.

 

[Anirudh_96]

Hmm, might work. I’ll look into that. Thanks!

 

[LittleInch]

Best not to mess with pig traps.

If you can isolate it just cut into it and weld a tee.