Pigging, elbows vs bends, procurement

[Robotaz]

Hi. I have searched and read through multiple threads here about pigging and proper fitting radii. I even read through the Industrial Pigging Technology book. I have 20 years of experience in natural gas engineering and project management in midstream, transmission, distribution, and compression. With overtime I have about 25 man-years of experience.

I’m really hung up on selecting the right 90’s and 45’s. I agree that it is best to use 5D fittings, at a minimum. However, I’ve never specified more than standard LR fittings. All of my customers, including TC Energy and other large companies, specify LR fittings. On the project I’m working on now, I’m building a 6-inch steel line that I’ll test for 1480 PSIG service, but it will operate 300-550 PSIG. I am not going to build the barrels until later for another project/phase. As I type this, I am 99% sure only having 92% use of hot bend strength will be fine, but that is yet to be confirmed.

How is a 5D bend specified for construction? I don’t know if it’s typical to throw into the BOM like a fitting. I also have no idea about part availability. And I have no idea what the specification and material description is to be if it’s not B16.9. I’m really at a loss here. I want to do the right thing and move a little outside of my comfort zone, but I have no experience with hot bends after all these years.

This is a very long-winded post, but I need help and I want others to know I’m not an idiot and genuinely need help to get on the right track. And FYI, I did talk to TDW and they claim LR fittings back to back are fine for 6-inch, but I just have a bad feeling about that reading what experienced people are saying here. I want to be in the group that doesn’t just listen to them, but I don’t know how to go about getting the hardware for the contractor.

Thanks in advance.

 

[LittleInch]

ISO 15590 is the go to code for pipeline induction bends.

You usually create a pipe bending specification and data sheet based on that code. You should be able to use the same pipe material as the main pipeline.

BS PD 8010 quotes a formula of 50 / (N + 1) to give you a percent wall thinning. , where N is the radius as diameter (5D etc). So a 5D bend is 8% thinning. That thickness determines the pressure rating of the bend. So sometimes you need to use a thicker "mother pipe" than normal to create the bend.

LR elbows are 1.5D. Only foam pigs really work at that radius and 2 elbows back to back creates a high risk of blockage IMHO.

What else do you want to know?


Remember - More details = better answers
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[Robotaz]

I really appreciate the quick response. This gives me some homework and a place to start.

Is it as simple as saying if my calculated design pressure is, say, 3,000 PSIG, that my actual design pressure when using 5D fittings will be 3,000 * .92?

Also, is a bend typically a BOM part, or is it just called out in the drawings as a part for the contractor to fabricate or procure? I have never seen a bend in a BOM in my life, so it’s a serious question. Also wondering about availability if such parts are procured with a BOM sent off to parts houses.

Thanks again.

 

[LittleInch]

"Is it as simple as saying if my calculated design pressure is, say, 3,000 PSIG, that my actual design pressure when using 5D fittings will be 3,000 * .92?"

No.

If you are right at the very limit of design thickness vs actual thickness of the pipe then you're good, but do it the other way around and say my pipe is 8% thinner than the main line pipe, what is the reverse calculation to get pressure from a wall thickness and SMYS. All depend son your design code.

It depends who is ordering and supplying the pipe usually. You normally create a bends list / data sheet and include that with a specification as the ISO code normally needs a little bit of additional clauses.

Induction 5D bends are created by specialist companies as you need to be very careful about heat up and cool down or you end up with brittle material - Not good. Hence why most companies buy direct from the vendor and free issue as you then are much more in control of quality and a direct line of responsibility if something goes wrong. Sometimes it gets tacked onto the line pipe order if you're ordering direct form a pipe mill not a stockist.

Incidentally, you really should have posted this in the pipelines forum - this one is a bit of a back water. but leave it here now.

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

 

[Robotaz]

I have a feeling I know the answer, but has there ever been a go-by data sheet that shows the minimum from ISO 15590 to get the bends ordered correctly?

I was planning on resorting to data sheets. I only have 4-5 bends needed for this project. I have informed my protege, who knows nothing at a company that knows nothing, that we’re using 5D from now on and dealing with it. It’s a curveball that sucks for me running every single facet of this project, including land and anything else you can imagine, even legal.

Thanks again.

 

[1503-44]

Think of it as keeping things interesting. I would think the last thing you want to be doing is sitting in a cube ordering bends day in day out. Its handling that other stuff that will get you noticed by the right people. Do it well and you'll go places.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

" It’s a curveball that sucks for me running every single facet of this project, including land and anything else you can imagine, even legal."

Welcome to pipeline engineering!

I don't have one to hand, but they are not fancy, normally just material info (grade, wt, SMYS, angle of the bend and how much straight length you want left (1m is usual))

Try calling Proclad or whoever your local supplier is and see if they've got a data sheet they give you.

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

 

[1503-44]

Some like to specify minimum remaining wall thickness after bending.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[GBTorpenhow]

If in ASME land, B16.49 is the ASME spec for factory made induction bends. There is an example datasheet in the back in one of the appendices.

 

[0707]

At your working pressure I would go for elbows, instead of hot bending. Hot bending put some problems of ovalizing and extrition (loss of thickness) wich is bad for pigging services.

 

[LittleInch]

But not as bad as having a radius of 1.5D versus 5D...

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

 

[1503-44]

If you make the bends correctly, it should not be a problem.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Robotaz]

Not sure why, but I cannot reply to specific posts.

My understanding is that elbows are not readily available beyond 1.5D, hence discussion of bends.

I see a comment about avoiding induction bends, but how does one specify with any accuracy that a contractor produces correctly constructed cold bends of no less than 5D?

I appreciate the heads up on the B16.49 data sheet. I had not seen that.

 

[Robotaz]

Well, a major manufacturer of ILI tools said I’m fine with 3D fittings and 5D ISO bends are overkill, for my situation.

Now I’m wondering if I can get segmentable 3D fittings to replace even everything easily cold bent, just to control ovality and wall thickness. I have a couple 17 degree and I guess the 12 degree sags for my HDD. I hope I can just segmentable and be done.

Thoughts?

 

[LittleInch]

This site just runs in a sequential manner so if you want to reply to a specific post just quote the person and time so e.g. @Robotaz, 18.04, ....

Elbows are max 1.5 D, After that it's "bends"

Yes 3D can be used, especially in the bigger diameter, but it could restrict your choice of ILI supplier. The key is usually not having more than one bend in the tool length (~4.5m) at the same time. Probably more suppliers can handle 3D nowadays, but if you get high angle ones (75 to 90 degrees) then it gets harder. Some of the 3D fittings may in fact be cast or forged instead of being made from pipe.

Not sure what you mean by "segmental 3D fittings"?? You can't use lobster back or mitre bends.

Cold bends you will struggle to get below 10D and 20D is more normal as a min Diameters. I once got a 10D cold bend made by packing it with special sand under pressure and bending it, but it was a struggle to find anyone to do it.

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

 

[akpipelineengr]

Segmentable bends are bends with additional ovality controls so that they can be field trimmed to the necessary angle. I'm used to seeing B16.49 bends with supplementary requirement SR15.3 specified (maximum 1% ovality through the bend). These are more costly, due to added complexity during bending as well as field work to prep and fabricate, so best to avoid them unless needed. If you know what angles you need, just order bends of that angle.

On a recent job we ordered all known bend angles in the line without additional requirements, and ordered a handful of segmentable bends as contingency.