Pipeline underground or aboveground 2

[wenchop]

Hello, a steel insulated pipeline will operate with a liquid stream to be maintained at aprox 140°C and ambient temperature is aprox 15°C minimum, is there a rule of thumb that determines whether this pipeline cannot be buried/under-ground, and that it has to be above ground? I am thinking that there would be problems with mechanical stress from expanding/contracting, so it needs to be above-ground? Thanks in advance.

 

[pennpiper]

dtmgo1,
You like many, many others ask questions and do not give us important details in order to base our answers.
What country is this project in?
How long in this pipeline?
Is the ground subject to permafrost?
If permafrost is present, what is the depth?
Is the route of this pipeline outside the plant on public land?


I am not a salesman, I am just a retired piper with some experience.
If you decide to bury the line I recommend you investigate this product: Gilsulate
(

http://www.gilsulate.com/).

I have worked on projects where this was used, it provides the insulation, corrosion protection and is flexible enough to allow for expansion and contraction and it is easy to install.

prognosis: Lead or Lag

 

[wenchop]

This is a field pipeline, 15 km, in the tropics.

 

[wenchop]

There is also the Ethafoam product from Dow....

http://www.qualityfoam.com/docs/ethafoam-220.pdf

 

[BigInch]

Right. Ethafoam should be really nice and soft way before reaching that 140[°]C temperature.

I hate Windows 8!!!!

 

[wenchop]

I do not think that irony is a way to make a point in this kind of forum.

Anyway, Ethafoam is a product that may help in some situations to help deal with pipeline expansions, not all of them.

 

[zdas04]

Irony is a fine way to make a point in this kind of forum. Sarcasm works well too. Both can make points in a way that helps people learn. Often very useful. Chastising an "Engineering Tips Fellow" on your 17th post, now that might be considered ill advised.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[wenchop]

I do not think so, irony and sarcasm do not belong in any serious forum, as by nature they are potentially confusing and in some cases be also passive-agressive.

 

[LittleInch]

Ok, back to the original question.

Is there a rule of thumb?, not really, but above about 80 to 90 C you do start to run into issues such as upheaval buckling and stress at bends / expansion. However that doesn't mean that you can't bury it. There are many lines in Canada which have similar temperature issues. Often the solution is to pre stress the life by heating it prior to burial.

I also recently saw a pipe in pipe system which included trace heating where they turned the heating on, the inner pipe grew several cms and was then welded to the outer pipe to avoid that issue.

Running above ground has issues, mostly about access across the pipe line and damage, but also undulating ground, crossings etc. If you have none of these issues then ag might work.

What are planning to use for insulation and to maintain the temperature?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[wenchop]

Littleinch

Thanks for the input, we have not decided on anything yet, just looking at feasibility.

Regards,

 

[SNORGY]

My personal experience with the comparatively infrequent pipeline design work I have done is that if you take the yield strength of the material in MPa and divide it by six, if that number is smaller than the difference in temperature from "installation" to "hot" measured in degrees Celsius, you will (at the very least) have a tough time getting a buried pipeline to pass a computer-based stress analysis. The governing Code in Canada states limitations on the combined longitudinal stresses,and at those temperature differentials for buried lines, those stress levels will be predicted to occur, and they will have the effect of governing over pure hoop stress towards the determination of minimum wall thickness. (FWIW, this is deduced by algebraic rearrangement of equations in CSA Z662 Clause 4 for sour lines in a Class 1 location.) The Code might be different, but the physics are probably similar in your situation.

Most of our hot steam / bitumen / dilbit lines in support of SAGD facilities up here (Alberta) are above ground. The aforementioned calculations in combination with unfavorable geotechnical properties make the burial of such hot lines somewhat difficult.

 

[KernOily]

Thanks Snorgy; that rule of thumb is a keeper. I copied it and put it in my bag o tricks. You get a virtual Molson, neither sarcastic nor ironic

 

[zdas04]

Snorgy,
I collect those odd empirical equations, and that is the first one I've come across that works in SI instead of fps. I start my 5-day class with a discussion of one that works in fps, and for my next class (in Brisbane) I'm going to replace it with yours--it will make the same point without the students focusing on "what the heck is a bbl?".

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[SNORGY]

It usually holds true. Be careful when using it in Class Locations other than Class Location 1, where the product of factors FxLxJxT < 0.72. I chose sour gas lines in Class Location 1 as a reference point because that's the bulk of stuff that I have been involved with over the years.

 

[LittleInch]

I'd go along with that. X65 runs into trouble in the stress based calcs beyond 75 odd degrees of "expansion". Whether this is a real stress is debatable but much past 100 C, you either need to pre stress or start laying lots of compressible fill or strain based designs. Laying the line such that you don't have long straight lengths is actually a good thing.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

dtmgo1,
You know, actually I have some suspicions about you.
You're a new member.
You ask a pretty lame question.
All of a sudden your pet product pops up. I won't repeat its name.
Guess who popped that product's name up. You!
Why mention the product by name, brand name?
Because it is an equally lame answer to your lame question.
I'd thought I'd through a spanner in your works and mention some poor characteristic your product has that would make it unsuitable for this app.
Rather than say "Thank you, I hadn't thought about that.", you get upset.
You have no other viable solution, so you're not an engineer, or a very good one, because you should have checked it for temperature compatibility, or a good one that's only interested in advertising.
You are surely not interested in our well being, since you didn't do a proper evaluation of the product before you proposed it as a bad solution and typed it up in our forum.
I'm red flagging you and this thread and we'll let site management sort it out. You can explain why it's not advertising and tell them your reason that you started this thread.
I'm betting you'll be erased by the end of the day.


I hate Windows 8!!!!

 

[BigInch]

If you're still around tomorrow, I will apologize, but in any case, raise the level.


I hate Windows 8!!!!

 

[SNORGY]

Again, from my experience in running CII to analyze hot (and by the way, not THIS hot) buried pipelines, I have found that there are times when soft-packing the bends resulted in worse strss states than when modeling them in well-compacted soils. In the instances when I HAVE modeled bends in say, for example, Ethafoam, then the issue of how to model the Ethafoam always comes up. What I have done, however goofy it sounds, is build myself a representative soil model with stiffness constants estimated from a "how big a dent would a length of pipe make in this stuff if I put it on top of it and left it for a day" approach. Invariably, back-feeding constants of those magnitudes into the soil model has produced a predicted bending stress failure when considered in combination with the virtual anchor lengths and thermal expansion seen in hot lines, and I have found that some amount of compaction or restraint helps to offset those bending stresses. In this instance, even if the Ethafoam or equivalent product could stand up to the temperature of the pipe, I would be looking for ways to get the soil properties that I wanted, and from that, specifying those requirements to go looking for suitable fill material from borrow pits.

In other words, this kind of design problem requires analysis of everything in the big picture and how it all interacts together - mechanical and geotechnical - before you start looking for cures in the form of a padding product.

 

[if7005]

I think, you shall cool it by fan cooler prior buried this pipe.
Otherwise it will be trouble for corrosion protection system and buckle stress. What standard is used ? For B31.8 gas pipeline, stress over yield is still allowed by maximum strain 2.5 %. Consult the CP protection specialist how to design ICCP/SACP at elevated temperature

 

[BigInch]

No If7005, I can't agree. Strains are limited to 2.5% yes, but stresses are limited by their respective allowable stresses.

I hate Windows 8!!!!