Expansion analyses in flexible pipes 1

[vanessa75]

Hi everybody,

Has anyone made an expansion analyses on flexible pipes? Is the poisson' effect taken into account in the analyses? How the temperature induced axial elongation influence the expansion?

Thanks in advance,

Vanessa

 

[LittleInch]

If the pipes are "flexible", then there should be no particular issues about temperature effects.

What type of "flexible" pipe are we talking about here?

Poissons effect is for solid materials.

My motto: Learn something new every day

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

 

[TLHS]

In the usuage I am familiar with, flexible pipe would be anything that will deform a certain amount prior to failure. So you have non-flexible pipes like clay and concrete and flexible pipes like most steel, HDPE and similar pipes. This is specially important when designing underground pipes.

I don't really know what 'expansion analysis' means in this case though. I would have thought it was an analysis of axial thermal expansion/stress if not for the third sentence.

 

[LittleInch]

Aaah, in piping and pipeline terminology, flexible means something other than steel, metal or solid material like PE or fibre glass - think hoses and similar items.

Stress analysis is common practice in the piping and pipeline world, especially if significant temperature differences are anticipated. For steel and similar solid materials poisons effect is used in the design or operating scenario.

Clay and concrete are still flexible, but less so than the others you mention.

My motto: Learn something new every day

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

 

[dhengr]

Vanessa75:
I think you should dig out your Strength of Materials text book and read up a bit on what Poisson’s Ratio and the Coefficient of Linear Expansion are, and may have in common, or don’t have in common. Then rephrase your question, with some specifics and details, so we don’t have to guess what you mean or what you want help with.

 

[vanessa75]

Flexible pipes are multilayers pipes (made of steel and polymer)commonly used in deep water applications. Each layer is designed to resist to specific loads (Ref. Code API17B and ISO 13628). This design is made by the pipe supplier.
My question is related to the global behavior of the pipe when it is laid on seabed and it is subjected to pressure and temperature.

Since the pressure armour layer (internal layer) is the one that has the funtion to resist to the hoop stress and bending, and the tensil armour layers the one that resists to the internal pressure and axial tensions, I need to simulate the global behavior of the system.
Please answer only those who have experience in the specific field.
Thank you
Vanessa

 

[LittleInch]

So you are talking proper flexible pipe. The issue is that each pipe, even with the same vendor, will have differing properties depending on the thickness of each layer, how many layers, the angle of any winding etc.

Hence you need to get this information from your particular flexible pipe vendor, which may require some lab type tests if not available.

In general because the layers are mainly filament / thin strip winding type, the thermal expansion is reduced and there is no poissons effect as there is no solid material tube on which this effect can occur.

The tensile armour layer has little impact on the internal pressure due to the longitudinal nature of the filaments, normally at some 30 degrees to the axial length, similarly the hoop stress filaments are at nearly 90 degrees to the axial direction and have virtually no impact on axial strength, bending or expansion force.

Application of pressure, especially sudden pressure increase, will have an effect on the pipe, but you need vendor data to try and see if you can simulate this or not.

My motto: Learn something new every day

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

 

[cvg]

regardless of whether the pipe is considered to be "flexible" or "rigid", layered" or not, all materials expand and contract both axially and radially to varying degrees with both pressure and temperature. the properties are of course completely related to the materials and construction of a particular type of pipe. the manufacturer could supply these properties or perhaps shed some light on the analysis of a particular type of pipe.

also, I would take issue with the definition of flexible proposed by little inch, depending on the particular usage for pipe, steel pipe is generally considered to be flexible for engineering analysis purposes, however much less flexible than say PE.

https://www.google.com/search?q=is+...7&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8

 

[LittleInch]

I accept steel pipe is "flexible", what I meant was that this is the accepted terminology in the pipeline / offshore industry. Basically if its an API 17J or 17K material, its a flexible, it its something made out of one material, it's rigid pipe.

My motto: Learn something new every day

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

 

[JStephen]

Vanessa,
If you want "only those who have experience in the specific field" to respond, you need to very clearly indicate what that field is and EXACTLY what the question is, we're not all psychic here. Your original post didn't say if you were sticking PVC pipe in your attic, designing swingsets, running pipelines across the Sahara, or what. You might also consider if the question is best referred to the Structural forum or, say, the "Pipelines, Piping and Fluid Mechanics engineering" forum.

 

[vanessa75]

Thank you Pollicino

I also thought that too.
But I've read articles that say conflicting concepts.

Upheaval buckling behaviour of flexible flolines, ISOPE 1995,
Flexible pipe on-seabed stability, upheaval buckling and hub protection method, ISOPE 2013

Anyway, If no data will be available by the vendor, I'm going to neglect the Poisson effect ( as claimed in the second article) and I'm going to consider the same coefficient for termal expansion as for rigid pipe ( as per the first article).