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High Pressure Pipe Wall Thickness

High Pressure Pipe Wall Thickness

High Pressure Pipe Wall Thickness

(OP)
I'm Starting from scratch!  I need the material specification and wall thickness for crude oil and/or natural gas line pipe of 24" and 30" diameter. MOP of 1440 psig and temperature to 180 deg. F.

I've assumed API 5LX60 as the material; ASME B31.8 as the code. I do not have the API formula for calculating the wall thickness.

Zally

 

RE: High Pressure Pipe Wall Thickness

Seems like you know the material.
The formula is not API.  You will find them in B31.8 (yes there's more than one.  To calculate wall thickness you must also know the class locations Table 841.114B.  Sections 841.11  Temperature factor is 1.00.  See sections 832 for expansion and flexibility requirements.  The elevated temperature will have special implications in regards to placement of bend angles and required depths to prevent overbends and sidebends from buckling up and out of the dirt.  Extra flexibility will undoubtedly need to be considered in many areas.  Now see section 833 for longitudinal stress.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: High Pressure Pipe Wall Thickness

You should add margin 10%-15% for Design Pressure first.So DP=1584 psig. Then it is easy calculate using formula from the code.

RE: High Pressure Pipe Wall Thickness

Fred.  

I just saved one of your clients about 50 million dollars.

There is no mention in the B31.8 code, or any other, for the use of such factors which can easily lead to poor economic design and selection of a very poor wall thickness to use for a long pipeline, not to mention cause much egg on small hidden red face.  If you applied your factors to 1000 miles of 24" pipeline with an operating pressure of 1460, it would lead to use of ANSI#900 class and what I think would be somewhere around 40 million dollars, just figuring some cost of cheap cs steel pipe in excess wall thickness... not including transportation and welding  costs.  I think you'd probably be looking at paying at least 2 X the cost for pumps or compressors.  While it may make the design pressure number "easy to figure", I really don't think that your inflated pressure would be so very easy to get past a client with a body temperature still greater than 70F.
 

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: High Pressure Pipe Wall Thickness

BigInch,
        Subtle reply!!

RE: High Pressure Pipe Wall Thickness

Too subtle???

This isn't high school.  The problem isn't working out the equation, its finding the answer to the real question.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: High Pressure Pipe Wall Thickness

Fred, nothing personal.

Hey, I like that.  I think I found a new byline.

**********************
"The problem isn't working out the equation, its finding the answer to the real question." BigInch - http://virtualpipeline.spaces.live.com/

RE: High Pressure Pipe Wall Thickness

To jump to Fred's defense a little, just because the flange class might jump from 600 to 900, there is no reason that the pipeline design (for wall thickness) needs to jump all the way to Class 900.

Line pipe is available in a wide range of different and relatively fine gradations of thickness so you can easily have a situation where the line pipe might be specifically sized for 1584 psig whereas the flanges have to be Class 900 and good for approx 2200 psig because there is nothing between 600 and 900.

Running a quick calc for 1440 psig (Z662, 24", Grade 359, Class 1 General, Sweet Gas) I get a wall thickness of about 11.1 mm. Jumping to 1584 psig moves me to 11.9 mm vs. going to Class 900 which would bump me all the way to 15.9 mm.

Not suggesting that adding an arbitrary 10 to 15% is the right answer (but in some situations that may be the right margin, who knows) but rather that the impact of the design margin is probably not as significant as you had suggested since we don't need to design the pipe to the full flange rating.

Actually, looking at the original post, I'm willing to bet that the 1440 psig MOP is not the real design number either. I'm guessing that it was taken as being the next highest "flange rating" above the specified operating pressure and that it already includes a heathy design margin that probably doesn't need to be there.

RE: High Pressure Pipe Wall Thickness

rneil, That's quite valiant of you.

To get the 50MM, I didn't jump the pipe wall thickness to the ANSI#900 class rating of 2160 psig.  You must jump the equipment, as they pretty much only come in "integer" ANSI steps.  So only pumps and equipment are 900#.  I left the pipe wt as you have it at 12 mm.

In many cases, when design pressures are in the vicinity of a ANSI pressure rating break, you actually do set a pipeline design pressure to a specific flange rating such as ANSI#600 because you really need slightly over that to reach your initial design flowrate, but then you immediately see that your equipment costs double, so you're forced to back it down to a flange limit, such as ANSI#600.  In other cases, with an initial design pressure requirement that is slighty below an ANSI pressure break, a client will sometimes agree to increase it, due to a high possibility of increasing the flowrate at sometime in the future.  That is especially true, such as when working offshore in a new development area with a high potential for more discoveries, where you often get many tie-in requests, or offers to partner in your pipeline, from other producers as soon as they hear that  somebody's going to build a pipeline into the area.

So both in my experience are quite common indeed.

 

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch
http://virtualpipeline.spaces.live.com/

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