Is the steel used to build pipelines the same as used years ago or do they make it thicker to handle the higher pressures

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That sould be, is the steel the same as used years ago or do they make it thicker to handle the higher presures

Read pages 12-14 in this gas pipeline technical overview from Argonne National laboratory.

http://corridoreis.anl.gov/documents/docs/technical/APT_61034_EVS_T...

Modern pipe is a high strength carbon steel alloy metallic blend.   

In the old days, mostly grade B pipe was used, 35,000 psi tensile strength.  For a higher pressure application, the pipe was simply made with thicker wall steel.

Fast forward... pipe is specified for the pressure and expected stresses.  Typically modern pipe is a higher strength carbon steel alloy which equates to a higher tensile strength metal.  

Typically, steel line pipe is now metallurgically engineered to a 52,000 psi tensile strength, or higher.  The pipe wall thickness may not necessarily increase, however the metal is manufactured to withstand higher stress levels.  The mill provides documentation and the pipe is typically required to be hydrostatically tested once welds are complete and before covered or buried, records are kept for life of facility for jurisdictional facilities.

There are two ways to look at this, you can make the pipe thicker or you can make the metal stronger to withstand the forces from within. Or both.

If you are seriously interested, do a web search for steel pipe, primary hoop stress tables and review the material.   

 

The 2 local pipe mills both use scrap to make their pipe. I'm no expert but when using scrap seems like there could be some less control of the final product then using new steel.

Tony-

Your comment is well worded. I'll add that the gas components also have a bearing on the alloy selection. Any carbon dioxide contained within the gas stream, if mixed with even trace amounts of water, will form carbonic acid, which pits and corrodes carbon steel. hydrogen sulfide does much the same thing. Any corrosion reduces wall thickness and strength over time, ultimately reducing service life of the pipe.

I've not seen any gas analyses from this basin, and I'm not aware of any sour gas being produced there.

Metallurgy selection from the well components to the sales point at the plant is an important and often critical design and selection point in the project life cycle. The mills can and should provide material certification ("Mill certs") for each item for record keeping purposes. A hydrostatic test with inhibited fluid may be performed; nitrogen gas is also used for integrity testing, but is often more costly.

Brian

Brian,

Good Points on gas properties (components) that have the potential to introduce internal corrosion issues to metallic pipe. 

Most transmission companies have gas quality tariff specifications that limit the percentage of CO2, water vapor content and H2S in the gas stream.  

Erosion may be another engineering life cycle concern in the production / field gathering systems.    

Record keeping and documentation, it is half the project or so it seems.

Ohiosam, You can make any quality steel from scrap by adding the proper ingredients to the mixture.

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