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Carbon Steel for High T pipeline

  1. Oct 19, 2012 #1
    This is my problem: I need to design a pipeline distribution system for steam service. But is thought in order to inject high P, high T steam into oil wells (upstream industry). Inlet conditions into the pipeline will be 650 ºF, 1900 psi. Pipes are several km long, and, because it is a network, diameters vary. My flowrates are quite high, so it would be good to use some 30" pipelines.

    I was designing with B.31.1 in order to get a pipe thickness, but the materials I found there give me about 2" thickness for 30", due to the low steel strenght.

    Is there any material suitable for my application?

    Thanks
     
  2. jcsd
  3. Oct 19, 2012 #2

    Astronuc

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    I believe 2 inches (5.1 cm) is in the ball park. High pressure (2500 psi) and high temperature (up to 700 F) has wall thickness on the order of 2.6 to 3.2 inches (6.6 to 8.1 cm) for nuclear power systems. The piping is often centrifigual cast, while elbow and fittings are statically cast.

    Here are some examples of materials:
    http://www.petrosteel.ca/ocgt/high_pressure_seamless_pipes.html

    And one should apply the appropriate code. It would difficult to use a material not covered by ASME code: B31.1 or B31.3.

    Here is an example - http://www.psig.sg/Don/B31.3 Process Piping Course - 17 High Pressure Piping.pdf


    A high pressure (2000 psi) pipeline is potentially hazardous. Corrosion and erosion are critical aspects. Depending on the geographic location, the piping should be appropriately insulated.

    Depending on the size of the system, it might be better to place the steam generator near a set of wells rather transport high pressure steam over km of pipeline.
     
  4. Oct 19, 2012 #3
    In an oil well, some km are vertical, so producing the vapour near the use isn't easy.

    For such T and P, carbon steel may not be optimum. You might give an eye to martensitic stainless steel: vapour turbines use alloys very similar in composition to Aisi 420 (=X20Cr13), which keeps essentially their good strength at this temperature, even over time, as Cr avoid long-term softening.

    Cr (but no Ni) makes them somewhat more expensive than carbon steel, but the better strength at heat allows to reduce the sections, which may save cost (or not). Their resistance to corrosion by steam is good.

    Some such alloys add a bit of Ni (1.4057, 19-4...) or V, Mo... (modified Aisi 420) to improve corrosion resistance or strength, but these are details over the cheap and common X20Cr13.

    Also, they are sometimes tempered at 280°C instead of 650°C for better yield strength, but I wouldn't go that way for service at 340°C.
     
  5. Oct 25, 2012 #4
    Thats really extreme conditions. you are probably approaching if not at supercritical conditions for Water and Other gases that may exist in your pipeline. You should probably review literature pertaining to the corrosive properties of supercritical water.
     
  6. Oct 28, 2012 #5
    The alloys I suggested are used in vapour turbines.
     
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