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  1. bngreene

    Why do austenitic nickel alloys become magnetic?

    Most people believe that carburization of nickel rich alloys is due to the depletion of chromium from the alloy matrix. Chromium is depleted from the matrix because various chromium carbides form in a carburizing environment transforming the remaining metal into an iron-nickel alloy...
  2. bngreene

    NaOH Pipe Sizing

    US1612 is correct that HDPE and LDPE are resistant to 50% caustic. Other non-metallics such as polypropylene and epoxies are also resistant. The problem here is that protection against freezing of the caustic is more difficult because of the lower thermal conductivity of the non-metallic...
  3. bngreene

    NaOH Pipe Sizing

    You certainly need to maintain a minimum velocity to prevent settling as well as a maximum velocity to avoid excessive pressure drop in the piping. Pressure drop is tricky here because of the caustic is both dense (1.5 specific gravity) and viscous. Other responders, however, have already...
  4. bngreene

    Foam Glass Insulation

    Cellular glass or Foamglas is commonly used to insulate vessels and piping when there would otherwise be concern about the accumulation of moisture or flammable chemicals in an insulation that absorbs and retains moisture, e.g. fiberglass. It is often used when the operating temperature is...
  5. bngreene

    PMI Testing

    There are many companies that use portable x-ray fluorescence or spectroscopic methods to do PMI. You can check the "Buyers' Guides" of NACE, ASM, or ASNT. If you are in an area with a large number of companies with similar needs, your telephone directory's Yellow Pages may be...
  6. bngreene

    P91 to SS Weld

    You are on the right track using the ERNiCr-3 wire for welding the P91 to an austenitic stainless steel. This is one of the methods recommended by Vallourec & Mannesmann, who are major suppliers of P91 tubular products. You can contact them in Houston (V & M Tubes 713-479-3200) if you want more...
  7. bngreene

    Corrosion rates of Carbon Steel in Sulphuric/Chloride environment ?

    The Materials Technology Institute of the Chemical Process Industries (MTI) has publications and some software that deal with corrosivity of concentrated as well as dilute/intermediate concentrations of sulfuric acid. The link is http://www.mti-link.org. If the acid is hot as you indicated...
  8. bngreene

    Comparison of Types304SS and 316/316LSS

    Maybe the simplest way to describe the differences between these two grades is to say that 316SS is equal or superior to 304SS in ALMOST all environments. For this reason, most pump and valve manufacturers use 316SS (or its cast equivalent) as their standard construction material when...
  9. bngreene

    Minimum Cl for pitting of 316 stainless steel?

    I think you may be asking only half a question. Temperature and initial chloride content are important. However, you must also consider velocity of the process fluid, likelihood of fouling or other deposits to be present, potential for crevice corrosion, possible mechanisms to concentrate...
  10. bngreene

    Wear and Stainless Steel

    If the 304 sheet is not wearing, it seems that the relative roughness of the weld metal is catching some particles and allowing galling or other form of wear to take place. If that is correct, could you adjust the weld procedure and have the welds ground flush?

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