Piping inspection and supervision, explained from scratch

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Notes

The topics on this site are reference material, written to stand alone and kept current. Notes are the other thing: a code edition changing, a figure we got wrong and corrected, a question that comes up often enough to be worth answering in public.

There is no schedule. A note appears when something is worth writing down, which is a slower rhythm than a blog and a more useful one.

  1. Does a Class 150 flange mean 150 psi?

    It does not, in either direction. A Class 150 carbon steel flange holds nearly twice that when cold and barely a third of it when hot. The class is the name of a rating curve, not a number you can use.

    ASME B16.5

  2. Is a 2-inch pipe two inches? And is Schedule 40 one wall thickness?

    No to both, and the two answers are connected. NPS is a name rather than a dimension, and a schedule number is a rule for setting wall thickness, not a value. The practical consequence is that changing schedule quietly changes your hydraulics.

    ASME B36.10M