PN ratings V/s ASME Pressure Ratings

PN16 means rated for 16bar.

ASME 150# (or ANSI 150) means rated for 150psi.

"PN16 means rated for 16bar."

Is that bara or barg? I would guess bara...

I got a gauge question wrong the other day

No, I would say bar or barg.

Usually if absolute or gauge is not specified you can assume it is either gauge pressure (In which case perhaps it should really be stated, rather than just assumed) or differential pressure (in which case absolute & gauge don't apply). In the case of pressure ratings for flanges, vessels or pumps, you are really rating the differential pressure, inside vs. outside, so strictly speaking it should just be bar, but since the outside is usually atmospheric (0barg), then you could also call it barg.

I hope this makes sense. There is a lot of room for confusion and misunderstanding in absolute and gauge pressures, particularly regarding pump suction where terms such as 'suction pressure', 'suction head', 'suction lift' and NPSH are thrown in.

No, it doesn't. Not without a temperature criterion, anyway.

You are absolutely right, the pressure rating means nothing without temperature, and what I really should have said is that these numbers relate to the pressure rating. Following is a chart of pressure/temp ratings for flanges to ASME/ANSI standards, and as we can see, 150# flanges are rated for anything but 150psi.