This comes from a P&ID where they provide specific details about the vessels/pumps/tanks in the drawing at the top of the page. In this case, it is a FWKO where it says:
SHELL MATERIAL: 0.973 MIN A-516-707
HEAD MATERIAL: 1.000 MIN A-516-700
I have seen these materials once before so I don't think this is just a typo. Is it coding for heat treating like how SA-105N indicates normalized?
No, it is not coding for heat treatment. Typically, the suffix designator is for Grade and the last digit could be the edition year,, A 516 Gr 70-0 would be 2000 edition
A 516 Gr 70 - 7 might be 2007 edition.
It looks like this vessel was made in 1977. Its hard to believe that it indicates the year with only one digit since you won't know the decade. And what would be the value in doing that? If there was a change in the allowable stress between when the head and shell materials were manufactured, I could maybe see the point, but there was no change in the Code allowables around that time.
