Tapped Blinds and Tapped pipe caps

I agree on NOT tapping the pipe or fittings, BUT I have seen where they tapped blind flanges. Actually this work very well in the refinery I was working at, the area was in a hydrocarbon environment and no welding was allowed so they just drilled a hole in the flange (at or close to pipe B.O.P.) and manually tapped the hole (3/4" in this case) then added the threaded nipple and valve ...saving the expense of welding.