These days, those kinds of jobs go to chemical engineers.
Mechanical engineers usually are the kind of 'jack of all trades, master of none.' engineers, which unfortunately means that they fall right into the Dunning-Kruger gap for alot of specific complex technical issues. For me, it is incredible to watch them make a design in Solidworks and yet completely neglect to leave space for hoses and cables. If it isn't simple, they want no part of it. lol
They usually don't make the same mistake twice, I will give them that, but I have seen younger mechanical engineers do some pretty silly shit.
I was specifically talking about tanks and stuff like that, not like a standard bracket material selection. Most piping and tanks and stuff is either a team of mechanical and chemical or purely chemical, sometimes with a process or controls engineer thrown in depending on how much money is floating around.
That said, my father tells me all of that stuff used to fall within mechanical engineering, with chemical engineering really being limited to Petro, pharma and agriculture.