Is there any standard of Chemical Industry Department for this kind of mirror, with pressure?

Is there any standard of Chemical Industry Department for this kind of spectacle? It's pressurized.
Can you give me a standard number? I found it in a circle. It's PN25 or PN40.
2019-07-29 Reply
Mirror-type glass plate level gauge seems to have no such high pressure. Choose other ones, such as transparent glass plate level gauge.
2019-07-29 09:13:09 Reply