We are currently installing an orifice plate in a gre line.. and following the 45 degree tapping orientation since it's for liquid service. Is there any limitation on gre that does not the 45 deg orientation?
Tap location is probably fine given that you have specified minimal detail, but check the plate if it has a gas bleed at the top of the plate near the pipe wall to vent accumulated gases down stream. It should also be marked on the orifice plate "paddle" as a hole so that it can be properly oriented.
Also check your front to back plate oriention is correct.
I had to google Gre Line.
= Glass re-enforced Epoxy, so I assume you might measuring something corrosive. If not, just follow normal orifice plate installation. I assume you will mount the transmitter below the tapping points so that any trapped air will find it's way back to the pipe.
If it's corrosive for 316, get back to us.
Orientation Vertical or Horizontal, Flow Up or Flow down, etc.?
I wrote an article about this issue including the measurement principle and graphic schemes to better understand the different solutions.
You can read it here: