Depends on whether you need to access the flow element for repair, maintenance or calibration, and how much you want your operators and maintainers to hate you. I¹ve hung off the basket of a cherry picker trying to calibrate a flow meter installed like that, and I am sure I will have problems in the afterlife due to the words I said when I was up there.
Seriously, you can, if you must. If you have nowhere more accessible to put the meter, then you probably have to do it that way, but I strongly encourage you to see if you can install it closer to the deck.
Walt
Walt Boyes, Life Fellow, ISA; Fellow InstMC
Chartered Measurement and Control Technologist
Spitzer and Boyes LLC