There are many technologies for liquid and gas flow measurement, but one of the first, orifice plates and differential pressure transmitters remain one of the most venerable and widely used in industry. ISA’s InTech magazine has published a good article with a lot of details to prevent inaccurate measurements due to improper installation. See the link below if you are interested in application, rules of thumb, and field practice on orifice plate installation.
ISA, Orifice Plate Installation
ISA, Orifice Plate Installation





