Purpose of Orifice Plate Or Orifice Meter

The orifice creates additional loss which will produce a pressure difference that can be measured and used to calculate the flow.

A pipe can also be used but the actual friction loss won't be significant enough to result in an accurate reading.

Please refer to the tutorial document at this link: http://www.omega.com/literature/transactions/volume4/

I am sure you will appreciate the content.

Rgds

As previously stated, the orifice produces a useful differential pressure to be measured. If one just tapped the pipe without a pressure dropping device (orifice or venturi), the distance between the taps would be so large that it would be impractical. This is due to the system occupying a defined space and most plants have a limited amount of space in which to work with.

Some other sources of info for self study;

ISO 5167-1, "Measurement of fluid flow by means of pressure differential devices - Part 1: Orifice plates, nozzles and Venturi tubes inserted in circular cross-section conduits running full"

ISO 5168,"Measurement of fluid flow - Procedures for the evaluation of uncertainties"

Instrument Engineers' Handbook, "Process Measurement and Analysis, Volume 1"

www.more-solutions.com

And as previously stated, Omega has some great training material.

Good luck