How Pitot Tube Flow Measurement Works

by | Jun 2, 2014 | Measurement Instrumentation

Jim Cahill

Chief Blogger, Editor

In prior posts, we’ve shared many flow measurement technologies, including averaging pitot tube flowmeters.

Katie Hausman Marketing Engineer

Katie Hausman
Marketing Engineer

Emerson’s Katie Hausman shared a new video that the Rosemount measurement brand team has put together that explains how averaging pitot tube technology work. The 3:42 YouTube video, How Averaging Pitot Tubes Work – Rosemount Annubar Technology provides a detailed explanation of how Annubar averaging pitot tubes operate and how this technology can lead to reduced permanent pressure loss compared with other approaches.

The technology is based on differential pressure measurement. Instead of an orifice plate being inserted into the piping where the fluid flow is occurring, a bar from the Rosemount Annubar flowmeter is inserted into the pipe. Mounting styles include insertion, hot tap, and the compact style inserted between raised-face flanges in the piping.

How it operates is that flow moving down the pipe encounters the front side of the T-shaped bar which creates high-pressure above the pipe static pressure, which is picked up by slots in the Annubar sensor. These slots capture the flow profile across the bar to get a more accurate measurement of the flow rate. Low pressure, below the pipe static pressure, is created on the back side of the bar. The differential pressure (DP) transmitter reads these pressure values.

The video highlights some unique aspects of the T-shaped bar which provides greater accuracy over a wide range of flows and reduced pressure drop saving energy. Installation is simplified over conventional DP flow measurement with orifice plates, impulse piping and a DP transmitter. Also, multivariable measurements are available for static pressure, DP, and temperature for mass and energy flow measurement.

Applications for Annubar technology include steam, gas, and liquid flow measurements.

You can connect and interact with other flow measurement experts in the Flow instrumentation track of the Emerson Exchange 365 community.

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