|
The
World Market for Primary Elements
Released
in September 2007
About Pitot
Tubes
The Pitot
tube is named for Henri Pitot, who invented it in 1732.
Henry Philibert Gaspard Darcy, another Frenchman, published a paper
in 1858 that made improvements on Pitot’s invention.
The first patent for the use of a Pitot tube to measure velocity in
pipes was given to Henry Fladd of
St. Louis,
Missouri, in 1889.
Pitot
tubes are of two types:
·
Single port
·
Multiport averaging Pitot tubes
 A
single port Pitot tube includes an L-shaped tube measuring impact
pressure. This tube is inserted
into the flowstream, with the opening facing directly into the flow.
Another tube measuring static pressure has an opening parallel to
the direction of flow. Flowrate
is proportional to the difference between impact pressure and static
pressure.
A multiport averaging Pitot tube
has multiple ports to measure impact pressure and static pressure at
different points. The DP
transmitter computes flowrate by taking the average of the differences in
pressure readings at different points.
Some
companies such as Emerson Rosemount and Veris have introduced proprietary
versions of the averaging Pitot tube. Emerson
Rosemount’s proprietary version is called the Annubar, and it was
formerly sold by Dieterich Standard, now part of Emerson Process
Management. Veris’ averaging
Pitot tube is called the Verabar.
Verabar
Multiport Averaging Pitot Tube. Photo courtesy of Veris.
For
further information on differential pressure, including studies and articles,
see www.FlowDP.com.
| 
