Environmental Engineering Reference
In-Depth Information
Transducer
Transducer
Transducer
Full penetration
Partial penetration
Poor penetration
figure 2.31 Particle concentration effect—the greater the number of
particles, the greater the error.
•
No interruption of flow•
•
No moving parts
•
Linear over a wide range
•
Wide range of pipe sizes
•
Low installation and operating costs
•
Bidirectional flow measurement
The disadvantages include:
•
It requires a minimum concentration and size of solids or bubbles
for reliable operation (see Figure 2.31).
•
It requires a minimum speed to maintain suspension.
•
Clamp-on type is limited to sonically conductive pipe.
2.13.7 velocity flow Meter
*
Velocity or turbine flow meters use a propeller or turbine to mea-
sure the velocity of the flow passing the device (see Figure 2.32A). The
velocity is then translated into a volumetric amount by the meter regis-
ter. Sizes are available from a variety of manufacturers to cover a flow
range from 0.001 gpm to over 25,000 gpm for liquid service. End connec-
tions are available to meet the needs of various piping systems. The flow
meters are typically manufactured of stainless steel but are also avail-
able in a wide variety of materials, including plastic. Velocity meters are
applicable to all clean fluids. Velocity meters are particularly well suited
for measuring intermediate flow rates on clean water.
The advantages of the velocity meter include:
•
Highly accurate
•
Corrosion-resistant materials
•
Long-term stability
*
This section is adapted from Oliver, P.D., in
flow measurement
, Spitzer, D.W., Ed.,
Instrument Society of America, Research Triangle Park, NC, 1991, pp. 373-414.
