OTHER FLOW METERS
Flow Detectors
OTHER FLOW METERS
Two other types of mechanical flow meters which can be used are the area flow
and displacement meters. In addition, there exists much more sophisticated
techniques for measurement of flow rate than use of differential pressure devices,
such as anemometry, magnetic, and ultrasonic.
EO 1.3
DESCRIBE the following types of mechanical flow
detectors, including the basic construction and theory of
operation.
a.
Rotameter
b.
Nutating Disk
Area Flow Meter
The head causing the flow through an area meter is relatively constant such that the rate of flow
is directly proportional to the metering area. The variation in area is produced by the rise and
fall of a floating element. This type of flow meter must be mounted so that the floating element
moves vertically and friction is minimal.
Rotameter
The rotameter, illustrated in Figure 6, is an area flow
Figure 6 Rotameter
meter so named because a rotating float is the
indicating element.
The rotameter consists of a metal float and a conical
glass tube, constructed such that the diameter
increases with height. When there is no fluid passing
through the rotameter, the float rests at the bottom of
the tube. As fluid enters the tube, the higher density
of the float will cause the float to remain on the
bottom. The space between the float and the tube
allows for flow past the float. As flow increases in
the tube, the pressure drop increases. When the
pressure drop is sufficient, the float will rise to
indicate the amount of flow. The higher the flow
rate the greater the pressure drop. The higher the
pressure drop the farther up the tube the float rises.
IC-04
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