Tapered Flow Tube.
The meter
comprises a vertically tapered tube through which the fluid to be
measured is passed, from the smaller end up to the larger. As the
fluid flows through the tube, it forces an indicator (float) upward.
The clearance space (area) between the float and tube increases as the
float approaches the top of the meter. This increasing area
requires a larger amount of fluid to force the float higher. By
varying the taper of the tube, the mass of the float, and the length of
the tube, different flow ranges can be calibrated.
The variable
area flowmeter must be plumbed into a piping system the right way: that
is, with the narrow part of the taper at the bottom. Usually
printed on, or next to, the tube are the flow increments (scale).
The flow rate can be read by matching the increments on the tube with
the edge of the float.
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