21-08-2013, 04:56 PM
VARIABLE AREA ROTAMETERS
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WHAT ARE ROTAMETERS
The variable area rotameter is used to measure a wide
SCALE
variety of industrial liquids and gases. This type of
rotameter operates in a closed pipe system and utilizes
a moveable float housed in vertically positioned tapered
tube. A calibrated scale mounted in front of or next to the
tube allows the float position to be translated into a
meaningful value.
It's operation is based on the variable area principle,
where a gas or liquid flow raises a float in a tapered tube
increasing the area for passage of flow.
The float moves up or down in the tube in proportion to
the fluid flow rate and the internal area between the float
and the tube wall. The float reaches a point of balance
when the upward force exerted by the flow of the liquid or
gas equals the downward gravitional pull of the weight of the float. The variation in percentage of repeatable is the result of scale
length. Long scale meters have better repeatability.
Significant aspect of excellent repeatability is one reason that variable area rotameters are so widely used in process industries
and other application that require this important feature. Flowstar engineering pvt. Ltd. Manufactures some meters can be
calibrated to an accuracy of ± 1% of full scale.
OPERATING PRINCIPLE
The essential working part is a tapered flow tube precision machined
inside the acrylic body. When flow occurs, the position of a float within
the tube indicates flowrate on a calibrated scale engraved on the acrylic
body. With integral construction, a needle valve and flow parts (Model
FSA & FSB) are built into the acrylic body, resulting in a very compact and
ecnomical
design. The unique "front plate"
design (Model FSB) the beauty of any panel
where the meter is installed.
BYPASS ROTAMETER
Flowstar Bypass Rotameter systems are designed
for the accurate measurement of fluid rate of flow in
pipelines 25 NB in diameter or larger design Standard
ISO 5167 or BS/1042. They accomplished this by
providing a bypass flow that is directly proportional to
the main flow. Since Rotameter measure bypass flow,
not static differential, flow ranges up to 10 to l are
possible with thease instruments. This provides a
decided advantage over other types of flow measuring
devices.