*ROTAMETERS*
*PRESSURE GAUGE*
*TEMP GAUGE*
*DIGITAL PROCESS CONTROL INSTRUMENTS*
VARIABLE
AREA FLOWMETER
PRINCIPLE
:
The Rotameter is a simplest form of fluid measuring instrument.
It consist of a borosilicate tapered glass tube placed vertically
with its smaller diamater at the bottom. The float used in the
tube is made up of heavier non-corrosive substance which resists
the vertical flow of the fluid passing through the annular space
between tube and the head of float. Here the fluid passing through
the orifice, balances the weight of the float up the metered
fluid and when in equilibrium position, indicates the flow of
the fluid which can be observed by an external scale fittied
by the side of the tube.
DIFFERENTIAL
PRESSURE FLOW REGULATOR
Principle
of operation: The
pressures P1 and P2 (fig. 1) upstream and downstream of the
needle valve are applied to opposite sides of the diaphragm,
the difference P1 -P2 being balanced by a spring. Variations
in the downstream pressure P3 result in a movement of the diaphragm
which opens or closes the regulator valve until the pressure
difference P1 – P2 is restored to its original value (approx.
0.2 bar). Consequently, the flow at the outlet remains substantially
constant until the outlet pressure P3 rises to a value approaching
the inlet pressure P1.
The
pressures P1 and P2 (fig. 1) upstream and downstream of the
needle valve are applied to opposite sides of the diaphragm,
the difference P1 -P2 being balanced by a spring. Variations
in the downstream pressure P3 result in a movement of the diaphragm
which opens or closes the regulator valve until the pressure
difference P1 – P2 is restored to its original value (approx.
0.2 bar). Consequently, the flow at the outlet remains substantially
constant until the outlet pressure P3 rises to a value approaching
the inlet pressure P1.