Tecfluid M21 Series - Manual (Page 3)

3
Working Principle
The flow meter consists of a calibrated orifice and a conical float.
The rising flow pushes the float to an equilibrium point. The area
between the float and orifice is proportional to the flow rate.
This type of principle is known as variable area.
The equilibrium point depends on:
− The weight of the float: Pf
− The force of the fluid flow: E
− Free area of flow: Al
The area which is proportional to the flow rate is:
Al = Ao -Af
where
Ao = Area of the orifice
Af = Float area
RECEPTION
The M-21 series of flow meters are supplied already calibrated in our calibration rigs, ready for
mounting and operation.
The meters are supplied packed for protection during haulage and storage. They also can have
float securing elements that should be removed before mounting.
If the inlet/outlet is vertical, with the meter in a vertical position check to see that the float moves
freely and that the indicator needle starting from the 0 position follows the float movement along all
the scale and returns back to 0.
The float movement should be done manually without jerks and with the flow meter in a VERTICAL
position and the 0 end of the scale at the lower end.
INSTALLATION. (Figures 1, 2, 3 and 4)
It should be mounted vertically with a rising flow direction.
It is important that the positioning be fully vertical as deviations of around 5º can give errors
through float friction of 8-10% of reading values.
In the case of horizontal flow installation the flow meter should be mounted as shown in Figure 1.
In case of a falling flow installation, the flow meter should be mounted as shown in Figure 2.
We recommend mounting regulation valves, PRIOR to the meter for use with liquids. (Figure 4)
For GASES regulation valves should be mounted AFTER the meter so as to maintain the
calibrated working pressure. (Figure 3)
The valves should always be opened progressively as to avoid sudden surges.
FILTERS
It is important to install a filter prior to the meter so as to prevent possible blockages or
breakdowns in the measuring system
The filter mesh should be maximum 200 microns.
If there are a lot of magnetic metallic particles in suspension a magnetic filter should be mounted at
the meter inlet to avoid particle accumulation within the float’s magnetic field which could
immobilise it.
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