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BGN Metal Tube Variable Area Flowmeter

The BGN range of metal tube variable area flowmeters has been designed for those applications where
conventional glass tube instruments may not be used on account of high pressures or liquid opacity, or for
safety considerations when metering hazardous chemicals.

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As opposed to the 'fixed float diameter tapered tube' principle used in conventional variable area meters,
the BGN utilises a fixed sharp edged orifice and tapered profiled float, the float profile being machined
to exacting standards to ensure a linear scaling.

More Info

Operating pressures are largely limited only by the flange ratings, and elevated temperature operation is
possible by extending the indicator coupling to remove the indicator and associated electrical or pneumatic
transmitters from the source of heat.

Large scale production and exacting machining specifications enable all parts of the flowmeter to be
mechanically interchangeable within a specific range size, and range conversions and replacement of
indicators can be carried out by any skilled engineer without difficulty.

Electrical transmitting system, or high and low alarm contact devices may be fitted in minutes within
the indicator housing.

Operating Principle

Operating principle
The measuring system comprises a sharp edged fixed orifice ring, and a tapered float.

When the fluid flows vertically upwards, the float rises until a point of equilibrium is reached where
the weight of the float is balanced by the buoyancy force 'A'.

This results in an annulus 'S' the area of which is directly proportional to the flowrate.
The vertical movement of the float is transmitted to an external indicator through a magnetic coupling
system such that glands and seals are avoided.


Simple robust and low maintenance all metal design.
High pressure and temperature resistance.
Suitable for steam tracing.
Linear flow indicator and output signals.
Short length of 250 mm enables versatile application in all industries.
Four interchangeable standard indicator systems.

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