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.

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 flow meter 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
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 flow rate.
The vertical movement of the float is transmitted to an external indicator through a magnetic coupling system such that glands and seals are avoided.

Advantages