Document No LM0670 Issue A Rev 2 November 2017 Page 1 of 15
INSTALLATION, OPERATING
AND MAINTENANCE INSTRUCTIONS
VFF SERIES ROTARY FLOWMETERS
DESIGN & PRINCIPLE OF OPERATION:
These VFF series flowmeters are defined as rotary piston meters of a type as detailed in British Standard
BS.7405:1991 which is a guide to flowmeters. They offer a wide metering range and can measure low and
high viscosity fluids. For most of the flow range the viscosity may be varied with minor effect on the output
characteristic.
Litre Meter provides a standard factory calibration representative of the application in terms of viscosity
and flow rate range. A calibration certificate is provided which details the calibration fluid and viscosity,
together with pulses per litre at a range of flow rates specifically for the application or the total meter
range.
The only moving part of the flowmeter is the rotor which is equipped with a top mounted central magnet.
The rotor oscillation is detected by a sensor or pair of sensors. The interaction between the magnet and
a sensor does not impose drag on the rotor which could otherwise affect the low flow rate measurement
capability. The certificate shows the number of active sensors. The reed-switch sensors are inherently
intrinsically safe.
Typical VFF Flowmeter parts
THE METER MAY NOT BE DESIGNED FOR USE ON WATER – PLEASE CONSULT THE
FACTORY. See
FAT Issues
on page 12.
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