Flowmeters demonstrate ‘robustness and reliability’

11 April 2008

Total Polyfilm has reinstalled two Litre Meter flowmeters that have operated in its factory for the past decade. The VFF rotary piston flowmeters were sent back to their Buckingham based manufacturer for service and calibration following approximately 85,650 hours of continual use.

VFF rotary piston flowmeters regulate a mix for Total Polyfilm’s products
VFF rotary piston flowmeters regulate a mix for Total Polyfilm’s products

Little signs of wear were found on the rotary flowmeters, according to the stretch wrap film manufacturer, which utilises 17 of the devices in its manufacturing process. It claims, during daily operation, the meters must withstand high temperatures and a highly viscous ingredient, polyisobutene (PIB).

The two devices, sent off for servicing, control the amount of PIB that goes into the product mix. They are calibrated in kilograms per hour and operate up to a maximum of 20 kilograms per hour.

‘We have only now, after ten years, had to send two of the meters back for checking and they will be returned to use after recalibration,’ said Paul Lockett, procurement manager at Total Polyfilm.

He added that the good service of the products occurred despite operation ‘at levels of use and wear well above what they were originally designed for’.

Each meter has a rotor within a measuring chamber, which rotates as the material flows through it, giving an output representing an increment of volume flow. The rotor is basically a disc shape with a circular cavity on its underside which can hold and transport flow from the chamber inlet to the outlet. The rotary piston design modifies the rotation to an oscillation.

The top of the rotor is equipped with a rare earth magnet that activates a reed-switch sensor. A volt-free contact closure output signal is therefore given for each oscillation, which represents a specific volume. The typical metering repeatability is better than 0.2 per cent with a meter accuracy if 1 per cent.

‘When we placed the meters from Total Polyfilm on our calibration rig it was discovered that the meters were still in full operating condition, requiring minimal repairs or alterations,’ said Steve Smith, applications engineer at Litre Meter.

He concluded: ‘With only one moving part, there is very little to go wrong with them and they are now going back into service. This is a very fine example of the robustness and reliability of Litre Meter VFF rotary piston flow meters.’

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