UK company first in the world to meter extremely viscous adhesive

UK Flowtechnik, a supplier of flowmeters, instrumentation, pumps, magnetic couplings, and hydraulic system components, has become the first company in the world to accurately meter extremely viscous adhesive with 55% aluminium filler.

The Nottingham-based company was approached by a manufacturer of glue and resin dispensing machines to see if it could accurately measure the flow rate of Araldite AW4804 aluminium filled adhesive and HW4804 hardener in a high temperature (210°C) application.

Andrew Biggs, technical sales manager at UK Flowtechnik, says the company has previously steered away from aluminium filler as its flowmeter run on tight tolerances and do not accommodate large particles.

‘This was a first for us and we had to start with a clean sheet of paper,’ Biggs says.

The resin media poses a challenge for flow measurement due to its viscosity of 300,000 to 1,000,000 cPs and 55% by weight aluminium filler content.

It is crucial that the ratio of resin to hardener is accurately controlled, as otherwise the strength of the composite assembly is reduced or in the worst case the resin does not harden, leading to components being scrapped.

Traditional gear flowmeters were not suitable for the application, as they would be large, expensive, impractical, and unreliable due to their low output frequencies, which can make them difficult to control.

UK Flowtechnik used a large RS Series helical screw flowmeter from the German company VSE Volumentechnik as the solution to provide a low pressure drop across the meter, while still providing enough accuracy and resolution for the control system.

The helical screw principle allows the resin to move through the flowmeter without loss or slippage of flow whilst also allowing a high degree of filler without shearing the media.

The flowmeter is fitted with interpolation electronics, which increase the resolution by up to 128 times, giving a high output frequency and allowing a greater degree of control and faster response time to changes in flow rate.

Biggs adds: ‘Measuring flow rates of viscous materials is a real challenge so we’re delighted with our success. With the high viscosity of most resins and the smaller ratio of hardener, flow rates are low but the flowmeters themselves are quite large in comparison. But the interpolation electronics allow us to have a large flowmeter with small flowmeter resolution and response time.’

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