32 food & drink processing
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requirements and is being used in by a number of food
processors.
Often the key requirement is to mix sufficiently to
achieve a uniform dish, but not to waste time and energy
by over-mixing.
This can be done by monitoring the applied torque
on the mixer's shaft, as it will move to a steady state
(within the characteristics of the given recipe) once fluid
uniformity is achieved.
Mixing
A TorqSense is helping analyse recipes’ mixing
properties in a project that could slash development
costs in the food and plastics industry and help
nanotechnology advances in the pharmaceuticals world.
Research and development is being carried out at the
UK’s University of Bradford to develop a miniature
mixer (5–25 grams batch) that incorporates a set of
integral instruments to monitor the properties of
materials as they are being mixed. The instruments work
in real time during the mixing process and their output
is captured to a PC for analysis. Software is being written
so that the analysis can be performed simultaneously
with the mixing and perhaps even used to interactively
control the mixer itself.
One of the key parameters to be measured is the
torque of the mixing element, as this will become
Fig. 3. TorqSense can neasure the applied torque on a
constant once mixing is complete. This is measured by a
mixer's shaft to help achieve a uniform mix.
TorqSense non-contact sensor that offers the
development team the great advantage of not requiring power consumption.
complex and delicate slip rings, making the mixer easier In horizontal axis washers (front loaders in domestic
to build (and rebuild between trials) and far more parlance), the load, ie the wet laundry, is lifted on one
robust in operation. side of the axis and falls on the other side. This is a
The Mini Mixer development and validation is the dynamic where regenerative energy recovery is very
result of a three year EPSRC sponsored programme of attractive if it can be practically achieved.
research. The results of this research are expected to A test rig has been built which subjects washing
have a major impact on formulation of viscous mixes machine systems to extensive tests using an industry
and scale-up of extruders. standard inverter to simulate the various washing cycles
Traditionally recipes for formulating say specific etc. A critical element of the programme was the ability
coloured plastics for consumer products are developed to make continuous accurate torque measurements, and
in 25 to 50kg batches, mixed in an industrial scale twin for this TorqSense is ideal.
screw compounder. Several batches may be required The time saving in setting the transducer, compared
before the recipe is finalised, so the cost and time to installing a slip ring based sensor, over a big project is
involved can be considerable. measurable and significant.
Clearly the development of a smaller mixer is By measuring the torque change the exact moment
advantageous, but the laboratory device must be able to when to switch the drive from power to regeneration
duplicate mixing in the larger scale and guide design and make the most of the potential energy released by
and operation of large machines and that is what the the falling load could be defined. Given that the motor
research programme has achieved. That fact that the could be rotating at up to 1500rpm, this called for very
technology will transfer to the plastic industry and other accurate data collection and equally responsive control
soft solid sectors means it is likely to rapidly recoup programmes.
development costs. This technique has proved so worthwhile that it is
planned to build into the next generation washing
Washing goes green
machines. With industrial sized loads energy savings of
High performance torque measurement is helping to 20-30 per cent could be achievable. p
improve the energy efficiency of industrial (and
domestic) washing machines. Process plant Tony Ingham is with Sensor Technology Ltd, Banbury, Oxon,
manufactures are redesigning their machines to reduce UK. www.sensors.co.uk
www.scientistlive.com
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