Yearbook 2013/2014 - ehedg

Spray cleaning systems in food processing machines and the simulation of CIP-coverage tests 57
Soiling
(a)
(a)
For the 3D soiling of surfaces from complex parts a method
similar to spray paint processes was chosen (Figure 6). In
that context, a model soil consisting of a polysaccharide
and luminescent tracer was used and the surfaces of the
test object were coated with the viscose test solution. The
maximum layer thickness was limited by the avoidance of
rinsing test soil.
(b)
(c)
Test rig for cleaning
For the experimental analyses a Washing Cabin test rig was
used. With it, cleaning tests for open surfaces of complex
parts up to a dimension of (1x1x1) m³ with several nozzle
systems are practical. Furthermore, tank cleaning systems
can be analysed by using a special test tank (Figure 7).
Figure 5. (a) Principle of projective texturing and the application of
projection for (b) a full cone nozzle; (c) and a flat fan nozzle.
A characteristic of the presented approach is that a spray/
impact map is only valid for a certain parameter configuration;
i.e., nozzle model, pressure, distance and duration. To
enhance this range further, spray patterns for different
distances were interpolated linearly between each other.
Cleanability test
Figure 7. Test rig ‘Washing Cabin’ (left) and test tank (right).
For a cleaning test the CIP station is started up by activating
the bypass (Figure 8). When the steady state is reached,
the threeway valve switches and the cleaning process starts.
During it, a camera takes continuous pictures while an
ultraviolet (UV) lamp system excites the remaining residual
soil.
Figure 6. Example for a cleaning test of a complex part: (1) Socket
with spray shadow in detail; (2) soiled test object; and (3) test
object after cleaning (green = soiled; black = clean).
For verifying the simulated scenes in contrast to real
experiments, an adequate cleaning test was developed.
With this method, it is possible to differentiate clearly
between areas with direct nozzle impact and spray
shadows. Even rinsing water does not destroy the resulting
spray pattern for a long period of time. Consequently, in
this context the test rig ‘Washing Cabin’ at Fraunhofer
AVV was used for testing single nozzles, different nozzle
combinations and tank cleaning systems combined with
different objects to clean.
Figure 8. Scheme of the test rig Washing Cabin.