Appendix 3: Procedure and parameter recommendations
using Expert Mode
© Elma Schmidbauer GmbH
BA_Elmasolvex_VA_EN_Vers.05.2018
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The programmable vacuum drying parameters in the sequence
Dry2
(
Fig. 16.6
bottom right) determine the
•
further duration of the evacuation, measured from reaching
the specified pressure (8 seconds, 120 mbar in
Fig. 16.6
),
with which even lower pressures on the pressure-time curve
p(t) in the cleaning chamber are reached when the vacuum
pump is running,
•
duration of the reaeration by opening the vent valve of the
cleaning chamber for the ambient normal pressure (2
seconds in
Fig. 16.6
) while the vacuum pump continues
running (for the purpose of maintaining the flow of the
supported vapour mist extraction for the cleaning chamber),
•
number of repetitions of this cycle of evacuation and
reaeration (12 times in
Fig. 16.6
).
It was established during tests of the vacuum drying that the
drying is accelerated in most cases if some short cycles with
evacuation only up to 600 mbar and 2 seconds reaeration for
the purpose of additional vapour mist extraction with generated
flow through the cleaning chamber are inserted after each
reaeration.
Therefore, three program-independent 600 mbar short cycles
are performed after each programmed cycle.
Compact metal parts, however partially with cavities in hollow
spaces (also pipes with wall thickness in the internal diameter
area) are still wet after the standard drying with 12 cycles of 8
seconds each at 120 mbar.
The heat capacity here is usually sufficient to pass to a lower
number of, yet longer duration, cycle to achieve lower
pressures – for example:
3 cycles, 8 seconds – after reaching 55 mbar.
If the monitoring of the drying behaviour in accordance with the
suggested process in this example results in cycle 2 having a
shorter time than cycle 1 until reaching 55 mbar and cycle 3
needs even shorter time than cycle 2 for this, the concept of
lower pressures for fewer cycles however longer time duration
is correct for the first cycles.
This is usually the case for rinsing media with low boiling points
such as IPA.
If no shortening of the time needed for reaching 55 mbar is
observed in the third cycle, the number of cycles must be
initially gradually increased – from 3 to 4 or 5.
If this shows that no shorter overall drying time than with the
parameters in the standard program is achieved, drying must
be performed in comparison with the standard program with
only slightly reduced pressure (for example, from 120 to 100
mbar) and initially the same number of cycles.
Example
