AAT MEGA II CLEANER, Руководство по эксплуатации

Страница: 63 / 92

Mega II Operating Manual Rev. 2.0 10/15/2005 55
B.3.1 SOLUTION CROSS OVER
The Mega II Cleaner with its closed loop, solvent regeneration system is capable
of using a number of different kinds of chemical solvents, as well as water, for
the cleaning process. While AAT typically recommends the use of the same
solvent solution for both the PreWash option and the standard Wash cycle, dual
chemistries can be utilized.
In order to effectively use dual chemistries with the system it is very important
to set up the cleaning cycle properly to minimize “cross over”. Even when using
the same chemistry for both PreWash and final Wash, a “tainting” of solutions
or solvents known as “cross over” occurs. Efforts have been made to minimize
“cross over” however, it is practically unavoidable.
When using dual chemistries it becomes even more imperative that once the
system is setup it should be monitored because of solution “cross over” and any
effects that may result from the use of different combinations of chemistries.
Monitoring the system for the first month or so after installation can provide
valuable information about when the chemistries become saturated to the point
that problems begin to arise in cleaning, drying, or any unforeseen effects.
“Cross over” is a process that occurs when the PreWash solution from the drum
leaves a residue in the process tank after the cycle is complete. We call this
residue “drag-in”. When the clean Wash solution is introduced into the process
tank it picks up and mixes with the residues (drag-in) from the PreWash. Thus,
the solvents have “crossed over” with one another.
Let us say, for example, that MegaSolv NOC is used as the PreWash solution.
Megasolv NOC does not dry, so a wet residue is left in the process tank after the
solution is drained back into the drum. When the final Wash solution, say IPA is
run, the Megasolv NOC residue from the PreWash mixes with the IPA. The result
is, cycle by cycle the final Wash solution becomes increasingly saturated with
the PreWash residues or “drag-in”. This reduces the effectiveness of the IPA in
its ability to completely dry the parts being cleaned.
Although “cross over” is unavoidable, proper parts orientation in the basket can
help minimize “drag-in”. Parts should be oriented in the basket so that they trap
as little of the PreWash solution as possible, allowing them to drain and *dry
properly.
Note: Certain chemistries do not dry as fast as others do and this
contributes to “cross over”. Choosing the right chemistry for the job is
important. The choice of solvents is application dependent. For
information regarding solvents, consult the MSDS (Material Safety
Data Sheet) or contact the AAT Applications Laboratory.