Ernst
Is the analysis of the anion bed what is causing the fouling or are the elements part
of exchanged anions? I find the S level astonishing. As you are feeding the cleaner
through a separate DI system, the only logical source (e.g. CaSO4 from borehole water
in a gypsum layer) cannot be blamed. It must be coming from within your closed circuit
but how? Do you use a lot of Ag-plated parts? I could conceivably think that Ag2S,
which is slightly soluble in hot water, might get there if the parts are tarnished.
However, I would much rather favour the idea that organics from the solder paste are
clogging the resin beads. A "carbon bed" will remove only a range of organic
contaminants and, if a component of the solder paste is outside the range of the
material adsorbed within the bed, then it will go straight through to the resin beds
which may become clogged. You may need to tailor your carbon to the contaminants in the
water coming from the machine. Or your carbon may simply be saturated.
I know closed loop systems are fraught with difficulties and I never recommend to my
clients to use such a system which does not also contain an RO unit before the resin
beds, adjusted to pass only ca. 85-90% of the water flow.
Brian
"Wallisch, Ernst" wrote:
> Hello Technetters,
>
> I am using OA paste and subsequently cleaning the CCAs in an inline
> cleaner using strait D.I. water. We have been using this process for about
> 5 years. In the past year we have suddenly experienced fouling of our D.I.
> water treatment system (on two separate occasions), requiring system
> rebedding (not just regeneration). The D.I. water treatment system
> consists of particulate filters, carbon bed, chelate bed, cation, anion &
> mixed beds. It is a closed loop system. The system is fed (due to vapour
> loss in cleaner's exhaust ) by a separate D.I. system, which in turn is fed
> by city water. This system does not get fouled up.
>
> An analysis on the anion bed from the cleaner's water treatment
> system resulted in the following:
>
> aluminum 65ppm
> iron 24 ppm
> sulphur 4200 ppm
>
> We have never had ppm counts like these!
>
> If anyone could shed some light on the reason(s) for the bed
> fouling, it would be greatly appreciated.
>
> Thank you,
>
> Ernst Wallisch
> Manufacturing Engineer
> Computing Devices Canada
> (Ottawa, Ontario, Canada)
> (613) 596-7536
>
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