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September 2008

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Thu, 11 Sep 2008 09:04:41 +0300
Content-Type:
text/plain
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text/plain (101 lines)
I'll go along with Kevin, at least partially. Monitoring your incoming 
DI water is a must, although I would use a conductivity, not a 
resistivity, meter. Why, you ask? Because the conductivity is directly 
proportional to the quality; resistivity is an inverse function and is 
therefore non-linear. In most cases 1 µS-cm is a good limit but, as 
someone on this list may say, it depends. Above all, it depends how you 
remove the water; mechanically is good - evaporatively is not so good.

If I understand you, the final rinse comes from a tank. Therefore, it is 
essential this be monitored as well (not instead of). Your incoming 
water may be pristine pure but you may have Dead Sea water in the tank 
(well, not quite!). This is also an 'it depends' situation with a dozen 
parameters governing it. Personally, I prefer the final rinse to be with 
the incoming, uncontaminated, DI water.

No matter how good your water, machine etc, you still need process 
control by qualifying your overall process and then sampling the results 
in production for, at least, ionic contamination.

Brian

Kevin Glidden wrote:
> John,
> 
> I would recommend you monitor your water resistivity, not PPM, and in your
> water system only, not the washer tanks.  The water from your water system
> should go directly to the final rinse.  The final rinse is the most
> important cycle and should use only virgin DI water in a range (my
> recommendation) between 2 and 5 Meg-Ohms.  I would classify 5-10 PPM water
> as "RO" quality only.  Do you perform any post cleaning verification?
> 
> The Myron L 750 series is a good meter.
> 
> 
> Kevin Glidden
> Manufacturing Engineer
> Luminescent Systems Inc.
> 
> -----Original Message-----
> From: John Anselmo [mailto:[log in to unmask]] 
> Sent: Wednesday, September 10, 2008 3:14 PM
> To: [log in to unmask]
> Subject: [TN] Electrovert Wash PPM (TDS) Monitoring
> 
> Hi everyone,
> 
> I have a couple of questions regarding how everyone monitors their DI wash
> process (those that still do water washing).
> We have an old Electrovert unit with 3 water tanks: the pre-wash, wash and
> rinse.  The water temp is set to 140 deg F.
> We currently have a hand held TDS meter and check the water at a minimum
> weekly, more often if we have washed a large number of parts.
> We are looking at adding a continuous monitor/controller (such as the 750
> Series monitor/controller from Myron) to the wash line.
> But, I have a few questions regarding what the general practice is for those
> using a water wash daily.
> 
> 1) What monitor/controller is most used/recommended?
> 2) What limit do you use for PPM? 5? 10?
> 3) Do you also have a chart recorder on your monitor?
> 4) Would you recommend monitoring all three tanks, or just the wash?
> 
> Thanks,
> 
> John 
> 
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