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RE: drain times & carry over
- Subject: RE: drain times & carry over
- From: "Kennedy, Judith C." <jken461@ECY.WA.GOV>
- Date: Fri, 30 Mar 2001 11:11:59 -0800
- Delivered-To: firstname.lastname@example.org
- Delivered-To: email@example.com
- List-Name: p2tech
- Reply-To: "Kennedy, Judith C." <jken461@ECY.WA.GOV>
For plating-type operations, it seems like the 20 seconds recommended for
additional drip time is small compared time in the process baths. Even if 6
tanks are involved in a process line, that's only 2 minutes extra.
Hazardous Waste and Toxics Reduction Program
Washington State Department of Ecology
Olympia, WA 98504-7775
Phone (360) 407-6385
Fax (360) 407-6305
From: Karl DeWahl [mailto:firstname.lastname@example.org]
Sent: Friday, March 30, 2001 11:19 AM
To: P2tech(response) (E-mail)
Subject: drain times & carry over
A common reservation (barrier) to increasing drain time on parts going
through an immersion process line (e.g. a plating line), is that increased
drain time increases production time and cuts production capacity (if the
line operates near full capacity). The cost of reduced production capacity
can dwarf the savings in chemicals and water.
This could be addressed by cutting hold times in the bath to compensate for
additional drain time.
I have thought about the theoretical trade off's (see below), but does
anyone know of:
1. studies looking at compensating increased drain time with decreased
2. an expert who might have experience with this?
3. work to identify optimal hold times for different immersion
On the positive side,
- Contact time with the chemistry or rinse remains constant.
- Drainage flow will induce some turbulence and in-film mixing that should
enhance the movement of contaminants away from the surface or active
chemistry to the surface.
- the longer the tank hold in standard practice, the less the effect of
reducing hold time.
On the negative side
- access to fresh solution is reduced
- increased drain time can enhance channeling on the surface, and
differences between the top and bottom of a part that could create uneven
surface effects (should be minimal in rinses)
- the stronger the tank agitation is, the greater the possible effect
lengthened drain time
MnTAP / University of Minnesota