Water is known as the "universal solvent". It is a weakly polar molecule, so it tends to be a solvent for both polar compounds (like salts) and non-polar materials (like organic solvents), to at least some degree. It "wants" to be filled up with as much of whatever material it possibly can be. This includes iron (depending on a lot of factors, iron concentrations in water tend to be around 4-6 mg/L), vinyl, chlorides, and many others. "Normal" tap water is relatively close to saturated in a lot of these things, so there isn't a huge difference between the concentration of the dissolved material in the water and the saturation amount. However, ultra-pure DI water has almost everything removed but H2O. There is a large difference between the concentration of the dissolved material in the water and the saturation level, so there is a large driving force to dissolve whatever is around it. This is about as simple as I can explain it. Although water chemistry is fairly well documented, it is amazingly little understood by most people (including professionals). It isn't "dangerous" like 50% sulfuric acid, but a lack of understanding of water behavior (chemistry) can result in potential danger, such as pipe wall thicknesses being much less than designed, leading to premature failure and significant plant downtimes, all because, "it's just water".
In the last year or so I have been getting an increasing number of phone calls and e-mails about water problems, and people asking me if I can provide some guidance or opinion about a water analysis. It used to be once or twice a year. It's now every 2 to 4 weeks. Water chemistry seems to be increasingly more important to a wide variety of industries.
... Bruce D. Bullough ...
Sebesta Blomberg & Associates, Inc.
2381 Rosegate
Roseville, MN 55113 USA
+ 651-634-7344
www.sebesta.com
-----Original Message-----
From: Sajit Viswan [mailto:sviswan@tebodin.co.om]
Sent: Saturday, July 10, 2004 12:20 AM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] water leak at PVC connection
[bcc][faked-from][bayes]
Bruce,
Why is deionized water more corrosive? Can you pls. reason.
Sajit
-----Original Message-----
From: Bruce Bullough [mailto:bbullough@sebesta.com]
Sent: Thursday, July 08, 2004 6:03 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] water leak at PVC connection
[bcc][faked-from][bayes]
Rommel:
You indicate that the PVC is being used for DI. I assume that is deionized water. Don't assume that DI water is an easy, straightforward use for PVC. DI water is quite corrosive and PVC (and typical PVC pipe cements) is not always a good choice for DI, depending on the conductivity of the water. CPVC and CPVC joint cement are better, but still often not the best solution. Your problem might not be the quality of the installation but the materials selection.
... Bruce D. Bullough ...
Sebesta Blomberg & Associates, Inc.
2381 Rosegate
Roseville, MN 55113 USA
+ 651-634-7344
www.sebesta.com
-----Original Message-----
From: rommel noderama [mailto:nrommelh@yahoo.com]
Sent: Wednesday, July 07, 2004 6:51 PM
To: pipingdesign@yahoogroups.com
Subject: [PipingDesign] water leak at PVC connection
[bcc][faked-from][bayes]
Dear All,
We are having a problem with our plant regarding the newly installed PVC pipes, we have encountered a lot of leaks from the joints, our current DI pressure is 80 psi.Can any one send me the procedure of PVC pipe installation, i know this problem is workmanship, they are using Weld-on as pipe cement for PVC joints.
Thanks,
Rommel
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