We have a customer who is requesting that we remove a 304 Stainless Steel ring main and replace for plastic due to corrosion issues associated with passing Demineralised water through the pipe work. I have always been of the thinking that Stainless should be fine for this application. Does anyone have any comments? The quality of the water will be in the region of 1 - 5 Microseimens. Many thanks
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Demineralised water - Effect on 304 Stainless Steel 5
- Thread starter Graham58
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Not so fast, mxmaciek. Review your own comments which are shown in quotes.
mxmaciek posts "Same time, demineralized water pH would be around of 7"
then why mxmaciek do you post graphs that show that the pH will not be 7?:
mxmaciek posts "Carbon dioxide (if present) would cause corrosion as well (5uS is deionized water rather than demineralized one, so I'd expect some sodium which can mask the CO2 in pH reading)."
mxmaciek, deionized water and demineralized water are the same thing. In addition, carbon dioxide is never present in the effluent of deionized water and/or demineralized water production equipment.
mxmaciek posts "deionized water: water after one or two stages of RO, typically with conductivity around 5uS. Same is if the final stage is anion exchanger only, without mixed bed or EDI.
demineralized water: water after mixed bed ion exchanger or EDI, typically with direct conductivity below 1uS."
mxmaciek, deionized water and demineralized water are the same thing. For example, Lenntech's definition of demineralisation: Any process used to remove minerals from water, however, commonly the term is restricted to ion exchange processes.
No competent water treatment professional would consider RO effluent (without additional treatment) to be demineralized water. There are many ionic elements still present in the RO effluent since the RO process is typically guaranteed to remove only about 90% of the ionic elements whereas ion exchange systems remove about 100%. The effluent from a cation unit is also not considered to be demineralized water either, since you have removed just 50% of the ionic parameters in the cationic demineralizer unit.
mxmaciek states "after RO it will be close to neutral."
mxmaciek, a mid-career water treatment professional like yourself should know that RO effluent typically has a lower pH than neutral because carbon dioxide passes through the membrane and will depress the pH until the carbon dioxide is removed.
mxmaciek posts "Same time, demineralized water pH would be around of 7"
then why mxmaciek do you post graphs that show that the pH will not be 7?:
mxmaciek posts "Carbon dioxide (if present) would cause corrosion as well (5uS is deionized water rather than demineralized one, so I'd expect some sodium which can mask the CO2 in pH reading)."
mxmaciek, deionized water and demineralized water are the same thing. In addition, carbon dioxide is never present in the effluent of deionized water and/or demineralized water production equipment.
mxmaciek posts "deionized water: water after one or two stages of RO, typically with conductivity around 5uS. Same is if the final stage is anion exchanger only, without mixed bed or EDI.
demineralized water: water after mixed bed ion exchanger or EDI, typically with direct conductivity below 1uS."
mxmaciek, deionized water and demineralized water are the same thing. For example, Lenntech's definition of demineralisation: Any process used to remove minerals from water, however, commonly the term is restricted to ion exchange processes.
No competent water treatment professional would consider RO effluent (without additional treatment) to be demineralized water. There are many ionic elements still present in the RO effluent since the RO process is typically guaranteed to remove only about 90% of the ionic elements whereas ion exchange systems remove about 100%. The effluent from a cation unit is also not considered to be demineralized water either, since you have removed just 50% of the ionic parameters in the cationic demineralizer unit.
mxmaciek states "after RO it will be close to neutral."
mxmaciek, a mid-career water treatment professional like yourself should know that RO effluent typically has a lower pH than neutral because carbon dioxide passes through the membrane and will depress the pH until the carbon dioxide is removed.
dear bmir, let's start from... an end this time.
When you'll be on that stage of career in water treatment, you'll discover such units like CO2 degassers added before RO to decrease the load, as a standard in developed installations designed not for home users.
Sorry, but you're contrary to yourself. I can provide several installations [working, not existing in Lenntech (there are many other companies, did you know that?) web page only] which RO effluent is on or slightly below 5uS. This stage is frequently (for me, because for you it seems to be something new) used without polishing for example to fill and maintain the district heating circuits, where use of polished below 1uS water would be waste of chemicals.
By the way, part of the stream usually is polished, in the amount needed to feed the steam cycle.
Anyway, it is entertaining to see some professional stating that "you have removed just 50% of the ionic parameters in the cationic demineralizer unit.", as during whole of my education some people were trying to convince me that on cation exchanger only I'm just replacing metal and other cations (like ammonia) with the hydrogen one (or sodium, depending from the regeneration media: brine or acid), and ionic load remains same.
Finally, about the pH of 7: as you can see on the graph, it starts with NaOH content of 0.1ppm, which gives pH of 8.4. I'm sure that having some knowledge what the pH is, you can calculate what would be the concentration of OH- ions for pH of 7.5, right? Alternatively, you could use software like the Visual Minteq.
Last but not least: carbon dioxide is a common problem in pure water applications. and for me it is a surprise that you do not know it... I'll disclose you a secret: you can have perfectly pure water leaving your EDI or mixed bed, and same time you can face CO2 problem in application. This is the effect of installation of (another surprise for you) equipment called: demin water storage tank (do not mix up with feed water tank), and mysterious phenomenons called air ingress and CO2 dissolution in the pure water. It will even speed up in the presence of sodium ions causing equilibrium movement due to the formation of sodium carbonate and bicarbonate.
I think that you must be a lucky man, if you did not experienced such issues yet.
If you'd be interested, I can provide you with more details, but I propose private messages exchange rather than this thread.
When you'll be on that stage of career in water treatment, you'll discover such units like CO2 degassers added before RO to decrease the load, as a standard in developed installations designed not for home users.
Sorry, but you're contrary to yourself. I can provide several installations [working, not existing in Lenntech (there are many other companies, did you know that?) web page only] which RO effluent is on or slightly below 5uS. This stage is frequently (for me, because for you it seems to be something new) used without polishing for example to fill and maintain the district heating circuits, where use of polished below 1uS water would be waste of chemicals.
By the way, part of the stream usually is polished, in the amount needed to feed the steam cycle.
Anyway, it is entertaining to see some professional stating that "you have removed just 50% of the ionic parameters in the cationic demineralizer unit.", as during whole of my education some people were trying to convince me that on cation exchanger only I'm just replacing metal and other cations (like ammonia) with the hydrogen one (or sodium, depending from the regeneration media: brine or acid), and ionic load remains same.
Finally, about the pH of 7: as you can see on the graph, it starts with NaOH content of 0.1ppm, which gives pH of 8.4. I'm sure that having some knowledge what the pH is, you can calculate what would be the concentration of OH- ions for pH of 7.5, right? Alternatively, you could use software like the Visual Minteq.
Last but not least: carbon dioxide is a common problem in pure water applications. and for me it is a surprise that you do not know it... I'll disclose you a secret: you can have perfectly pure water leaving your EDI or mixed bed, and same time you can face CO2 problem in application. This is the effect of installation of (another surprise for you) equipment called: demin water storage tank (do not mix up with feed water tank), and mysterious phenomenons called air ingress and CO2 dissolution in the pure water. It will even speed up in the presence of sodium ions causing equilibrium movement due to the formation of sodium carbonate and bicarbonate.
I think that you must be a lucky man, if you did not experienced such issues yet.
If you'd be interested, I can provide you with more details, but I propose private messages exchange rather than this thread.
The graph shown is useless for defining DI water for semiconductor processing. If your semiconductor industry DI water is anywhere near 0.1 ppm NaOH, it's seriously fubar and unusable for processing of wafers.
Perhaps there is a simple difference of nomenclature. There are many levels of DI water, but the semiconductor industry only uses the purest level:
TTFN
faq731-376
Perhaps there is a simple difference of nomenclature. There are many levels of DI water, but the semiconductor industry only uses the purest level:
TTFN
faq731-376
mxmaciek and irstuff for that matter,
This posting started off with a simple question about demineralized water and corrosion. The original post stated demineralized water without any details about the application. Demineralized water is a very basic concept, but is limited by definition. (Some even want to argue about definition of demineralized water.)
What it has turned into is an off topic extraneous discussion about all sorts of assumptions where a oouple of people with some experience in water treatment are making all sorts of assumptions.
People are posting about degasifiers, condensate polishing, RO systems, carbon dioxide dissolution, water for processing ssemiconductor, storage tanks, power plant water treatment, mixed bed units, water quality and on and on. It is obvious that you have not worked long enough to have had the joke about the word ass/u/me cross your desks.
Demineralized water is not synonymous with condensate, or ultrapure water, or RO water, or decationized water, etc.
Would strongly suggest that you read:
Eng-Tips.com Forum Policies
faq731-376
This posting started off with a simple question about demineralized water and corrosion. The original post stated demineralized water without any details about the application. Demineralized water is a very basic concept, but is limited by definition. (Some even want to argue about definition of demineralized water.)
What it has turned into is an off topic extraneous discussion about all sorts of assumptions where a oouple of people with some experience in water treatment are making all sorts of assumptions.
People are posting about degasifiers, condensate polishing, RO systems, carbon dioxide dissolution, water for processing ssemiconductor, storage tanks, power plant water treatment, mixed bed units, water quality and on and on. It is obvious that you have not worked long enough to have had the joke about the word ass/u/me cross your desks.
Demineralized water is not synonymous with condensate, or ultrapure water, or RO water, or decationized water, etc.
Would strongly suggest that you read:
Eng-Tips.com Forum Policies
faq731-376
That's, of course, your opinion, but you concede that the OP never specified his "demineralized water," so I fail to see why attempting to define the problem is off topic. Obviously, the OP is AWOL, but the fact that people continue to disagree about the definition suggests that this was never a "simple question."
TTFN
faq731-376
Yes, the OP never specified his "demineralized water,". But a water industry person will not say demineralized water is synonymous with condensate, or ultrapure water, or RO water, or decationized water, etc. Someone with limited experience may think those terms are interchangeable.
OK, going to definitions: demineralised water is water without any ionic impurities, with the conductivity of 0.055uS, and pH of 7.0
This is definition not related with water industry, but purely chemical. Please do not mix with distilled water or ultra pure water, this last would be with organics and non-ionic compounds removed as well (@IRStuff: I think you'll agree with that).
Regarding the demineralised water, and common use of ion exchange - the ionic impurities level can be reduced to (according the spec of existing plant after one year in service, so NO brand new resins):
- fluoride 0.1
- acetate 0.3
- formate 0.3
- chloride 0.7
- sulfate 0.7
- sodium 0.1
- ammonia 0.5
- magnesium 0.0(nd)
- calcium 0.6
all above values in ppb or ug/L, resulting with the conductivity of 0.058uS/cm
And again, not in water industry, but in power applications, these values are nothing unusual, as if you really need the pure output, you can look into the special resins with e.g. chloride leak below 30ppt (ng/L).
finally, I think that OP is not interested in this thread anymore, otherwise he would precise his specs...
This is definition not related with water industry, but purely chemical. Please do not mix with distilled water or ultra pure water, this last would be with organics and non-ionic compounds removed as well (@IRStuff: I think you'll agree with that).
Regarding the demineralised water, and common use of ion exchange - the ionic impurities level can be reduced to (according the spec of existing plant after one year in service, so NO brand new resins):
- fluoride 0.1
- acetate 0.3
- formate 0.3
- chloride 0.7
- sulfate 0.7
- sodium 0.1
- ammonia 0.5
- magnesium 0.0(nd)
- calcium 0.6
all above values in ppb or ug/L, resulting with the conductivity of 0.058uS/cm
And again, not in water industry, but in power applications, these values are nothing unusual, as if you really need the pure output, you can look into the special resins with e.g. chloride leak below 30ppt (ng/L).
finally, I think that OP is not interested in this thread anymore, otherwise he would precise his specs...
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