D.I. water in small steam boilers

[GenB]

Are there any precautions to take in using D.I. water in small steam boielrs?
(High pressure boilers 100 - 500 psi 10 - 30 HP)
genb

 

[lownox]

DI water is reasonably aggressive and will begin to pit many materials. if the heat exchanger of your boiler is 316 SS, then I say move forward. avoid anything less.

this is rule of thumb as I know it.

 

[GenB]

Thanks for the reply,
These are standard steam boilers/generators out of C/S
not SS, I found out that it is possible to use them on DI water with chemical treatment, not what's the treatment.
Then I may have to talk to the chemists!
Regards, genb

 

[unclesyd]

Was just going to post that the only place that I've seen untreated DI water used in boilers was in montube boilers.

For water treatment chemicals I would look to someone who specializes in water treatment like GE(Betz) or Nalco.

http://www.gewater.com/products/chemical_water/index.jsp

http://www.nalco.com/ASP/index.asp

 

[StoneCold]

I have two fire tube boilers that run on D.I. Water.
One is a 40hp and the other is a 150hp. They run on D.I. water to reduce the amount of blowdown water. They run a Nalco treatment package. So it can be done. It is more expensive than softening the water but in this case it is offset because I don't have a cheap place to dispose of my blowdown water.
We have not seen pitting in the boiler due to the D.I water.

Regards
StoneCold

 

[GenB]

Hello,
I will contact NALCO for advise,
Thank you very much to my good advisors,
this will be of great advance in my business,
GeeneralBoiler GenB

 

[lownox]

Stonecold, in your boiler application maybe it is a closed loop with little or no makeup water??? The DI water is hungry for metals. I apologize for my vague post earlier. In my typical application (humidification/steam boilers) we are constantly replacing the water as it boils off... thus the water tends to "eat up" the metal. These type units use 316 SS. In a closed loop, the DI water will "get" some of the metal that the boiler is made of, but as it dissolves the water becomes less aggressive. Hope this makes sence... not always good with words.

 

[StoneCold]

lownox
Good point that I did not mention. We recover better than 90% of our condensate. We also add our makeup chemicals right with the makeup water in the boiler feed tank. So we are putting say three gallons of D.I. water into a 100 gallon tank of condensate and conditioning chemicals. We have not seen any problems with the feed tank and it is 15+ years old. But our situation would be considerably different if we were loosing a lot of our condensate and making up with strictly D.I. water. That would be bad.

Regards
StoneCold

 

[steris]

At the risk of being repetitive, I strongly agree with lownox. We manufacture steam boilers and if the water is DI or has purity greater than 2 Mega-Ohms then we construct the boiler from 316L. As we operate at 100 psi 4HP, no condensate return, using Schedule 40 pipe. With this setup if we use CS with DI we have noticed aggressive pitting in the boiler. Best of luck.

 

[Trogdor]

We have a small (20 gallon) electric boiler which we feed with DI water. At first we had problems with false low-level signals. The system uses a resistive probe to detect for presence of water and the DI water had high enough resistivity to make the boiler think there was no water present. The boiler company sent us a different probe which fixed the problem. Our boiler is 316 stainless steel.

 

[CaptainKvar]

Why not just use water softeners? Demineralizers are very expensive and wastewater licenses may be needed to regenerate them. At those Boiler(100-500psi) pressures DI water isn't neccessary. Usually 600psi and above DI water is needed particularly when using steam turbines where silica would be an issue and boiler water conductivity is more critical.

 

[GenB]

Trogdor
Do you have know the brand/type of probe control are you using?
I always use floats on my small SS steam generators,
I can never make them work with probes.

CaptainKvar I use soft water and probes on 1000psi boilers/steam generators, I have not had any problems on conductivity.

genb

 

[CaptainKvar]

GenB,
I didn't mean you would have a problem with conductivity,
it just that water chemistry/treatment is more critical at higher steam pressures and demineralizers are nessary.

CaptainKvar