corrosion rate of carbon pipe from DI water 1

[centorr]

We designed a fin-tube heat exchanger assy using carbon steel pipe and fins. Our Customer has now advised he plans on running DI water in this water circuit. The water will probably enter heat exchanger tubing bundle (12 tubes x 120"lg) at 45-60F and exit at 100-110F after absorbing transferred heat. Will the DI water attack and corrode the 1-1/2" sched pipe(.145"wall thk) rapidly or take years before corrosion will create leaks/pin holes in tubing?
We can change pipe material to stainless steel but then we lose significant heat transfer properties.

 

[kenvlach]

Closed loop or once through?

The DI water will get contaminated from the HX pretty rapidly.
In a closed loop, the dissolution will slow when the water approaches saturation, but dissolution in warm areas & precipitation in cooler areas will continue. Unless you can add water treatment chemicals, I heartily recommend not using CS.

Perhaps you can use thinner wall material in stainless. Electropolish the insides of the SS HXer for better DI water purity.

 

[centorr]

Thanks for quick response...
Our Customer will be chemically treating the closed loop DI water system, but I am not positive of the particulars(what chemicals, how often, etc). He has a 1,000gpm total capacity so the water passing thru the heat exchanger assy will get dumped back into the main reservoir to be cooled and recirculated. The DI water will enter the heat exchanger bundle and travel thru all 14 tubes before exiting and returning to his recirculating DI water system which will cool the water back to 60F.

 

[unclesyd]

Is this a system where the customer is going from a system with a DI water loop to a treated water loop?
What is the material of construction of the cooling loop outside the cooler?

You don't want to get DI water anywhere near CS as the corrosion rate will be extremely high and result in degrading the DI water quality as mention above.

Aside from the corrosion and water degradation problems unless the water treatment is top notch and maintained you have the real possibility of MIC corrosion caused by Iron Bacteria. They love the area where the make water is added. If the conditions get right the bugs can penetrate your piping in as quick as 6 months.

 

[centorr]

Thanks again for your guys responses. I'm definitely convinced that DI water and cs is not a good combination. Design going forward will be utilizing s/s pipe.
- But, I still am curious about the effect on the carbon pipe itself. I understand the water will get contaminated quickly from contact with carbon steel, but will the carbon pipe also corrode from the DI water. Will the DI water "steal" materials or elements from pipe that would cause a rapid loss of cross-section thickness of pipe and eventually create porous pits/holes?