Is CS a suitable material for cooling water with high chloride content?

[mthausif123]

Hi,

I am designing a cooler with open recirculating tower cooling water as cooling media. Tube side fluid is cooling water. The maximum chloride content of cooling water is 500 wt ppm. I have selected carbon steel as tube material. Client has raised concerns whether I can guarantee 10 years life for tube bundle. I want to know whether CS can be suitable for cooling water service with 500 wt ppm chloride? What is the maximum limit of chloride in cooling water for which CS remains suitable?

Thanks in advance...

 

[LittleInch]

In your other post you said 45C return temp.

Even without the CL level, warm aerated water and carbon steel are not a good combination.

Add some salt / chlorides and it gets worse.

Guarantee 10 years is pushing it. Some small part will always corrode faster than any generic corrosion allowance. Plus you end up with lots of particles of rust in your system.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

I agree with LittleInch ..... Carbon steel materials in aggressive and ever-changing cooling-tower water service will not last !!!

Your recommendation of the cheapest material, carbon steel, will rapidly become a mess and poison the tower basin for any future repairs, replacements or upgrades.

It is important to note that the quality of the cooling tower water significantly affects both the choice of construction materials and fill pack material. In case of particularly aggressive or acid water, non-corroding and long-lasting material, as stainless-steel or fibreglass, are most commonly specified.

It is equally important to recognize that, through evaporation, cooling towers require lots of expensive make-up. Therefore, they become a magnet for any available waste water in the area. This ensures an eternally changing water chemistry. You really have no guarantees on future chloride or sulfate levels ...

https://www.cedengineering.com/userfiles/M05-009 - Cooling Water Problems and Solutions - US.pdf

The "Nalco Guide to Cooling Water Systems Failure Analysis" book was written specifically to answer most of your questions. You could buy it on AMAZON (but you won't) Several stolen .pdf versions of this NALCO developed book are available on Pakistani, Indian and Iranian website


Some Questions:

1) Is this part of a power plant cooling system with a steam surface condenser ? Give up more details about the rest of the system
2) Recognizing the massive investment in CT systems, some clients elect to use cathodic protection for condensers/tubesheets
3) You mention "tubes" .... What is your tubesheet material and is the tubesheet clad or coated
4) Is this the first cooling tower/condenser system that you have ever specified ?

As always, Much more information is required for a competent answer !!

MJCronin
Sr. Process Engineer

 

[EdStainless]

It might be possible with very aggressive (and expensive) chemical treatments.
But if there is ever break in treatment then the material will be lost.
500ppm Cl at 45C?
That limits you alloy options.
A lot of this will depend on what the rest of the system is made from and how the water is being treated.
Tell us more.

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P.E. Metallurgy, consulting work welcomed

 

[mthausif123]

Hi,

Thank you everyone. I understand that CS is not suitable for my case. I am opting for SS316L instead.

 

[LittleInch]

Beware of pitting corrosion, but maybe the CL level isn't high enough.

Even 316L might not be good for 10years. Chlorides are a bugger to deal with long tem hot aerated water.

Also at 45C beware of legionnaires sop you will need to does with biocides etc.

https://www.cdc.gov/legionella/heal...tain water,towers then spread these bacteria.

A better link

https://www.hse.gov.uk/legionnaires/cooling-towers.htm

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

316L won't cut it without chemical treatment as well.
You list is down to some Cu alloys and 2205 for SS.
This is actually very similar to what you would see in steam condenser service.
You might look there for some guidance.
If you go with a Cu alloy, be very mindful of the velocity limits.
Even with clean water and watching the limits you will lose 1/2 the wall in 20years.

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P.E. Metallurgy, consulting work welcomed

 

[EdStainless]

I'll expand a little bit.
316L would likely work if this was never shut off even for just a few minutes.
If it had to be shut off, it would need to be aggressively flushed with fresh water.
Doing this wrong once would destroy the entire unit.
I have seen equipment operated this way and invariably about every 3 or 4 years someone forgets to flush well enough, and they have to rebuild the entire thing.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed