Cooling Water Exchanger Tube Selection

[pengin40]

I have a project to install a smaller cooler that will use either copper or cupronickel tubes on the cooling water side. Does anyone know of good references to compare life expectancies for these two materials in cooling water service?

 

[unclesyd]

You need to post a little more information concerning your specific conditions, such as temperature, water quality, and what is on the shell side.

 

[pengin40]

I don't mind doing some of the legwork on this but I'm really just looking for good reference material such as a NACE document.

However, the temperature is 50F to 120F. I have no idea what the quality of the water is and the shell side has lube oil.

 

[metengr]

Yes, visit the Nickel Development Institute, and search for technical articles on these materials

http://www.nidi.org/index.cfm/ci_id/80.htm

 

[SnTMan]

pengin40, we use 90/10 all the time in these and other applcations, including seawater sometimes.

Regards,

Mike

 

[EdStainless]

and look at docs from Copper Development Assoc.

http://csaweb113v.csa.com/ids70/quick_search.php?SID=u82aiu2upgc5gv60sqisnsqjd3

You really need to know why existing tubes have failed. I have seen a number of brass and CuNi failures recently that were related to MIC (SRBs).

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Plymouth Tube

 

[rmw]

EdStainless, That link didn't work. I'd like to see what it says. Is there any other path to the information. I'm making a big pitch at work any day now - actually against CuNi tubing in favor of something much more bullet proof.

Penguin four Oh, you BETTER know what your cooling water quality is regardless of what tubing metallurgy you pick. Most tubing metallurgies have some enemies and a few have many enemies.

Pure copper tubing is fairly soft and any abrasives will be real detrimental to it.

There are a few things that really don't like Cu and Cu based tubing, or maybe I should say like it too much. That would include sulfides and ammonia based compounds. You have to be real careful if any of those are present on either side of the tube.

If your water has a lot of sedimentation, the upper velocity limits of Cu and CuNi tubing may not allow you to have enough tube side velocity to keep the sediments in suspension.

rmw

 

[pengin40]

rmw, we have an existing copper tube exchanger in service. We want to replace it with either copper or cupronickel tubes. I'm just trying to get some reference material that would help us decide which one lasts longer.

I did find some kind of reference in an old Metals Handbook that gave corrosion rates for different materials in seawater. There might be some experts out there that can correct me but I would think this would be a sufficient estimate for determining between these two tube materials.

 

[Metalguy]

Why does it need replacement? You must be careful using "corrosion rate" data, because very slight differences between YOUR water/conditions and theirs can make huge differences in performance.

I'm not a big fan of 90/10, but 70/30 *usually* does pretty well, at a lot more $$$.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[metengr]

In the 30+ years of Power Generation I found that 90-10 CuNi exhibits satisfactory corrosion resistance and exhibits very good anti-macro fouling behavior, provided design flow rates are followed. If stagnant conditions or low flow develops resulting in a sediment layer, under deposit corrosion will persist with possible SRB MIC.

The 70/30 CuNi alloy seems to exhibit enhanced macro fouling resistance and seems slightly more resistant to MIC, SRB action.

 

[EdStainless]

copper.org
resources
technical reference library
then search away....

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Plymouth Tube

 

[rmw]

Ed,

Thanks, I found that route on my own earlier today and have been reading almost all day on their site. They do tend to be pro-copper; I wonder why. But some of the papers that they present have what seems to be objective analysis in them.

Most of their information tends to be about sea water applications. I didn't find much fresh water reading.

metengr,

Re your last post, interesting..., I just read on the copper.org site earlier today in one of the papers that the reduced cu in 70/30 lessens the macro fouling resistance from that available with 90/10. Hmmm....

In the days that I had a lot to do with CuNi tubing (pre entry into the Power Industry) 90/10 was used for commercial equipment (desal stuff) and 70/30 was used only by, but exclusively by the US Navy.

In the power industry, I have seen CuNi (always 90/10) in condensers that was so thin that you could almost read a newspaper through it. But it was after lots of years and lots of dirty water through it. Now, I'd call that a good service life.

rmw

 

[metengr]

rmw;
Macrofouling between 90/10 an 70/30 CuNi from the reference I have indicates very similar reistance. Where they seem to diverge is microfouling resistance and susceptibility to MIC from SRB's. Here according to the information I have, 70/30 performs better.

 

[Guest102023]

Water is probably the single most loaded word a corrosion engineer can encounter. It is never just 'water'! Aside from all the concerns previously raised, is there possible exposure to zebra mussels? If you are using once-through cooling water (OTCW) anywhere on the Great Lakes, you can assume they will find you. I have investigated many failures of admiralty brass HX tubes, and sometimes recommended replacement with 90/10 cupronickel; however, I have also seen failures of those in the same service. Ammonia ions generated from biological decomposition are the presumed common thread. (Ammonia ions are to copper alloys as chloride ions are to 300 series stainless steels).

I am just doing some research for a part that will be resident in fresh water, and found that the cupronickel alloys are best against mussel adhesion, due to the toxic copper they slowly release. Probably the same reason they are biofouling-resistant in general. The 90/10 grade is apparently best, followed by 70/30.

Keep in mind that the copper alloys in general have lower limits for fluid velocity (although cupronickels are among the better Cu-based grades). ESPECIALLY be careful if it is a OTCW design - leaking could have environmental consequence$. All the plants in my area are weaning themselves off of cheap, accessible OTCW for that reason.

 

[EdStainless]

brimstoner, There is another reason that plants are trying to move off of OCTW, it is the EPA.
Step one is to limit Cu discharge levels to number so low that Cu alloys are no longer suitable solutions.
Step two is to declare that Once Through is not 'best available technology' and begin denying renewal of water permits.
This has happened to a Nuclear power plant in NY blocking their license extension.

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Plymouth Tube