Ductile Iron - Corrosion/ erosion?

[Hercules28]

Dear all,

I have a ductile iron reduced that was only 5 years in service in a chilled water system.

It appears as erosion/corrosion to me.
There is some Bromine in the water. Service temps were 72F and below.

In Pic 1 it appears as if it was never 100% filled and that's how only half of it got corroded. It actually penetrated through the wall as you can see in pic 2.

Then I assume they must have rotated it 180 degrees so it won't leak and that's how it started corroding on the other side.

Any ideas?

Thanks,

Herc

 

[Hercules28]

Pic 2

 

[EdStainless]

Was this welded into a system? What was it mated to?

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Hercules28]

It was mechanically joined with similar metal (ductile iron coupling). So probably not galvanic corrosion here.

 

[rconner]

This looks pretty unusual. I also have a few questions, as more information would help to have good idea what's going on here:

1. If it is possible, could you post a representative water analysis, with excursion ranges etc. of whatever chemicals are involved?
2. Could you also post the historical flow range (discharge?) through this reducer? [In this regard, I think a fitting might have about a nominal or even little smaller inside diameter of 4" on the small end and 6" on the larger, to result in I suspect substantially different flow velocity from end to end.]
3. Is fitting lined? -- ductile iron pipe has been for many years been predominantly most cement mortar lined, but more often fittings were specified without cementlining for many years (and I am having a hard time clearly making out anything resembling normal lining on even the larger end).
4. While I realize you have said there are some sorts of ductile iron "couplings"involved on the ends, I will repeat Mr. Ed's good question of what kind of "pipe" is connecting to this thing on both sides, and by the way what are the pipes or whatever lined with, and how did the adjoining piping as well as the "couplings" look on the inside?

I will await your answers, in hopes I can help more.

 

[metengr]

This looks more like flow induced cavitation damage on the surface rather than corrosion or erosion/corrosion.

 

[Hercules28]

rconner I ll try to get all that info.
I thought about cavitation. That usually requires high speeds. Will I be able to tell with a micro?

 

[metengr]

Yes, a metallographic examination will be most important in this location. Usually, cavitation damage results in a spongy surface texture.

 

[metengr]

PS; Do yourself a favor and read-up on cavitation damage before you decide otherwise.

http://www.iceweb.com.au/Valve/Control Valves/Masoneilan/ControlValveCavitation.pdf

 

[mrfailure]

In addition, you should also consider SEM/EDS analysis. I wonder if MIC is a possibility since it never completely filled; you might find residue of SRB bacteria (such as high sulfur peaks) if this was the case.

Aaron Tanzer

http://www.lehightesting.com