erosion of stainless steel piping with steam and oxygen
erosion of stainless steel piping with steam and oxygen
(OP)
There is a process in my facility that uses live steam (160 psig saturated) mixed with oxygen which is piped to the process in 316L stainless steel piping. The piping just after the point of oxygen injection in the steam line is eroding rapidly. The line has to be patched every 3 months or less. Does anyone have any experience with this problem? The piping upstream of the oxygen injection point is fine, it's just the pipe after the introduction of oxygen that is troublesome. Other information: The line is under high frequency vibration caused by injecting live steam into the process a few feet after the oxygen injection point. I have pics if anyone is interested. Question: Would 2205 (duplex) stainless steel be a better metallurgy in this situation? Any response would be greatly appreciated. One response I've received pointed at Moly as an alloy in 316L as the culprit due to rapid oxidation due to the oxygen and high temps. Any ideas?





RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
2205 would help a lot. The other thing that you need to do is to inject the oxygen into the center-line of the pipe and to assure mixing.
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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: erosion of stainless steel piping with steam and oxygen
If my memory serves me well I think the problem was resolved with the following piece of equipment from Komax.
http://www.komax.com/det-gasliquidcontacting.html
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
S.
http://www.corrosionist.com
RE: erosion of stainless steel piping with steam and oxygen
The highly oxidizing conditions would tend to keep the material passive.
I like the thought of thermal fatigue if you are sure that you have no liquid phase.
Your injection/mixing quill should be made from 625 or a similar alloy. And it needs to extend a ways right down the center line of the pipe. A series of small slots will help you get even distribution.
= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: erosion of stainless steel piping with steam and oxygen
regards
S.
http://www.corrosionist.com
RE: erosion of stainless steel piping with steam and oxygen
oxygen is not the problem at these temperatures, if anything it helps. were you using carbon steel, different story
one problem that carries over from the piping forum is the possibility of erosion due to incomplete vaporization in the desuperheater
by the way what you are desuperheating with
BFW?
RE: erosion of stainless steel piping with steam and oxygen
Any other ideas?
Thanks for everyone's responses. It has been very interesting.
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
no wonder you are having problems
RE: erosion of stainless steel piping with steam and oxygen
Actually I am a little surprised that this isn't a CSCC thread considering your conditions.
= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: erosion of stainless steel piping with steam and oxygen
http://www.corrosionist.com
RE: erosion of stainless steel piping with steam and oxygen
you need to be using dearated desup water, and definitely with the chorides removed, you need something along the lines of Hast. C
Look carefully at what you are doing process wise. For example, if the chlorides are a part of the process, higher grades materials may be required depending one the reactions going on.
Do you really need to desuperheat? Have you explored alternative desup methods?
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
Not at all, but it does concentrate in the ferrite phase of the weld metal itself. That could decrease the oxid. resistance. However, the Cr also partitions to the ferrite, and that's where the oxid. resistance comes from. The aust. phase of the weld metal has less oxid. resistance.
"When the eagles are silent, the parrots begin to jabber."
Winston Churchill
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
The first is to eliminate the addition of chlorides since the desuperheating fluid is simply treated water, not boiler condensate. By "treated" I mean treated with sodium hypo to kill the bugs. If the process requires desuperheating in the future we will probably route boiler condensate to the desuperheating nozzle instead.
The second reason is to eliminate a possible issue with condensation of the steam caused by the O2 injection as BronYrAur has suggested. The oxygen temp is 90 degf.
RE: erosion of stainless steel piping with steam and oxygen
Also, depending on the water treatment method used from the upstream boiler, there could be other volatile species in the steam, from a breakdown from the water treatment chemicals.
I am not convinced you need to use SS in this application. Have you considered an inconlnel lined or 9Cr alloy lined ferritic pipe?
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
RE: erosion of stainless steel piping with steam and oxygen
I may not have thought that all the way through, but it seems like a good idea as I sit here and type this.