Rapid (erosion?) of stainless pipe in steam/oxygen service
Rapid (erosion?) of stainless pipe in steam/oxygen service
(OP)
There is a process in my facility that uses live steam (160 psig and desuperheated) 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.





RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
Using a 304 stainless steel might provide better performance in this application. The duplex stainless steels are limited to lower service temperature (600 deg F or lower) but still contain Mo.
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
In my experience gaseous oxygen is a material to be handled with care. I rather suspect that JLSeagull is right, that the problem is one of velocity and impingement. Usually monel or inconel are appropriate materials for oxygen impingement areas. I think it would be worth your while to get a copy of CGA G-4.4 Edition 4 Oxygen Pipeline Systems.
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
Thanks for your response.
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
how close to saturation do you control? you may be getting wetsteam erosion-corrosion . along this line 30 ft may not be enough distance between the desuperheater and the oxygen injection, typically 40-60D is required just for the temperature measurement
you can always add metal and the duplex stainless will likely stand up better than 316L, if you can keep it in place,
I am not sure that I buy the moly argument, especially with oxygen present, since moly improves resistance at least in wet steam services.
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
my experience is that stainless is good to 500F in O2, given caveats of corrosion in any service.
160 # steam has a sat. temp of 370F, most desup installations can get to 5-10F superheat at best, and depending on the amount of run to the process.
what sort of desuperheater are you using?
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
I will have to get back to you on the type of desuperheater (not sure).
Are you saying that 316L stainless steel should not corrode at 370-500 Degf. with a steam and oxygen mixture?
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service
If anwsers are yes and no, the oxygen may be locally condensing pockets of steam as it heats up in the flow. If there is swirl in the flow, the droplets will move to the pipe wall due to centrifugal effects, and erosion can/may/will occur.
RE: Rapid (erosion?) of stainless pipe in steam/oxygen service