Flow Assisted Corrosion (FAC)
Flow Assisted Corrosion (FAC)
(OP)
Has anybody got any info on FAC rates of CrMo - We are looking to change the MOC from C/S to CrMo (tubes)in a fixed shell and tube heat exchanger (steam on the shell side)3.5Barg / 100 Deg C aprox





RE: Flow Assisted Corrosion (FAC)
Even small amounts of Cr help a lot. I have seen reheat lines fail from FAC. Sections of pipe with 0.15%Cr are fine and ones with 0.05% are eroded.
The T21 and 22 alloys are an order of magnitude better than plain CS.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Flow Assisted Corrosion (FAC)
Where is your FAC occur ing and what is the media on the tube side?
What your flow velocities in the area of concern?
Your temperature is rather suspect on having several different problems with boiling or condensing.
I have never seen any difference in the behavior of the two materials in respect to corrosion and flow problems.
RE: Flow Assisted Corrosion (FAC)
it is correct that a higher amount of Cr is better for areas suseptable to FAC.
i also believe that FAC is also more prevalent (where low Cr is used) just downstream of elbows (approx 1.5X the dia of the pipe).
RE: Flow Assisted Corrosion (FAC)
Yes, Cr helps a lot in improving resistance to FAC. Even the normal variation in Cr seen in CS pipe can have an impact.
There are many factors in FAC, water chemistry is important and velocities. The worst cases involve two phase conditions. The wet steam in Nuc plants is real bad for FAC.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Flow Assisted Corrosion (FAC)