Flare pipe material selection
Flare pipe material selection
(OP)
thread338-270504: HIC and SCC tests could they be done on stainless steel?
Hello ,
for horizontal flare (flare piping - buried to burn pit):
during flare scenario, MDMT is -95 deg C and service is sour with 5110 ppm of chlorides and 3.5 % H2S. pressure is 35psia. Client prefers to select alloy 625 pipe material. Now question is about last spool (around 12 m) including so-called flare tip (which in fact is pipe open end itself), process team calculated 1650 deg C and material has to be selected for this high temperature spool. i believe this last spool will have very less pressure like atm to 5 psia. i need your advice regarding possible materials which could withstand this temp. service is occasional only during startup. i think SSC and SCC is not a concern at such a lower pressure. i have seen SS310 flare tips and pipes up to some lengths in vertical flares but i dont have experience with such a situation and high temperature pipe. kindly share your experiences with similar situations. thanks in advance. are below options practical? design life is 20 yrs.
1. SS310
2. Inconel 625
3. Inconel 600
Hello ,
for horizontal flare (flare piping - buried to burn pit):
during flare scenario, MDMT is -95 deg C and service is sour with 5110 ppm of chlorides and 3.5 % H2S. pressure is 35psia. Client prefers to select alloy 625 pipe material. Now question is about last spool (around 12 m) including so-called flare tip (which in fact is pipe open end itself), process team calculated 1650 deg C and material has to be selected for this high temperature spool. i believe this last spool will have very less pressure like atm to 5 psia. i need your advice regarding possible materials which could withstand this temp. service is occasional only during startup. i think SSC and SCC is not a concern at such a lower pressure. i have seen SS310 flare tips and pipes up to some lengths in vertical flares but i dont have experience with such a situation and high temperature pipe. kindly share your experiences with similar situations. thanks in advance. are below options practical? design life is 20 yrs.
1. SS310
2. Inconel 625
3. Inconel 600





RE: Flare pipe material selection
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Flare pipe material selection
Think about this, 1650C is above the melting point of any common alloys.
310 is the least expensive
625 will have the highest strength
600 will resist sulfidation and carbonization the best
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P.E. Metallurgy, Plymouth Tube
RE: Flare pipe material selection
I discussed with process and they confirmed the temperature of the flare last spool is maximum 1100 deg C. initially they provided the flame temperature which was also surprising for me.
Here the question is now " what is your opinion to use SS310 (NACE). I am concerned about Cl-SCC externally because of high temperature. my opinion about internal Cl-SCC is that since oxygen is not present so Cl-SCC is not a concern internally. Externally pipe is buried and some portion is above ground in burn pit area. process confirmed that around 12 m spool will undergo 1000 to 1100 deg C). This flare will be used only during only initial start-up and in case of any downstream process interruption. there is no flare KOD and this is wet sour gas directly coming from well head. can we take credit of short well life say around max 10 years we will have approx. 5 times flaring as worst case.
just to summarize ( H2S: 3.2%, CO2: 6% , chlorides 2000 ppm and 5200 ppm) two chlorides because two different cases.
Client insists on 625 or reasoning for SS310. (do you think external coating for SS310?? and which one?
RE: Flare pipe material selection
For burn pit flare piping in gas plants, Incoloy 800 is generally used. Then, of course, economics plays a big part, specially if you take credit for short well life.
RE: Flare pipe material selection
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P.E. Metallurgy, Plymouth Tube
RE: Flare pipe material selection
EdStainless,
thanks. so probably applying expensive zirconium oxide coating is not worth for shorter design life. it will be better to keep SS310 with a repair/replace strategy in place?
RE: Flare pipe material selection
RE: Flare pipe material selection
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Flare pipe material selection
The alloy selection is much greater, alloys based on the HU (20%Cr 40%Ni) composition have been used in heat treat applications for decades where high temp and exposure to S and C are issues.
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P.E. Metallurgy, Plymouth Tube
RE: Flare pipe material selection
i just want to have clear understanding of your sentence below:
"With H2S, oxygen is not the issue for internal SCC"
KR
RE: Flare pipe material selection
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Flare pipe material selection
The inconel 625 is more specific for high cloride and h2s partial pressure, but is not the case, in fact both Chloride and H2S is relative low compared to the services typically used for Inconel 625 material.
The partial pressure of CO2 and H2S is not so high so the inconel 625 is in my opinion to much for such application.