replace process piping.
replace process piping.
(OP)
Hello ,
I have process piping is high critical due to stream fluid ,constructed material is carbon steel ,maximum operation pressure 20 bar and temperature 30C.
piping class 3103 , size 6'' Sch.80 NT=10.97mm . as per the thickness measurement the minim actual thickness 6.0mm and the next opportunity for replacement after three years corrosion rate 0.9mm/year.this is unform corrosion along pipe (sulfidation).
Now, i want to understand when the replacement of process piping constructed as per ASME31.3 REQUIRE , Is there any critical or philosophy behind it ?
when i reviewed the history of process piping in area where i worked , i could not figure out the rule of thumb of replacement .
some piping replaced for the same reason when the corrosion allowance consumed and others not.
API570 and API574 are not covering this point.
regards,
I have process piping is high critical due to stream fluid ,constructed material is carbon steel ,maximum operation pressure 20 bar and temperature 30C.
piping class 3103 , size 6'' Sch.80 NT=10.97mm . as per the thickness measurement the minim actual thickness 6.0mm and the next opportunity for replacement after three years corrosion rate 0.9mm/year.this is unform corrosion along pipe (sulfidation).
Now, i want to understand when the replacement of process piping constructed as per ASME31.3 REQUIRE , Is there any critical or philosophy behind it ?
when i reviewed the history of process piping in area where i worked , i could not figure out the rule of thumb of replacement .
some piping replaced for the same reason when the corrosion allowance consumed and others not.
API570 and API574 are not covering this point.
regards,





RE: replace process piping.
You can always calculate the remaining life as per ASME B 31.3 which would give you quite a margin.
However, piping replacement philosophy depends on other things like opportunity, economics, criticality of service and as you have mentioned, rule of thumb. Some call it experience, though.
RE: replace process piping.
A corrosion rate of 0.9mm/yr sounds far too precise. Corrosion rarely occurs uniformly and is often concentrated in certain locations
There are simply too many factors to consider to come up with any single ROT on these issues.
Looks to me like you have the wrong material for safe and effective operation.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: replace process piping.
If the corrosion is indeed even then, once down to the original allowance then the pipe will have to be completely design checked for all stress not just hoop stress. The pipe wall is not just required for hold in pressure. It also supports the pipe and resists earthquake and wind loads etc.
RE: replace process piping.
Further,ASME B31G (which is much simpler to analyse than API 570) will guide to determine whether a corroded piping can remain in service, repaired or replaced.
Ganga D. Deka, P. Eng
Canada
RE: replace process piping.
Thanks,
Ehzin
RE: replace process piping.
Determination of replacement is based on safety (fitness for service) and cost.