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Estimating rate of corrosion

Estimating rate of corrosion

(OP)
Hello.

What is the basic steps of estimating rate of corrosion for piping runs?

Assuming uniform corrosion and erosion.

The fluid contains following in mg/kg:

CO2: 56,7
H2S: 85,3
SiO2: 694,8
Na: 152,2
SO4: 18,9

other parameters:
Temp: 210 degree Cecius
Velocity: 40m/s

Is there a way I can estimate the corrosion rate? i'm designing a pipe run that must have life span of 25years and preferebly I want to use Carbon steel. I am designing in accordance with ASME B31.3

RE: Estimating rate of corrosion

The issue is: will there be liquid water present? Normally, the CO2 corrosion rate would be assessed by corrosion predictive modelling

http://www.eng-tips.com/viewthread.cfm?qid=407990

However, 210 deg C is beyond the validity range of most, if not all, models.

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: Estimating rate of corrosion

(OP)
Thank you for your quick response

RE: Estimating rate of corrosion

Silica at 48 metres per second will see off the pipe in double quick time. Erosional models are not quite as advanced as corrosion models, but modelling probably isn't really necessary in this case. Given the conditions, carbon steel on its own appears to be at the bottom of a short list of choices

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: Estimating rate of corrosion

(OP)
SJones Thank you very much for your specific informative answer.

Maybe you have some references or some materials to investigate. To me it seems like the temperature is won't let me chose a non metallic material.

Regards

RE: Estimating rate of corrosion

That is high velocity, very high.
Even without sny suspended solids plain carbon steel will have a short life.
Any elbows in this run?
I would guess that you are looking at 5-9-12% Cr grades for this service.
Even then 25 years may be optimistic.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Estimating rate of corrosion

You did not mention if there is any moisture as asked by SJones. If there is then corrosion will be high. Once worked on a Project where there was Carbonic Acid in the pipees but the liquid also included high concentration of chlorides and the temperature was around 125 Deg C. No-one would give me a corrosion rate from the Client side . We could not use Stainless - Duplex was too costly so we had to go with Carbon Steel. I ended up taking 9mm for the corrosion allowance but could not guarantee the lifetime of the pipework.

RE: Estimating rate of corrosion

What is the fluid? Oil/water/sand? Gas/water/sand? Other? Erosion corrosion (even erosion alone) will highly limit life expectancy. Any chlorides? High temp negates use of rubber and other nonmetallic liners.

RE: Estimating rate of corrosion

(OP)
I have discussed the high velocity and brought up that it will be a big problem and we came to a conclution that the nominal pipe size could be increased to lower the rate of erosion.

This is produced water, I was allowed to reduce the velocity by increasing the nominal pipe size. As DSB suggest the erosion would be to high with such a speed. I have reached a conclution that I will work with carbon steel.

It is just hard to estimate the corrosion/erosion allowance

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