High pressure piping life expectancy

[MechDesign105]

Hi,

I need to determine the life expectancy of high pressure piping (stainless Steel), between 600 to 3600 lbs in a compressed air system maintained at -80C dew point. The system is located inside, so it is not subjected to rain, snow, or UV. The air flowing inside the pipes is very dry.

We have had a very good long term experience with these systems (>30 years), but in my search for life expectancy determination, I would like to be able to use technical data, standards, tests (maybe Xrays) to determine the life expectancy of the system. I basically want to be backed by real values. If a thickness test is done, what criteria should i use in determining the piping is still in good condition? Standard?

Thank you very much for your help!

 

[dcasto]

is it cycling between 600 and 3600 psi? If it isn't, use a UT tester and the stress eqaution from B31.3. If you are that worried, take sample of the line to a lab and test the sample for yield strenght.

I've seen 50 year old plants with carbon steel air lines.

 

[Guest102023]

It all depends ...

 

[Duwe6]

Hire a certified API-570 [piping] Inspector. He/She will take the appropriate qty of thickness measurements, evaluate anchor points for possible Mag Particle MT testing for stress cracking. Will also 'run the calc's' for your pipe and tell you Date of Next Inspx, and Estimated End of Useful Service. One stop shopping.

 

[MechDesign105]

No cycling in the line at all, it is always at 3600 psi for a part of it, and at 600 psi for the other

The idea of an experienced inspector calculating and taking the necessary measurements is very interesting.

Is the API accreditation the only one usually used in piping? Does it refer to ASME or ANSI for the acceptable criteria? I have never worked with API standards before...

Thanks!

 

[BigInch]

I think your perspective is from the backside. Pipe doesn't die, unless something is killing it. Do you have inernal corrosion? At what rate is the corrosion taking place? Do you have external corrosion? Are you using cathodic protection? Do you have excessive cycling that will affect its fatigue strength? Do you have fluidic or mechanical abrasion? Determine the rate of deterioration due to the factors that affect your piping, quantify them and design the pipe for the lifetime you require.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus