PipeLines - Remaining Life Assessment

[IFTI]

Hello,

My client is available with more than 1000 Meters of NPS 42 & NPS 36 pipelines designed and constructed per ASME B31.4. Client would like to salvage and re-use these section for another similar services. Future Service is recycle cooling water (less erosive, non-corrosive).
As a start point we would like to get UT readings to perform engineering analysis and to perform remaining life assessment. I would like to know what would be the frequency of UT measurement of NPS 42 & 36 pipelines (i.e., every 5, 10, 25, 50 or 100 Meters????. I am talking about the straight lengths of pipelines. Intention here to get a reasonable data to calculate remaining life. Also, any API or ASME standards to be consulted in this regards.
Note: We have no plan to do a detailed analysis as per API579-1/ASME FFS-1.

For ASME B31.3 (process piping), because of short span of piping we usually recommend UT readings at-least 3 FEET away, as well as for all fittings. In addition to this API 570 guidelines are available for remaining life assessment. I never done this exercise for ASME B31.4 pipelines, that's why would appreciate your thoughts.

Thank You for your feedback.

IFTI
Mechanical Engineer

 

[1503-44]

Don't worry. You will not have to do that in accordance with B31.4, or B31.8, because your future use does not appear to be at all related to pipeline service. Process, power and cooling water pipe is not "pipeline" related, because it is not involved with the Transportation of either gas, ammonia, hydrodarbons, etc., so therefore it would not qualify as "pipeline" work. Therefore your testing should be in accordance with B31.1, or B31.3, or whatever B applies to the specific service into which it will be placed. If B31.1, or .3 reference API 570, I'm not sure that they do, since API is typically related to petroleum and hydrocarbon handling, then you would have to comply with that standard.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[SJones]

Start with owner inspection records to see if any hot spots were identified. Review the previous service and try to predict where any damage might have occurred, and the morphology of damage. Develop an inspection programme that gives sufficient coverage for statistical confidence in establishing a minimum remaining wall thickness to allow design of the next application. Focus on hot spots. Rather than manual point measurements, you might want to think of area scanning UT, or even guided wave UT. Don't forget the power of visual inspection if the internal surface is accessible. Table F-1 in DNVGL-RP-G101 might be useful. As a point of interest, what predicted corrosion rate will you use for the cooling water?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[Dhurjati Sen]

Arrange for blast cleaning of both the surfaces of the pipes.
Then use your eyes.

DHURJATI SEN
Kolkata, India

 

[IFTI]

Thanks for your inputs. Really appreciate that.

To answer SJohns question, the potential candidate pipe for re-use is already in same service. The current CA/year can be calculated from the number of years in service. For future i will get an idea from the Client's Pre-engineered piping class(es) for same service. Any additional thoughts on this from your side?

 

[0707]

The frequency of UT will be determined by a corrosion rate at least you need two measurements, after these inspections in time you can extrapolate a corrosion rate and forcast the next UT inspection. Cooling water is not a very corrosive environment unless we are dealing with buried piping.

luis

 

[SJones]

What was the client's water treatment and water/corrosion monitoring programme like? Has the piping been mothballed with a good preservation programme? What inspection techniques do you have at your disposal?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[LittleInch]

I really don't know why you''re trying to do this.

You either do it properly and get an internal inspection tool in there or you find any old bit of pipe you can get to do a bit of U/T on, find the wall thickness and use that.

Anything else is a waste of time and money.

We know nothing about the location (U/G or A/G, coating condition, age, use, fluid, was it in constant use or have you have air/water interfaces, has there been any contamination / biological growth etc etc.

Best thing is figure out a decent design pressure based on the known data ( pipe strength, thickness etc, then pressure test the existing pipe and qualify it that way.

If it doesn't leak then you're good for a while.

Then when you cut the stuff up to move it?? or is it being re-purposed in position?, then look at each section, wash it off and do a few random u/T tests on anything that looks bad.

Re-using something which is already there always sounds like a good idea, but rarely is and ends up taking longer and costing more than buying what you want for the duty. Especially if the service life is >10 years.

Trying to do spot checks on a 1000m of pipe just doesn't get you anywhere beyond a possible.

And if it is actually substantially corroded you'll never find the worst bit which will then leak after a few months in it's new service. And you will get the blame for saying it was OK for > 5 years.





Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Or just hydrotest it for your expected design pressure.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"