Lamination in pipeline material

[Dario2002]

As result of inline inspection, some of the anomalies are calsified as "possible lamination", and recomendation is to uncover pipeline and inspect anomaly. After that if it is really lamination which is not parallel to pipe surface, repair should be done.

Question is, HOW TO INSPECT LAMINATION ANOMALY?

We have hand-held US device for measuring wall thickness. Idea from one college is to use that, and device should show "shallow thickness" on lamination point (measure until first lamination surface, not complete through material until other side of pipe wall). If it is not parallel, then moving device should change readout value. Is this realistic and usable way to check anomaly?

Another point is what are possible repair options i lamination is not parallel to pipe surface? I believe that composite wraps are not option? Only cut-out and metal clam shells?

 

[jmiles]

Hi Dario,

I must admit i dotn know much about Lamination, however i did some checking and it seems US is the way to go to detect lamination.

http://onlineshowcase.tafensw.edu.au/ndt/content/mag_particle/defects/accessible.htm

As for the repair, I know my preference is to just do a cutout and replace the section, it costs more and takes longer to do this, but then its done and you know its done right. if you use a clam shell your basically waiting for the pipe to fail and then the inevitable leaking of the clamshell starts, it can make a mess underground and in my opinion you are just introducing way mroe future fail points than you need to, gaskets bolting and the clam shell itself.

If course all that being said it comes down to schedule and economics, if its going to cost a fortune to shut down the line and do the cut out then that might not be practical.

 

[metengr]

Dario2002;
Laminations are the result of melting practices used to produce plate. In my experience with pipe exposed in steam or lowe temperature aqueous service most laminations are benign in pipe because their orientation is such that they will not affect the pressure retaining capability of the pipe under the service conditions I mentioned.

Laminations are detected by ultrasonic examination. In some cases, laminations can be detrimental where service conditions require specific notch toughness of the pipe or in certain corrosion environments, laminations can promote cracking of pipe (stress corrosion cracking).

For repair, you are best to replace the section of pipe if laminations are detected by UT and you determine that they are harmful to the pipe under specific service conditions.

 

[stanweld]

Concurring with metengr, normally laminations are benign. If your pipeline has been in service for many years, I would not be overly concerned unless the lamination is in a bend location, in which case you should UT inspect to determine lamination size and confirm that no cracks have initiated. Laminations are also highly problematic when making a branch connection in that location and when the line is in sour service.

 

[BigInch]

Remove when they are located in an area to be welded, otherwise see above.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[brimmer]

Get a level 2 ultrasonics technician with a flaw detector to measure, your hand held wall thickness device will not be enough. Have them search around the lamination for cracks as well, can use shear wave and normal 90 degree. Also MPI the surface of the pipe as the lamintaitons could be surface breaking. Laminations usually benign as mentioned above, only repair if non-parallel/near weld/on bend. Check your local codes for repair options but you are correct, composite wraps not approved for non-blunt defects, could use a compression sleeve. If lamination surfacr breaking, leave it, only smooth out edges with file for recoat if required.

 

[MJCronin]

dario

Just a little question here about material quality...

One of the biggest diferences between "structural" grade carbon steel and "piping grade" carbon steel is that the piping is supposed to be made by a "fully killed" process.

Some structural grade carbon steel plate is more prone to lamination defects than the equivalent "pressure vessel/piping grade" material

The steelmaking process to "fully kill" an ingot is more expensive...people have a tendency to cheat the purchaser.

Was this steel piping from China ?

Also see :

http://www.eng-tips.com/viewthread.cfm?qid=224973&page=32

-MJC

 

[SJones]

Review the ILI specification data to ascertain what the probability of detection and probability of false call parameters are for laminations to get an idea of the actual likelihood of laminations. Also review the pipe mill NDT data, if you still have it, for cross correlation. Are laminar imperfections the result of an expected degradation mechanism for the pipeline, e.g. H2S cracking (HIC)? Also, bear in mind that 'laminations' should have no through thickness direction otherwise they are not 'laminations'. Once there is a rational basis for believing the presence of laminations then move into exploratory mode whilst also performing a fitness for service evaluation as per API 579-1, Part 13.

Repair options are detailed in the PRCI Pipeline Repair Manual R2269-01R

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Dario2002]

Thank You all for answers, I will only update some facts. Pipeline is over 30 years old 18" gasline which transport dry and clean natural gas. Laminations are probably there from from start, but first ILI conducted by PII 7 years ago has not detected lamination (older generation of tools). Last inspection from Rosen reported this.

After reading Your answers and some other chapters from various books and standards, I think we will uncover pipeline, see if anomaly is in area of some weld or deformation, if there is any visible cracks, and we will try to measure thickness by hand US device to determine if it is parallel or not with surface. If all above seams ok, then repair is not necessary?

However, when pipeline is already uncovered, we will probably reinforce the spots with composite repairs (TDW RES-Q which we have available), and schedule cut-out repair for first pipeline stop of operation.