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05:38 Apr-03-2004
Re: lamination evaluation

----------- Start Original Message -----------
: : hi
: : i am looking to find out how you be can evaluate a lamination area(spot laminations with variable depthes-fm. 3 to 7.5 -area size 300 x 600 mm starting fm. weld ) in a gas pipe line 16" -sch. 40 /700psi-30years old.
: : at ut the wall thickkness into that area shown echoes at 3 -5-7 mm and we seldom i found the 13-12.5
: : most of peaple said that is without inportance, but....
: : i want to know other opinions
: : thanks
: TOFD
------------ End Original Message ------------

i had still the same prolem and i found a new portion.

06:31 Apr-05-2004
Re: lamination evaluation

Hello,

I would write up the indication, and let the owner of the pipeline make the call. It our job to report, let them do the fracture mechanics.

08:10 Apr-05-2004
Re: lamination evaluation

Herewith I suggest that the laminar indications observed at various depths can be evaluated accoding to AS1710-1986 (Table 5.1)as given below:

Maximum total area of discontinuity in any area 1m×1m:

Lamination (Sq.mm)
3 000
10 000
20 000

Inclusion cluster (Sq.mm)
5 000
16 000
40 000

This can be applied irrespective of depth (for plates).

From your description it seems that you encoutered service induced defects such as HIC or HSSC.

Regards,
N.Kuppusamy

----------- Start Original Message -----------
: : : hi
: : : i am looking to find out how you be can evaluate a lamination area(spot laminations with variable depthes-fm. 3 to 7.5 -area size 300 x 600 mm starting fm. weld ) in a gas pipe line 16" -sch. 40 /700psi-30years old.
: : : at ut the wall thickkness into that area shown echoes at 3 -5-7 mm and we seldom i found the 13-12.5
: : : most of peaple said that is without inportance, but....
: : : i want to know other opinions
: : : thanks
: : TOFD
:
: i had still the same prolem and i found a new portion.
------------ End Original Message ------------

05:06 Apr-14-2004
Re: lamination evaluation

In general, laminations found in pipeline steels are parallel to the surface of the pipe and therefore, do not affect its structural integrity. However, a lammination that has a sloping extent would be classed as a significant defect and its severity woud need to be assessed. Also, you say that the lamination is adjacent to a weld - you therefore need to be confident that there is no associated through-wall cracking at the weld toe (I'm told this can be difficult to detect with UT as the lamination can mask the weld crack). There has been very little research done on the assessment of laminations (even though there have been a number of recorded pipeline failures due to laminations), so any assessment method applied will be conservative. We tend to assess the lamination as a crack using BS7910 or API 579.

An internal inspection with a UT tool should really be considered if you suspect that the lamination problem may be extensive.

Hope that helps.

Andrew

04:40 Jan-15-2005
help

I am a student at the norwegian state diving school and i have an exam on next wensday. I have some homework to do and one of the questions we got from the instructor is the following:

Wich NDT-method (non destructiv method) will normally show a lammination (defect) in steel:
- Ultrasound
- MPI
- Radiography or
- Eddy current

Actually i know the answer. The intructor says it is radiografy. But how does it work ? and i don´t really understand lammination. Could you please explain it to me ? how does a lammination occurs ? do you have any picture(s) showing a lammination ?

Thank you

Morad

08:32 Jan-15-2005
Re: help

Actually, the answer is Ultrasound. A lamination is typically a disbond in the steel caused during the rolling process when an edge is rolled over onto the surface. It is generally parallel to the surface. As it basically has no thickness, the radiograph will not see a density change. The Ultrasound will show a refelction from the disbond and/or a reduction in backwall signal.

03:43 Jan-17-2005
Re: help

DJ Kallhof

05:27 Jan-17-2005
Re: help

To detect a lamination into a steel piece, ultrasound technique is the best choice. You can also detect it by radiography; in that case you must be sure that your lamination is normal (not perpendicular) to your X ray source emission. As the other poster says a lamination is a sandwiched impurity, which lays parallel to lamination sheet surfaces direction inside steel material.

Regards

Luis Marques

08:48 May-16-2012
Re: help

Dear DJ Kallhof and Andrew

Thanks.. it was good and very simple to understand..

10:44 Sep-22-2017
Re: lamination evaluation

Is lamination crack on plate will able to detect by UT 100 %. Or may chance to UT can't identify lamination. One of the reason that UT waves will not transfer through vacuum / air gap area of lamination.
Pls. advise.

19:04 Sep-22-2017
Re: lamination evaluation

Detection of any discontinuity depends on several factors and laminations are no exceptions. Thus, asking for a 100% detection is idealistic and impractical.

The reason we can detect laminations using UT is precisely because ultrasonic waves are reflected by the lamination interface and thus we get an echo much before the back echo. Back echo may drop slightly or disappear all together depending on the area of the lamination, the frequency and diameter of the probe, thickness of the plate etc.

For thinner plates / sheets, it is better to look for a change in the screen pattern instead of looking for reduction of back echo. The echo pattern gets lifted up because of multiple echoes generated by the lamination.

In practice, it is always good to create natural / artificial standards to help the operator get the correct idea of interpreting the presence of a lamination.

21:04 Sep-22-2017
Re: lamination evaluation

Sanjay,

Swamy is correct in that UT Will not always detect laminations. While UT will detect most forms of laminations, there are situations where a lamination may go undetected.

Laminations at or very near the far surface may go undetected due to its proximity to the actual back wall.

Another common defect in composite and laminated materials are "Kissing Bonds" these are laminations (and true defects) which have an air gap that is so minimal that the vibrations emanating from one side of the lamination are still able to cause sonic vibrations to emanate beyond the lamination and continue to the far surface and return. There are tricks and means to discriminate these but it takes skill and a profound understanding of how the sonic waves propagate in the materials being examined.

Hopefully this provides you with a little more understanding. Cheers...

James Scalf