Corrosin defect assessments in Gas pipe lines
Corrosin defect assessments in Gas pipe lines
(OP)
Hi ALL,
When analysing corrosion defects, will the Defects interaction applies to from the centre axis of the pipe to one side of the pipe or else needs to consider both sides of the pipe.
E.g. can the 3 o'clock and 9 o'clock defects interact?
When analysing corrosion defects, will the Defects interaction applies to from the centre axis of the pipe to one side of the pipe or else needs to consider both sides of the pipe.
E.g. can the 3 o'clock and 9 o'clock defects interact?





RE: Corrosin defect assessments in Gas pipe lines
RE: Corrosin defect assessments in Gas pipe lines
I'll try to be bit more specific.
The defect we got was
Defect 1
340mm(Wide)x 1.5 M (Long) at 3o'clock position
Defect 2
390mm(Wide)x 1.8 M (Long) at 9 o'clock position.
Due to the large diameter of the pipe these two defects won't interact in the circumferential direction. If the defect 2 starts at the end of defect 1 (Crossection view- due to 3o'clock and 9 o'clock positions))can the total length of the defect be 1.5+1.8 = 3.3 meters,
RE: Corrosin defect assessments in Gas pipe lines
In any event to specifically answer your question, if there is no circumferential interaction, then these are 2 seperate features that do no interact, so you have the lenghts as reported, not combined for the 3.3m. Same with all features, if they are not within 6t in any direction(or whichever method your company uses for interaction)then they do not interact. Hope this makes sense.
RE: Corrosin defect assessments in Gas pipe lines
Thanks for your reply.
Well our pipe line is over 30 years old.In past there were reports about repairs which carried out for large cluster type defects.
Resently MPI tests shows few cracks like defects.Can we assessed these by Kiefner's softwear.For e.g How can I assessed a 20mm in length crack? Do i have to make them into grids similar to river bottom profile ? If the crack length is limited to 20mm in length how will i do the calculation? Photo attached herewith.
RE: Corrosin defect assessments in Gas pipe lines
You might consider a course in pipeline defect assessment or the contactors/consultants you use have training in this.
RE: Corrosin defect assessments in Gas pipe lines
Thanks for the information.One last question regarding the cracks.One of the cracks i came across resently was circular in shape, in that case if i'm using KAPA the total length have to be the circumference length ?
RE: Corrosin defect assessments in Gas pipe lines
Pl find the attached photo for your reference (Circumferencial crack)
RE: Corrosin defect assessments in Gas pipe lines
This is a good photo. This is not a crack!, it is a lamination, much different than a crack. I would not assess these, there is no integrity threat here, if you wish you can buff these out of the pipe, but there is not much use in this as the area you buff will be larger than the original indication area. The only potential problem from laminations is if they may be through welds, or are not planar in the mid-wall, so are not consistent depth in the wall of the pipe, and usually you can get UT readings to confirm this. Why your NDE contractor is classifying these as cracks or crack like and does not know what they are is poor knowledge. If you must assess, (I am not sure how you are going to get a depth of something like this with out buffing as it is probably too shallow to be out of the dead zone with UT, in which case you are completing your standard effective area calculation after buffing), I would take the axial length of the longest part of the crack, not the entire circumference. Remember, the pipe will be full of these internally as well, you just can't detect them with MT, but you will see them with UT.
RE: Corrosin defect assessments in Gas pipe lines
Many thanks for your advice.We have managed to UT this defect and it shows no indication of depth.It proved to be
lamination.Pitty that MPI contractor couldn't figure it out.
If the crack depth is less than 1mm, will the UT can detect
the depth of this defect?
RE: Corrosin defect assessments in Gas pipe lines