RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
(OP)
Hi All,
Following are the summary of two defects( Named as 7&7A) found in
one of our pipelines. As these two defects are 300mm apart under the defect interaction rule we can consider as one defect.(Named as 7 com.)
defect 7 ( Assessed defect length of 2.060Meter with an effective defect length of 1.340 Meter)
defect 7A ( Assessed defect length of 1.6 Meter with an effective defect length of 0.850 Meters)
If we consider pipe line design factor of 1.39, both defects need to be repaired under the RSTRENG mythology. Further as per the attached RSTRENG calculations show that when two defects combined together, effective length only pointing out to area where the defect 7 is. Combined defect effective length is smaller than if we consider the two defects separately. Appreciate if any one could explain this situation.
Following are the summary of two defects( Named as 7&7A) found in
one of our pipelines. As these two defects are 300mm apart under the defect interaction rule we can consider as one defect.(Named as 7 com.)
defect 7 ( Assessed defect length of 2.060Meter with an effective defect length of 1.340 Meter)
defect 7A ( Assessed defect length of 1.6 Meter with an effective defect length of 0.850 Meters)
If we consider pipe line design factor of 1.39, both defects need to be repaired under the RSTRENG mythology. Further as per the attached RSTRENG calculations show that when two defects combined together, effective length only pointing out to area where the defect 7 is. Combined defect effective length is smaller than if we consider the two defects separately. Appreciate if any one could explain this situation.





RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
You mean using the the RSTRENG method not mythology.
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
Please ignore the grid 2 reading where it shows all the depth with 20% added to the original reading.Therefore 2.91mm is the correct reading taken from the field. As you have seen I have attached above in my mail defect 7 and the combined defect (7 Com). Herewith I will attach the 7a defect which you see in the 7 Com starting from the 2360mm mark to 3950 mm. As mentioned above
defect 7 & defect 7a both has failed but if you combined the two defect with the gap only one defect has failed. Further when you are carrying out the repair do you consider the repair to the effective area only given in the softwere or else do we have to consider the total length of the defect what you find it in the pipeline. In some defects I have noticed that effective area doesn't seem to be correct when you consider the area which is ignored from the calculation. Have you come across similar situations?
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
I have to go back to interaction, these 2 corrosion areas are not interacting, I am not understanding why you consider these interacting when there is a 30cm gap between them? Can you look at the KAPA manual and what it uses for interaction?
The program will pick out the worst area, which it has done (the same area in both sheets). The program is also seeing these areas are not interacting. Keep these areas in separate calculations, burst pressure did not get worse combined because it is not worse combines, these are 2 different areas that would burst independently of each other and not interact, the program is seeing this.
7a was not attached, but I will copy grid and run through tomorrow when I get back to my office and write you then as well.
Other question, what is considered failure in your case? Burst pressure below 10177 kPa?
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
Correct.Safety factor 1.39 gives you 10177.
Herewith I will attach you diffect for your reference.
Another noticable issue in this years dig up program is that significat difference in diffect lengths compair to pgging data.
We used the combine (CDP/AFD) pigging tools in our latest pigging run.
CDP - Corrosion detection tool
AFD - Axial flow direction tool
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
I'm having difficulty of uploading the file.
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
KAPA is only picking out the worst area in the calculations, I believe that is all it will do, not show two separate areas. Remember, corrosion less than 10% is not a threat and considered normal wall in B31G and modified, RStreng anything less than 18% I believe.
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
Dear 09091960,
Do you mind to share the output (KP, depht, length, WT, ...) from IP with us? I am working on something and need it badly.
Thanks in advance,
RE: RSTRENG MYTHOLOGY FOR PIPELINE DEFECT ASSESSMENT
Thank you so much for sharing!