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Gents (Brimmer/LttleInch) - Thanks for your feed back. This section of the pipe was excavated and repainted 8 years ago. Under the most recent DCVG carried out in this year shows that overall coating condition of the pipeline is good. Having said that vendor couldn't carryout DCVG for this...

Yes the 12Meter section is protected by sacrificial Anode system. Further as you understood the 12M section is on the plant side and unable to polarize it. Have you come across burried IJ as similar to our pipeline condition?

As we are in the subject of On potential, I thought that I should discuss the following to get others opinion. In few of our compressor stations which separates the main pipeline from the station the insulation joints are buried. Therefore there is a section, which immediately goes under ground...

Thanks Brimmer for the explanation.

Wow, excellent explanation from "brimmer". Lots of facts that I can take it back to our CP vendor and request for his justification for limiting the on potentials for -1400mV. "brimmer" talks about limiting to -2500mV,mainly for safety reasons. What are the safety conserns under high on...

Thanks LittleInch for your comments and encouraging others to join in this discussion.

Under CP,Our burried gas pipelines are protected through 850 off criteria. This is referred to variously as “850 off”, “polarized potential” or “instant off potential”. This criterion is applicable to impressed current and galvanic systems where the protective current can be interrupted...

Thanks "brimmer" for the above two posts.We have already decided to follow the 100mV criteria for this pipeline. Having said that for certain areas(near compressor stations,foreign crossings etc) we are unable to use 100mV criteria. For my interest I will search into NACE reserch papers relates...

Hi Guys, Happy new year to all. The articles which I read so far are not directly addressing my point relates to the "ON" potentials. Can someone forward me the details directly adressing my point? Many thanks in advance.

The criteria for the protection of a buried ferrous structure is to maintain a potential on all parts of the structure equal to, or more negative than, -850 mV with respect to a saturated copper/copper sulfate reference electrode.Further we limit the off potentials to -1150 mV to avoid the...

In 2008 test has been carried out by running a CDP tool followed by AFD tool to only a slected sections of the pipe line. Results shows that significant increased in ERF>1 values when analysis carried out by the pigging company by using AFD/CDP combined method and it was the case in the field...

Hi Brimmer, I'm having difficulty of uploading the file.http://files.engineering.com/getfile.aspx?folder=6dab77c8-bda4-4792-a232-ce8901dd1188&file=Dig_7a.xls

Hi brimmer, 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...

Hi Brimmer, 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...

Thanks for pointing it out. I mean "RSTRENG methodology"

Please find the attached combined defect calculations (Defect 7 com)http://files.engineering.com/getfile.aspx?folder=2017c70f-b09f-48d8-969e-5db71de9f773&file=Dig_7com.xls

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...

Thanks guys. Its always good to have others opinion.

Some of the issues related to tape coated old pipelines (> 40 years) is that vast deterioration of coating which leads to corrosion in the pipeline. To mitigate the issues operating companies have to adequately upgrade the CP systems as per the current requirements and carryout pigging...

Thanks Brimmer & all those who were involved in the discusion on SCC which was very helpfull to improve my knowledge in this area.