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...
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...
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...
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...
Hi All,
Factors that considered to be effecting in a pipe line to have SSC is that its operating stress, operating temperature, distance from compressor station, age of pipeline and coating. Under these extreme conditions will the SSC cracks appear in a colony or else can it be just a single...
Hi All,
Please find the attached the CuSO4 and Zinc Reference Potential Comparison chart for your help to understand that both Reference Electrode potential values are not proportional to each other. Is there a equation to find the conversion as we required to enter the coversion factor to...
Pipe line with MAOP of 7332 Mpa with a DF of 0.72 got a burst pressure of 7332x1.39=10191Mpa.
Which means pipe line defects with burst pressure lower than 10191 Mpa requires repairing. In terms of estimated repair factor for a corrosion defect define as ERF=MAOP/ P where P define as safe...
Hi All
In general buried gas pipe line going pass high consequence areas required to be heavy wall to avoid the risk involvement. Given the pipe line dia 559 mm, wall thickness of 7.92 mm and MAOP of 7322Mpa to safely operating under the above conditions, instead of having the heavy wall can...
If one have to carryout fracture controll plan for 40 years old gas pipe line what methods use to address the issues related to interaction with weld heat effected zones, considerations for corroded pipe etc. For a newly fabricated pipes sample testing is a possibility where as old corroded...
If one have to carryout fracture controll plan for 40 years old gas pipe line what methods use to address the issues related to interaction with weld heat effected zones, considerations for corroded pipe etc. For a newly fabricated pipes sample testing is a possibility where as old corroded...
Over 30 years of operating our gas pipe lines we haven't had much issues to deal with internal corrosion. Currently we are doing a study to implement some internal corrosion monitoring technique to our pipelines.
We have come across software solutions for characterization of corrosion in...
In a recent cleanning process of a Gas pipe line, we have found considerable amount of black powder from the internal surface of the pipe line. Mineralogy sample shows that
Mackinawite (FeS-0.9)- Dominant
Metacinnabar(HgS) - Trace
Halite(NaCl)- Trace
What is the approach to find these...
Hi All,
Based on the ILI data, we are planning to excavate internal corrosion defect in our pipe line. Once excavated what sort of NDT methods can be used to find out the length, bredth and wall loss of this internal corrosion defect?
One of our pipe line transport gas 292 TJ/day. Compersition
of the gas from the main plant shows that 0.497 mg/m^3 of sulpher in it. Can any one tell me how to calculate the quantity of sulpher collected per day under the given conditions ?
Hi,
Despite the defect size standards say that reduction of pressure have to be 80% 0f the MAOP.I belive that pressure
reduction should be based on the size of the defect.Therefore by considering the ILI defect size (based from the ERF value and safe operating pressure) can i establish an...
Recently we had our ILI run for our 22” gas pipe line. One of the major out comes of this 2008 ILI run going to be the prediction of corrosion growth rate and our repair plan for the next 5 years. As the vender had done 2003 run as well as 2008 ILI runs they are going to overlay the data for the...
When fit up is concern for type “A” steel sleeves for gas pipe line, to accommodate the pipe Seam- Weld Reinforcement one of the options to be used is listed below.
1)Removal of the seam weld ( Required Area) by grinding
2)Grinding an accommodating groove in the sleeve
3)Locating the gap...
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?
Resent ILI data shows that 75% Wt loss for 10mm x 15mm area for a API 5L X52 (7.9 mm thick)
Gas pipe line. As per the effected area method calculation this defect can be attended by blasting the surface and by applying epoxy coating to the surface. Apart from coating for an in service pipe line...
I'm looking for a coating repair procedure for 22" burried pipe line.Originally different sections of the pipe consist of Armathene,Plicoflex Tape, Yellow Jacket to name few.I would like to know the product to be used to recoat and application method, thickness to be achived, curing time before...
