Thickness gauging of Pipe

[sumon emam]

While working as an inspection engineer I faced some questions which answers are not clear to me. Please help me in this regard:

1. We are taking thickness record as per previous locations. I want to know how the locations are selected to record thickness on the pipe lines.
2. Sometimes we found higher thickness from the previous record. In this condition we recheck the thickness. Is there any alternative or tolerance limit?
3. How the retiring thickness of the pipe line is calculated?
4. Is there any suggestion while inspection of pipe line commenced?

[rathore_mbm2002]

retiring thickness of pipeline can be calculated with help of ASME B31G or API 579.
we have design pressure of pipeline then we can calculate the retiring thickness basis of ASME B 31.4 & B 31.8 for pipelines and B31.3 for process piping.

[agit]

1. I don't have a clear understanding if the subject is pipe line (I'm a PV eng) but basically, we pick a location which have critical condition due thickness loss.
2. In PV Code such ASME Sect VIII there a thickness tolerance for pipe about 12.5% form nominal thick.
3. I don't have any basic knowledge for giving such suggestion, but if more safe if you search the rules and code for justification of your action.
4. Try conduct a Pipeline Risk Assessment, so you have some information of risk level classification, form this risk level classification, you can decide which segment form your pipeline that need a extra attention and type of inspection that you must do.

regards

[Oilandgas]

Please refer to API 570