Interpretation Response #PI-81-014 ([Memo: Internal])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
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Response text:
ACTION: Request for Interpretation of Section 192.455(a) Relative to the Use of Metallic Sleeve Crack Arrestors on Large Diameter Pipelines
Melvin A. Judah
Acting Associate Director Gas Pipeline Project
Lloyd W. Ulrich
Director, Alaska Natural Gas Pipeline Project, DMT-50
Your memorandum of March 17, 1981, asks whether the crack arrestor sleeves designed for the Northern Border Pipeline Company would affect compliance with sections 192.455(a) and
192.463(a) for segments of pipeline underneath the sleeves.
You have raised a proposition, based on pipeline casings, that once the sleeves are in place, they may shield the pipeline from cathodic protection needed to comply with section 192.455(a) and make it difficult to determine whether protection is at the level required by section 192.463(a).
Regarding pipeline casings, experience shows that if casings are properly installed in a manner which assures that the casing is electrically isolated from the pipeline, and will remain so, and the pipeline in the casing is effectively coated and free of holidays, the pipeline will be protected against corrosion by standard corrosion protection methods. Of course, if casings become electrically shorted, the pipeline beneath the casing will not be cathodically protected as required. We do not know any reason why a crack arrestor sleeve would not behave in this same way. It seems, therefore, the problem facing Northern Border is verification of electrical isolation through inspection during construction and subsequent operation of the pipeline.