Minimum allowable remaining thickness in corroded B31.1 pi 1

[Bamend]

The scope of B31G "Manual for Determining the Remianing Strength of Corroded Pipelines" does not include reference to B31.1; it only references B31.4, B31.8, and B31.11. What methods are acceptable for determining the minimum acceptable remaining wall thickness for localized internal corrosion in piping designed and operated to the B31.1 standard?

 

[metengr]

Well, B31.1 is a construction standard for new Power Piping, not an in-service repair or assessment standard. If this is new power piping, and the internal wastage was caused by poor storage or handling practices replace the section of pipe.

IF this is pipe that has been in-service and the internal wastage was detected by in-service inspection, I would recommend using API 579 to assess the extent of locally thinned regions.

 

[Bamend]

Thanks Metengr - yes this question is related to corrosion detected during an in-service inspection. It is not related to new construction. I knew B31.1 relates to new construction but am hoping to find something in writing in another code or standard that states that the guidance in that document is applicable to B31.1, just like B31G says it is applicable to piping built to B31.4 and B31.8. I'll check the API std. you referenced.

 

[Bamend]

Someone outside this forum pointed out to me that Append. IV of B31.1 does reference ASME B31G as a source of "An acceptable evaluation procedure..." EPRI Report NP-5911M is also referenced. However, the references are included in section IV-5.0 which relates to erosion corrosion. IV-5.1 specifically states that the entire section 5 "...does not apply to other wall thinning mechanisms, such as general corrosion, microbiologically influenced corrosion, or cavitation."