Inspection Intervals

[picasa]

When you are rerating an existing old vessel, one can calculate the required minimum design thickness (without any corrosion allowance). Then make measurements to find out the available plate thickness and available thickness in excess of the calculated required thickness may be used as the available corrosion allowance. Then you need to decide the inspection intervals after the re-rated vessel is put into service. Are there any publications available that provide recommended pracices for the determination of this inspection intervals and how it is tied with the chemistry of material, service, and available corrosion allowance?

 

[metengr]

Your best bet is to use API Standard 579 for this approach. API 579 is a comprehensive document and in some cases will require certain technical expertise for assistance. This standard is also referenced in the National Board Inspection Code. Re-rating can be considered an alteration, and as such, should be reviewed by your local Jurisdiction, authority and/or your boiler/machinery insurer.

 

[JoeTank]

API-510 ad API-653 both address inspection intervals as a function of remaining corrosion allowance and corrosion rate.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[weldtek]

If you are referring to pressure vessels I would stick with Metengr's recommendation of API 579. Metengr, correct me if I'm wrong but I believe NBIC also references API 572, and, as Steve mentioned API 510 covers the topic.

 

[picasa]

Thanks!