Session: CS-06-01 The Martin Prager Memorial Session on API 579/ASME Code Fitness-for-Service Activities

Paper Number: 123513

123513 - Assessment of Asme Viii-1 Ug-20(f) Using Fracture Mechanics per Api 579-1/asme Ffs-1 (2021) 

Paragraph UG-20(f) in ASME BPVC Section VIII, Division 1 provides guidance on applicable impact test exemptions for design temperatures no colder than -20 degF (-29 degC) under certain conditions (e.g., material/thickness combinations; hydrostatically tested; no shock loadings).  Functionally, this paragraph allows for design at colder temperatures than is currently permitted in UCS-66 for equivalent material/thickness combinations without the requirement for impact testing.

A similar provision to UG-20(f) was included in Part 3 of API RP 579 (2000) and in API 579-1/ASME FFS-1 (2007); however, it was removed in the 2016 edition of API 579-1/ASME FFS-1 and has not been reintroduced.

This study reviews the requirements of UG-20(f) using the fracture mechanics perspective from the latest (2021) release of API 579-1/ASME FFS-1.  The provisions in API 579-1/ASME FFS-1 (2021) for considering constraint effects (Annex 9H) and crack front integration (Annex 9I) are included in this analysis so that the magnitude of their effects can be understood.  Since UG-20(f) requires a hydrotest for most situations, a review of the warm pre-stress effects per Annex 9F is also included.

The results of this study indicate that an update to the current thickness limitation for Curve B materials is recommended.

No recommendations for the overall disposition of paragraph UG-20(f) are provided in this study; however, it is anticipated that the analysis contained herein could assist various Standards Development Committees in decisions related to potential future updates.

Presenting Author: Thomas Finn ExxonMobil Technology and Engineering Company

Presenting Author Biography: Mr. Tom Finn is a mechanical engineer with ExxonMobil Technology and Engineering Company in Spring, Texas. He has over 10 years of experience with ExxonMobil, including as a Lead Mechanical Engineer at the Baytown Complex. Tom is a voting member on Subgroup Toughness.

Authors:

Thomas Finn ExxonMobil Technology and Engineering Company
Clifford Hay ExxonMobil Technology and Engineering Company
Julian Bedoya ExxonMobil Technology and Engineering Company
Greger Pioszak ExxonMobil Technology and Engineering Company