Session: CS-01-01 Structural Integrity of Pressure Components

Paper Number: 107684

107684 - Meridional Direction Limits for Local Primary Membrane Stress Between Sm and 1.1sm 

BPVC Section VIII Division 2 defines primary membrane stress in a region of stress as local if the distance over which equivalent stress exceeds 1.1Sm does not exceed √(Rt) in the meridional direction. Current edition of Section VIII division 2 code does not define the local primary membrane stress that does not exceed 1.1Sm as local. When primary membrane stress less than 1.1Sm_, is considered as local, meridional distance for primary membrane stress between S_m and 1.1Sm  is not addressed in the current edition of the Section VIII Division 2. As a result, treating as general primary membrane stress would lead to failure in stress analysis of the component.

Existing research and data by Ferry et al on ASME Section III in 1983 indicate that there is a need to address meridional distance where stress is below 1.1 Sm. Currently there are no limits to meridional distance and that conservatism in the code ends when local primary membrane stress is between Sm and 1.1Sm. This paper presents the possible scenarios with lower primary membrane stress. Considering the same slope of the meridional distance to change in stress, this paper evaluates meridional distance limits 1.25√(Rt)  when maximum local primary membrane stress is between S_m and 1.1S_m.

Presenting Author: Qi Li T.D. Williamson

Presenting Author Biography: Technical leader in finite element analysis and elastic-plastic analysis.

Authors:

Rafal Sulwinski T.D. Williamson
Qi Li T.D. Williamson
Rusty Johnston T.D.Williamson
Sreelatha Kilambi T.D. Williamson, Inc