Temporal superposition of thermal transient stresses for piping analysis
Conference
·
· Am. Soc. Mech. Eng., (Pap.); (United States)
OSTI ID:6150689
The fatigue damage evaluation of piping components, such as elbows, using Equation (11) of Article NB-3650 of the ASME Boiler and Pressure Vessel Code, Section III, requires the specification of the range of stresses due to the thermal expansion moments and thermal gradients through the pipe wall thickness. In a simplified code evaluation, the thermal expansion stresses and the stresses due to through-wall temperature gradients are calculated by independent analyses and the maximum stresses from the two loadings are assumed to be occurring concurrently, i.e., their temporal variation is ignored. For thin-wall elbows, typical of Liquid Metal Fast Breeder Reactor (LMFBR) sodium piping, the high thermal expansion stresses, when combined with the steep through-wall gradients, result in a fictitiously high stress range. This conservatism in calculation is studied here using typical LMFBR transients for the heat transport system (HTS). For typical sodium transients, the results show that the maximum thermal expansion stresses based on the average pipe temperature and the maximum through-wall stresses do not occur at the same instant and a significant reduction in the calculated maximum stress range can be achieved by the temporal superposition of these two effects. The corresponding fatigue damage for the piping components is also expected to be considerably lower. A simple post-processing approach is proposed to calculate a realistic stress intensity range.
- Research Organization:
- Westinghouse Electric Corporation, Madison, Pennsylvania
- OSTI ID:
- 6150689
- Report Number(s):
- CONF-840647-
- Conference Information:
- Journal Name: Am. Soc. Mech. Eng., (Pap.); (United States) Journal Volume: 84-PVP-5
- Country of Publication:
- United States
- Language:
- English
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