Document: NRC Regulatory Guide
Document ID: a4944d20-ef6e-480b-a45d-14425bedd2e5
Document Type: regulatory_guide
Title: ASME Code Cases Not Approved for Use (Rev. 8)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2219/ML22196A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.193
CFR Part: 
CFR Title: 

Content:
x A of the code case for pipe ovality, through wall bending, soil and surface pressure, compressive stress in side walls, buckling due to external pressure, buoyancy and flotation are the same as used in American Lifeline Alliance Report, NUREG/CR-6876, and Moser’s Book and therefore are acceptable. However, the NRC staff determines that the factor of safety used for buckling due to external pressure is inappropriate. The code case uses a factor of safety of 2 in the equation A-18 while American Lifeline Alliance Report, NUREG/CR-6876, and Moser’s Buried piping Design Book recommend a higher factor of safety of 2.5 when C/D equals to 2, or 3.0 when C/D is less than 2, where C/D is soil depth to pipe diameter ratio. (4) The NRC staff noted that Appendix A of the code case considered pressures from soil and surcharge which are basic loads that need to be considered in the design of buried pipe. However, for a buried metal piping, the NRC staff determines that the following additional loading shall be considered. (a) Buried pipelines shall be designed to resist earthquake-induced stresses (soil-pipe interaction). (b) Earthquake- induced soil landslides and permanent ground deformations (surface faulting) shall be considered. Buried pipelines shall be designed to resist earthquake-induced deformations. (c) Effects due to soil failures such as liquefaction and lateral spreading shall be considered. Induced axial and bending loads need to be considered in the analysis. (d) The load and or stress due to cycles of freezing and thawing of the embedment shall be considered. (e) Thermal expansion of the buried pipe shall be considered. (f) Under the effect of soil and surface loads, a buried pipe may be deflected. Therefore, the through-wall bending stress needs to be considered and combined with other calculated stresses to obtain the overall stress in the pipe. (g) When buried pipe is subject to large cyclic ground surface loads, such as under heavy traffic loads,