Document: NRC Regulatory Guide
Document ID: c94378e6-d5f2-4911-8d1d-2a16783d9866
Document Type: regulatory_guide
Title: Installation of Overpressure Protection Devices
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1306/ML13064A109.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.67
CFR Part: 
CFR Title: 

Content:
6. Materials and Plant Protection 10. General discharge, a reasonable position to assure adequate strength is to require consideration of the most severe potenlial sequence of discharges; e.g., either the simultaneous discharge of' all the relief valves on any single run pipe in a multiple-valve installation and the restiltani combined dynamic load or, where forces may cou.lllei:act each other, a sequence of discharges such that the dynamic effects combine in that phase relation which is estimated to induce the maximum effect at any po)int. Multiple discharge reaction forces which act to induce forces or moments in directions opposite to each other should not be considered to act with their Dynamic Load Factor (DLF) applied simultaneously. 4. The requirements of Code Case 1569 do not clearly state that the reaction forces and moments are to be included in evaluation of stresses for all components and all connecting welds of the pressure relief station and the run pipe. Also, the Code Case does not clearly state that maximum instantaneous values of forces and moments should be used in the calculation of both primary stresses and secondary stresses. The maximum instantaneous value should be determined either by applying a Dynamic Load Factor to the steady-state forces and moments or by performing a dynamic hvdraulic/structural system analysis, as stated in the Code Case. Regulatory Positions C.3. and C4. are included to clarify these requirements. A Dynamic Load Factor of 2.0 may be Used in lieu of a dynamic analysis to determine the DLF. 5. Code Case 1569 indicates in Category 4 that ,Jet:_iited reeps ar. under consideration fnr the design of piping of a pressure relief valve installation with closed discharge systems, open discharge systems with a long discharge pipe, and systems with slug flow as from a water seal. The scope of this regulatory guide does not include such systems. C. REGULATORY POSITION For those pressure relief valve stations2 within its scope,