Document: NRC Regulatory Guide
Document ID: 7da9830f-b2a1-484a-82ce-5b0a588c4fce
Document Type: regulatory_guide
Title: Protection Against Pipe Whip Inside Containment
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1229/ML12298A123.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.46
CFR Part: 
CFR Title: 

Content:
defined herein as less than four inches nominal pipe size) are of seamless construction (i.e., with no longitudinal weld seam and associated stress index). As expected from the type of fabrication and as confirmed by stress analysis, the probability of longitudinal breaks occurring in piping smaller than four inches nominal pipe size is considerably less than the probability of circumferential breaks occurring in these pipe sizes. Therefore, longitudinal breaks need only be postulated for piping runs and branch runs four inches nominal pipe size and larger. 1.46-2 .3,. Pipe Whip Protection Measures Measures for the protection of structures, systems, and components important to safety should be provided after piping break locations are determined for Code Class 1, 2, or 3 fluid system piping. Exceptions may be made for situations where (1) plant features such as concrete encasement or other barriers physically separate piping from other components or restrain piping from whipping or where (2) a plastic hinge is assumed to develop at a pipe whip restraint and whip of either end of the ruptured pipe in any direction cannot damage a structure, system, or component important to safety. Further exceptions are made if the internal fluid energy level in piping is not sufficient to propel a broken pipe. For example, if the piping system is pressurized at 275 psig or less in conjunction with a design temperature of 200 F or less (as specified for ANSI "150 psig class welding end or flanged end pipe fittings), then protection against pipe whipping need not be considered. In addition, pipe whip protection need not be provided when the energy associated with the plastic hinge formation is not sufficient to impair the safety function of any structure, system, or component to an unacceptable level (e.g., a system damaged by pipe whip may be capable of performing its safety function but not capable of completely fulfilling its design function such as delivering design rated flow).