Document: NUREG-0800
Document ID: d51db4b1-0b68-4e27-8107-a41ccdbd671a
Document Type: srp
Title: ASME CODE CLASS 1, 2, AND 3 COMPONENTS, COMPONENT SUPPORTS,
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070337.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.3
CFR Part: 
CFR Title: 

Content:
components, acceptable criteriaCriteria for snubber operability assurance should 46 contain the following elements: (1) Structural Analysis and Systems Evaluation. Systems and components which utilize snubbers as shock and vibration arresters must be analyzed to ascertain the interaction of such devices with the systems and components to which they are attached. Snubbers may be used as shock and vibration arresters and in some instances as dual purpose snubbers. When used as a vibration arrestor or dual purpose snubbers, and when so used fatigue strength must be considered. 47 Important factors in the fatigue evaluation include: (i) unsupported system component movement or amplitude, 48 (ii) force imparted to snubber and corresponding reaction on system or component due to restricting motion (damped amplitude), (iii) vibration frequency or number of load cycles, and (iv) verification of system or component and snubber fatigue strength. Snubbers used as shock arresters do not require fatigue evaluation if it can be demonstrated that: 3.9.3-7 DRAFT Rev. 2 - April 1996 (ia) the number of load cycles which the snubber will experience during normal plant operating conditions is small (<2500) or (iib ) motion during normal plant operating conditions does not exceed 49 snubber dead band. Snubbers utilized in systems or components which may experience high thermal growth rates, either during normal operating conditions or as a result of anticipated transients, should be checked to assureensure that such thermal growth rates do not exceed the snubber lock-up velocity. (2) Characterization of Mechanical Properties. A most important aspect of the structural analysis is realistic characterization of snubber mechanical properties (i.e. spring rates) in the analytical model. Since the "effective" stiffness of a snubber is generally greater than that for the snubber support assembly (i.e., the snubber plus clamp, transition tube extension, back-up support structure, etc.) the