IEEE 628:2020 pdf free download – IEEE Standard Criteria forthe Design, Installation, and Qualification of Raceway Systemsfor Class 1E Circuits for NuclearPower Generating Stations
4.1.2 Structural integrity
Raceway systems for Class 1E circuits are not Class 1E per IEEE Std 308TM; however, they shall be designedto seismic Category l requirements to prevent failure during a seismic event. Documentation requirementsfor the raceway system shall be in accordance with Clause 7 of this standard. Individual components (conduit,tray,etc.) within the raceway system are a subset of, and distinguished from, the raceway system. Thoseindividual components shall meet the industry standard requirements (i.e.,Certificate of Conformance toANSIC80.1 and UL6, see 4.7) necessary to support the structural and seismic calculations. Standard industrypractice has allowed different requirements for conduit as to cable tray.All materials shall be manufactured torequirements that support the 10 CFR 50 Appendix B calculations, which show the structural integrity of theseismic raceway system for Class 1E circuits.
As a minimum, the design shall adhere to the basic requirements of this standard and of IEEE Std 384TM.This will help ensure that the raceway system is designed to perform its functions, and not degrade the safetyfunctions of adjacent safety-related systems during and after experiencing all conditions postulated to occur inits environment.
Clearances with respect to other systems shall be established and provided to help ensure that movement dueto loads and load combinations (see 4.10.1 ) will not affect the integrity of the raceway system.
Relative displacement of the raceway system to other systems, equipment, or structures shall be considered inthe design of raceway systems. The raceway supports shall be designed to accommodate differentialsettlementand deflections between structures.
4.1.3 Layout
Raceways shall not be located close to heat sources unless cables are selected or derated for the highestexpected ambient temperaturc. Longitudinal expansion of raceways shall be considered in areas with varyingtemperatures.
The design of raceways shall accommodate the installation of qualified fire stops where raceways penetrate afire barrier. For additional fire considerations, see IEEE Std 690TM.
4.10.2 Structural acceptance criteria
The structural acceptance criteria shall be developed for the raceway system. The criteria should be obtainedfrom industry experience, applicable codes and standards, manufacturing standards, or ultimate load valuesfrom test data.Annex C contains additional guidance with respect to the use of the elastic design method.
4.10.2.1 Displacement limits
Movement of the raceway system may occur due to design considerations,such as thermal expansion or ascismic event. Displacement limits shall be imposed on raceway systems so that all required clearances aremaintained and cables remain intact to prevent loss of circuit continuity.
4.10.2.2 Testing
Where cable tray and wireway characteristics, such as section properties and deflections, cannot be acceptablydetermined by analysis, a test shall be performed to determine these parameters.
4.10.3Structural analysis
The structural analysis shall be performed for the loads specified in 4.10.1.1.Two analytical methods forcalculating the effects of dynamic loads on raceway systems are commonly used: dynamic analysis andequivalent static-load analysis. The selection of the analysis method shall take into account the complexity ofthe system and the adequacy of the analytical technique to properly predict the response of the system whileunder dynamic excitation and other dynamic loads (see 4.10.1).
4.10.3.1 Dynamic analysis
Dynamic analysis of a raceway system shall be performed by using the mathematical model of the racewaysystem that best represents the mass distribution and stiffness ofthe various system components.RS applicableto the raceway system location shall be utilized to define the dynamic loads. The RS is selected for the dampingvalues defined in 4.10.3.3.
The spectral accelerations for each mode shall be obtained for each component of the earthquake from theappropriate RS.The representative maximum design values of the individual modal responscs of interestin design shall be combined in accordance with the requirements of IEEE Std 344TM—other methods maybe used, provided they are justified. The responscs obtained for each of three orthogonal directions shall becombined by the square-root-of-the-sum-of-the-squares (SRSS) technique.The resulting seismic responsesshall be combined with respective responses due to other loads according to the load combinations specifiedin 4.10.1.2.