IEEE Std 628:2020 pdf free download – IEEE Standard Criteria forthe Design, Installation, and Qualification of Raceway Systemsfor Class 1E Circuits for NuclearPower Generating Stations
4.10.1.3 Abnormal loads
For raceways internal to the station, abnormal loads are those generated by a postulated high-energy pipe breakaccident, accident pressure loads, jet impingement loads, pipe whip missile loads, and equipment missiles. Forexternal raceways, abnormal loads would be an externally generated missile. Gencrally, thesc loads have ahigh magnitude and are localized. It is not practical to consider these loads in the structural analysis of theraceway system. See IEEE Std 384 for the design considerations associated with abnormal loads.
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 aseismic event. Displacement limits shal 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.
4.10.3 Structural 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 stiffiness 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 responses of interestin design shall be combined in accordance with the requirements of IEEE Std 344TM—other methods maybe used, provided they are justified.The responses 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.
4.10.3.2 Static-load analysis
Equivalent static-load analysis shall be performed as required to obtain the responses due to dynamic loads.The mass of the system multiplied by an appropriate factor (see IEEE Std 344)times the peak response valueof the applicable RS curve at an appropriate damping value shall be used to obtain the dynamic load.Theeffects of simultaneous application of these components of motion, from the three separate analyses in eachorthogonal direction, shall be combined by the SRSs technique.The representative maximum value of aparticular response for designs, such as deformations or stresses, may then be calculated and combined withthe response to other loads as per the load combinations specified in 4.10.1.2.18
4.10.3.3 Damping
Damping values for each raceway system shall be established and justified.Refer to B.2.3， for additionalguidance on damping.
4.11 EMC/EMI Shielding
Metallic raceways with solid bottom and solid tray cover may provide additional shielding for instrumentationcircuits from EMC/EMI interference.See IEEE Std 690.