From a historical perspective,the traditional approach to deal with"unknown magnitude of nozzle loads"can be summarized here.In EN 13445-3(EU)~1 clause 16.4.6.3 and 16.5.6.3,if the ratio Φp = 1,then the other ratios,ΦZ and ΦB,must be zero for the interaction requirements to be met,although there is some provision in equations 16.4-15 and 16.5-15 for the other ratios to be slightly greater than zero.The equivalent clauses,as indicated in PD 5500(UK),2 are,respectively,G.2.8.2.4 and G.2.8.3.4,and the equations G.2.8-13 and G.2.8-39.This means that for the initial design,some provision must be made for nozzle loads that are not yet known.This has always been the case,and many companies have produced their own data tables of nozzle loads that are used for the initial design.The piping stress analysts then know that they must maintain the calculated nozzle loads to less than the tabulated values and design the piping accordingly.
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