To N. Venkat,
Ductile iron piping systems can be analyzed, however the analysis is not as straight forward as a carbon steel welded system, as John Luf does point out.
Your ductile iron pipe spools could have threaded flanges on the pipe barrels, or the flanges could be cast integral with the pipe, depending on the diameter or length limitations. Fittings will have integrally cast flanges. Dimensions are all different from carbon steel pipe and fittings. Pipe O.D./I.D. and fitting dimensions (radius and lengths) will be different with effects on flexibility. The pipe, if centrifugal cast, will have different properties than sand cast pipe or fittings. The DIN standard ductile iron piping would have some additional differences from ANSI ductile iron piping in dimensions and materials.
Most ductile iron piping systems are not operated near the material limits. The weight of flanged joints is probably the next most significant load after pipe and contents for designing adequate supports. I would recommend modeling a rigid element for the length of pair of flange thicknesses with weight of flanged joint including the bolts. If the pipe spool has threaded flanges, then add SIF for the spool flange connection.
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R Yee