Hello Michael,

Request you to please reply serially to my queries.

As far as keeping the stresses within allowable limit are concerned, please note that this is a 5 stage centrifugal compressor. The team at Hexagon / Intergraph are yet to come up with a solution to an approach where in an inter stage piping and nozzle load analysis of a multi-stage centrifugal compressor is required. The application engineering expert them selves have said to me that they have yet to come up with a module in CAESAR-II where in such an analysis could be performed.

Also based on our firm's study we go along with an approach where we model the piping as per geometry of the inter stage piping. Then the flanged ends of the pipe which are coupled to various nozzles of the inter stages are anchored. These anchor points are assigned with finite stiffness values as per VDI stiffness. Then the results are obtained for such model.

We then compare the global loads obtained for the anchor points with the equation of clause 8.4.6.1 of NEMA SM-23 or Appendix-2E of the API 617 to conclude whether the imposed loads on the nozzles are within their allowable limits.