The casing of a steam turbine, or a power recovery turbine in an FCC plant for instance, tends to be quite thin, and very hot in the FCC case, consequently local casing deformation and blade contact are a real risk with excessive nozzle loads.

Regarding a NEMA limited compressor, the casing is usually very robust and the weak point is commonly the frame or plinth. I have seen 10x NEMA on a compressor that was 420 bar outlet pressure and had a casing around 6 inches thick. The nozzles were machined directly into the barrel, so it didn't actually have mating flanges as such. Clearly very different to a steam turbine.

To get your S160 pipe nzzle loads down, have you considered routing the pipe around the turbine to cross both machine axes, then applying line stops on the axes ? This should cancel out local expansion, reduce direct forces and consequent moments to secondary effects and might get within allowable limits.