For recent chemical plants and LNG plants, the size of turbomachinery increases according to the increase of plant capacity and then very large size nozzles are used for the turbomachinery for larger capacity. Especially for offshore facilities, simpler piping arrangement is required even for the larger capacity trend because the space around the turbomachinery is limited and therefore piping design has less flexibility of arrangement. Additionally, heavier total weight of the turbomachinery and larger size of piping nozzles make it more difficult for plant contractors to handle external piping forces and moments. Although NEMA SM 23 (1994) or API Standard 617 (2002) have been normally referred for allowable load in turbomachinery piping arrangement design, the need to relax this specification is recently raised according to plant capacity and piping size increase and larger machine installation for offshore facilities.
In this study, the possibility to relax the maximum allowable load on MHI centrifugal compressors and steam turbines is investigated based on MHI design philosophy of turbomachinery, MHI experience and analysis of quantitative influence using FEM (Finite Element Method) of typical machines with piping load of 1.85 times allowable limit specified by NEMA SM 23. Various key components including nozzle deformation, stress level, clearance and misalignment of shaft end are examined and, as a result, the bottleneck which should be taken into account for MHI centrifugal compressors and steam turbines is clarified in case of excess piping load. Finally, applicable solutions from machine manufactureâs side are suggested in order to relax this specification of piping load on turbomachinery.
