Objective and Challenges:

The objective of the analysis was to analyze the Compressor Casing and establish a working load limit for external piping loads. The model was consisting of full model compressor casing with nozzle.
A stress investigation of the junction area of a typical nozzle in casing with imposed connected piping forces was necessary to assure that the design is adequate for the intended service. A limit load analysis of the casing with pressure and external force loading was conducted. The limit load was defined by increasing the nozzle external loads proportionally until collapse occurred. The evaluation of the limit load analysis was conducted in accordance with ASME BPVC Section VIII Division 2.

Methodology: 

Limit load analysis was performed to validate the design for specified design conditions. The acceptance criteria shall be per ASME Section VIII Div. 2 Para. 5.2.3.4.
The allowable load on the component was established by applying design factors to the limit load such that the onset of gross plastic deformations (plastic collapse) will not occur. Limit analysis can provide an assessment of the integrity of a mechanical component during operation by applying the appropriate boundary conditions and geometrical behavior.
All parts of the model were given elastic-perfectly plastic material properties with yield stress Sy = 1.5 S. This is in agreement with the requirements stated in Section VIII, Div. 2, 5.2.3.5.
The limit analysis is run as a “small deflection” analysis.
The von Misses yield criterion is used for the limit analysis.