This project presented the assessment results of the analysis of the pressure-containing part of an actuator. The focus was on evaluating the actuator’s integrity through various finite element method (FEM) analyses to ensure compliance with potential failure mechanisms.
Analysis
Several FEM analyses were conducted to validate the actuator’s integrity against possible failure mechanisms. The assessment adhered to the Pressure Equipment Directive (PED), utilizing the Dutch Rules for Pressure Vessels (RToD) as the applicable recognized code.
For the purpose of the analysis, the actuator was divided into five basic parts: the top plate, the driving piston, the bottom plate, the cylinder, and the tie-rods connecting the bottom to the top plate. Some parts were subjected to internal pressure. Each component of the actuator was evaluated separately under appropriate boundary conditions and external forces to simulate interactions between the separate components.
Results
The analysis results concluded that the actuator met the requirements set by the RToD. From a fatigue perspective, the cylinder, especially the stress distribution near a rectangular opening, was identified as the limiting factor. The actuator was deemed fit for a maximum of 320,000 complete load cycles. For a 30-year operational lifetime, this allowed the actuator to undergo a complete cycle once every hour.
However, all parts, except for the tie-rods, complied with the requirements set by ASME VIII Division 2. This indicated that the actuator, in its current configuration, did not fulfill the ASME requirements. Notably, the fatigue assessment results between ASME and RToD showed no difference, meaning the load cycle limit remained consistent across both analyses.
Conclusion
The FEM analysis verified that the actuator complied with the RToD requirements but fell short of ASME VIII Division 2 standards, particularly due to the tie-rods. The stress in the cylinder posed a constraint on the number of operational cycles, highlighting the need for further design optimization to remove this limitation and achieve compliance with both RToD and ASME standards.
