This case study focuses on the finite element analysis (FEA) conducted for a filament wound coupler designed for 42-inch centrifugal cast fiberglass pipes. The objective was to evaluate the performance of the fiberglass coupler under various conditions to ensure it meets the required specifications.
Analysis
The filament wound couplers (FWC) are cylindrical sleeves lined with an EPDM gasket. These couplers feature four individual rings that provide a pressure seal. They are engineered to handle a maximum long-term pressure of 10 Barg.
The finite element simulations aimed to calculate the stresses and strains within the coupler and compare these against an allowable stress envelope based on the Tsai-Wu failure criterion. The analysis included the following scenarios:
- Case 1 (Nominal Case): The fiberglass reinforced plastic (GRP) pipes are aligned with coinciding centerlines and the system is pressurized.
- Case 2: One end of the pipe is mitered at an angle not exceeding 3°, with the pipe inserted into the coupler at this deflected centerline.
The finite element model was constructed using axisymmetric elements, which excluded ovalization effects. To address this, additional calculations were performed to ensure that all potential ovalization impacts were considered.
Results
The finite element analysis revealed that the primary stresses in the coupler resulted from axial bending. This bending stress is due to the internal pressure acting on a portion of the internal surface of the coupler. The influence of the centerline angle was minimal within the range of miter angles examined.
“Additional calculations were performed to ensure that all possible ovalization effects were taken into account.”
The analysis showed that stresses caused by ovalization or bending of the mitered inner pipe, resulting from the force imbalance at the mitered pipe end, were negligible. However, stresses due to coupler ovalization during installation could be significant depending on the miter angle of the pipe.
Overall, the FEA results demonstrated that pressure-induced stresses are nearly independent of the range of miter angles and centerline deflection angles considered.
The finite element analysis of the filament wound pipe coupler confirmed that the design can accommodate the required pressures with minimal impact from ovalization and miter angle variations. This analysis ensures that the coupler performs reliably under the specified conditions.
