Reinforcing Large Diameter Elbows Using Composite Materials Subjected to Extreme Bending and Internal Pressure Loading

A study was conducted to evaluate the use of E-glass/epoxy composite materials for reinforcement of large-diameter elbows. Using a combination of sub-scale and full-scale testing, the study demonstrated that when properly designed and installed, composite materials can be used to reduce strain in reinforced elbows considering bending loads of up to 3.6 million ft-lbs (4.88 million N-m), cyclic pressures between 720 psi (4.96 MPa) and 1,440 psi (9.93 MPa), and burst testing. The stresses measured in the composite material were well below designated ASME PCC-2 design stresses for the composite materials. During testing, there was no evidence that previously applied bending loads reduced the overall burst pressure capacity of the composite-reinforced elbows. Finite element modeling was used to optimize the geometry of the composite reinforcement. The resulting design guidance from this study was used to provide direction for possible reinforcement of large-diameter elbows for in-service pipelines.