FRP System & Component Design

System design

Fibre-reinforced plastic (FRP) piping behaves different than conventional metallic piping. FRP piping is relatively flexible and is built up from multiple layers of non-isotropic material. As a consequence the circumferential and axial strengths often differ depending on the fiber orientation in each of the layers and on the layer orientation. These characteristics require a different design philosophy than that for the design of steel pipes. The governing design code is ISO14692 which is predated by the currently obsolete UKOOA code for FRP. DRG has executed the mechanical and hydraulic design of dozens of FRP-piping systems among which are very large bore cooling water systems, heavily PVC-lined chemical transport lines and smaller diameter firewater lines.

 

Component Design and verification

Most of the FRP-related codes are performance based codes that require proof of the strength of the final component. The capability of components needs to be proven with the use of pressure testing. The objective of the qualification procedure is to verify the proposed qualified pressure of each component.

 

Qualification tests are proof tests of specific representatives of a given product family and do not need to be repeated for each order or project. However, changes to any of the product family characteristics details shall require re-qualification. The changes that require re-qualification of the product group are changes in the fibers used for reinforcement, the resin and adhesive, the internal surface thickness or composition as well as the geometry and dimensions of the component.

 

For large diameter components qualification the costs of qualification can be reduced by performing FEA analyses. To get accurate FEA-results an FEA of a benchmark qualification test is performed to determine acceptable material stresses and strain. A modified but similar geometry can then be accurately optimized using FEA-tools such as FE/Pipe, Creo or Ansys. This optimization using software reduces the amount of failed qualification tests and thus the cost for the qualification.