Advanced Scanning and Computational Fluid Dynamic Analysis on Safety Related Impeller

Utilizing advanced scanning and computer analysis to validate the performance of impellers from a repaired pattern

Hayward Tyler supplied a replacement impeller for use in a Nuclear Safety Related Component Cooling Water application within a nuclear power plant. The original equipment was supplied in the early 1970s and the original pattern used to cast the impellers had been subject to degradation through the years. In order to validate the pattern repairs and avoid large-scale performance testing, Hayward Tyler used computer modelling and analysis to validate the refurbished pattern and impellers produced from it.

The refurbished pattern was used to pour a new impeller that was machined complete to the original drawings. The impeller was dimensionally inspected and then sent to Shape Fidelity, an industry leading inspection company, to create a 3D Computer Aided Design (CAD) model. Traditional 3D scanning of impellers can be difficult, given the sweeping vane geometry and blind internal surfaces. This can require the CAD modeler to interpolate geometry that cannot be scanned in the center of the hydraulic passage, causing differences between the model and actual impeller geometry. Given the importance of the entire hydraulic passage to generate the required duty, a new proprietary technique was used to scan the entire passage and create the model. This new technique is non-destructive, and provides data for all surfaces.

Hayward Tyler engineers combined the 3D CAD model with the pump case model and other key features of the original pump to create the entire fluid body, which was then exported to be analyzed using Computational Fluid Dynamics (CFD) software. They used their NQA-1 Commercial Dedication Program to validate the CFD software. The results of the CFD were compared to the original test pump curves and proved that the finish machined impellers, based on the pattern modifications, would meet the original contract requirements.

The entire process, from the start of scanning to completed and validated CFD results, took less than 2 weeks. This new approach can be used to validate pattern changes, reverse engineer existing equipment, or upgrade existing equipment, all without the need to performance test.