Window Failure Repair
In the early days of testing the shock tube, a window used for high-speed schlieren optical access failed at a pressure well below rated test pressure. Luckily no one was injured as a result. An internal investigation uncovered a configuration error and a suspected flaw (scratch or chip) in one of the glass windows led to the failure. As a result, changes were made to both the design of the optically accessible section of the shock tube and to the equipment operation procedures. Glass windows were replaced with 60% thicker acrylic windows and were lined with 2 mm glass to provide greater temperature and abrasion resistance. To accommodate this, spacer plates with integrated seals were designed to bolt directly onto the original apparatus. An operator shield was also constructed with a steel frame and polycarbonate viewing window, separating the shock tube control panel from any potential fragments from window failure. Changes to the gas loading procedures during operation ensured the prior failure condition could not be achieved.