Description of Driving Event:
The principal cause of pressure vessel rupture is overpressurization. This overstressing of the tank could result in failures after experiencing normal temperature pressure cycles. Tanks that contain heater elements are most likely to experience high pressures if the electrical circuitry fails to cut off the heater elements. High-pressure tanks scratched or impacted after proof testing, i.e., during installation, checkout, or crew operation, cause dangerous stress risers leading to potential tank failures.