Failure of Pyrotechnic Operated Valves with Dual Initiators

Investigation of recent pyrovalve failures reveals timing of redundant initiator firings is crucial for reliable operation of pyrovalves. Simultaneous firing, i.e., within a very narrow time frame, was found to be the primary cause of the valve failing to operate. Testing of both single and dual initiators revealed important design characteristics affecting pyrovalve device performance. They include Primer Chamber Assembly (PCA) geometry and material properties, as well as operational effects on combustion product flow, and resulting energy transfer to the booster. The CONAX PCA design has evolved slowly over time undergoing incremental changes to correct known issues. These piecewise changes were verified by limited test, without a full understanding of the overall system impact or effect on margins. Adequate system performance margins may be adversely affected in existing or future systems incorporating a pyrovalve actuated by simultaneous firing of dual initiators.