The Selas automatic firecheck, or flame arrestor, is basically a check valve which is closed by actuation of a thermal release. Components include a shut-off valve, check valve, corrugated fire screen, and a thermal latch. In normal operations, the combustible fuel/air mixture passes freely through these components. If flashback occurs, the sudden increase in back pressure will cause the check valve to close and momentarily interrupt the forward flow of the fuel/air mixture. The reduced flow and the internal configuration of the firecheck allow the backward-traveling flame to stop at the fire screen. The tiny holes and chilling capacity of the fire screen hold the flame on the screen until the thermal element is heated and releases the latch to close the shut-off valve. This valve-closure stops fuel/air flow and prevents the flashback from proceeding past the firecheck. The shut-off valve remains closed until manually reset.
