Two-way vent cap for controlled atmosphere furnace

摘要

A vent cap for a heat treating furnace provides bidirectional pressure relief. The cap is weighted and balanced over the furnace vent such that the vent is closed as long as the furnace has a slightly positive internal pressure. If the internal pressure exceeds a preselected upper limit the cap opens the vent to relieve the overpressure. The vent cap has a controlled inlet which opens to equalize the pressure differential if the internal pressure falls below a preselected lower limit below the ambient pressure outside the furnace. Such controlled equalization prevents the formation of undesirable combustible mixtures of air and treating gas in the furnace.