The 106-EF-8837BX and 206-EF-8837BX excess flow valves are based on the 106-PT and 206-PT double-chamber main valves. Each valve is designed to shut off tightly when flow exceeds a predetermined amount. The 625-RPD pilot senses the pressure drop of the valve and closes it when the tripping flow is reached; the typical pressure drop at tripping is 5 psi (0.35 bar).