The Type I ACME pigtail features a green nylon nut that swivels on a black bushing that is heat sensitive. Between 240 deg. and 300 deg. F the bushing will yield (melt) allowing the springloaded module in the valve to push the brass nipple back approximately 1/4″ closing the module and stopping the flow of gas from the container. Inside the brass nipple is a flow-limiting device designed to sense excessive gas flow. If an excessive flow is sensed the flow-limiting device shuts the flow down to a maximum of 10 SCFH. This is also referred to as the by-pass flow.