What is the primary purpose of an excess-flow valve?

The primary purpose of an excess-flow valve is to close when the flow exceeds a predetermined rate. This is a critical safety feature in gas systems. When there is an abnormal increase in flow—potentially due to a leak or a rupture in the line—the excess-flow valve detects this change and promptly shuts off the flow of gas. By doing so, it helps prevent the risk of fire, explosion, or other hazardous situations that could arise from uncontrolled gas release.

Other options may appear relevant to the functioning of various components in gas systems, but they do not align with the specific function of an excess-flow valve. For instance, increasing flow rate or regulating temperature are not roles associated with safety valves; rather, they pertain to different aspects of system design. Likewise, while preventing leakage is important in gas systems, it is not the direct function of an excess-flow valve, which is focused explicitly on flow control in emergency scenarios.