Abstract: Each gas expansion station of a distribution network fed with gas in accordance with the invention comprises at least one regulator-expander provided with a valve member disposed on a main duct, a pilot valve, a safety valve provided with a valve member disposed in the main duct, and a differential member co-operating with the pilot valve and the safety valve which is disposed upstream from the regulator-expander to close the safety valve automatically under the control of the pilot valve in the event of the downstream pressure in the main duct downstream from the expansion station concerned exceeding a predetermined threshold value, and to operate automatically, after the downstream pressure has been restored to below the predetermined threshold value, either to reopen the safety valve if the regulator-expander of the expansion station concerned is not itself giving rise to a leak at its valve member, or else to keep the safety valve closed if the regulator-expander is not itself providing gastight sealing a