A propane leak occurred on a loading station in an LPG depot that distributes product to trucks. The depot manager secured the site by pressing the emergency button, in accordance with the site’s standard operating procedure. The emergency services were contacted as a preventive measure. The automatic devices associated with the emergency shut down operated correctly, including: automatic disconnection by closure of the valves, flooding by fixed sprayers (spray booms and monitors), disconnection of power supplies. The spraying systems are designed to dilute the cloud. The operator then went to the pump station and closed all the manual valves. No trucks were being filled at the time of the accident.
The leak was located on a purge line (VOC recovery) used to drain the hose after loading operations are complete. The line runs between the tank’s manual valve and that of the loading arm and to direct the residual liquefied gas to the storage tank. This recovery function is fairly recent. The piping consists of a rigid part and a flexible part connected by an “olive” type screw connector. The piping is also equipped with valves, at the loading station, enabling it to be connected to either the pressurised LPG intake system (purge), equipped with a device in the pump house allowing it to be conveyed to the storage facility, or to the venting section (fumes), depending on how the valves are configured. The leak was caused by the rupture of union (due to ageing) between the rigid and fixed parts. In addition, owing to the position of the valves, the piping was connected with the product intake circuit: the leak was thus being fed, as the product system was not equipped with a device preventing its backflow through the purge.
The operator immediately implemented the following measures: the hose was replaced with an identical model, locking out of valves, temporary shut down of the recovery operation. Modifications were foreseen: the installation of hoses adapted to the stresses associated with product recovery, and automation of the purge system valves (with the system being secured when an alarm sounds or at the end of the loading operation). Additional investigations are planned in the long term (expert evaluation of all hoses, cataloguing of the installations having this device, identification of potential sources maintaining hoses under pressure…).