At around 8 p.m. on a Sunday, an HCl leak occurred on a vibrating blade level detector in a distillation column undergoing testing before being placed into production. The level sensor had become disengaged from the flange. The transmitter had been ripped off, and the leak went through the flange. It was estimated that 323 kg of 100% HCl had leaked. The HCL detectors and the gas alert were triggered. The column to be distilled was then secured. An individual intervening during the accident was burned on the neck while trying to find a shut-off valve to isolate the leak. He was wearing his PPE at the time.
The level sensor was immersed in the liquid HCl. The sensor’s membrane was made of enamelled C4 alloy. The corrosion rate of the C4 alloy under the temperature and pressure conditions in the column to be distilled was 512 mm/year, and the corrosion rate (loss of thickness) of the enamel is 0.8 to 1 mm/year under the same conditions. The choice of materials for this accessory was not adapted to its conditions of use. The operator believes that there was some sort of miscommunication of the requirements between the supplier of the distillation skid and its own accessory supplier.
Following this accident, the operator had all the equivalent nozzles checked throughout its installation. The level detector, which was not required for the installation, was replaced by a solid plug. All of the material and equipment in the facility were inspected to check their resistance to corrosion. A procedure outlining the operations to be following in the event of a leak on the installation must be written, and the technicians must be trained in this procedure. This incident occurred just two days after another leak had been reported (ARIA 48555).