At 7:40 a.m., the employee of a contractor working at a pharmaceutical plant gave the alert after seeing irritating white vapours coming from the plant’s tank farm. On reconnaissance, the plant’s firefighters spotted hydrobromic acid (HBr) leaking from under a tank (orangish stain on the ground). It was not possible to pinpoint the source of the leak or assess its volume because it was covered by lagging. The plant operator implemented the internal emergency plan at 8:15 a.m. At the same time, the site’s external emergency plan alarm was mistakenly set off in the security office, prompting questions from local residents. A 30 m cordon was set up around the tank farm. A water mist was sprayed to knock down the vapours. Production facilities using HBr were shut down. The lagging was removed from the pipe. The leak was found to be on a flange of the HBr tank recirculation line. Purging of the line was impossible because a non-return valve was located downstream of the flange. A connection was made on the purge to blow the HBr into the production reactor with nitrogen. At 9:20 a.m., the leak was stopped and the line was emptied and blown out. The internal emergency plan was lifted at 9:50 a.m.
An estimated 20 l of HBr spilt into the tank’s secondary containment. The vapour cloud was knocked down by the water mist. The secondary containment was rinsed. This rinse water and the firewater were neutralised at the site’s wastewater treatment plant.
The leaky flange, which was on a flowmeter, was eaten by corrosion. An analysis showed that the flowmeter was not made of the right material. The supplier had mistakenly sent a stainless steel flowmeter instead of one made of PTFE-coated stainless steel. This flowmeter had been received and fitted without the error being identified (only documents were checked at reception and no checks were made at the time of fitting). The operator is working on improving the series of checks required when materials are received.
This site has already seen a number of accidents involving leaks of substances from bulk-transport tanks (ARIA 47726, 47730). More generally, multiple events related to issues with monitoring the condition of equipment and insufficient checks following maintenance operations have been identified (ARIA 36102, 35773, 36103, 44929).
