Pollution
Humain
Environnement
Economique

Fumaroles escaped from a container of anhydrous hydrofluoric acid (HF, an extremely corrosive superacid) that had just been delivered to a chemical plant. The personnel in charge of unloading operations discovered a leak upon removing the protective transport plug. They found that product had leaked from the blind flange and corroded the top valve located just underneath it. The facility operator measured concentrations of 2○ppm in the unloading room. The container was connected to the workshop’s vent and a pipe was installed in place of the leaky plug and the container was unloaded without any particular problems.

According to the facility operator, the procedure to be followed by the technician at the end of filling operation consisted in closing the valve on the hose, then closing the valve on the container before disconnection.

The technician appears to have closed the container valve too quickly, leaving no time for the residual liquid to drain completely into the tank. The technician (equipped with a protective mask) may not have seen the transparent residue when he secured the plug above the valve. The cover was then closed and sealed before storage.

As this residue was minimal and confined under the cover, it had not been detected during storage or loading. It had caused superficial oxidation around the container’s valves, which attracted the attention of the personnel in charge of unloading operations.

Following the incident, the operator set up a working group to review the operating procedure and test new elastomer seals. The intention was to replace the Teflon seals currently used. Elastomer seals have better sealing characteristics but less chemical resistance than Teflon seals.

The operator stated that it was the first time in seven years that this type of incident had been reported, though they handle 10 to 15 shipments per week.