One morning, a leak was found on the bottom valve of a tank of 30% hydrochloric acid located at a polyethylene/polypropylene plant. An employee closed and set the valve with barrier tape, a chain, and a padlock. He then drew up a maintenance notification and email to be processed the following morning (Monday). At 8:45 p.m, a larger leak was found on the same valve; the acid was flowing into the sewer system and releasing toxic fumes. At around 9:15 p.m., the onsite firefighters set up a water curtain to knock down the vapours. Wearing hazmat suits, they directed the leak toward the containment pit. At 9:45 p.m., they covered the acid with a blanket of foam to limit its evaporation. Between 300 and 400 l of acid was directed outside the pit. The plant operator monitored the pH at the site’s outlet and adjusted it with sodium hydroxide. At 11:40 p.m., it pumped the flow of acid into a second tank. At 5:00 a.m. on the following day, the firefighters took the precaution of prohibiting all daytime personnel from accessing the site. The leak was stopped at 9:00 a.m. and repairs on the valve ended at 12:00 p.m. The plant operator informed the authorities and issued a press release.

The leaky valve was not designed for use with hydrochloric acid. The last time the valve was replaced, the maintenance scheduler had checked its characteristics and its Ebonite body in particular. After realizing that the valve’s dimensions were different from those stated on the sheet, he went back to double-check and delayed the release from the warehouse. After checking a few days later, he went back to his work station and mistakenly selected a W101 valve (a non-Ebonite valve) instead of a W107 valve.

After analysing the causes of the incident and developing corrective actions, the plant operator:

• now requires the maintenance contractor to always compare the markings on valves whenever they are replaced with identical valves in order to identify potential ID code mistakes.
• now requires that materials be checked to ensure they are compliant with pipes.
• now purchases Ebonite valves that are not the same colour as other valves.
• is considering the possibility of removing the transparent level gauges and replacing them with another measurement technology that eliminates the risk of low-point leaks.
• installed a backup solution for the storage of large volumes of acid.
• checked the integrity of the containment pit.