In August 2024, while loading anhydrous ammonia into a railcar at a manufacturing site, a shear coupling on the loadout arm failed to function. Two out of three bolts failed, causing the coupling to open and resulting in a loss of primary containment (LOPC) of pressurized liquefied ammonia, which formed an ammonia vapor cloud.
A proximity sensor adjacent to the shear coupling was not actuated. Consequently, release of the toxic gas continued until other gas detection activated a safety instrumented system (SIS) shutdown of the NH3 flow.
As the first responder, the operator escalated their risk by entering the rapidly forming toxic vapour cloud without respiratory protection, increasing their exposure potential to an acutely hazardous atmosphere.