An ammonia (NH3) refrigeration leak occurred around 9 pm in a 400-m² plant producing frozen dishes. The installation had introduced 900 kg of NH3 in 2 reservoirs. An NH3 detector triggered the alarm. As specified in the plant’s internal emergency plan, the services notified set up a safety perimeter. A water nozzle brought down the gaseous NH3. Shortly after midnight and in a difficult manoeuvre, since the facilities were placed 5 m off the ground, fire-fighters wearing diving suits located the leak on the flanges of a ball valve at the base of one of the 900-litre reservoirs.
NH3 was discharged at a height of 11 m via the extractor, yet it also spilled onto the ground in the form of a whitish water/NH3 liquid that reached the natural outlet via the stormwater network given the absence of a seal on the plant’s retention zone and delayed activation of the stormwater network closing device on the hydrocarbon separator. Once these additional difficulties had been identified, the closing device was activated and an earthen dam installed in order to prevent polluted effluent from spilling into a nearby brook; its pH was eventually neutralised with 95% phosphoric acid (H3PO4).
It was unsuccessfully attempted to reduce this non-insulated leak by means of an ice coating. At 2 am, the emergency services decided to call in a third party to drain the unit and store the NH3. Unable to contact this specialist or find a suitable mobile reservoir (the mobile phone numbers of company managers were unavailable), responders considered dissolving the NH3; a water tanker lorry was scheduled to arrive an hour later, with another 2 hours then being necessary to transfer the NH3 (involving heat release).
The municipality cancelled a flea market scheduled near the facility to begin at 6 am. At 6:30, the NH3 transfer was finally completed, with the solution obtained shipped to an authorised treatment centre. The networks and hydrocarbon separator were pumped. During the morning hours, fire-fighters secured the reservoir by neutralising the residual gaseous phase using 250 litres of H3PO4; moreover, they recorded 300 ppm of NH3 at 4 pm inside the ventilated building.
The operator planned on introducing several improvements: sealant on the cold processing plant’s retention tank; permanent reservoir for all eventual NH3 transfers; level cutting plane with installation photographs in order to visually and numerically position the valves / other safety devices; NH3 safety fact sheet available inside the plant; faster problem detection / calling of fire-fighters; list of names and phone numbers of contact personnel (besides company switchboards); modifications to the internal emergency plan to overcome operational insufficiency and lack of technical response (by integrating the missing critical scenario); improved knowledge of chemical products stored onsite and their locations for subsequent use; reorganisation of technicians’ on-call schedules / crisis supervision; a backup set of keys to the logistics office / stormwater treatment unit; contact numbers (phone, fax) more accessible to responders and plant technicians.
