Pre-Treatment (Ammonia Bunkering)

Pre-treatment in ammonia bunkering is the conditioning of lines, tanks, and equipment before and after transfer to control the toxic and corrosive hazard of NH3. Steps include inerting with nitrogen to remove air and moisture (ammonia plus water forms corrosive ammonium hydroxide), cooling and purging transfer arms, leak and gas-detection checks, and managing vapor return so displaced ammonia is captured rather than vented. The sequence is set by the bunkering safety case and quantitative risk assessment, since a release exposes crew and bystanders to a gas with an IDLH of 300 ppm. Proper pre-treatment also limits stress-corrosion cracking in carbon-steel tanks.