Ammonia leakage thresholds have been set at 25 parts per million (ppm) in enclosed spaces and 110 ppm in secondary enclosures, reports Engine.
Guidelines to use ammonia as a marine fuel
IMO’s Sub-Committee on Carriage of Cargoes and Containers (CCC) has finalized interim guidelines for the use of ammonia as a marine fuel, Gianpaolo Benedetti, principal advisor at the Society for Gas as a Marine Fuel (SGMF), said in a social media post.
SGMF was part of the delegations contributing to the drafting of the guidelines.
The guidelines specify ammonia concentration thresholds at 25 ppm for enclosed spaces and 110 ppm for secondary enclosures in case of gas leakage. Ammonia concentration exceeding 220 ppm should trigger alarms and automatic shutdown systems on ships.
These specifications align with suggestions from the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping, the Royal Institution of Naval Architects, and multiple classification societies.
Meanwhile, the US Environmental Protection Agency (EPA) has set the exposure limit for ammonia to 30 ppm. Exposure at this level has reversible effects, while exposure at 220 ppm carries a risk of irreversible or serious long-lasting effects. Exposure to ammonia concentrations of 2,700 ppm is life-threatening or fatal, according to the US EPA.
The IMO’s interim ammonia guidelines also distinguish between “toxic areas” located on open decks and “toxic spaces” found within the ship’s structural boundaries, Benedetti wrote.
The guidelines stipulate that ammonia fuel must be stored in a refrigerated state at atmospheric pressure on ships. Alternative storage solutions may be considered, but only if approved through an alternative design pathway.
The guidelines state that ammonia must not be released directly into the environment during ship operations and must be properly stored to prevent leakage. If ammonia needs to be released for maintenance or system testing, appropriate treatment measures must be in place to ensure its concentration remains within safe limits. Uncontrolled releases are only permissible in extreme cases, such as catastrophic failures, when safety mechanisms can be activated to mitigate additional risks.
Mitigation systems must maintain ammonia release below 110 ppm during controlled abnormal scenarios, while emergency releases fall outside this threshold.
The guidelines “will need to be revised shortly as more information becomes available”, SGMF’s Benedetti noted.
The final draft of the interim ammonia guidelines is expected to be reviewed and approved by the IMO’s Maritime Safety Committee (MSC) in December.
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Source: Engine
