Advanced Outflow Calculations Using MEPC.122(52) When the Simplified Method Falls Short

SARC supports designers and shipyards with probabilistic oil outflow calculations in accordance with MARPOL Regulation 23. In many projects, the standard simplified method provides a quick and efficient first assessment. However, when these initial results do not meet the required criteria, the extended approach based on MEPC.122(52) offers an effective alternative.

Outflow calculations using the simplified method

Using the information supplied by the client, SARC constructs a complete 3D model of the vessel in PIAS, including tank arrangement, hull form and stability data.
Based on this model, we perform the probabilistic outflow calculations using the simplified method as defined in MARPOL Regulation 23. This method is fully implemented in the PIAS Outflow module and provides a clear first indication of the vessel’s compliance.

If the results are not sufficient, a more detailed calculation method is applied.

Hypothetical subcompartments according to MEPC.122(52)

When the simplified method does not meet the required performance, SARC can conduct a second round of calculations using the hypothetical subcompartments approach, as described in MEPC.122(52).
In this method, existing tanks are computationally subdivided into smaller units to better represent the probability of damage across a range of scenarios.

This technique:

• improves the accuracy of the damage‑probability modelling,
• approximates the results of full numerical integration,
• and can be performed within the existing PIAS environment through targeted post‑processing.

Numerical integration

Using the methods described above, SARC was able to provide a solution for a client whose design did not comply when using the simplified method alone. While some post‑processing was required, this could be incorporated efficiently into the PIAS suite.

Alternatively, instead of a discretized approach such as the hypothetical subcompartment method, a full numerical integration method can be implemented in PIAS. This technique accounts precisely for the actual hull and compartment geometry and offers the most accurate and optimal result.
Such a method is explicitly mentioned as an acceptable alternative within the regulatory framework.