PTQ Q3 2026 Issue

12 13 11 10 9 8 7 6 5 4 3 2 1 14 16 18 17 15 19 22 28 27 26 25 24 23 21 20 29

30 32 34

36 38 40

42 44

46 48 50

54 56 58 60 62 64 66 68 70 72

X (East) in m

Figure 2 Leak components dispersion from stabiliser reboiler

conditions, including wind speed, temperature, and atmos- pheric stability. Despite this consistency, dispersion behav- iour and flammability risk varied significantly across cases. The primary differentiating factor is fluid composition. Light hydrocarbon releases disperse rapidly and remain below flammability thresholds under the evaluated con - ditions. In contrast, heavier hydrocarbon releases exhibit limited dispersion, higher localised concentrations, and increased flammability potential. The results: Leak location alone is insufficient to determine hazard severity. Two leaks within the same system may require different response actions depending on the composition of the released material. This distinction becomes relevant in operational envi- ronments where rapid decisions are required following leak detection. In the absence of composition data, similar leak signals may be treated with the same level of urgency, despite representing fundamentally different risk profiles. Integrating composition and dispersion analysis enables a more differentiated response, reducing unnecessary inter- vention while minimising the risk of underestimating haz- ardous releases. Implications for risk assessment Estimating composition and evaluating dispersion behav- iour provides a more consistent basis for classifying fugitive emissions. Based on the results from digital twins using dispersion tools, operators can assess: • Whether a release is likely to form a flammable vapour cloud.

streams. These materials exhibit lower volatility and reduced dispersion rates compared to light hydrocarbons. Dispersion modelling shows that vapour clouds from these releases remain more concentrated and persist closer to the source. As a result, calculated LFL percentages increase sig- nificantly relative to light hydrocarbon scenarios, indicating elevated ignition potential under identical conditions. • Scenario 4 : Represents a stabilised naphtha stream, where Table 1 presents dispersion governed by the vapour- phase behaviour of C 6 + naphtha components within a broader boiling range. LFL calculated values approach 10-12% at the leak source, indicating a substantial increase in flammability potential under the same meteorological conditions and leak assumptions. • Scenario 5 : Evaluates a higher-temperature system asso- ciated with a reboiler, where elevated temperatures pro- mote partial vaporisation of C 5 + components. Dispersion is therefore driven by a narrower subset of more volatile components, while heavier fractions remain predominantly in the liquid phase. Despite increased vapour generation, dispersion remains limited relative to light hydrocarbon releases, and localised concentrations remain elevated. The resulting dispersion profile highlights the persistence of elevated concentrations near the source, as shown in Figure 2 . Across both scenarios, dispersion behaviour is con- strained by limited volatility, resulting in higher near-source concentrations and elevated LFL values. These results demonstrate that heavier hydrocarbon compositions pro- duce fundamentally different hazard profiles compared to light-end streams, requiring more immediate and conserv- ative response strategies. Comparison of results All five scenarios were evaluated under the same external

• How quickly concentrations will decrease. • Whether immediate intervention is required.

This approach improves response prioritisation and reduces uncertainty during incident management. In addi- tion, a shared analytical framework supports alignment

PTQ Q3 2026