In the master thesis, an uncontrolled release of methyl methacrylate was simulated, which
occurred at the end of the transport, when the tanker truck brought the substance to its
final destination. The accident occurred in the car park of a company that uses the
substance in its downstream processes, where it is processed into end products such as
acrylic Plexiglas. The uncontrolled release of the substance was caused by deterioration
of the material at the bottom of the tank, where an opening was created through which
the substance leaked out onto the ground and formed a puddle. In carrying out the
experimental work, I used the ALOHA programme, which is very suitable for carrying
out this type of simulation. The programme allows the input of the type of hazardous
substance involved in the accident, and also allows the selection between different
accident scenarios, where for the purpose of the master's thesis the scenario of a substance
leaking from a horizontal tank was chosen. In addition, any meteorological data that is
expected to be present on the day of the accident can be entered into the software. In the
master thesis, the simulation was carried out for two separate events, each with three
possible scenarios. The first event was simulated under summer meteorological
conditions and the second under winter meteorological conditions. These conditions were
also the only parameters that varied between the two simulations.
After the simulation, it turned out that ALOHA is suitable for simpler accident events
where only one substance is involved, while it would not be suitable for simulating an
event where several substances are involved. This is also one of the major drawbacks,
besides the fact that it does not take into account surface relief differences when plotting
the area of hazardous concentrations and the area of thermal radiation, which can also
have a key influence on the extent of hazard propagation. For each incident, the hazard
zones were plotted and represented in red, orange and yellow, with the highest
concentrations of substances or thermal radiation in the red zone and the lowest in the
yellow zone.
The results of the simulation itself are quite similar in the two cases where thermal
radiation to the surroundings was studied. So in the BLEVE explosion scenario and in the
scecear scenario, where the material leaks out of the tank onto the ground, where it forms
a puddle that ignites and burns like a pool fire. There were some differences only in the
first scenario, i.e. when the substance is released from the tanker also onto the ground,
except that the substance does not then ignite, but only evaporates into the atmosphere.
In this case, the hazard areas plotted by the programme are slightly larger for summer
meteorological conditions, when stronger winds were also present.
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