The discharge models aim to determine or estimate the amount of material (liquid or gas) released to the environment due to the occurrence of catastrophic failure (break, crack, leak) of valves, pipelines, vessels and others.
The Riskan has four discharge from vessel models, all based on Bernoulli's equation for the fluid and thermodynamic properties, as described in Yellow Book of TNO. Are they:
- Liquid phase of liquefied gas vessel
- Vapor phase of liquefied gas vessel
- Liquid in atmospheric tank
- Gas vessel
It also has three models to discharge from duct, based on the models of Yellow Book of TNO:
It also contains three fixed models that consider only fixed discharge values:
Selecting the model
The choice of model follows the logic described in the figure below. In the case of a pressurized liquefied gas, leaks can be considered in the liquid phase or the vapor phase.
The decision on the main force acting on a leak is usually the reservoir unless the leak occurs in a very distant duct tank or shortly after a bomb. When in doubt, simulating the three situations and consider that the result of which gave greater.