DNV PHAST is a system for risk analysis and management in the event of a leak and spreading of a substance from tanks of vessels carrying liquid cargo, e.g. liquefied gases. The system calculates the initial leak quantity, amounts escaping to the water and atmosphere, determines the extent of mixing with air and dilution of the substance, and toxic or combustible effects. The system comprises a wide range of leakage models (leak and rupture of a short or long pipeline, catastrophic ruptures, failures of safety valves, collapse of tank cover, vapour leak to the atmosphere, vapours in the superstructure) and spreading of flammable, explosive and toxic substances, as presented graphically.

Figure.... Functionalities of the DNV Phast system

Source: www.dnv.com

In the context of scientific and industrial research on operational risks of ships and discharge terminals, the system is used for:

• estimation of accident consequences, particularly the estimation of spills from a ship hull or tank through a hole (e.g. crude oil, LNG or other gases, chemicals), quantitative assessment of evaporation, penetration into the ground, emulsifying with water etc.; estimation of gas cloud volume, fire or explosion size, etc. The system also allows to plan the elimination of consequences taking account of available resources and costs,
• calculation of accident probability, that is undesired chemical reactions of spilled substances (e.g. explosions, fire, etc.),
• assessment of pollution level or spill size for projected accidents,
• estimation of the quantity of undesired discharge of a substance to the water environment.