METHOD OF DETERMINING THE AREA OF OPENINGS IN THE ROOF OF THE RESERVOIR FOR STORAGE OF LIQUID HYDROCARBONS Russian patent published in 2016 - IPC A62C3/00 

FIELD: oil and gas industry; fire safety.

SUBSTANCE: invention relates to determination of the area of openings (valves) in the roof of vertical steel tanks, required to prevent mechanical damage and destruction of the tanks for storage of liquid hydrocarbons in case of actuation of automatic gaseous fire suppression unit (AGFSU). Values of geometrical dimensions of the reservoir are taken in the method for a specific type of reservoir. Using calculation-analytical method based on developed mathematical model of non-stationary gas-dynamic processes at the supply of gaseous fire suppression agent to the reservoir as the result of the AGFSU actuation, ratio of phase states of fire-extinguishing substance at the nozzle outlet and dispersion of particles of the fire-extinguishing substance being in solid phase are defined. Parameters values for gas-air mixture in the tank are determined: vacuum pressure P in the reservoir and gas-air mix temperature T, as well as the value of the time period τ of supplying the gaseous fire suppression agent to achieve maximum vacuum pressure in the reservoir. Area of openings in the reservoir roof F_C is determined needed for compensating negative pressure in the reservoir, which is required to prevent destruction of the reservoir at actuation of the AGFSU, in accordance with the following formula:

where K - safety factor; m_air - air mass in the tank (kg); ΔP - absolute value of difference of maximum allowable vacuum pressure inside the tank and pressure in the open air (Pa); ρ_air - air density (kg/m³).

EFFECT: invention allows to exclude the risk of accidents related to excessive vacuum pressure inside tanks equipped with AGFSU.

4 cl, 2 dwg, 1 tbl, 1 ex