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Overpressure within zone II varies from 1350 to 300 kPa and can be
determined at a given distance R0 from the center of explosion by the formula:

kPa (7.4)

In the zone of action of the air shock wave (zone III), the radius of the zone
is unlimited, and the value of overpressure ΔР , is determined by the formula or
f 3
by the graph. The shock wave front is formed in this zone.
To determine the overpressure at the front of the air shock wave, it is
necessary to calculate the intermediate coefficient according to the formula:

(7.5)

The overpressure of the air shock wave is determined by the formula:
(7.6)

(7.7)
It is also possible to determine the amount of overpressure of the air shock
wave at the explosion of the gas-air mixture according to the Figure 7.2.

Figure 7.2 – The graph of dependence overpressure from the number of
explosive gas mixture

More of two values, calculated or according to the graph, are accepted for
ΔP fmax. .

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