Protection in emergency situations. Calculation of the emergency zones in case of the of gas-air, air-fuel mixtures explosion in the open space

Practical work 6

The most common emergencies are explosions and accompanying fires when working with gas, fuel, dust and air mixtures (GAM, FAM, DAM).

The explosion is an extremely rapid release of energy in a limited volume, associated with a sudden change in the state of matter and accompanied by the formation of a large number of compressed gases capable of producing mechanical work.

FAM are a mixture of fuel and air in certain proportions. A greater probability of emergencies related to explosions and fires is typical for the following enterprises:

– chemical, oil refining, pulp and paper industry;

– gas and oil pipelines;

– all types of transport;

– food industry;

– gas stations;

– producing and using paint and varnish materials;

– using gas and oil products as raw materials for energy carriers.

Typical features of such explosions are discussed below.

There are three types of such explosions (detonation is the process of explosive transformation of matter with supersonic speed, deflagration is explosive combustion with subsonic and combined).

The power of the explosion depends on the parameters of the environment (ambient air temperature, wind speed, housing density, relief of terrain).

Detonation or combined explosion of  GA/FA mixtures can occur if the product concentration in the air exceeds the lower concentration limit (LCL), and the explosion of  DA mixtures if the upper concentration limit is exceeded;

In case of explosion, the affected zones are formed: a blasting (detonation), a fireball (the zone of action of the combustion products), a shock wave, heat damage and toxic smoke.

The damaging effect of the explosion is assessed by the following parameters:

– overpressure on the explosion zones (ΔP_f, kPa);

– thermal impulse (U, кJ/m²), i.e. then the amount of heat that is released as a result of the explosion of matter per unit area.