Источник: Mine Planning and Equipment Selection 1999 & Mine Environmental and Economical Issues 1999, Pivnyak A Singhal (eds) ® 1999, NMUU, Dnipropetrovsk, ISBN 966-7476-1-X

Abstract. Procedure for assessment and forecasting of blind workings explosion hazard in coal mines when using electrical equipment is given. The procedure enables feasibility study for available standards concerning protection means maintenance schedule and offers new standards providing level of safety according to GOST 12.1.004-76 that permits to eliminate electricity caused explosions in blind workings.

  MakNII statistics indicate that in recent twenty years (1978-1998) 35 electricity-caused methane-air and coal dust mixtures explosions occurred at Ukrainian coal mines that included 24 cases in blind workings. Explosions took place due to accidental coincidence in time and space of dangerous methane-air concentration and explosion hazardous electrical source.

  Given data have revealed workings explosion hazard forecasting as one of the main scientific problems arising when using electrical equipment complex in coal mines.

  Suggested approach to blind workings explosion hazard estimation is appeared to be the improved idea described in "Procedure for identification and assessment of hazards in panel using electricity at coal mines" worked out in MakNII by Professor P.F.Kovalyov as early as 1986.

  It is impossible to predict an explosion taken as a specific event, though observation of events generating this catastrophic phenomenon enables to derive relations which can be used for both current situation evaluation and forecasting in new conditions. In turn, this permits to keep required standards of working activity.

  Quantiative assessment of all means ensuring blind workings safety can be expressed depending on probability, rate and longevity of occurrence of the events defined above.

  Available codes of practice specify the probability of explosion at the facilities. Technological processes should be developed to enable that annual explosion probability at a facility does not exceed .

Thevalue means that only one explosion a year is admissible for a million of similar facilities hazardous in terms of explosibility.

  Taking into consideration current explosion probability standard, the aim to provide explosion hazard protection in a blind working is as follows: statistical information about tested blind working should be available during a time T to obtain the hazard level and if the value is below standard (explosion probability over ) to indicate organizaton and tehnical measures to be taken to assure standard hazard value completely excluding explosions with minimum running expenses.

  For this, dependences for an explosion probability in a blind working and electrical equipment condition, working environment, protection means reliability and their maintenance schedule should be determined.

  With dependencies and relations described above it will be possible to determine special measures ensuring standard level оf safety in blind workings. All these measures together with available procedures introduction will contribute to minimizing the explosions:

1.Electrical equipment with normally sparking and non-sparking parts provided with flameproof enclosures or another explosion protection (automatic switches, switchgears for machines and mehanisms, magnetic starters, mains lighting appliances, etc.).

2.Electrical equipment with only normally non-sparking pails provided with flameproof enclosures (motors with sport-circuit type rotor, flameproof bus boxes, etc.).

3.Electrical equipment without normally sparking parts, non-sparking parts thereof arc not provided with flameproofness (cables, cable accessories in normal construction, etc.).

  The hazards are:

1. Switched off short circuit.

2. Short circuit without switching off and without subsequent combustion of insulation.

3.Short circuit without switching off, with subsequent combustion of insulation.

4. One phase fault with switching off.

5. One phase fault without switching off.

6.Reduced sparking or dangerously heated contact of power circuit in enclosure with normally non-sparking parts.

7.Switchgear sparking or heating of power circuit reduced contact in enclosure with normally sparking parts.

8. Flameproofness failure of the enclosure comprising elements with non-sparking in normal conditions parts.

9. Flameproofness failure of the enclosure comprising elements with normally sparking parts.

10. Protective ground failure.

11.Methane explosible concentration.

12. Air monitors failure.

13. Methane monitors failure.

  Equations enable feasibility study for protection means maintenance schedule in blind working electrical equipment and offer new standards assuring blind working explosion hazard level according to the GOST 12.l.004-76.Р

  Similar approach to explosion and fire hazard assessment and forecasting of facilities at Russia gas industry was used by Donetsk State Tehnological University, Russia I.N.Gubkin Academy of Oil and Gas and Russia joint stock company "Gasprom" when working out branch code of practice "Procedure for assessment of explosion hazardous situations probability at gas extracting facilities power supply systems and their locations.

The document was agreed with Russia Mining Inspectorate (Gosgortechnadzor) in 1995.