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Safety Alert

Flammable dust explosions

Circulation

Safety Circular

On 6th February 2002 a coal dust explosion in the absence of firedamp occurred in a 132m long drivage being advanced by boring and firing in a Polish mine. All 10 persons in the heading were killed. 2 persons in the vicinity of stonedust barriers sited outside the heading were burned but survived. The stonedust barriers operated and stopped the explosion: 35 other persons in the adjacent longwall district were uninjured. The explosion was of low intensity and investigators concluded that water trough barriers were unlikely to have been activated.

Investigation showed that shots were being fired to make room to set the legs of the arch, using explosives equivalent to the UK P5 Group. It appears that:

  1. The shotfirer was also trying to dispose of unwanted explosives and detonators by firing them other than in a shothole (which would be contrary to Regulation 30(2) of the Coal and Other Safety Lamp Mines (Explosives) Regulations 1993 in the UK). This action raised a cloud of coal dust and ignited it.
  2. Not all persons were withdrawn from the heading before firing (a requirement under Polish law)
  3. At some places in the district the mine dust contained only 5% of incombustible matter. Polish law requires +80% within 200m of the face.

This explosion came 15 years after the previous coal dust explosion, and complacency was thought to be a factor. General stonedusting to the required standard and the correct siting of barriers erected to the approved specification have prevented coal dust explosions in the UK since the 1934 Gresford colliery disaster in which 265 men were killed. Only vigorous compliance with stonedusting standards will maintain this record. In the last year 27 samples of roadway dust taken by HM Inspectors of Mines were found to have less than the required percentage of incombustible matter. (These areas were stonedusted and resampled to confirm compliance)

Managers should ensure that their stonedusting arrangements are adequate to maintain at all times the percentage of incombustible matter required by the Regulations. Details of the incident should be brought to the attention of shotfirers.

Yours sincerely

S P Wing
HM Principal District Inspector of Mines
2012-11-27