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Mine Health and Safety Act, 1996 (Act No. 29 of 1996)

Notices

Guideline for the Compilation of a Mandatory Code of Practice for the Prevention of Flammable Gas and Coal Dust Explosions in Collieries

Annexures

Annexure 4 : Design, installation, maintenance and monitoring of barriers to prevent the propagation of coal dust explosions (This annexure must be complied with and incorporated in the COP)

2. Water Barriers

 

2.1. The use of water barriers

 

2.1.1. The use of concentrated water barriers is an alternative to employing stone dust barriers or bagged stone dust barriers.
2.1.2. The minimum quantity of water must be 200 l/m2 of cross sectional roadway area or 5 l/m2 of roadway volume over the length of the barrier, whichever is the largest. The distance between the first and last row of troughs must be at least 20m but not more than 40m.
2.1.3. All troughs must be fitted with lids to prevent ingress of foreign material and minimise evaporation. Troughs and lids must be constructed from a material of such composition as to be readily shattered by the action of the pressure wave. The minimum quantity of water for large troughs (90 litres capacity) must be 80 litres and for small troughs (45 litres capacity) 40 litres. An indication must be provided to show the minimum water level in the trough.
2.1.4. Troughs should be placed with the longer sides of the trough at the right angles to the line of the roadway. Exceptionally, one trough in a group may be placed longitudinally. The design of troughs further requires that:
2.1.4.1. The troughs remain serviceable for as long as possible under the effect of heat,
2.1.4.2. The water contained in the troughs is released and dispersed under the effects of the dynamic blast pressure of the explosion;
2.1.4.3. The trough material is flame resistant to a defined flame application. It must not continue to burn independently after removal of the flame;
2.1.4.4. The material must not allow any static electrical charge, capable of igniting mixtures of air and flammable gas, or firing electrical detonators, to build up or be discharged from the surface of the trough; and
2.1.4.5. The composition of the material in normal use will not have characteristics detrimental to health.
2.1.5. Troughs may be suspended from the roadway support or mounted on equipment within the roadway. The sides of any troughs inside or mounted on cross-members of frames must not have more than 5cm of their height covered by such cross-members.

Where troughs are mounted on equipment, a form of retaining lip must be provided which must be not less than 3cm.

2.1.6. With reference to the sketch below, the following is applicable when troughs are installed in a single layer:
2.1.6.1. For roadways, up to 10 m2, X+Y+Z must cover at least 35% of W.
2.1.6.2. For roadways up to 15 m2, X+Y+Z must cover at least 50% of W.
2.1.6.3. For roadways in excess of 15 m2 X+Y+Z must cover at least 65% of W.
2.1.6.4. Distance of A or B or C or D must not exceed 1,2m.
2.1.6.5. The total distance of A+B+C+D etc must not exceed 1,5m.
2.1.6.6. Distance V1 must not be less than 0,8 m and must not exceed 2,6m.
2.1.6.7. Distance V2 should not exceed 1,2m. Whenever this distance is exceeded, additional troughs must be placed above and they may be more than 2,6m above floor level, but there should not be more than 1,2m between the base of layers of troughs.
2.1.7. Where more than one layer of troughs is required the following will apply:
2.1.7.1. When troughs are arranged in rows less than 1,2m apart, measured along the roadway, troughs in one row must not conceal troughs in the adjacent row from the blast effect.
2.1.7.2. No trough must have any part sheltered from the effect of a blast wave by a rigid installation in the roadway.
2.1.7.3. In circumstances where the dispersion of water over the cross-sectional area of the roadway might be obstructed by equipment, additional troughs must be installed to improve distribution.

 

2.2. Siting of water barriers

 

2.2.1. Conveyor belt roads

A barrier must be provided in every production section in the road carrying a conveyor belt. The barrier must not be sited closer than 120m and not further than 360m from the last through road.

2.2.2. Single Entries

Every single entry must be protected with a barrier, sited as above.

2.2.3. Return Airways

Unless the incombustible matter content by mass of the dust is maintained at a minimum of 80% up to 1 000m from the face, a barrier must be provided in each road carrying return air.

The barrier must be installed not closer than 120m and not more than 360m from the last through road.