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 2 : Guidance Note for the prevention of flammable gas and coaldust explosions in collieries

4. Preventing the Accumulation of an Explosive Concentration of Flammable Gas
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4.1. Ventilation system

 

4.1.1.Primary ventilation

The purpose of primary (general section) ventilation is to ensure that ventilation systems are in place to ensure that sufficient air reaches the last through road/longwall or shortwall face to prevent the possibility of secondary ventilation systems recirculating.

 

To achieve this objective, the following is required:

4.1.1.1.Mechanical miner sections
4.1.1.1.1.The average air velocity in the last through road should be at least 1 m/s, with a minimum velocity not less than 0,6 m/s.
4.1.1.1.2.Relative to the heading where the machine is cutting, a minimum velocity of 1 m/s should be maintained in the split that is upstream with regard to the ventilation flow.
4.1.1.1.3.The auxiliary force fan should not recirculate and should be so positioned to discharge fresh air directly on to the working face.
4.1.1.1.4.Sufficient air flow shall be provided to ensure compliance with specified gas and dust concentrations.

 

4.1.1.2.Conventional drill and blast sections
4.1.1.2.1.The average air velocity in the last through road, measured in each split, should be at least 0,6 m/s.
4.1.1.2.2.The auxiliary force fan should not recirculate and should be so positioned to discharge fresh air directly on to the working face.
4.1.1.2.3.Sufficient air flow shall be provided to ensure compliance with specified gas and dust concentrations.
4.1.1.3. Longwall and shortwall sections
4.1.1.3.1. The average air velocity measured along the face should be at least 1 m/s.
4.1.1.3.2.Sufficient air flow shall be provided to ensure compliance with specified gas and dust concentrations.
4.1.2. Secondary ventilation

Secondary ventilation may be defined as the air moving mechanisms (auxiliary fans, spray fans and dust scrubber fans) being utilised in a coal winning heading or face. It is in this working place where all three ingredients required for an explosion (fuel, source of ignition and oxygen) may be present, and hence it is this part of the section into which effective ventilation should be directed.

Of the three ingredients only one is required to be removed from the equation to prevent an explosion from occurring. This is achieved by efficient ventilation systems.

To satisfy the objectives mentioned above, the secondary ventilation system in mechanical miner sections should aim:

4.1.2.1 At diluting the flammable gas and the dust generated to acceptable levels.
4.1.2.2 At rendering the flammable gas and dust generated harmless and to remove them in a controlled manner.
4.1.2.3 At capturing the dust and convey it to a cleaning mechanism.

 

The system which is employed should ensure that acceptable levels (dust and flammable gas) are maintained in the heading at all times.

 

On board force system e.g. spray fans and on board or off board dust scrubber units should be in operation prior to the commencement of any mining with a mechanical miner.

 

The secondary ventilation auxiliary fan e.g. force or exhaust fans should be in place prior to the commencement of any mining. These systems should be put into operation once the heading has advanced a distance of 12 m from the last through road.

 

Mining should immediately cease should any of the above requirements not be complied with.

 

Dust scrubber units are to be designed to ensure a minimum airflow of 0.4 m/s past the operator’s position. Maximum recirculation factor of 50% is permitted for on board scrubbers.

 

NB: It is imperative to ensure that delivered fresh air from the last through road scrubs the working face area.

 

All non-coal winning headings in an advancing section should be positively ventilated so as to ensure that flammable gas does not accumulate.