Environmental conditions underground:
- A working place will be stopped if the wet bulb temperature exceeds 32.5 degrees Centigrade wet bulb and 37 degrees centigrade dry bulb or where a wet kata reading of less than 6 is recorded.
- If the wet kata is less than 8, remedial steps will be taken immediately to improve the conditions. Minimum air velocity 0.30m/s on stope working face.
- Minimum air volume for development ends 0.25m3/s/ m2 of face.
Compliance with laid down standards
- To ensure that no work takes place where the wet bulb temperature exceeds 32,5°C Shift Supervisors are to be instructed in the use of a whirling hygrometer and to be issued with a whirling hygrometer.
- Any auxiliary fan ventilating a development end or a stope without through ventilation must be installed at a position where sufficient through ventilation is available to prevent any re- circulation of air. The fan must be installed at least 3m in through ventilation.
- The shift supervisor, Miner and team leader must check the ventilation appliances as part of the re-entry examination and record the results.
- In cases where it is found that these maximum and minimum distances have not been complied with, will be stopped until the substandard ventilation appliances or conditions have been rectified.
- In areas identified as High Risk environmental conditions (WB temp Over 31.5°C Wb) the miner should also take temperatures during the shift and the Shift Supervisors should record the temperatures in his log book.
- The miner must measure the air velocity with the tape-dust method and record the result in his note book. Dist / time.
- Method to determine volume in a development end.
- Measure the velocity by using the tape-dust method in the development end on the return side of the ventilation column discharge, this velocity must be > 0.25m/s. Or determine the volume in m3/s by multiplying the velocity at the column discharge with the area of the column. Divide the volume by the face area to determine the m3/s ÷ m2 of face.
Environmental conditions surface.
- No work must be performed when temperature exceeds 37°C Db.
- Mini risk assessments should be performed before any work can be done in a confined space.
- No cutting or welding work should be done in a confined space unless adequate ventilation is supplied by means of a blower directed from a position of fresh air onto the person working inside a tank or confined space.
- When other work than cutting and weld must be performed in a confined space the supervisor must be satisfied that it is safe for workers to enter before work may commence. Compressed air may be used to flush the area if required.
- Workshops must be properly ventilated by ensuring through ventilation and if required blower fans must be used.
Ventilation pipe distances & installation of ventilation pipes.
Force ventilation system
- Any working place that will advance further than fifteen (15) meters from through ventilation will be ventilated according to the standard.
- The maximum distance of the force pipe from the face will not exceed 15m.
- Fans must be installed 3.0 metres in through ventilation to prevent any re-circulation of air.
- Sufficient air must be available for the specific size and KW rating of the fan used.
- Only galvanised iron pipes must be used at the intake side of force fans.
- Rubber gaskets to be used when vent pipes are being joined to prevent either positive or negative leaks
- When ducting is installed, plastic sealant (Seal a duct) must be used to prevent leakages.
- Bolts and nuts must be used in all the holes to ensure proper jointing.
Force-exhaust system
- When it is required to make use of a force-exhaust system a proper risk assessment should be carried out to determine the ventilation layout and fan positions prior to installation.
- The Exhaust column must be installed as soon as the end has advanced more the 20m from through ventilation. Normal force standards will apply until the end has reached a distance of 30m.
- The maximum distance of the exhaust column from face will not exceed 30m prior to blasting.
- The maximum distance of the force column from face will not exceed 15m.
- The minimum overlap distance between the exhaust column and the force column intake should not be less than 10m and not exceeding 25m.
- The force fan must be positioned only in the overlap section of the ventilation system
- The volume of air available in the overlap must be at least 1½ times the intake volume of the force fan.
Ventilation
Exhaust ventilation system
- Exhaust system may be used in situations where the underground layout makes the use of a force system impractical depending of the outcome of a risk assessment.
Haulages, reef drives and ramps
- Install a 7.5Kw or 11Kw fan with a 570mm column.
- Normal force ventilation standards will apply.
- Long development ends in excess of 200m a 22Kw fan with a 760mm ventilation pipe must be used.
Other development ends
- All incline development ends e.g. ore passes, steep raises longer than 25m.
- Install a 4 KW fan with a 410mm vent column.
- Normal force ventilation standards apply.
- The column must be installed with a Y piece at the bottom to remove any rock accumulation. The bottom side of the Y piece must be blanked off.
Travelling ways sill drives and raises longer than 20m.
- Install a 7.5 KW fan with a 570mm vent column up to the first box and the column may be changed to a 410mm from the box.
- Normal force ventilation standards apply.
Fan ventilated stopes.
- Production stopes must be designed to have through ventilation with an intake and return airway as far as reasonable possible, where through ventilation has not been established it must be ventilated with a force fan.
- Working places which will not be ventilated by through ventilation must be discussed on planning meetings and it must be designed to install a 760mm ventilation column.
- The force fan must be installed in through ventilation as per the development standards.
- The stope must be ventilated with a 22KW 760mm fan and column.
- The minimum volume at the delivery must not be less than 5 m3/s on all new stopes.
- Stopes ventilated by fans is a high health risk as fumes, dust and heat may accumulate and special percussions should be taken in these stopes.
Stopped ends
Temporally stopped ends.
- When it is required to temporarily discontinue work in an end, the end must be barricaded off as per standard.
- If it is decided to re-start a stopped end the ventilation must be restored and normal safe making re-entry procedure must be followed.
- The Environmental department must be notified when ends are stopped and re-started. Prior to restarting an end a risk assessment must be conducted. In the event of a high risk, the Environmental department must be notified prior to re-entering.
Permanent stopped ends.
- Permanent stopped ends must be sealed off as per standard. The Environmental department must be notified of these permanently stopped ends and must be barricaded off as per SOP 2 : STANDARD PROCEDURE FOR THE BARRICADING OF WORKED OUT OR ABANDONED AREAS.
Sketch indicating installation positions
Ventilation
Fans and winches installed beyond through ventilation
- All fans and winches installed beyond through ventilation may only operate when ventilated with an auxiliary fan. Switches must be clearly marked or labelled with the numbers of the fans they serve.
- The switch serving the first fan in any ventilation column must be positioned on the intake side of the column.
Circulation of ventilation/occupational survey reports
- Reports received from the Environmental Department must be signed off with relevant comments/remarks (where applicable) by the persons listed in the circulation list.
- Reports being circulated must be returned to the Manager Mining’s Office within FIVE (5) working days of it being forwarded from the Environmental Department. This is to ensure compliance with the Mine Health and Safety Act requirements in this regard.
Underground environmental controls and appliances
To ensure the effectiveness of underground environmental controls, systems and appliances, the following instructions regarding such controls and appliances shall be strictly adhered to at all times:
- Doors, regulators, seals, etc.
- All doors directly assisting or in any way affecting the ventilation of a mine shall be fitted with a self- closing device;
- Any person who opens a ventilation door, brattice or sheet shall ensure that it is closed again after passing through;
- Any ventilation door, brattice or sheet and its frame shall be taken down when it is no longer required for Ventilation purposes; and no person shall construct, alter, remove or by means of any other act interfering with anything that may have an influence on the flow of ventilating air.
