Maia

5.1.1 VENTILATION COMPULSORY QUESTIONS Question 1 Why is a mine ventilated? Answer c) a) To provide oxygen for breathing purposes and must be above 19% by volume. b) To remove heat and moisture to provide comfortable working conditions. To dilute and remove harmful gases that may be encountered during mining operations. d) To dilute and remove hazardous airborne pollutants created by various mining operations underground. Question 2 With respect to Mine Standards and Code of Practices, how must a development end be ventilated? Answer a) The workings of every part of a mine, where persons are required to travel or work, shall be properly ventilated so as to maintain safe and healthy environmental conditions. b) The ventilation air shall be of a quantity and quality so that it will remove and dilute harmful gases and airborne pollutants in the ambient air. c) Fans to be installed and operated in a position so as to prevent dangerous accumulation of flammable or noxious gases and airborne pollutants. d) Fans to be installed and operated in a position to expel and remove all harmful gases and airborne pollutants before expiry of the re-entry period fixed by the Manager. e) Fans and ventilation appliance shall be installed in such a position as to ensure, as far as possible, that it is not damaged by the blast. f) When fans are installed in the force/exhaust overlap system the fans are to be electrically interconnected to ensure that the force fan is not re-circulating when exhaust fan has tripped or stopped. g) When a development end is ventilated by means of a force exhaust system, the overlap distance of the two ventilation columns must be such that the minimum distance prevents recirculation and the maximum distance prevents static air. h) Every fan must be installed at a position indicated by, and in a manner, prescribed by the Manager or Mine Overseer. The positioning of fans require guidance from the mine’s Ventilation/Environmental control Department by means of a layout. i) When a fan is installed to operate in the return airway from a ventilating district, the fan motor must be situated in intake air. Question 3 How can heat be controlled? Answer a) Ensure that ventilation supply is directed to the working face. A Development Ends: 7 i. By means of fans and ventilation columns/ducting B Stopes: i. Installation of centre gully brattices ii. Installation of vent curtains for strike control b) Prevent recirculation of air in the development end. c) Control distribution of ventilation flow by means of doors, walls/seals, regulators, brattices. d) Keep the intake haulages and crosscuts dry as wet conditions add moisture to the air and increase the wet bulb temperature of the air. e) Prevent any accumulation of material which could cause an obstruction in the intake or return airway to a stope. Question 4 What quantity of air must be supplied on the working face of any development end? Answer Each mine will determine the quantity of air required for a development end through a “Risk Assessment” and will differ from mine to mine. An acceptable quantity of air at the working face of every development end, such as a tunnel, drive, crosscut or winze which is being advanced and at the bottom of any shaft, in the course of being sunk, must not be less than 0.15 m3/s for each square metre of the average cross-sectional area of the excavation. Question 5 What must the velocity of ventilation air be in a stope? Answer Each mine will determine the velocity of air required in a stope through a “Risk Assessment and will differ from mine to mine. An acceptable velocity of the air current along the working face of any stope must not be less than 0, 25 metre per second over the working height. Question 6 What measurements are made with the whirling hygrometer? Answer a) The dry bulb temperature (thermometer without the wet sock) measures the actual temperature of the air. (Sensible heat) b) The wet bulb temperature (thermometer with the wet sock) together with the dry bulb temperature gives the humidity of the air (percentage moisture in the air) c) The closer the two temperatures are to each other the more moisture is present in the air and the larger the difference between the two readings the dryer is the air and the cooling power is increased. Question 7 What checks must be done on the Whirling Hygrometer before proceeding underground? Answer a) Check thermometers that alcohol columns are not broken. b) The thermometers must not be cracked c) Thermometers must be checked against a standard and if more than 0.2 0C difference, discard d) Thermometers are to be set so that both can be read without moving the instrument. e) The sleeve must fit snugly around the thermometer bulb 3 mm beyond the bulb and tied with a string. f) The sleeve must be clean and new sleeves are to be boiled before fitting. g) Reservoir to be filled with distilled water and must not leak. h) Frame and handle must be mechanically sound. 8 i) Spindle must be able to rotate freely.