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Key to Schematic Diagram

Cost of compressed air wastage (Back To Top)

The major portion of the cost of producing and transmitting compressed air is the cost of the electrical power used to drive the compressors. Other costs, such as labour, materials and workshop charges relating to the maintenance and supervision of the compressors and mains are small by comparison and are usually less than 10% of the total.
Based on the power cost of R0.12/kWh for mines consumption (R1050 per annum for a kilowatt used continuously), it cost approximately R35 per hour to produce 1.0 Kg/sec or 1.0 m3/sec of free air (Environmental Engineering in South African Mines).
A mine consuming 1,6 million m3/day (18.5 m3/sec) compressed air could waste up to 800,000 m3/day (9.25 m3/sec), which means wastage of R2.8 million per annum.

Cost of service water (Back To Top)

The major portion of the cost of producing and transmitting chilled service water is the cost of the electrical power used in the pumping system and the refrigeration system. Other costs, such as labour, materials and workshop charges relating to the maintenance and supervision of the pumping stations, refrigeration plant, water treatment plants and the piping reticulation system are small by comparison.
Based on the power cost of R0.12/kWh for mines consumption (R1050 per annum for a kilowatt used continuously), it cost approximately R1630 to chill and pump out, from 1800m deep shaft, 1.0 lit/sec of chilled service water per month.
A mine utilizing 10 million litres/day (116 lit/sec in average) chilled water, waste up to 2.0 million litres/day (58 lit/sec in average), which means wastage of up to R1.8 million per annum.

Automatic isolation of compressed air and water lines (Back To Top)

A practical solution to overcome the compressed air & water wastage is the automatic isolation of the compressed air & water line by means of timer-activated valves.

• The N.G.D timer-activated valve is a natural normally open type valve, to ensure no lose of   production as a result of valve failure occurrences.
• The valve piston is the valve's actuator and the line pressure actuates the valve through a solenoid valve.
• A 7-day programmable type timer switch controls the automatic opening and closing of the valve.
• The solenoid valve and the timer switch are housed in an intrinsically safe box, mounted on top of the valve and inaccessible to unauthorized personnel.
• The N.G.D timer-activated valve is the simplest and the most reliable product in the market, mainly because: -
    - It has only one moving part, which is the valve's piston.
    - It does not have an external actuator.
    - The valve is made of stainless steel alloys.
    - The valve is a natural fail-to-open type valve.

Utilizing cooling water as service water (Back To Top)

The N.G.D flow and bleed control enable the practical and simple utilization of chilled water, used in air cooling plants, as service water for mining purposes. The valves are actuated and controlled by the line fluid pressure and do not necessitate any instrumentation or computerized control.
A mine utilizing 10 million litres/day (116 lit/sec in average) chilled water, waste up to 3.0 million litres/day (77 lit/sec in average), which means wastage of up to R2.7 million per annum.