Industrial Axial Fans in South Africa

South Africa has the deepest mines in the world, a large steel, cement, and chemical industry, and a power system under strain. Those three facts shape fan selection. Deep-level mining puts auxiliary and booster fans at the centre of safety and productivity, the high plateau where most industry sits thins the air, and unreliable grid supply makes starting behaviour and speed control matter. This page covers how each changes what you should specify.

Highveld Altitude and Air Density

Johannesburg and much of the industrial heartland sit at about 1,750 m. At that altitude and a 30 °C summer day, dry-air density is about 0.94 kg/m³, or 78% of the standard 1.204 kg/m³. A fan rated at 500 Pa at standard density develops only about 391 Pa at the same speed, and ventilation airflow for heat removal is well above a standard-air calculation.

Example. A processing building gains 500 kW of sensible heat, and you allow an 8 K rise. At 0.942 kg/m³ the airflow needed is 500 ÷ (0.942 × 1.006 × 8) = 66.0 m³/s, or about 237,400 m³/h, roughly 28% more than a standard-air calculation. That suits two fans of about 118,700 m³/h each, both within our range. Selecting from a sea-level catalogue would leave the building under-ventilated. See how to size an axial fan and fan laws and air density.

Deep-Level Mining

South African deep-level mines rely on auxiliary and booster fans to push air through long ducts to working faces. The evidence from real installations is sobering. An evaluation of underground auxiliary fan systems in four South African deep-level gold mines found an average fan efficiency of 38% across 33 fans and a total system efficiency of only 5% across six systems, with fans operating far from their design points. The same research reports that fan assemblage components can consume 40 to 80% of the energy of primary ventilation fans. The lesson is that the system around the fan often matters more than the fan itself.

Practical measures include selecting for the duct’s real resistance and leakage, checking the operating point at the longest duct length, matching fans in series and parallel, and using blade-pitch adjustment or speed control so the fan can follow changing conditions. Read our page on underground mining and the guide to reading an axial fan curve. We cover auxiliary and booster duties. We do not build primary main fans, which are far larger, and we do not manufacture gassy-mine Group I fans.

Load-Shedding and Grid Reliability

Power interruptions and restarts are a fact of life. For fans this means frequent starts and stops, and voltage dips on restart. Soft starting and variable-speed drives reduce inrush current and mechanical stress, and a drive can bring a fan back to its set speed gradually after a supply returns. Plan restart sequences so that many fans do not start together, and check that motors and drives cope with repeated starts. Where ventilation is safety-critical, as underground, arrange standby power and confirm what runs on it.

Speed Control and Energy Cost

Electricity tariffs have risen sharply, so fan energy is a significant cost. Because power falls with the cube of speed, following the load with speed control saves a great deal. See adjustable pitch versus VFD control.

Steel, Cement, and Metals

Steel plants, foundries, and cement works need heat-removal ventilation, electrical room supply, and equipment cooling. Furnace, kiln, and dedusting fans are centrifugal and outside our range. See steel plants, cement plants, and foundries and metal casting.

Power Generation

Power stations need turbine hall and boiler house ventilation, with redundancy. Boiler draught fans and large air-cooled condenser fans are outside our range. See power plants.

Cold Winter Mornings

At altitude the air is thin, but on a cold winter morning it is denser than in summer. A fan started in cold air absorbs more power than in the heat, so size the motor for the coldest, densest condition. Frost and cold also matter for outdoor equipment.

Inspection Routine for Underground Fans

Underground fans work in dust, moisture, and blasting vibration, with restricted access, so a simple routine catches most problems. Check duct joints and hangers for leaks and sags every shift. Read vibration and motor current at each fan monthly and record them, since a change at the same airflow warns of deposits, damage, or a change in the duct system. Inspect blades for erosion and cracks, clean deposits, and check guard and inlet condition at planned shutdowns. Test standby fans and power changeover regularly. Review the fan’s operating point whenever the duct lengthens, because the safe operating point at the start of a heading may sit close to stall at the end. See axial fan vibration, balancing and maintenance.

Where Our Range Fits

NextAir Systems manufactures axial fans with impeller diameters up to 1,600 mm, static pressure up to 2,400 Pa, and air volume up to 185,000 m³/h. That covers building ventilation, equipment cooling, small cooling systems, and auxiliary and booster mine ventilation. Primary main fans, furnace and kiln fans, and very large cooling fans are outside our range.

What to Specify

1. Site altitude and seasonal temperature range.
2. Heat load and allowed rise, or air changes.
3. For mines: fan role, duct size, length, and leakage.
4. Restart behaviour and supply reliability.
5. Control approach and redundancy.
6. Hazardous-area or gassy-mine requirements.

Get a Fan Selection for Your South African Site

Send your altitude, duty, and application, and we’ll size the fans and check the operating point. Contact us for a free quote.

Related NextAir Solutions in South Africa

Facilities in South Africa working with Axial Fans often need more than one of these covered — see our guidance for the same region across our other product lines:

• Dehumidifiers in South Africa
• VOC Adsorbers in South Africa
• Odor Control Adsorbers in South Africa
• Air Purification Systems in South Africa

Frequently Asked Questions