Underground Mine Ventilation in Ghana: 7 Checks Before Selecting a Fan

Underground mine ventilation is one of the systems that quietly determines whether a mine can operate safely, consistently and at its planned production rate. When fresh air does not reach active working areas, the result may include excessive heat, poor visibility, dust accumulation, blasting fumes, diesel emissions and avoidable interruptions to production.

For mining projects in Ghana, ventilation should not be treated as a simple equipment purchase. It is an engineered system involving air quantity, pressure, mine resistance, duct condition, contaminant sources, working depth, electrical supply and future development plans. Selecting a fan only by motor power or fan diameter can therefore lead to inadequate airflow, excessive energy consumption or unstable operation.

Ghana's Minerals and Mining (Health, Safety and Technical) Regulations, 2012, L.I. 2182 require adequate ventilation in underground areas where people work or travel. Regulation 179 addresses oxygen, harmful gases, dust, heat, humidity, diesel equipment and minimum air quantities. This makes ventilation both a compliance obligation and a fundamental part of mine planning.

1. Define the Fan's Actual Ventilation Duty

The first question is not how many kilowatts the fan should have. The first question is what the fan must do within the ventilation network.

A main fan generally moves air through the principal intake and return routes of the mine. An auxiliary fan supplies air to development headings, blind ends, stopes or other areas that are not adequately ventilated by the main circuit. A booster fan may be used within a larger network to overcome resistance in a particular branch.

The project must also identify whether the system will operate by forcing, exhausting or a combination of both. A forcing system delivers fresh air through a duct toward the working face. An exhausting system draws contaminated air away from the face. The correct arrangement depends on the source of contaminants, roadway layout, duct position, working activities and the location of personnel and equipment.

A technical comparison of the common fan duties, configurations and selection parameters is available in this guide to mine ventilation fans .

2. Specify Airflow and Pressure Instead of Motor Power Alone

A request such as “we need a 75 kW fan” is not enough for engineering selection. Two fans with the same motor rating may produce very different combinations of airflow and pressure.

Airflow describes how much air must be delivered, usually expressed in cubic metres per second or cubic metres per minute. Pressure describes the fan's ability to overcome resistance created by shafts, roadways, bends, regulators, doors, ducts, reducers, silencers and other system components.

The correct fan is selected from the required operating point: the airflow that must reach the working area and the pressure needed to move that airflow through the complete system. Motor power is then determined from the required duty, fan efficiency and operating margin.

Oversizing a motor does not automatically solve a ventilation problem. If the fan curve does not match the resistance of the system, a larger motor may only increase electricity consumption without delivering the required air quantity at the face.

3. Calculate Duct Resistance and Air Leakage

Auxiliary ventilation performance is strongly affected by the duct system. A fan may produce sufficient airflow at its outlet while only a fraction of that air reaches the end of a long duct.

Resistance increases with duct length and generally becomes more significant when the duct diameter is small. Sharp bends, damaged duct sections, poor joints, sudden reductions and partially collapsed flexible ducts can further restrict airflow. Leakage at every connection can also reduce the final air quantity delivered to the working face.

For long headings, the selection process should therefore include:

• Total duct length
• Internal duct diameter
• Duct material and condition
• Number and angle of bends
• Reducers, branches and fittings
• Expected leakage rate
• Required airflow at the end of the duct

Projects involving development headings or blind workings should evaluate the fan and duct as one system. Guidance on pressure, duct length and local ventilation applications can be found on the page for auxiliary ventilation fans .

4. Include Diesel Equipment, Blasting Fumes and Dust Sources

The required airflow must reflect what is happening underground, not only the physical size of the roadway. Diesel loaders, trucks, drilling equipment, blasting operations, welding, crushing and material handling can all add heat, fumes or airborne contaminants to the mine atmosphere.

The United States National Institute for Occupational Safety and Health notes that diesel engines used in underground mines contribute aerosols and gases including carbon monoxide, carbon dioxide, nitrogen oxides, sulphur dioxide and hydrocarbons. Its guidance recommends an integrated approach involving ventilation, equipment maintenance, exhaust controls, fuel quality and exposure monitoring.

Ghana's Regulation 179 also specifies an airflow requirement related to the installed power of diesel equipment. Mine planners should therefore document the number, type, engine power and expected operating schedule of underground diesel machines before finalising the ventilation duty.

Blasting cycles must also be considered. The ventilation system should be capable of clearing fumes within the mine's approved re-entry period, while preventing contaminated air from recirculating into occupied areas.

5. Account for Heat and Humidity

Heat becomes more difficult to manage as mines deepen, equipment fleets grow and haulage distances increase. Motors, diesel engines, electrical installations, broken rock and groundwater can all add heat or moisture to the underground environment.

High air temperature combined with high relative humidity can reduce workers' ability to lose body heat. Increasing airflow may improve conditions, but the effectiveness depends on air temperature, humidity, heat sources and the overall mine layout.

Regulation 179 requires ventilation to maintain working conditions free from dangerous temperatures and high relative humidity. A ventilation study should therefore consider more than gas dilution. It should also examine seasonal conditions, rock temperature, groundwater, equipment heat loads and whether cooling may eventually be required.

6. Match the Fan to the Available Electrical Supply and Control Strategy

Before ordering a fan, the project should confirm the actual electrical conditions at the installation point. Important details include voltage, frequency, phase, available transformer capacity, allowable starting current and cable length.

Starting a large fan directly may impose a high current demand on the mine's electrical system. Depending on the project, the design may use a soft starter, variable-frequency drive or another starting and control arrangement.

A variable-frequency drive can provide useful airflow adjustment where the required duty changes during mine development. However, the motor, insulation, cooling arrangement, control system and fan operating range must all be compatible with variable-speed operation.

The project should also determine whether standby capacity is required. For critical main ventilation duties, reliability planning may involve two fans, a duty-and-standby arrangement, independent power considerations or a design that allows maintenance without leaving the mine unventilated.

7. Review the Fan Curve, Operating Range and Installation Details

A quotation should not be accepted solely because the stated maximum airflow appears sufficient. The supplier should provide a performance curve showing airflow, pressure, efficiency and power across the fan's operating range.

The selected duty point should lie within a stable and efficient part of the curve. Engineers should also check whether the motor can operate safely across the expected range and whether the fan has enough margin for reasonable future changes in mine resistance.

Installation details are equally important. Poor transitions, restricted inlets, unsuitable foundations, sharp outlet bends or recirculation between intake and discharge openings can reduce actual performance. For underground auxiliary fans, duct connection, suspension, clearance, noise control and access for inspection should be considered before installation.

The project should request information on balancing, vibration, bearing arrangement, lubrication, inspection intervals, spare parts and performance testing. A well-selected fan can still perform poorly if it is installed incorrectly or allowed to operate with damaged blades, blocked guards or deteriorated ducting.

Information to Prepare Before Requesting Fan Selection

A mine or engineering contractor can obtain a more accurate recommendation by preparing the following information:

• Required airflow at the fan and at the working area
• Required static or total pressure
• Mine type and ventilation duty
• Main, booster or auxiliary fan requirement
• Forcing or exhausting arrangement
• Shaft, roadway or duct dimensions
• Duct diameter, length, fittings and expected leakage
• Diesel equipment quantities and engine power
• Voltage, frequency and starting method
• Installation location and available space
• Temperature, humidity, altitude and dust conditions
• Any explosion-protection or certification requirement
• Expected future expansion of the mine

Ventilation Is a System, Not Just a Fan

The most important lesson is that mine ventilation performance cannot be guaranteed by choosing the largest available fan. A successful system requires the fan, airways, ducts, controls, doors, regulators and monitoring arrangements to work together.

For Ghanaian mining projects, the design should begin with the applicable legal requirements and a realistic assessment of the underground duty. Airflow and pressure calculations should then be supported by fan curves, duct-resistance analysis, equipment data and a clear installation plan.

This approach helps a mine avoid both under-ventilation and unnecessary oversizing. It also creates a stronger basis for safety, energy management, future expansion and consistent underground production.

This article provides general technical information and does not replace a site-specific ventilation survey or engineering design. Final ventilation systems should be reviewed by qualified mine ventilation professionals and comply with applicable Ghanaian regulations.

Contributor: Shandong Bofeng Fan Co., Ltd., a China-based manufacturer of mine ventilation and industrial fan equipment.

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