Replacing an Undersized Jet Fan with a High-Pressure Ventilation Solution for Long-Distance Air Delivery

Project Overview

A coal mining customer was experiencing insufficient ventilation in an underground mine tunnel.

The existing system used a conventional jet fan. However, because fresh air needed to travel a considerable distance through the tunnel, the original fan could not generate enough pressure to maintain the required airflow at the far end of the ventilation route.

Instead of simply replacing the old fan with another unit of similar specification, we recalculated the ventilation requirements based on the mine tunnel dimensions, airflow demand and air delivery distance.

The final solution combined a Ø500 mm contra-rotating axial fan as the main ventilation fan with an additional Ø315 mm jet fan installed further inside the tunnel to support long-distance air delivery.

Challenge

The problem was not that the original jet fan could not move air.

The problem was that it could not move enough air over the required distance.

As air travels further through an underground ventilation route, the fan must overcome the resistance of the system. The existing conventional jet fan did not provide sufficient pressure, resulting in inadequate airflow further inside the mine.

At the same time, installation space was limited.

The customer therefore needed a solution that could provide:

· Higher pressure for long-distance ventilation

· Sufficient airflow for the mine tunnel

· Compact dimensions suitable for restricted underground space

· Additional airflow support deeper inside the tunnel

· Equipment suitable for the mining environment

Our Solution

1. Recalculating the Fan Based on the Mine Tunnel

Rather than selecting the replacement fan according to the specifications of the old unit, we started again from the actual application.

We reviewed the tunnel dimensions, available installation space, required airflow and long air-delivery distance and recalculated the fan duty point.

Based on these conditions, we selected a Ø500 mm contra-rotating axial fan as the main ventilation unit.

Main Contra-Rotating Fan

Airflow: 10,600 CFM
Total Pressure: 2,695 Pa
Motor Power: 7.5 kW × 2
Impeller Diameter: Ø500 mm
Configuration: Two-stage contra-rotating axial fan

The two-stage contra-rotating design was selected specifically to provide substantially higher pressure while maintaining the required airflow.

Its 500 mm compact diameter also allowed the fan to fit within the restricted space available in the mine tunnel.

2. Adding a Jet Fan for Airflow Relay

One high-pressure fan alone was not the entire solution.

Because of the long ventilation route, we added a second Ø315 mm jet fan further inside the tunnel.

Auxiliary Jet Fan

Airflow: 4,500 CMH
Thrust: 15 N
Motor Power: 0.75 kW
Fan Diameter: Ø315 mm
Motor: Explosion-Proof Motor

The auxiliary jet fan works as an airflow relay point inside the tunnel.

Rather than relying entirely on the main fan to push air through the complete ventilation route, the Ø315 mm jet fan helps maintain air movement further inside the mine.

Together, the two fans form a coordinated ventilation solution:

Main contra-rotating fan → High-pressure primary air supply

Auxiliary jet fan → Airflow support deeper inside the tunnel

Solution & Results

After replacing the original conventional jet fan with the new ventilation arrangement, the customer achieved more effective long-distance air delivery through the mine tunnel.

The Ø500 mm contra-rotating fan provides 10,600 CFM at 2,695 Pa total pressure, addressing the pressure limitation of the previous ventilation setup.

Further inside the tunnel, the Ø315 mm jet fan provides additional airflow support, helping maintain air movement along the extended ventilation route.

Most importantly, the solution was not based on simply installing a larger fan.

It was designed around the actual tunnel dimensions, system resistance, ventilation distance and restricted installation space.

Key Results

Higher Pressure for Long-Distance Ventilation
The 2,695 Pa total-pressure contra-rotating fan addresses the insufficient pressure of the previous jet fan system.

10,600 CFM Main Airflow
The main fan provides the airflow required for the mine ventilation route.

Compact Ø500 mm Design
High airflow and pressure capability were achieved while keeping the fan diameter suitable for the restricted tunnel space.

Airflow Relay Inside the Tunnel
A Ø315 mm jet fan was positioned further inside the tunnel to support air movement over the extended ventilation distance.

Explosion-Proof Motor
The auxiliary jet fan was matched with an explosion-proof motor for the mining application.

Application-Based Fan Selection
Instead of replacing the old fan with a similar model, the new solution was recalculated according to the actual mine tunnel and ventilation requirements.

We Didn't Just Replace the Old Fan. We Redesigned the Airflow.

When an existing ventilation system cannot deliver enough air to where it is actually needed, installing a larger fan is not always the right answer.

You first need to understand where the pressure is being lost, how far the air needs to travel, and how much installation space is available.

For this coal mining project, we combined a high-pressure Ø500 mm contra-rotating axial fan with a strategically positioned Ø315 mm jet fan to improve long-distance air delivery within the limitations of the existing tunnel.

The result was not simply a fan replacement.

It was a ventilation solution redesigned around the mine itself.