A mining ventilation project in Kalimantan, Indonesia, specified 200 explosion-proof axial fans carrying CNEX Ex d IIC T4 certification, the order confirmed in January 2026 for underground applications.
Underground mine ventilation is a life-safety system first and an air-moving job second, because the airstream can carry methane and any spark or hot surface in the equipment is a potential ignition source. Flameproof 'Ex d' construction answers that by enclosing live parts in a housing rated for the site's gas group and temperature class, containing any internal explosion so it cannot ignite the surrounding atmosphere. The T4 class, capping surface temperature at 135°C, sits comfortably below methane's auto-ignition point, which is the core safety argument and the gate to deployment rather than a bonus feature.
Why Underground Mines Need Explosion Protection
Underground mining air can carry flammable gases such as methane, and any spark or hot surface in the ventilation equipment is a potential ignition source. Explosion-protected construction eliminates that risk by enclosing live parts in a flameproof "Ex d" enclosure rated for the gas group and temperature class of the site. For coal and sulphide environments, Group IIC and a controlled surface temperature are the relevant limits that define how the equipment may be used safely.
Axial fans suit mine auxiliary ventilation because they move large volumes at moderate pressure through ducting, and their inline form fits narrow headings where space is tight. The 200-unit quantity reflects a distributed ventilation layout rather than a few large main fans, which improves fault tolerance: one unit's failure degrades a section rather than collapsing the whole mine's air supply.
Safety certification is not a sales feature here; it is a contractual and legal prerequisite. Mines cannot commission equipment that lacks the correct hazardous-area certification, so the CNEX Ex d IIC T4 mark is the gate to deployment, not a bonus.
Specified Fan and Protection Levels
The selected fans pair an axial impeller with a flameproof motor and certified termination. Key parameters are listed below.
| Parameter | Specified value | Reason |
|---|---|---|
| Protection | Ex d IIC T4 | Methane-capable |
| Airflow | Up to 15,000 m³/h | Heading ventilation |
| Pressure | Up to 1,200 Pa | Duct resistance |
| Quantity | 200 units | Distributed layout |
The T4 temperature class caps the maximum surface temperature at 135°C, comfortably below the auto-ignition point of methane, which is the core safety argument for the certification. The flameproof enclosure contains any internal explosion and prevents it from igniting the surrounding atmosphere, which is the defining function of Ex d construction.
Duct resistance grows with length and bends, so the 1,200 Pa rating must include the actual installation layout, not a free-air figure. Under-specifying pressure is a common error that leaves headings under-ventilated exactly when gas risk is highest.
Checklist for Mine Ventilation Fans
Specifiers should verify these points before releasing an order for hazardous-duty fans:
- Match the zone: Confirm gas group and temperature class against the mine's hazard study, because a wrong class invalidates the protection.
- Verify certification: CNEX Ex d IIC T4 must cover the exact motor and termination, not just the impeller or a similar model.
- Size on duct loss: Include bends and length in the pressure duty, not just free-air performance, to guarantee flow at the face.
- Plan redundancy: Distributed fans mean one failure degrades, not stops, ventilation, so layout matters as much as the unit.
- Spares strategy: Keep flameproof motor spares to avoid long stoppages that would idle an entire section.
- Document compliance: Retain certificates for the mine's safety authority and for future re-ordering accuracy.
Significance for the Operation
Keruite manufactures axial fans including the T35-11 series at its 80,000 m² Dezhou facility, and supplying 200 certified explosion-proof units demonstrates capability in hazardous-duty ventilation. With 30+ years of fan manufacturing and ISO 9001:2015 certification, the company supports mining projects where safety certification is a contractual prerequisite.
For mine engineers, the takeaway is that certified protection and correct duty selection are both non-negotiable underground, and a supplier must deliver both. the company backs the selection with in-house testing so the quoted airflow and pressure are measured, not assumed.
For mine engineers, certified protection and correct duty selection are both non-negotiable, and the certificate must cover the exact motor and termination, not just a similar model, or the protection is void. Duct resistance grows with length and bends, so the 1,200 Pa rating must include the real layout, not a free-air figure, and distributed fans mean one failure degrades a section rather than collapsing the whole air supply. With 30+ years of fan manufacturing and ISO 9001:2015 certification at the 80,000 m² Dezhou facility, the company supports mining projects where safety certification is a contractual prerequisite and in-house testing confirms the quoted airflow.
Engineers in Dezhou respond to selection enquiries within 24 hours, and the factory ships most standard fans from its 80,000 m² site within agreed lead times.