Explosion-Protected Equipment for Coal Mines

The Mine Health and Safety Act (MHSA) in South Africa’s context obligates mining companies to apply Ex Techniques to mitigate their operations from the risk of methane-gas-induced explosions. Aim Equipment has the expertise to help mining companies make informed selections in their respective requirements for Explosion Protected Equipment.

There is an increased demand for coal globally, and as expected, leading coal miners are ramping up production to capitalize on the favourable market. Nonetheless, the challenge is that, usually, with increased activity, there is a simultaneous rise in safety risks.

Explosion Regulations (Ex Regulations)

One of the inherent safety risks, typical in coal mines, is explosions due to methane gas leaks. Methane gas forms in coal mines through a natural process called coalification. As ancient plant matter decays and undergoes pressure and heat over millions of years, it transforms into coal. During this process, methane gas gets trapped within the coal seams.

When coal is mined and exposed to the air, the trapped methane can be released, posing a potential hazard if not properly managed. Consequently, cognisant of this, the Mine Health and Safe Act (MHSA) covers Explosion Regulations (Ex Regulations). Ex Regulations obligate mining companies to adopt suitable Ex Techniques to mitigate the risks.

Carl Pretorius, the General Manager of Aim Equipment, calls on mining companies to be very conversant with the scope of Ex Regulations for them to apply appropriate Ex Techniques relevant to the identified risks. “The Ex Regulations stipulate that the use of Ex Techniques is not merely a recommendation but a mandatory requirement in all Fiery Mines.”

The Scope of Ex Regulations

Fiery Mines refer to those where the coal seam or seams worked on emitting a significant amount of methane gas. However, the Ex Regulations have a wide scope. Ex Regulations not only apply to fiery mines but also an environment that carries the risk of combustion if sufficient energy, such as a spark or high surface temperature, is introduced.

Ex Techniques

There are several categories of techniques for distinct areas in coal mines. Thus, considering this, Pretorius points out that the selection of Ex Techniques must be based on informed choices.

1. Categories

Ex Protected has several categories but is not limited to:

• Flameproof (Ex d)
• Increased safety (Ex e)
• Non-sparking (Ex n)
• Intrinsic safety (Ex i)
• Pressurization (Ex p)
• Encapsulation (Ex m)
• Sand filling (Ex q)
• Double Protection (combination of different categories)

2. Distinct areas 

Usually, for a coal mine, which falls under the category of a fiery mine, two areas apply – Safe Area (no methane gas expected) and hazardous location (consisting of zone 0 – high exposure and zone 1 – Normally expected gas concentrations)

• Safe area

According to MHSA, any location beyond 180 meters from the mining face is classified as a ‘Safe Area.’ However, all equipment used in this area must still adhere to the surface temperature limit of 200 degrees Celsius, as specified in SANS 868-4 (Non-hazardous locations in coal mines), because of the risk of igniting coal or coal dust in coal mines).

• Hazardous location

On the other hand, any area within 180 meters (including return airways) from the mining face is designated a ‘Hazardous location.’ In this area, all equipment must be safeguarded using the appropriate Ex Technique, depending on the exposure frequency.

Informed Choices, Suitable Product

Considering the escalating risks in fiery mines, prevalent in distinct areas, suitable Ex Protected Equipment should be used unfailingly.

Understandably, there are many suppliers of Ex Protected Equipment. And naturally, to a casual observer, seemingly, there is little differentiation among the products. But there is.

And so, Pretorius states that decisions should be based on informed product selection, as the equipment is used in hazardous environments. “Equipment intended for use in explosive atmospheres should typically fulfil specific requirements or ‘tick the boxes‘ in various areas.”

Particularly, the following are some of the key features that such Ex Protected equipment should possess:

• Explosion Protection:The equipment should have appropriate measures firmly in place to prevent the ignition of explosive atmospheres, such as sealing against the ingress of flammable gases or dust, and the ability to withstand potential external explosions without causing an internal explosion.

• Robust Construction:The equipment should be built to withstand the harsh and challenging conditions typically encountered in mining environments, including resistance to impact, vibration, moisture, and dust.

• Temperature Ratings:The equipment should be designed and rated to operate within specific temperature limits, ensuring that surface temperatures do not exceed the permissible levels for the relevant hazardous area classification.

• Gas Group Compatibility: A fiery mine is classified as a result of a possible release of methane gas, therefore categorized as group I as this covers the risk of methane gas. The equipment installed in the defined hazardous location must cover Group I requirements as a minimum. For commercial purposes, some equipment manufacturers design equipment to comply with both Group I (mining) group II (surface gas) and Group III (surface combustible dust) explosive atmospheres.

• Electrical Protection:Electrical components of the equipment should be designed to prevent the occurrence of sparks or arcs that could potentially ignite the surrounding atmosphere. This may include the use of flameproof (containment of spark), intrinsically safe circuits (energy limitation), increased safety measures (limitation of spark), or other appropriate techniques.

• Compliance with Standards: The equipment should comply with relevant standards and regulations specific to mining and explosive atmospheres, such as SANS 868 (Explosion-protected diesel engine systems), SANS 60079-1 (flameproof protection), and SANS 60079-11 (intrinsic safety), which outline the requirements for Ex-protected equipment.

• Proper Certification: The equipment should be certified by an Approved testing laboratory (ATL) to ensure that it meets the necessary safety standards and regulations for use in explosive atmospheres. Guidelines for the certification process are outlined in the readily available ARP0108 issued by the Department of Minerals Resources and Energy department (DMRE).

Efficient and Safe Coal Mining

Generally, as they aim at delivering high yields, Aim Equipment stresses that mining companies must not lose sight of mitigating the escalated high risks that they face, mainly methane-gas-induced explosions. “The importance of selecting the right Ex-Protected Equipment does not have to be overemphasized. Wrong decisions are a high risk in themselves. Informed decisions enable efficient and safe coal mining.”