Entrained air can lead to continuous foaming, which can lead to erratic system performance and cavitation-like damage in pumps and gear surfaces. That’s why premium gear oil formulations are essential for mining gear oils because they include advanced air release additives. This is especially important in mining applications where gear oil is typically thick, viscous and vulnerable to air release issues.
In this guide, we’ll talk about why air release matters, how gear oil foam forms and the tell-tale signs of air-related problems in mining gear oils.
Why air release matters
Gearbox reliability is essential for ensuring projects are completed on time, within budget and without costly damage, causing delays. Because mining equipment operates in dirty and demanding environments, these are prime conditions for introducing air into gearbox oil and can compromise performance.
To ensure your gearbox is reliable, effective air release management, through high-quality lubricants and frequent oil changes, can reduce component wear and improve the reliability of your gearbox.
How foam forms in gear oil
Foaming reduces gear oil’s ability to lubricate and cool components, which can lead to equipment damage and failure. Lubricant contamination is one of the leading causes of foaming gear oil, along with ageing oil and the churning action of the gears, whipping air into the oil. As lighter air bubbles form and rise to the surface, they create a foam which can be problematic as the amount of foam continues to rise. Other causes include:
Aeration from gear movement: In vertical or deep mining shafts, air and contaminants can be drawn into the oil, causing foaming to occur.
High operating temperatures: Oil viscosity can be reduced, along with the efficiency of air separation, which can accelerate oxidation and cause air bubbles, leading to foaming.
Oil degradation: Prolonged exposure to moisture, dust, and other contaminants can accelerate foaming tendencies by depleting anti-foam additives.
From aeration to foam: What happens inside mining gear systems
Constant motion, heavy loads and extreme environments in mining create the perfect conditions for air to enter the lubricating oil in mining gearboxes. Aeration is particularly prevalent in deep shafts or steep-angle drives where oil movement is more turbulent. If the trapped air is not released quickly enough, the bubbles combine together to form a foam layer, which doesn’t lubricate or carry heat. The foam takes up space in the gearbox and can lead to:
- Pressure drops in circulating systems
- Erratic lubrication flow due to air pockets
- Reduced film strength, increasing metal-to-metal contact
- Higher operating temperatures, since foam insulates rather than cools
Excess heat can speed up oxidation, while degraded oil traps more air, which leads to more foam. This can cause a damaging cycle of foam formation, overheating, oil breakdown and more foam, accelerating wear and leading to failures. That’s why it’s critical to choose heavy-duty mining gear oils with anti-foam additives and fast air release properties to prevent failures and unplanned equipment downtime.
The impacts of poor air release
Poor air release in mining gear oils can lead to a variety of problems stemming from improper lubrication. From premature component wear to complete equipment breakdowns, poor air release can cause a host of problems which cannot be ignored.
Through regular oil analysis and preventive maintenance, you can detect early signs of air entrainment and oil degradation. This gives you the opportunity to perform gearbox oil changes before oil degrades further and air entrainment becomes more prevalent, so you can avoid failures and unplanned downtime.
Mining-specific challenges
Mining operations push equipment beyond typical operating conditions. Equipment operates under irregular load cycles, steep angles and extreme environmental stress, which increases the risk of air entrainment and foaming. That’s why proper air release is essential for mining equipment longevity.
1. Vertical and inclined gear systems
Hoists, conveyors, and shaft-driven equipment often operate at steep angles. This can cause an uneven flow of oil and draws air into the lubricant, starving critical gear components of lubrication.
2. Extreme load spikes
Shovels, crushers, and draglines experience shock loading and rapid torque changes, which churn the oil, increase aeration and force bubbles into the system. Poor air release collapses the oil film when it is needed most.
3. High ambient and operating temperatures
Surface mines may see ambient temperatures well above 40°C, while gearboxes can run even hotter. High temperatures reduce oil viscosity, slowing down air separation and accelerating oxidation, making the oil more prone to foaming.
4. Dust, moisture, and contaminants
Mining equipment is exposed to dust, water ingress and abrasive debris, which can all contaminate the oil and make foaming worse. Natural air release performance drops, increasing the chance of gear wear and varnish buildup.
Our range of specially formulated mining gear oils is enhanced with additives to resist foaming and maintain film strength under shock loads, and remain stable even if temperatures and contaminants rise. By using gear oils that are specifically engineered for mining, you can ensure that they are robust enough to handle aggressive operating cycles or heat saturation.
How to spot air-related gearbox issues in mining equipment
Air release problems don’t materialise overnight. Your mining equipment may display subtle symptoms that there is an issue with the gearbox oil long before the problem becomes obvious, but you need to know what to look for.
- Visible foam and bubbles on dipsticks or sight glasses shortly after turning off the machine, that are persistent and make the oil look cloudy, indicate air entrainment.
- Spongy or inconsistent gear performance from air in the system makes the oil more compressible and can make performance sluggish and lead to slow responses.
- Increased operating temperatures are often caused by air in the system, as aerated oil is a poor heat dissipator. You may notice smoke from seals, discoloured paint from the housing or water evaporating quickly when sprayed on the housing.
- More frequent top-ups are often caused by high internal pressure, which forces oil to leak out past seals, dropping the levels. Meanwhile, oil discolouration, like milky or foamy oil, is the most obvious visual sign of entrained air.
If you notice any of these signs, consult your lubricant supplier or maintenance expert to assess your gear oil health and prevent the issue from getting worse.
Speciality lubricants are key to equipment longevity
Efficient air release in gearbox oil is critical to mining equipment reliability. Without it, air entrainment can lead to a variety of problems like critical components starved of proper lubrication, leading to seizure, failures and unplanned downtime. By working alongside a mining lubrication expert, like Gulf Oil, we can recommend the right heavy-duty lubricant for your mining processes as well as tailor a bespoke maintenance programme through Gulf Care.
Discover our range of high-performance lubricants for mining and other industrial applications now.