The Complex but Rewarding World of Lubricants

Lubricant Choice And Management May Not Be The Subject Of Much Discussion At Mines. It Should Be. 

By Jonathan Rowland

When it comes to selecting a lubricant, the decision is often based on price. This is understandable in an industry facing operating cost inflation; it is, however, often a false economy. As any lubrication specialist is quick to point out (and North American Mining talked to four in the writing of this article), a mine may actually end up increasing expenditure if the lubricant selected does not perform as required. 

Lubrication selection should instead be considered a part of a mine’s overall reliability equation. As Shell & Whitmore Reliability Solution noted, while lubricants themselves account for only about 1% to 3% of a mine’s budget, they can affect up to 50% of the same budget. By selecting the right lubricant for the application, components operate with less friction, less heat, less wear and longer lifecycles – with significant reductions in costs possible. 

“Lubricant selection affects operating costs in a variety of ways, particularly if the mine is spending a lot of money on equipment maintenance or replacement – or losing revenue to downtime,” explained Shawn Whitacre, senior staff engineer – engine oil technology at Chevron. 

“The choice of lubricant has a direct impact on equipment durability: if an oil can help you extend an asset’s useful life, you can avoid or at least defer replacement costs. The lubricant also affects reliability, which translates to uptime and availability – critical to maintaining production levels. And if a large piece of equipment breaks down inside the mine, it takes a lot of time, at a great expense, to get it out of the mine, repair it and put it back in service.”

Meanwhile, mining equipment is getting bigger and becoming more efficient. As a result, operating temperatures in mining equipment are increasing. There is also a concurrent push by OEMs to extend service intervals. “These converging trends call for a more robust lubricant with a high-quality base oil and advanced additive package that can perform under pressure,” continued Whitacre. 

Finally, the choice of lubricant can also impact fuel economy and drain intervals, while having implications for safety. And there is growing pressure on the mining sector to mitigate its environmental impact in line with climate and sustainable development goals. Demand for greener lubricants is rising – but if they come with a performance penalty, the costs may outweigh the benefits. All of this makes selecting a lubricant a complex equation. 

What Lubricant? 

According to Jon Brown, senior global segment manager – mining at Quaker Houghton, there are three sets of factors that should go into any lubrication selection: OEM recommendation, on-site process optimization and sustainability goals. 

The OEM recommendation outlines the basic properties necessary in a lubricant to ensure smooth operation, including ISO grade, viscosity, temperature constraints, flammability ratings and load carrying capability. “While some approved lubricants may be specific, others could be general classes with a wide variety of options available,” explained Brown.

“It is also important to understand that the initial recommendation is based on ideal settings in a controlled environment, which may differ from conditions seen in practice.”

“OEMs spend substantial amounts of time and money testing lubricants to determine what qualities work best in their equipment,” added Jim Salmon, technical manager at D-A Lubricant Company. “They require a lubricant that meets or exceeds the standards they deem necessary to maintain the life expectancy and performance on their equipment, and to comply with their warranty program.” 

The next step, according to Brown, is to suit lubricant selection to specific site conditions. This will cover all ancillary factors that may affect lubricant performance and optimize equipment functionality, such as whether to use conventional or synthetic lubricants, or additive packages, to increase performance, as well as equipment-specific (e.g., age, current lubricant) and site-specific conditions.

Climate, for example, can “play a major role in how your equipment and lubricant performs,” explained Salmon. “In humid areas, a lubricant must be able to absorb or shed moisture, depending on OEM requirements. High temperatures can cause lubricants to thin down or lose viscosity. Extremely cold climates can cause equipment to be sluggish due to low lubricant temperature.” 

The final set of considerations relates to health, safety and environmental concerns. Centered on sustainability and long-term goals, these are “often the most overlooked,” according to Brown. 

“While many lubricants may work in a given operational parameter, there may be substantial differences with regard to environmental friendliness, worker safety, sustainability initiatives, and best practices. Costs may be difficult to quantify initially, but the value is easy to measure when a long-term perspective is taken. To understand the true cost of a lubricant, a holistic approach must be taken to select a product that will optimize performance while creating sustainable value.”

With such a network of overlapping and interrelated factors involved, it is important that lubricant selection is a team decision. As Whitacre summarized: “It’s important to have procurement work with operations and maintenance teams to ensure the oil meets the specifications for the application in question. Even the finance team should be involved to help assess the impact of lubricant selection on the mine’s overall finances.”

Maintaining Healthy Lubricants

Selecting the right lubricant is only part of the job; making sure it is working effectively is equally – if not more – important. Having a lubricant expert involved in the day-to-day operations of a mine can have dramatic results, noted Shell & Whitmore. An effective oil monitoring and analysis program is another effective strategy in maintaining optimal lubrication. 

“In a perfect scenario, a lubricant operates in a fully-enclosed system, free of contamination and in ideal operating parameters,” summarized Quaker Houghton’s Brown. This “utopian scenario” is however just that – and therefore impossible to achieve in real-world conditions. In reality, normal operating conditions effect lubricants as they age, contributing to changing characteristics over time. Oil monitoring and analysis “allows the operator and supplier to evaluate not only the performance of the lubricant, but also understand how the machine is performing in service.” 

It also helps avoid every mine’s nightmare: unplanned downtime. “If a comprehensive oil analysis program is utilized, equipment failure can be prevented,” said D-A Lubricant’s Salmon. “Sample results can pick up abnormalities that can then be addressed to prevent failure.”

Both Brown and Salmon use a medical metaphor to illustrate the point, lubricant being the lifeblood of the machine. Lubrication monitoring and analysis is akin to a blood test, taken as part of a routine physical, that helps medical personnel gain a picture of how the body is working and any treatment that might be required.

Lubricants are designed to meet critical specifications outlined by OEMs, which define parameters for significant properties to ensure optimal performance. As in the human body, aging and contaminants may change typical values. If a lubricant is found to be operating outside of those values, corrective action must be taken. 

“Data generated from oil analysis can help signal any issues that are occurring in the internal workings of a piece of machinery,” explained Brown. “This can allow for planned maintenance, root cause analysis, CAPEX allocation, production scheduling and allocation of resources. The ultimate goal is to garner data that can be used to make informed decisions for critical assets used onsite.”

Finally, just as medicine relies on specialists, “to determine the most appropriate properties to monitor, the lubricant supplier should be consulted to determine what the critical parameters for performance are,” concluded Brown. This commonly includes monitoring and testing of the following: 

  • Cleanliness;
  • Oxidation;
  • Microanalysis (bacteria and fungi);
  • Metals analysis;
  • Concentration;
  • Water content;
  • FTIR spectrometry; 
  • Compatibility; and
  • Corrosion.

“Fluid analysis is really a low-cost diagnostic and maintenance tool that can save thousands of dollars in repair costs and downtime,” said Whitacre. “To get started, put together an equipment list, then sit down with your lubricant supplier and OEMs to map out service intervals. Consider operating conditions and temperature fluctuations, which will also influence how often you need to do an analysis. When you send samples to a laboratory, make sure you’re providing complete data, including the precise lubricant product used, make and model of the equipment and the oil age (hours since last oil change). Complete and accurate data is essential for the laboratory to deliver reliable results.”

Digitalization and Lubrication

Playing an increasingly important role in lubrication management is a wave of new digital technologies. Although such technologies may be easily dismissed as unnecessary or too expensive, “early adopters have a distinct advantage over those who are hesitating,” argued Quaker Houghton’s Brown. 

“Monitoring equipment has become smaller, less expensive and more readily adaptable for onsite activities,” continued the expert. “Though the proper control device will vary depending on the lubricant, machinery and industry, nearly all have become commercially available to measure critical values in real-time. The combination of values allows a user to properly analyze performance and plan accordingly.”

According to Brown, the true advantage of real-time monitoring lies in removing human error and the time lapse between sampling, analysis and response: “Critical values are collected, analyzed and communicated at the time of sampling. All necessary parties receive the information and can determine the best course of action. Based on the sophistication of the system, corrective actions can be programmed to occur automatically based on the values received.” In short: digitalization of lubricant management allows for enhanced performance optimization, planning and efficiencies. All of which equal cost improvements.

Help! My Lubricant is Contaminated

Although in an ideal world, lubricant sampling and analysis would never turn up anything untoward, in reality the mine site and process is an environment full of potential contaminants. And these pose a particular challenge for lubricants. Indeed, contamination is the leading cause of lubrication-related equipment failure.

According to Chevron’s Whitacre, there are five different sources of contamination: 

  • Raw materials. “It may come as a surprise that new lubricants are usually not clean enough for OEM specifications,” said Whitacre. “If you are not starting with a clean lubricant, damage is bound to occur. Making sure a lubricant is certified to meet or exceed the OEM’s ISO specification is critical.”
  • Operational discipline. Operators “must maintain lubricant cleanliness,” explained the Chevron expert. “Without the appropriate in-line filters, breathers or controls on air and water ingressions, contaminants will get into the lubricant while the equipment is running.”
  • Maintenance workmanship. Tools such as funnels and open-air containers used to relubricate equipment collect small particle contaminants from the environment and transfer them into the lubricant during change-out or top-offs. 
  • Material storage. Old-style flip caps on bulk tanks, open bungs on drums, or storing lubricants outside, where they are exposed to the elements, all enable contaminants to get into the lubricant. “If you see water or rust on top of a drum, you most likely also have that inside the drum,” noted Whitacre. “If you have totes or bulk tanks without an appropriately-managed breather, you have contaminants getting into the oil.”
  • Built-in. Replacement or newly installed components may have contaminants in them from the manufacturing process or from exposure to the open environment.  

Controlling contamination “must be at the top of every equipment owner’s to-do list,” said D-A Lubricants’ Salmon. But how does a mine – so rich in potential contaminants – go about doing so?

It starts, according to Shell & Whitmore, with a Contamination Control Audit, during which every aspect of an operation should be assessed to identify where contamination could occur. This will also include an awareness of how contamination risks may change through the day or during operations. As noted above, it is then important that any oil used is certified clean, at the required ISO 4406 cleanliness level. This avoids the hassle of on-site filtration. 

When it comes to handling, storing and managing lubricants, our experts had the following tips: 

  • Implement the correct tools, e.g., desiccant breathers and air filters.
  • Avoid changing the oil until needed.
  • All hoses, fittings and devices used in the lubricant transfer process should be capped and kept clean.
  • All lubricant sources and equipment should be clearly identified to prevent cross contamination. 
  • Keep lubricants and fluids in a climate-controlled and clean area.
  • Never leave a drum or container open to the environment.
  • Filtering lubricants before dispensing them to a final application can reduce the amount of any contaminants that may enter your component.
  • Use a labeling program to properly manage the chain of custody and eliminate mixing incompatible fluids.

Maintenance crews should be correctly trained on top-off procedures to eliminate human error. It is also important to consider around the lubricant: “Routine replacement and or cleaning of lubricant filters must be scheduled and carried out,” said Salmon. “Seals are also one of the biggest culprits for dirt ingestion. If a seal is leaking fluid, you can bet it’s also breathing contaminants in.”

Lubrication and Sustainability: A Growing Demand?

A final – but increasingly important – consideration for mines is sustainability. In the context of lubrication, this is often taken to mean the use of “eco-friendly” or “green” lubrications. It is, however, first important to acknowledge the sustainability value that high-performing lubricants bring. These not only reduce mining costs (as outlined above) but – by working toward extended oil drain intervals and dialing in automatic lubrication systems – there is a strong focus on reducing the quantity of lubricants used. As Shell & Whitmore note, a lower volume equates to less exposure of any chemical or lubricant to both workers and the environment.

When it comes to environmentally acceptable lubricants, these are required to perform “as well, if not better, than traditional lubricants,” said D-A’s Salmon, and demand is growing. It is not necessarily a simple decision, however; adoption can be slowed by increased cost, compatibility issues, life span of the lubricant, performance concerns or a general lack of knowledge that the different classes exist, added Quaker Houghton’s Brown.

The terminology can also be unclear: biodegradable and non-toxic are often used interchangeably – but mean different things. Biodegradability is defined in two categories: readily and inherently. A readily biodegradable lubricant must decompose > 60% within 28 days; inherently biodegradable lubricants must degrade > 20% but < 60% within 28 days. Meanwhile, a lubricant’s toxicity level is determined by its effects on aquatic organisms. “Keep in mind a product may be classified as readily or inherently biodegradable and still be toxic,” said Salmon. “It is important to know which of these properties are required for the application.”

Despite the above, it is clear that demand for greener lubricants is growing: vegetable-based, zinc-free, and inherently- and readily-biodegradable products are now offered by many lubricant providers, as are low- or non-toxic lubricants.

Best practice around environmental sustainability is not just about choosing green products, concluded Brown, but is a combination of factors that take in both use and disposal. “Consideration should be given to accidental release protocol, responsible sourcing, total carbon footprint, proper waste oil disposal procedures and activities to lower overall usage of lubricants. While environmentally friendlier products should be considered where feasible, an overarching lubricant lifecycle plan is necessary to ensure that environmental exposure and impact can be minimized in everyday use and as part of an emergency response plan.”

Complex but Rewarding

Brown’s last comment echoes a theme running through this article: lubrication – so often judged on price alone – is a much more complicated business. The benefits of taking the time to understand the subtleties is well worth the effort, however. In a world of heightened awareness of costs, health and safety and environmental sustainability, getting the lubricant right is a key foundation for improvement.  

Lubrication Selection for Specific Applications 

Drivelines

The critical question when it comes to driveline components is how long you can get them to last. Factors to consider include cleanliness, operating temperatures, additive formulation and drain intervals, said Chevron’s Shawn Whitacre. “Look for a fluid that is certified to the cleanliness standards for the component. Loads of up to 400 tons generate very high temperatures in the rear of mining haul trucks, so look at using synthetic lubricants in these applications because of their ability to withstand extreme temperature variations. Look, too, at whether the additive formulation offers sufficient wear protection for the components. Finally, you don’t want to change-out a driveline fluid for 4,000 or 5,000 hours – in other words, once every couple of years – so you want a fluid that can handle heavy loads, high temperatures, and rugged operating conditions, without degrading, over an extended period of time.”

Engine oils

Engine oil is one of a mine’s largest volume lubricants – so there is a substantial focus on cost, according to Shell & Whitmore. Using synthetic lubricants can safely extend oil drain intervals from 250 hours up to 1,000 hours. High-performance synthetic lubricants have also been shown to improve fuel consumption (another critical cost) by up to 5%. Ultimately, however, the job of the lubricant is to protect the engine and maximize its operating life; durability is therefore the paramount consideration. 

A further factor that mining operators may be less aware of is the effect of engine oils on the aftertreatment systems on newer Tier IV engines. “Metallic oil additives are the primary cause of non-combustible ash accumulation in diesel particular filters (DPFs),” explained Whitacre. “When you have to take a piece of equipment out of service to clean or repair the DPF, it means downtime and lost revenue. A clogged DPF can also diminish fuel economy. To mitigate those issues, take a look at using an ultra-low ash (ULA) engine oil.”

Engine coolants

Mines are asking more of their engines today than in the past, while emission reduction requirements result in engines running as higher temperatures. As a result, a “surprisingly large percentage of engine failures are due to cooling system failures,” according to Whitacre. A “strong, advanced coolant with good heat transfer capabilities and that can last a long time,” is therefore required. “You also want to avoid having to change coolants frequently, partly because of the time and expense involved, but also because of the environmental impact of coolant waste. By extending coolant life, you reduce the amount of coolant you use, thereby decreasing waste and improving sustainability in your operations.”

Open gears

Some of the most critical equipment at mines rely on open gears, including electric shovels, draglines and mills. Electric shovel and dragline open gears are multi-directional and may be exposed to wide temperature ranges. The open gear lubricant (OGL) also needs to be pumpable through a centralized lubrication system. Achieving both pumpability and protection can be a challenge, especially in winter months, and highlights the importance of utilizing specialty expert-backed lubricants, Shell & Whitmore said. In contrast, mill open gears are one directional and often located in a processing plant with semi-controlled climate. It is, however, critical for an OGL to remain fluid on a mill, so it does not build up in the tooth root or bull gear cover.

According to Shell & Whitmore, most OEMs have approved specifications for grease-type, asphaltic and high-viscosity compound-type OGLs. Asphaltic OGLs are typically the least expensive but also have the largest amount of waste and environmental concerns, while greases tend to thicken in place – a benefit on a shovel but a potential deterrent on a mill. The latest technologies are high-viscosity (15,000 cSt at 40˚C) compounds (synthetic and mineral), which work on a hydrodynamic lubrication regime, rather than the boundary lubrication regime of other alternatives. The high-viscosity fluids are typically transparent, making mill inspections easier, and eliminate the cost of cleaning the teeth for inspection; they are typically also more environmentally friendly than their asphaltic counterparts.