Choosing the right lubricant for cold-weather operations
From the point of view of a lubricant supplier, experience suggests that typical purchase decisions often begin with the product rather than the application. The final purchase decision is often driven by basic interchange criteria, typical properties and which option has the lower price or local availability. Given the range of lubricant options available in the market today and the increasingly specialized nature of production machinery operating at higher speeds and in more hostile conditions than ever before (including polar extremes), however, this is increasingly becoming a short-sighted approach. It can also lead to costly repairs and unplanned breakdowns.
Instead, lubricant purchasing decisions are better served first by defining the application; more specifically, the environmental and operational conditions that characterize the boundaries of the application itself, while recognizing that each situation is truly unique. The data, especially when extreme low temperatures are involved, will define the end-purchasing decision.
Defining the application
Proactive data collection really is the key to making good lubricant decisions. Even when basic operating conditions are known, the reality is that critical environmental conditions are sometimes overlooked. This is especially true in extreme low-temperature applications. The following outlines a few examples of factors to consider when it comes to extreme cold:
- Operating characteristics of a given application may be very different in extreme low-temperature conditions; applications may run hotter, colder or at different rpm levels;
- The extent of direct exposure to the elements can be significant, including the maximum coldest temperatures that are likely under load, when idle, during overnight shutdowns and again at start-up;
- The effect of extreme cold on applications under heavy load;
- The overall range and frequency of temperature variations;
- The extent and presence of fresh or salt water, ice, snow, chemically active fluids and other potential contaminants, including dirt, rock, grit and wood fibres;
- The effect of extreme pressure, shocks and pounding, which are often more severe in the deep cold when things are really frozen;
- The location and terrain of the equipment, as well as the distance to areas of warmth for maintenance, overhaul and repair in the event of breakdown; and
- Frequency of lube cycles and the ease of access to machinery and components, especially for the service crews on the job site.
Oil and grease in polar extremes
What makes a lubricant effective in polar conditions is its ability to maintain viscosity and flow as temperatures drop. As they get cold, all lubricants will naturally stiffen and harden to some degree. As a result, this prevents the ability to protect an application. Depending on the characteristics of the lubricant itself, it may even start to take on certain properties of a solid and essentially "freeze" (for lack of a better description) with catastrophic results. Most base oils and grease are able to withstand moderate temperature dips to zero degrees Celsius and many to -10 degrees Celsius without much decrease in performance. At the level of -20 degrees Celsius and beyond, however, certain lubricants become unsuitable, while others continue to perform.
Low down on oils
PAO (polyalphaolefins) synthetic oils are among the front-runners in performance for base oils in the resource industry at cold extremes of -20 degrees Celsius and lower. PAOs are hydrolytically stable with strong oxidative properties and low volatility, especially when compared to an equal weight ISO grade mineral oil. They’re compatible with conventional products and the low absence of wax allows for excellent flow, even at low temperatures. Other advantages include:
- High viscosity index;
- Excellent low-temperature fluidity and pumpability with pour points down to -45 degrees Celsius;
- Excellent metal polarity in cold temperatures (even when idle), which maintains critical boundary fluid-film protection under load and especially at start-up when most wear generally occurs;
- Heavy-duty load, anti-wear, corrosion and extreme-pressure protection;
- Excellent water separation from internal components;
- Low coefficients of friction;
- Compatibility with metals and mineral/synthetic oils; and
- Excellent additive solubility, including non-leak, anti-foam, anti-wear and extreme-pressure additives, as well as emulsifiers, viscosity index improvers, tackifiers and solid additives, including molybdenum disulphide (MoS2).
Let’s talk about grease
Grease, in its simplest form, is base oil emulsified with a thickening agent to create a semi-solid, which serves as a carrier for the base oil and any additives that have been included. For polar extremes, PAO base oils are a mainstay for grease composition (for the reasons outlined above). As for thickeners, aluminum complex is a front-runner among other options, including soaps, calcium and lithium. Aluminum complex provides a high level of overall protection, including excellent water, rust and corrosion resistance, high load-carrying abilities, excellent temperature range variation and pumpability in cold conditions.
It’s also "reversible" and will revert to its normal consistency after having been heated and cooled repeatedly. This makes it ideal for the large temperature ranges of cold extremes. Additives also play an important role. There’s a broad spectrum of additive combinations, which enhance extreme cold performance. Fully formulated grease with a balance of base oil, thickener and additive package will offer definite performance advantages including:
- Excellent water emulsification;
- Heavy-duty load, anti-wear and extreme-pressure protection;
- Tackifiers for extra adhesion;
- Resistance to salt and fresh water, chemicals and other contaminants;
- Compatibility with metals and mineral/synthetic oils;
- Clean and free of heavy waxes; and
- Low start-up torque and smooth operation.
Other factors to consider
The other key point when dealing with lubrication in polar extremes has little to do with the lubrication itself and more to do with prevention and planning. Being proactive can make a big difference when it comes to avoiding the risk of breakdown, which results from lubrication failure in extreme cold conditions. A few things to consider include:
• Most wear occurs at start-up when machinery is coming up to operating temperatures. Anything that can be done in advance to pre-warm the application and the lubricants prior to start-up will help, including block heaters, indoor storage and even basic shelter from the wind and snow;
• Allow for extended warm-up periods to ensure that lubricants and machinery are at operating temperature prior to subjecting them to heavy load;
• Service applications and switch over to winter lubricants early in the year when you still have good conditions and are able to control the timing and location;
• Choose lubricants that are compatible if different products are used during the summer and the winter;
• Use more robust lubricants with PAO base oils. They may be more expensive than some alternatives, but they will extend lube cycles, provide better protection and considering the cost of maintaining equipment in the field or, even worse, the potential risk of a breakdown, they will save you money in the long haul;
• Do regular inspections and remove snow and ice build-up in critical areas;
• Avoid unplanned breakdowns at all costs. Access to applications during the winter can be much harder, more expensive and sometimes even impossible until the spring thaw;
• Plan out jobs and locations ahead of time to provide for access to warm areas at key times for service and maintenance; and
• Contact equipment manufacturers. Draw upon their experience and recommendations for extreme cold performance. Also inquire about critical areas, potential vulnerabilities and possible solutions to any design issues.
And finally, build a relationship with a lubricant supplier you trust and can provide the required data to better define the critical requirements of your application and not just products or product interchanges. A good supplier will help you select an appropriate product that optimizes your requirements, while taking into account things like base fluids, thickeners, additives and cost.
When it comes to polar extremes in the resource industry, there simply isn’t room for trial and error. By adopting a proactive focus on the specific conditions of a given application, taking into account the range of lubricant options available and building a solid relationship with a good lubricant supplier, however, it’s possible to simplify the process. You can also engineer a solution that will result in better purchasing decisions. In the long run, it will save you time, money and headaches.
Mario DiBartolomeo is the general manager of Mississauga, ON-based Davley Darmex Precision Lubricants. For more information, call (800) 361-9458 or visit www.davley-darmex.com.