Choosing the right lubricant for cold-weather operations
Written by Mario DiBartolomeo
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.
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.
