Engine oil and open gear lubricants excel in temperate climates. But as more projects ramp up in Northern Canada, lube manufacturers have been forced to
re-evaluate their products to accommodate sub-zero temperatures with additives and synthetic options.
Mineral oils, the byproducts of crude oil refinement, have dominated the lubrication market since the 19th century. While they work well at warmer
temperatures, these oils often contain wax molecules that crystallize when the mercury drops, thickening the oil and limiting its flow.
In an engine, lube needs to get moving quickly once the engine starts. “You’ve got oil down in the sump of the engine, and you’ve got to make sure that
that oil flows up to lubricate all the components of the engine as quickly as possible,” says David Dingle, sales manager at Imperial Oil distributor
Cold weather already places certain demands on an engine: it takes more power to turn the engine over and the performance of the battery declines as
the temperature goes down. For all these reasons, says Dingle, 80 per cent of engine wear can occur during start-up for equipment operating in cold
regions. While not all equipment needs to be cold-started – say, if it operates 24/7 or if it is possible to keep the engine heated – the number of
engines running purely for warmth has fallen as more mines implement no-idle policies to reduce fuel costs and emissions.
Lubricants used on open gears, on the other hand, have a unique set of problems. Open gear lubricants are typically high-viscosity and tacky fluids or
greases. They need to be pumped through the equipment, lubricating open gears, plain bearings, sliding surfaces and house rollers and rails. Some of
these applications and the distribution system are directly exposed to temperatures below -40 degrees Celsius. Pumping system failures result in
lubricant starvation and component failure.
The first question that arises for open gear lube is if it can be pumped throughout the distribution lines to the points of application at the lowest
anticipated temperature. The second concern is venting residual pressure within the distribution system. Bret Jenkins, director of the mining division
at Bel-Ray, points out that lubricant piping and injectors (a lubricant measuring device) on a walking dragline with a 300-foot boom build up to 10,000
pounds per square inch (PSI) of pressure to push the lubricant to the point of application. Once the measured lubricant is applied, the remaining
pressure needs to vent to as low as 600 PSI in order to reset the injectors for the next application of lubricant. “If your lubricant is too thick, it
won’t vent,” he says. “The pressure will still be there because you pumped it up.”
Some users address the problem simply by using a less viscous oil in cold temperatures. Dean Hammes, western regional sales manager at U.S.-based
Lubrication Engineers, Inc., says many of his customers will use very thin gear grease in winter to ensure the lube can make it through the lubrication
pump. It slips out of bearings more quickly than thicker grease does once it warms up with use, but for some that presents an acceptable trade off.
Jenkins notes, however, that lubricants used in very demanding applications will need more staying power. “When we’re talking about cold weather in
Canada, you still have the extreme pressures that you do in Mexico or South America because you’re dealing with the same kind of equipment,” he says.
“Your open gear lubricant needs sufficient viscosity to protect the machine components, but it also needs to be able to get all the points of
application and allow the pumping system to function correctly regardless of how low the ambient temperature is.”
For companies using mineral oil in their equipment, the solution to the thickening problem is a blend of additives. For example, there are additives
that keep the wax crystals in solution, lowering the temperature at which the lubricant remains fluid. These are called pour point depressants. There
are also polymers that contract in the cold so they have no impact on a fluid’s viscosity and expand in heat to increase fluid viscosity. These types
of polymers are known collectively as viscosity modifiers or viscosity index improvers.
Viscosity modifiers have existed for a long time. However, they continuously improve in shear stability, according to Dingle. “These viscosity
modifiers are basically just rubber molecules, and when you put them under load or under shear, they’ll break down,” he explains. “In the initial
period of use, the viscosity actually drops as these viscosity modifiers shear or break down, and then as the oil continues operating, it starts to
thicken up as it oxidizes and gets contaminated with soot from the combustion process.” The key, he says, is to make sure the oil stays at an
appropriate weight, or grade, throughout its use, and this is something that manufacturers have been better able to manage over time.
For equipment exposed to the elements in more demanding environments, synthetic lubricants offer an increasingly popular alternative.
Synthetic base fluids are custom molecules. Their composition is more uniform and their behaviour is more predictable than that of mineral oils. Most
importantly, synthetic fluids remain more pumpable and mobile as the ambient temperature drops than comparable mineral oils. This behaviour is
generally true for most types of synthetic lubricants including engine, gear and hydraulic oils, open gear lubricants and greases.
As a result, synthetics are more flexible. Historically, operators using mineral oil have changed their oil grade by the season; Dingle says a mine
might use 15W-40 in summer and 10W-30 in winter. But the cost of oil changes adds up. The right synthetic can be used year-round.
Poly-alpha-olefin (PAO) can be used as the base fluid of a synthetic lube. A lubricant manufacturer might use other additives as well. For example, the
Mobil 5W-40 and 0W-40 oils are formulated by starting with a lower viscosity oil and adding viscosity modifiers. “A Mobil Delvac 1 ESP 0W-40 or a Mobil
Delvac 1 ESP 5W-40 is a lighter oil but it acts like a 40-weight oil at operating temperatures,” says Dingle.
The right mix
A full synthetic can cost several times more than a mineral oil-based lubricant. There is also the choice of semi-synthetic lubricant, which occupies
the middle ground of price and performance.
When would a mine want to invest in synthetic lube? It depends on many factors including the application. Carlos Nazario, a senior product manager at
Bel-Ray, recommends a full synthetic gear oil if the application needs a lubricant with good fluidity below -25 degrees Celsius. An enclosed gear case
is a good example of such an application. However, if the application is an open gear set, he’d recommend a semi-synthetic gear lubricant.
The risk involved in trying out a synthetic lube has lessened over the years. Before PAOs came to the forefront, diester-based lubes and other
synthetics caused problems with seal material and painted reservoirs, says Terry Thomas, technical services advisor at distributor Star West Petroleum.
He adds that they also lacked backwards compatibility.
One fluid fits all
At the same time, mine operators want to simplify their lube shopping and use. Jenkins says original equipment manufacturers (OEMs) used to make
recommendations or put specific products on their approved list, but the more recent trend is for an OEM to provide specifications and let mines find
their own solutions.
“The trick is to have one lubricant that will work in the summer and the winter, and it doesn’t matter what the OEM is, it’ll still qualify for their
specifications,” says Jenkins. That can be tricky. For instance, one useful additive is the metal compound molybdenum disulfide (Moly), which creates a
protective coat on the component surface. The gear grease for some mine equipment at a specific site might not be able to have more than three per cent
Moly, while other equipment at the same mine might have an OEM specification requiring five per cent Moly. Sometimes there is no way around this, but
Jenkins says Bel-Ray has had some success in getting OEMs to test and approve its three per cent Moly grease for other uses. “It outperforms many of
the approved five per cent Moly greases,” he explains.
Hammes says Caterpillar sets industry standards. Because Cat began requiring five per cent Moly, Lubrication Engineers recently developed a new five
per cent Moly product specifically for pins and bushings used in the mining industry. “Caterpillar has been at the forefront to specify cold weather
products for its off-road equipment,” agrees Thomas. He says Phillips 66 recently introduced a 0W-20 lubricant for transmissions and drive trains,
called PowerDrive Synthetic Arctic TO-4 Fluid, a PAO-based product, which operates at temperatures down to -40 degrees Celsius.
The standards from one manufacturer to another, however, can be difficult to negotiate. One OEM might have a minimum viscosity requirement, while the
next OEM might specify that the lubricant needs to meet a standard anti-wear test. “Product A may only meet one requirement while product B would meet
both,” says Jenkins.
For open gear lube, Bel-Ray has been working on its flagship Molylube SF 100 Semi-Synthetic Open Gear Lubricant, to produce formulas that can be used
as widely as possible. “The SF 100 that we use in the mines in Alberta and Saskatchewan, we’re able to use one single lubricant the whole year-round,”
Jenkins says. It is a semi-synthetic, part PAO and part mineral oil, and it uses an aluminum complex as a thickener, which “is essentially a sponge
that’s holding all the base oils and the additives in a semi-solid state,” he says. Bel-Ray’s newest formulation, Molylube Ultra Open Gear Lubricant,
can be used for priming, running in, and service lubrication, and it is designed for a -40 to +50 degree Celsius temperature range.
Major petroleum companies like Shell, Petro Canada, Imperial (ExxonMobil), and Conoco Philips supply the bulk of the lubes sold by manufacturers that
are used on site, and they continue to improve their products as well. Imperial is reformulating its synthetic engine oil to allow for better
filtering, according to Dingle. Even synthetic oil thickens in cold weather and that can make it more difficult to filter. While some engines have a
bypass on the filter to allow dirty oil to reach the engine if necessary, it would be ideal to have a more easily filtered lube. The new formulation of
Mobil Delvac 1 ESP 0W-40 has been reformulated to pump and flow easily through filters at low temperatures.