
From multi-purpose agricultural oil and rust preventatives, to cutting fluids and HTFs (heat transfer fluids), a wide range of lubricants keep mechanical equipment systems running.
From their key role as lubricators to cleaning, cooling and protecting, cutting-edge products are formulated by leading lubrication makers like CPI Fluid engineering, Fuchs and Kluber.
However, regardless of their design, like machinery, all lubricants have limits in terms of operating temperatures, and the cold impacts them in many ways. Read on for an in-depth account of lubricants working at low temperatures.
Increased lubricant viscosity in cold conditions
In lubrication, viscosity refers to the thickness of a product. When a standard lubricant encounters lower temperatures, it starts to thicken and stops flowing as freely. This can result in many unwanted outcomes.
At exceptionally low temperatures, when equipment is located outside, it can struggle to start because the lubricant is too viscous to reach the area where it is required. In extreme cases, it may congeal completely until it can’t flow. This limitation is referred to as the “pour point”.
In equipment featuring circulating systems, viscosity can become so high that the flow of lubricant becomes restricted. As a result, components are starved of lubrication, and as moving parts encounter each other they grind together, causing friction and wear.
Left unchecked, unlubricated metal on metal abrasion leads to damage and equipment failure, causing mechanical downtime and expense for new parts and labour.
Lubricant separation at low temperatures
The impact on the viscosity of the lubricant is not the only issue arising from the cold. At low winter temperatures, blended base oils often start to separate into their different phases. This process is referred to as “stratification”.
Lubricant additives are also prone to insolubility in colder conditions. As they become insoluble, they tend to separate from the base oil, forming deposits right at the sump’s bottom.
When mechanical equipment needs these additives to run properly, but they are in a sludge format at the bottom of the sump, the performance of the lubricant is greatly lessened, and the machinery can become damaged.
At what temperature is lubricant impacted?
Different lubricants are designed to deliver performance at specific temperature ranges. Many base oils and lubricating greases can manage moderate temperature drops to 0°C, and some can even cope with -10°C without their effectiveness lessening. However, at -20°C and below, some solutions become unfit for purpose as they start to near their pour point.
A lubricant’s pour point is determined by the quality of its base oil, but also the inclusion of certain additive types. As a rule, operators are advised to select a product that has a pour point at minimum10°C or lower than the lowest anticipated start-up temperature.
When operating temperatures reach -20°C or lower, lubricants that use standard mineral oil as their base can no longer perform properly, so an alternative solution must be deployed.
PAO lubricants for use in extreme cold
Polyalphaolefin, or PAO for short, are synthetic oils that are a leading choice as base oils for manufacturers creating lubricants designed to work in extremely cold temperatures of -20°C and below.
PAO-based oils don’t contain wax content unlike cheaply refined, low-quality mineral oils. This allows them to flow well even at exceptionally low temperatures. For instance, some PAOs provide pour points of -50°C.
A property of PAO-based oils that helps them cope with cold weather is that they have a high viscosity index (VI). In simple terms, VI is the rate that viscosity changes in relation to changes in temperature.
Lubrication products marked with a higher VI means that their viscosity will not alter at as high a rate as an oil or fluid that has a lower VI. Effectively, the useful viscosity range is extended over a wider temperature distribution.
Best practices for lubrication use in cold conditions
To assess cold-weather operation performance, many standardised methods are used like tests for low-temperature torque, pour point and flow pressure.
Research and development regarding lubricants working in extremely cold conditions have advanced in recent years, and products are now being specifically formulated to perform sufficiently in cold-weather environments and applications.
While correct lubricant selection is always of prime importance, other key steps can support operator efforts to answer cold-temperature problems. These include, but are not limited to, bigger feed lines, heaters, pumping systems with fewer pipe restrictions and altering and adapting application methods.
For lubricants designed to deliver performance in colder conditions, you can count on us. Browse our extensive products range or connect with our team at Oil Store today for further product details.