Today’s leading industrial lubrication solutions play a central role in the effective maintenance of production equipment, hydraulic systems, and heavy industrial machinery alike. Such products are of fundamental importance for reducing friction, minimising wear, and extending equipment lifespan.
However, the task of selecting the right lubricant for a particular application involves far more than simply opting for whatever oil or grease might seem vaguely appropriate.
Among the various properties that lubrication products have, one of the most critical is viscosity. This is because of the direct effect that viscosity has on how well the given lubricant protects moving components under different operating conditions.
What Do We Mean By ‘Lubricant Viscosity’?
The “viscosity” of a fluid measures its resistance to flow. To put it in simple terms, it describes how thick or thin a lubricant is.
- If a lubricant has low viscosity, this means it flows easily, like water. The users of such lubricants, then, can generally expect them to circulate quickly through machinery.
- If a lubricant has high viscosity, this means it flows more slowly, like treacle. Lubricants in this category are thicker and provide a more substantial protective film between moving parts.
There isn’t a single, specific level of viscosity that all industrial lubrication products should have.
Instead, the appropriate viscosity for a particular situation or task will depend on the machinery, the operating environment, and the equipment manufacturer’s specifications.
In general, though, a balance needs to be struck somewhere between the two “extremes” of viscosity. Whatever lubricant is chosen, it must be fluid enough to reach all critical components, at the same time as having sufficient thickness to prevent direct metal-to-metal contact.
A Quick Introduction to Viscosity Classification Systems
Industrial lubricants in the UK and Europe are mainly graded by the ISO Viscosity Grade (VG) system (ISO 3448).
ISO VG classifies oils according to their kinematic viscosity at 40 °C. Common grades under this system include the likes of:
- ISO VG 32 and 46, which are frequently used in hydraulic systems and circulating oil applications.
- ISO VG 68 and 100, which are typically suitable for many industrial gearboxes and compressors.
- ISO VG 150 to 460, which are higher grades frequently specified for heavily loaded gears or slower-speed equipment.
Another system for grading lubricant viscosity is the SAE one, often used for automotive and some plant oils. Examples of SAE viscosity grades encompass the likes of SAE 5W-30, SAE 10W-40, and SAE 75W-90.
Nonetheless, most fixed industrial plant relies on ISO VG ratings rather than SAE grades.
Whatever grading system you might look to when assessing lubricant viscosity, the overriding principle will be much the same: you will need to select a viscosity that is the right match for the anticipated operating temperatures and loads.
The Implications of Lubricant Viscosity for Machine Performance
Lubricants perform several crucial functions. These include:
- Reducing friction
- Preventing wear
- Carrying away heat
- Protecting against corrosion
- Helping suspend and transport contaminants to filters in circulating lubrication systems.
The viscosity of a given lubricant influences all these functions.
If a lubricant has too low a viscosity, for instance, this can lead to consequences like:
- Inadequate film thickness, thereby allowing metals to come into direct contact with each other.
- Heightened friction, increased heat generation, and accelerated wear.
- An elevated risk of component failure, particularly under load or at higher temperatures.
- A shortened lifespan for both the lubricant and the machine, thanks to a self-reinforcing cycle in which increasing temperatures reduce viscosity, thereby weakening the lubricating film and generating even more heat.
As for if a lubricant has too high a viscosity, this can cause:
- Excessive fluid friction, thereby driving up ongoing temperatures and energy consumption.
- Poor flow and slower circulation, which can mean the delivery of lubricant to critical surfaces at start-up takes longer.
- Higher pumping losses in hydraulic systems and lower all-round efficiency.
- Difficulty in cold starts. This is especially pertinent for unheated workshops and outdoor plant in cold parts of the world at the height of winter.
Also Read: Ramneek Sidhu: who he is, what Digital Kings actually is, and which “facts” hold up
The Bottom Line: Lubricant Viscosity Is of Fundamental Importance
Ultimately, when it comes to such crucial aspects of industrial operations as machinery reliability, efficiency, and component life, lubricant viscosity can’t be overlooked or ignored.
A lubricant being too thick or too thin for a particular setting or application can contribute to increased wear, worsening inefficiency, and the premature failure of equipment.
The good news is that all is not lost. When maintenance teams take the time to understand viscosity grades, assess operating conditions, and adhere to equipment manufacturers’ recommendations, they can be well-placed to preserve and enhance machinery performance. In the process, they can also help reduce periods of downtime and their organisation’s long-term operating costs.
