Industrial oils are used in a variety of conditions, including low or high-temperatures, wear-reduction or pressure protection on metal services, marine environments or outdoor applications, possible or incidental contact with edible substances, corrosion-resistant additives, and environment concerns requiring low-toxicity industrial lubrication. These oils are typically offered in a wide array of viscosities to handle any type of application. Industrial oils are used in a variety of conditions, including low or high-temperatures, wear-reduction or pressure protection on metal services, marine environments or outdoor applications, possible or incidental contact with edible substances, corrosion-resistant additives, and environment concerns requiring low-toxicity industrial lubrication. These oils are typically offered in a wide array of viscosities to handle any type of application.
What is Viscosity?
Viscosity is the measurement of a fluid’s internal resistance to flow. However, temperature, pressure and speed place additional demands of lubricants.
Many lubricant marketers address the matter of viscosity breakdown. Although the ads make it appear that viscosity is difficult to understand chemical property of a fluid, it involves physical property measurement. For instance, one ad compares two oils: one easily flows from the bottle while the other does not:
• Resistance to flow (viscosity) increases when the temperature decreases.
• The ad shows the importance of considering viscosity in selecting the best lubricant for an application.
Original equipment manufacturers (OEMs) frequently direct the user to a specific lubricant for use on their equipment. Lubricant marketers typically offer lubricants by viscosity grades, e.g. AGMA 3 or ISO 46. For most lubricant industry manufacturers, the viscosity is considered the most fundamental factor in proper lubrication.
Importance of Viscosity
The viscosity of fluid impacts the thickness of a fluid film in specific temperature conditions and load in various lubrication applications. It also affects the generation of heat as well as removal of gears, bearings, and cylinders.
In addition, viscosity is the key determinant is the ease with which a machine may be started in a low-temperature environment or maintained in higher temperature conditions. It is also essential to controlling the sealing ability of a fluid. Effective sealing ability equals lower consumption of the fluid.
Consistency and Viscosity Grades
Most users equate consistent grade to viscosity grade:
• “Grease consistently” is determined by a cone penetration test.• The National Lubricating Great Institute created grade ranges commonly in use by industry.• The ranges consider grease flow properties.
Several elements must be known before recommending a lubricant for a specific application, including:
• Operating temperature: In most cases, as temperature rises, viscosity declines; as temperature declines, viscosity increases. The fluid’s viscosity should be high enough to offer a sufficient lubricating film. If the viscosity is too high, friction in the film may be excessive. The user should consider at what temperature a certain piece of equipment is started or operated.
• Speed(s) at which a specific part is or should move: In equipment operated at high speeds, it’s important to realize that higher viscosity lubricants won’t flow as well in contact zones. Conversely, a lower-viscosity lubricant won’t properly lubricate a slow-moving piece of equipment.
• Load placed upon a specific part: Lubricant film is compressed under heavy loads. Higher viscosity lubricants are needed. Higher viscosity fluids typically offer greater strength. The user must consider whether the equipment will be operated in a shock or continuous load: 1) A shock load is a non-steady or “pounding” load, and 2) a continuous load is steady and to be maintained when operating the equipment. Low viscosity fluids won’t provide sufficient film strength to remain in place in a shock load. High viscosity lubricants cushion and remain in place in the contact area.