Some customers think grease selection can be complicate […]
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Different types of greases are typically formulated with three grease components: base oil, thickener and additives.
What Does Base Oil Do in Lubricating Greases?
Base oils in lubricating greases are present in majority (> 80 %) and main function of lubrication is taken care by base oil, thickeners acts as carrier of oil and act like sponge where it releases oil at point of application. Base oils inﬂuence pumping and ﬂow-ability of lubricating greases. High viscosity oil based greases ﬂow / pump slowly compared to low viscosity oil based greases. This is the reason, where ever application speeds are low and bearing diameters are comparatively large, high viscosity oil based greases (e.g., VG 460) are preferred. On the other hand, in applications where bearing run under high speed, low viscosity oil based greases (VG 32 –VG 68 ) oil based greases may be recommended. Base oil also greatly inﬂuences the low temperature characteristics of greases; mineral oil based greases are generally recommended up to -18 °C with appropriate viscosity adjustment. The choice of a viscosity depend on intended service, for higher DmN factor, low viscosity is preferred while for higher loads and low DmN factor heavier oils are more suitable.
What Does Thickener Do in Lubricating Greases?
Thickeners on the other hand, are considered backbone of the greases. The thickener system may be a simple metal soap, a complex soap, a synthetic organic thickener, or inorganic gelling agents. Whatever the thickener type be, many of the important properties and performance characteristics of the fully formulated grease comes from the actual thickener system. High temperature capabilities of grease are function of thickener though base oil does play some role. Water resistance characteristics of grease are also controlled by type of thickener, like soda base greases are poor in water resistance whereas aluminum complex and sulfonate base greases are known for its superior water resistance properties.
What Does Thickener Do in Lubricating Greases?
Consistency- the extent to which the grease resist deformation under the influence of force
Shear Stability- the ability of the grease to resist changes in consistency during mechanical shearing
Oxidation Stability- the ability of the grease to resist chemical deterioration
High Temp. Stability- the ability of the grease to retain consistency at elevated temperatures
Water Resistance- the ability of the grease to withstand against water ingress
Rust/Corrosion Resistance- the ability of the grease to protect metal surfaces against rust and corrosion
What Does Additives Do in Lubricating Greases?
An additive is any material added to a lubricating oil or grease formulation to improve that product’s ability to perform the task called for. In fully formulated grease, the base oil imparts certain characteristics and thickeners also bring certain characteristics to the formulation. The additives doped in the formulation may either add to these characteristics, or may boost desired characteristics already present. These pressure properties, corrosion and rust inhibition, water resistance, low temperature ﬂuidity, color, and odor etc.
Different Types of Greases and their Applications
Lithium soap with suitable oil viscosity and additives, Operating temperature up to + 120 °C max
• Multi purpose / Automotive chassis and wheel bearings / Non-critical Industrial
Li-complex soap with suitable oil – viscosity and additives, Operating temperature up to +150 °C max
• High temperatures / High pressure and shock load
Aluminum complex soap with suitable oil – viscosity and additives, Operating temperature up to 150 °C max
• Heavy water environments / High temperatures / Food processing and pharma industry / Mining, fertilizers, petrochemicals operations
Poly urea with suitable oil-viscosity and additives, Operating temperature up to +180°C max
• High Temperatures / Oven, conveyor bearings / Electric motors / Refining and petrochemicals / Foundry, metal processing
Clay, Operating temperature up to 150 °C
• High temperatures / Food processing
Sulfonate Greases with suitable oil viscosity and additives, Operating temperature up to 180 °C
• Water prone / Mining and Marine / Oil & gas / drilling and refining
Lubricating Greases: General Recommendations
The application recommendations of a grease depends on the properties of a particular grease which are inﬂuenced by type of thickener, base oil present in it and also on the additives. For example lithium grease can be recommended up to + 120°C operating temperatures. Different greases, their operating temperatures formulated in different oils and their general applications are indicated as above.
Application Conditions and Grease Recommendations
1- Environment- Moderate Load, Temp (-18°C to+120°C), High Speed, less water ingress
Industry- Agriculture, Farm, Truck & Auto WB, General purpose
Recommendation- XG/L2 Lithium EP (VG 150-220 oil; NLGI 2)
2-Environment- Heavy Load, Temp (-18°C to + 150°C), Moderate Speed, some water ingress
Industry- Agriculture, mining Construction, Farm, Truck & Auto (NLGI GC-LB), Heavy Duty
Recommendation- Lith. Complex EP (VG 150-220 oil; NLGI 2)
3-Environment- Extreme Load, Temp (-18°C to + 150°C), Low Speed, humid and Dusty Environment
Industry- Oil & gas, drilling, fertilizer plants, agriculture / Farm, Off Highway, Mining, Heavy Industry
Recommendation- Lithium Complex EP Greases (VG 460 ; NLGI 2) or Sulfonate Complex
4-Environment- High Speed, Moderate Load, Temp (- 40 °C to + 180°C ), Moderate water
Industry- Agriculture / Farm, Off Highway, Mining, Heavy Industry, petrochemicals
Recommendation- Synthetic Greases (Lithium Complex, Polyurea, Sulfonate Complex)
5-Environment- Incidental Food Contact, Hot & Cold Temp, High speeds, Moderate loads
Industry- Food & Beverage Industry And pharmaceuticals
Recommendation- H1 Food Grade Greases (Aluminum Complex )