What is Grease?

Grease is a semi-solid lubricant used to reduce friction and wear between mechanical components. Unlike oils, which are liquid lubricants, grease remains in place and provides long-lasting lubrication even under harsh conditions.

Can You Mix Different Types of Grease?

Mixing different types of grease is generally not recommended. This is mainly due to potential compatibility issues that can impact performance, cause separation and leakage, shorten the grease life as well as increasing maintenance costs from unplanned downtime.

If you are changing to a different type of grease, make sure to thoroughly clean out the old grease from bearings, gears, and other components to avoid contamination.

If mixing is unavoidable, ensure that the greases are compatible. Refer to the grease manufacturer's guidelines regarding compatibility with other greases.

NLGI Grades and Consistencies

The NLGI (National Lubricating Grease Institute) scale is a classification system that measures the consistency of lubricating greases. It is crucial for determining the appropriate grease for specific applications, based on its thickness or stiffness. The scale ranges from 000 to 6, with each grade corresponding to a different level of hardness.

The consistency of grease is measured using a penetrometer, an instrument that determines the depth to which a standard cone penetrates the grease under controlled conditions. The test is typically conducted at 25°C and involves dropping the cone into the grease for a specified time. The depth of penetration, measured in tenths of a millimetre, determines the NLGI grade.

NLGI Consistency Grades	Worked Penetration	Consistency Food Analogy
			NLGI 000 (Very Soft Grease)	445-475	Very fluid, similar to cooking oil.
			NLGI 00 (Soft Grease)	400-430	Fluid, similar to apple sauce.
			NLGI 0 (Semi-fluid Grease)	355-385	Similar to brown mustard
			NLGI 1 (Slightly Soft Grease)	310-340	Similar to tomato paste
NLGI 2 (Standard Grease)	265-296	Similar to peanut butter
NLGI 3 (Firm Grease)	220-250	Similar to vegetable shortening
NLGI 4 (Very Firm Grease)	174-205	Similar to frozen yogurt
NLGI 5 (Hard Grease)	130-160	Similar to smooth pâté
NLGI 6 (Very Hard Grease)	85-115	Similar to cheddar cheese

Applications of Different NLGI Grades

NLGI 000 and 00 (Very Soft Grease)

• Centralized Lubrication Systems: Used in automated lubrication systems where grease needs to flow easily through narrow pipes and fittings.
• Gearboxes: Ideal for gearboxes where a more fluid grease is required to ensure thorough lubrication of gear teeth.
• Low Temperature Environments: Suitable for applications in cold environments where thicker greases would become too stiff.

NLGI 0 (Soft Grease)

• High-Speed Bearings: Used in applications where the grease needs to flow easily but still stay in place at high speeds, such as electric motors.
• Gearboxes: Suitable for moderate-speed gearboxes where a slightly thicker grease than NLGI 00 is needed.

NLGI 1 (Slightly Soft Grease)

• Moderate Speed and Load Bearings: Used in industrial applications where a balance between fluidity and staying in place is required.
• Electric Motor Bearings: Suitable for bearings in electric motors operating at moderate speeds and loads.

NLGI 2 (Standard Grease)

• Automotive Bearings: Widely used in wheel bearings and chassis components in vehicles.
• General Industrial Machinery: Common in a variety of industrial applications, including conveyors, pumps, and fans.
• Agricultural Equipment: Used in tractors, combines, and other farming machinery.

NLGI 3 (Firm Grease)

• Wheel Bearings: Especially in heavy-duty vehicles where higher load capacities are required.
• High-Load, Low-Speed Bearings: Suitable for applications like crusher bearings in mining operations.

NLGI 4 (Very Firm Grease)

• Very High-Load Bearings: Used in heavy machinery that operates under extreme loads and where minimal leakage is crucial.
• Vertical Shaft Applications: Ensures grease remains in place in vertical shaft applications under heavy loads.

NLGI 5 and 6 (Hard and Very Hard Grease)

• Specialized Applications: Used in specific situations requiring very thick grease, such as certain types of enclosed gear systems or heavy-duty industrial applications with minimal movement.

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