The importance of grease dropping point

[Dhanush G]

Dropping Point
“Grease does not have a melting point. Instead, on heating, it becomes softer until at some point it no longer functions as a thickened lubricant. While being heated, grease may soften gradually or sharply. A common test called ‘dropping point’ tries to measure the end point of this process.” – Lubricating Grease Guide, 5 Edition NLGI.
The dropping point of grease is the temperature at which it transitions from a semi-solid to a liquid state and falls through an orifice, indicating its maximum heat resistance and structural integrity. It is a key quality control metric for determining high temperature usability.
The test is static and does not predict performance under dynamic, high-speed, or extreme load conditions. If a grease’s dropping point is exceeded, the oil separates from the soap, leaving behind ineffective soap residue and could be detrimental to health of the bearing.
It is crucial to distinguish between the dropping point and the maximum use temperature of the grease. This temperature will always be below the dropping point, and is the maximum temperature to which the grease is recommended to be exposed for optimal performance. Beyond this point, the oil will not separate, but the degradation of the grease will be greatly accelerated.
The dropping point is a measurement commonly found in data sheets and is used as a quality control measure after the production of greases, particularly in soap thickener greases, to ensure that the thickener has been correctly formed.

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