Dropping point

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The dropping point of a lubricating grease is an indication of the heat resistance of the grease and is the temperature at which it passes from a semi-solid to a liquid state under specific test conditions. It is dependent on the type of thickener used and the cohesiveness of the oil and thickener of a grease. [1] The dropping point indicates the upper temperature limit at which a grease retains its structure though is not necessarily the maximum temperature at which a grease can be used.

Grease is a semisolid lubricant. Grease generally consists of a soap emulsified with mineral or vegetable oil. The characteristic feature of greases is that they possess a high initial viscosity, which upon the application of shear, drops to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. This change in viscosity is called shear thinning. Grease is sometimes used to describe lubricating materials that are simply soft solids or high viscosity liquids, but these materials do not exhibit the shear-thinning properties characteristic of the classical grease. For example, petroleum jellies such as Vaseline are not generally classified as greases.

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Dropping point is used in combination with other testable properties to determine the suitability of greases for specific applications and for use in quality control.

ASTM test procedure

The dropping point test procedures are given in ASTM standards D-566 [2] and D-2265. [3] The test apparatus consists of a grease cup with a small hole in the bottom, test tube, two thermometers, a container, stirring device if required and an electric heater. The inside surfaces of the grease cup are coated with the grease to be tested. A thermometer is inserted into the cup and held in place so that the thermometer does not touch the grease. This assembly is placed inside a test tube. The test tube is lowered into the container which is filled with oil in D-566 and has an aluminum block in D-2265. Another thermometer is inserted into the oil/block.

ASTM International standards organization

ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services. Some 12,575 ASTM voluntary consensus standards operate globally. The organization's headquarters is in West Conshohocken, Pennsylvania, about 5 mi (8.0 km) northwest of Philadelphia.

Thermometer device to measure temperature

A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements: (1) a temperature sensor in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value. Thermometers are widely used in technology and industry to monitor processes, in meteorology, in medicine, and in scientific research.

An oil is any nonpolar chemical substance that is a viscous liquid at ambient temperatures and is both hydrophobic and lipophilic. Oils have a high carbon and hydrogen content and are usually flammable and surface active.

To execute a test, the oil/block is heated, while being stirred, at a rate of 8 °F (4.4 °C) to 12 °F (6.7 °C) per minute until the temperature is approximately 30 °F (17 °C) below the expected dropping point. The heat is reduced until the test tube temperature is at most 4 °F (2.2 °C) less than the oil/block temperature. Once the temperature has stabilized the sample is inserted. The dropping point is the temperature recorded on the test tube thermometer, plus a correction factor for the oil/block temperature, when a drop of grease falls through the hole in the grease cup. If the drop trails a thread, the dropping temperature is the temperature at which the thread breaks. D-2265 explains that the dropping point is useful to assist in identifying the type of grease, and for establishing and maintaining benchmarks for quality control. It adds that the results are not sufficient to assess service performance because dropping point is a static test.

Other test procedures

Equivalent to D566 and D2265: [1]

International Organization for Standardization An international standard-setting body composed of representatives from national standards organizations

The International Organization for Standardization is an international standard-setting body composed of representatives from various national standards organizations.

Deutsches Institut für Normung National standards organisation of Germany

Deutsches Institut für Normung e.V. is the German national organization for standardization and is the German ISO member body. DIN is a German Registered Association (e.V.) headquartered in Berlin. There are currently around thirty thousand DIN Standards, covering nearly every field of technology.

Other:

GOST refers to a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification (EASC), a regional standards organization operating under the auspices of the Commonwealth of Independent States (CIS).

Japanese Industrial Standards technical standard

Japanese Industrial Standards (JIS) are the standards used for industrial activities in Japan, coordinated by the Japanese Industrial Standards Committee (JISC) and published by the Japanese Standards Association (JSA). The JISC is composed of many nationwide committees and plays a vital role in standardizing activities across Japan.

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