LAGUNA STATE POLYTECHNIC UNIVERSITY STA. CRUZ LAGUNA COLLEGE OF ENGINEERING
DROP AND HARDNESS TEST OF GREASES ME LABORATORY 1 ME 4112
SUBMITTED BY: ANDA, JANE N. DE LEON ESPERANZA M. BSME 4A
SUBMITTED TO: ENGR. ROMEO D. SOLITARIO JR.
AUGUST 14, 2017
DROP AND HARDNESS TEST OF GREASES Grease
A true grease consists of an oil and/or other fluid lubricant that is mixed with a thickener, typically a soap, to form a solid or semisolid. Greases are a type of shearthinning or pseudo-plastic fluid, which means that the viscosity of the fluid is reduced under shear.
Drop Test of Greases
The dropping point of soap-thickened lubricating grease is the temperature at which it passes from a semi-solid to a liquid state under specific test conditions. It is an indication of the type of thickener used, and a measure of the cohesiveness of the oil and thickener of a grease. Dropping point is used in combination with other testable properties to determine the suitability of greases for specific applications. It is applicable only to greases that contain soap thickeners. Greases with other thickeners, such as many synthetic greases, do not change state. Instead, they separate oil, and the dropping point as a phase transition does not apply. ASTM test procedure The dropping point test procedures are given in ASTM standards D-566 and D-2265. 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 pl aced 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. 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 suffi cient to assess service performance because dropping point is a static test. Hardness Test of Greases
Grease is made up of base oil, a gelling agent or soap thickener (sometimes called filler) and additives, which perform in much the same way as oil additives.The consistency of grease is controlled by the type and ratio of the gelling agent to the oil and its viscosity.Grease can harden or soften in service due to the effects of contamination, loss of oil or mechanical shearing. Grease Consistency Consistency is defined as the degree to which a plastic material resists deformation under the application of force. In the case of lubricating greases, this is a measure of the relative hardness or softness and has some relation to flow and dispensing properties. Materials Penetrometer (capable of indicating depth in tenths of a millimetre) Standard Penetrometer Cone Grease Worker (Grease Cup, Cover and Plunger) Grease Worker Drive (Manual or Motorized) Grease Cutter Temperature Bath Spatula Temperature-Measuring Device Overflow Ring (Optional)
Unworked Penetration or P0 Procedures: 1. The sample is brought to 25 ± 0.5°C (77 ± 1°F) in a worker cup or other suitable container. 2. The cone assembly of the penetrometer is released and allowed to drop f reely into the grease for 5 ± 0.1 s, creating a hole in the grease. 3. The technician records the depth in a tenth of a millimeter of this hole. This value is known as the P0 or unworked penetration. 4. Three determinations are made and averaged to give the reported result.
Worked Penetration Procedure: 1. The sample is brought to 25 ± 0.5°C (77 ± 1°F) and placed in the worker cup. 2. The sample is subjected to 60 double strokes in the grease worker. 3. The penetration is determined immediately by releasing the cone assembly from the penetrometer and allowing the cone to drop freely into the grease for 5 ± 0.1 s. 4. Three determinations are made and averaged to give the reported result. This value is known as the P60 or worked penetration.
These values determine the stiffness of the grease and how a grease will react over time to service and wear.The higher the penetration value, the softer the grease. The lower the penetration value, the stiffer the grease. A grease that is too soft may migrate away from the area that needs to be lubricated. A grease that is too stiff may not effectively migrate into those areas that need to be lubricated.
