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Lubrita Lubrication Greases Tests
CONE PENETRATION OF LUBRICATING GREASE
Penetrometer:
Used in the application of the cone to the surface of the sample and for measuring the penetration at the conclusion of the test. Constructed so that by means of a slow motion adjustment, the tip of the cone adjoins the level surface of the sample, while maintaining a zero reading on the indicator. The cone falls when released without appreciable friction. Cone – Consisting of a conical body of brass, magnesium or other suitable material with detachable hardened steel tip. The total weight of the cone and its movable attachments shall be 150g ± 0.10g. Grease Worker – The worker may be constructed for either manual or mechanical operation provided a rate of 60 ± 10 strokes per minute can be maintained.
Procedure:
With the sample at 77 ± 1 F, place into worker cup until it overflows at least one pound of the desired sample. The inclusion of air is avoided by packing with a spatula. For a worked penetration, place the plunger on the worker and within one minute complete 60 full, double stroke. Prepare the sample in the cup for testing so that a uniform and reproducible structure of grease will be obtained. Scrape off the excess grease extending over the rim of the cup by moving the blade of the spatula, held inclined toward the direction of motion at an angle of 45°, across the rim of the
cup, retaining the portion removed. Place the cup on the penetrometer table making sure it cannot teeter during the test. Observe that the cone is in its “zero” position, then lower, as a unit, the cone and indicator of the container. Lock
the cone and indicator assembly in position and bring the tip of the cone down to just touch the surface of the grease by means of the slow motion adjustment and with the aid of the shadow obtained in the mirror assembly. Press the release lever allowing the cone shaft to penetrate into the sample for the required five seconds. Gently depress the indicator shaft until it is stopped by the cone shaft and read the penetration from the indicator scale. Repeat the last procedure for the remaining two test that are required, making sure that the cone has been wiped clean and smoothing the surface of the grease each time. The average of the three tests is the penetration of the sample.
What is Penetration?
Penetration, with respect to a lubricating grease, is the depth (in tenths of a millimeter) that a standard cone penetrates a sample of the grease under prescribed conditions of weight, time and temperature.
Why the Test?
Penetration is a measure of consistency of a grease to determine its plasticity. How to Determine Penetration The grease is brought to a standard temperature in a container which is then placed directly below the cone tip. Release of the plunger permits the cone to drop into the grease.
LUBRICATION TESTS
GREASE SHEAR STABILITY
The Motor-Matic Grease Working Machine is used for determining the ASTM standard cone penetration of grease at 77 F (25 ºC). It is used extensively for ASTM Method D-217.
Purpose:
To determine the relative increase or decrease in consistency of a grease after being worked for 10,000 or more strokes. This determination is a measure of the mechanical stability of the lubricant.
Apparatus:
A Motor-Matic Grease Worker machine equipped with two ASTM grease workers, one having 1/4- inch holes and the other having 1/16-inch holes. The mechanical counter determines the number of strokes.
Procedure:
Place the required amount of grease (approximately 1 lb) in the worker*. Assemble the apparatus using the cover with 1/4" holes in the worker plate. Work the sample for 60 strokes; then take the ASTM standard cone penetration reading for a worked grease. Reassemble the apparatus using the cover with 1/7.6" holes in the worker plate. Operate for a
designated number of strokes as shown on the mechanical counter. The sample is cooled to 77 ± 1 F, reworked for 60 strokes, then final penetration is taken. Ten thousand strokes is a moderate amount of working and change in penetration between 60 strokes and 10,000 strokes indicates the degree of mechanical stability for the lubricant under test.
What is Shear Stability?
Shear or mechanical stability of a grease is its ability to with-stand repeated working with minimum change in its structure or consistency.
Why the Test?
The shearing action in the test apparatus simulates the working of the grease in service.
Test Procedure
The consistency is measured at 60 strokes and repeated after 10,000 or more strokes producing a
numerical evaluation according to the following formula:
(FINAL READING — INITIAL READING) / (INITIAL READING) = % Change
TO 5% EXCELLENT
5.1% TO 15.0% GOOD
15.1% TO 30.0% FAIR
30.1 % AND OVER POOR
LUBRICATION TESTS
DROPPING POINT OF GREASE
Definition:
The ASTM dropping point is the temperature at which a grease passes from a semisolid to a liquid state under the conditions of the test.
Apparatus:
Consists of a grease cup, a special test tube, thermometers, 400 ml beaker with a suitable oil as a heating medium, an electrical heater, and a metal rod, 6" long, 3/64" to 1/16" diameter, polished.
Procedure:
Place the cork on one of the thermometers so that the tip of the thermometer bulb will be about 1/8" above the bottom of the grease cup when the apparatus is assembled. The other cork is placed equidistant between the lower end of the upper cork and the grease cup this cork will have to be worked and cut to fit inside the test tube. Suspend the other thermometer into the oil bath so that its bulb will be about the same level as the test thermometer. Fill the grease cup with a sample of grease and gently press the grease into the cup until a small amount is extruded at the small opening. Using the metal rod, cut a wedge of grease from the cup by revolving the cup against the rod and simultaneously pushing the rod upward. A smooth film of grease shall remain in the cup. Assemble the apparatus, start the stirrer and heat at a rate of 8 to 12 F per minute until the bath reaches a temperature approximately 30 F below the expected dropping point. Reduce the rate of heating so that the temperature in the test tube will be within 4 F or less of the bath temperature. As the temperature increases, the grease will slowly protrude through the orifice of the cup. The temperature at which a drop of grease falls to the bottom of the cup is the dropping point. If the drop has a tailing thread, the test is continued until it breaks completely.
WHAT IS DROPPING POINT?
The dropping point of grease is that temperature at which grease passes from a semi-solid to a liquid state.
Why the Test?
The dropping point is a qualitative indication of the heat resistance of grease on applications where a semisolid lubricant is required.
How to Determine Dropping Point?
When the first drop of grease falls through the hole in the bottom of the cup, the average of the readings on the two thermometers is considered the dropping point of the grease.
Typical Drop Point Ranges
Calcium Base grease (Hydrous) 160-210 F (70-98 Celcius)
Sodium Base greases 275-350 F (135-177 Celcius)
Lithium Base greases 350-400 F (177-204 Celcius)
Bentone Base greases over 500 F (above 260 Celcius)
Silicone greases over 500 F (above 260 Celcius)
LUBRICATION TESTS
GREASE PUMPABLITY
Preliminary Instructions:
One pound sample of fresh lubricant is required. The lever gun must be carefully filled with lubricant to avoid air pockets.
Test Procedure:
1. Open valve "1" (to purge and charge system).
2. Lever gun filled with sample lubricant (free of all air pockets) is coupled to the lubricant fitting.
3. Operate lever gun until lubricant begins to flow from system.
4. Close valve "1."
5. Operate lever gun and build up pressure to gage reading of 1800 psi.
6. Place paper cup at outlet of valve "2." Open valve "2" to vent pressure.
7. Gage indicator hand will start to drop as soon as valve "2" is opened. Wait 30 seconds to take the reading of the indicator hand. Repeat test three times and take an average reading to determine supply-line size.
Cleaning Instructions:
1. The Ventmeter should be cleaned as soon as possible after each test. The gage should be checked for accuracy. Gage must read zero psi when system is empty and clean. Recalibrate if necessary by resetting- indicator to zero.
2. Flush petroleum solvent through Ventmeter until solvent appears clean. With Ventmeter full of clean solvent, let Ventmeter stand for at least one hour. Flush solvent from Ventmeter. Caution: Pressure must be vented from Ventmeter before disconnecting coupler.
3. Attach an air-line to the air nipple and pass air through the Ventmeter until all solvent has been removed and Ventmeter is dry.
What is the Ventmeter Test?
The Ventmeter Test is a rapid means of determining at a given temperature: 1. What types of grease according to consistency can be used in a given grease supply line or 2. What size of line should be used for a type of grease and supply line length. The pressure reading on the gage of the Ventmeter after 30 seconds of venting is called the Ventmeter Viscosity.
Why the Test?
By using the Ventmeter and related supply line charts, the performance of a grease in a given system can be predicted or a grease supply line can be easily designed for a given grease.
Procedure:
The Ventmeter is an instrument for measuring the Ventmeter viscosity of a pumpable grease. It consists of a 25-foot coil of 1/4-inch copper tubing with a gage at one end and a grease fitting at the other. Manual vent valves are located at either end of the test coil. The lubricant to be tested is pumped into the ventmeter by a lever gun until the pressure has developed to 1800 psi. The pressure is then vented and the venting rate timed; the pressure on the gage at the end of 30 seconds is the vent-meter viscosity.
LUBRICATION TESTS
GREASE OXIDATION
This method outlines a test for determining the resistance of lubricating greases to oxidation under static conditions.
Outline of Method:
The sample of grease is oxidized in a bomb heated to 210 ±1F and filled with oxygen to 110 psi. Pressure is observed and recorded at stated intervals. The degree of oxidation after a given period of time is determined by the corresponding decrease in oxygen pressure.
Apparatus:
Oxidation Bomb—Norma-Hoffman type. Bath—Containing oil and capable of maintaining a temperature of 210 ± 1F throughout test. Pressure gages graduated to 1 psi with a maximum reading of at least 120 psi. Dish holder and
pyrex dishes.
Procedure:
Fill each of five dishes with 4 grams of grease, distributing the grease so that a smooth level upper surface is achieved. Place the dishes in the dish holder and place carefully in the bomb. Assemble the bomb and tighten the fastening bolts uniformly. Introduce 100 psi of oxygen into the bomb—let stand overnight. If no leaks are apparent, place bomb in oil bath previously heated to 210 F. As the pressure rises, intermittently release oxygen from the bomb until a constant pressure of 110 ± 0.5 psi is obtained for at least two hours. Observe and record the pressure at least every 24 hours.
Continue the oxidation for 100 hours. Report the pressure drop in pounds per square inch for the 100 hours.
What is the Oxidation Bomb Test?
This test is a method for deter-mining the resistance of lubricating greases to oxidation under static conditions for long periods of time.
Test Procedure
Each of 5 dishes filled with 4 grams of grease are placed in the bomb. The bomb is then charged with 100-psi-of oxygen and after a- 24Thour leak-proof test, placed in an oil bath at 210 F adjusting the pressure to 110 psi. Results are reported as psi gage pressure drop after 100 hours.
Why the Test?
To evaluate resistance to oxidation by measuring oxygen absorption. The absorption of oxygen
prevents free movement and results in costly corrosive action on bearings.
Typical Results
0 to 5 lb psi drop—Excellent
5 to 10 lb psi drop—Good
LUBRICATION TESTS
WATER WASHOUT
Apparatus:
1. Test unit as illustrated
2. Ball bearing (No. 204K Conrad type 8 ball bearing)
3. Thermometer
4. Distilled water
5. ASTM precipitation naphtha
6. Balance
Procedure:
Clean the test bearing with precipitation naphtha and air dry. The tared bearing is packed with 4.0 ± .05 grams of the grease sample and is then inserted along with the tared shields into the housing to complete assembly of the unit.
A minimum of 750 ml of distilled water is placed in the reservoir; making sure that the water level is below the bearing housing. If the test is to be run at 100 ± 5F, the apparatus will generate sufficient heat to maintain the temperature within the range. However, if the test is to be run at 175 -± 3F, it will then be necessary to use the heater and controls.
When the water reaches the selected temperature, the by-pass valve is adjusted to give a water flow rate through the capillary jet of 5 ± 0.5 ml per second. The water jet is positioned so that it impinges on the end plate 1/4" above the outer opening of the bearing housing. The test is continued for one hour with the bearing operating at a speed of 600 Li.- 30 rpm. At the end of the hour period the unit is turned off, the bearing and shields are removed and placed on a
tared watch glass which is then placed in an oven for 16 hours at 170 10F. At the end of the drying period, the watch glass and contents are cooled and weighed to deter-mine loss of grease through water washout.
What is the Water Washout Test?
This test is a method for deter-mining the water washout characteristics of lubricating greases from a bearing under pre-scribed laboratory conditions
Test Procedure
A fixed amount of grease is packed in a tared ball bearing which is inserted in a housing with specified clearances and rotated at 600±30 rpm. Water con-trolled at a specified temperature of 100 F impinges on the bearing plate at 5±0.5 ml per second. The amount of grease washed out in one hour is a measure of the resistance of the grease to water washout. The test is repeated with a water temperature of 175 F.
Why the Test?
Water washout of grease from bearings is costly and harmful to efficient maintenance. Water washouts can also become very costly.
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