Extended range Scanning Brookfield techniques

Details Extended range Scanning Brookfield techniques Extended range Scanning Brookfield techniques

2000-05-04

2002-10-15

Larkin, Daniel S. (Department: 2856)

Measuring and testing

Liquid analysis or analysis of the suspension of solids in a...

Viscosity

C073S054260, C073S054320

Reexamination Certificate

active

06463793

ABSTRACT:

FIELD AND PURVIEW OF THE INVENTION
The present invention concerns a method of determining a physical property of a liquid sample to include a viscometric and/or Theological property if not a structural physical property such as gelation and/or crystallization, which employs a rotating viscometer, especially a Scanning Brookfield Viscometer technique which employs a Brookfield-type head having a high torque capacity; as well as a device useful for carrying out the same, which is the Brookfield-type head having the high torque capacity in combination with temperature-scanning equipment. In essence, the invention provides ways and means to measure low and/or high temperature viscosity of a liquid, for example, a motor oil having a very high viscosity and/or a gelation point owing to its intrinsic properties, oxidation and/or sooting and so on, with an accuracy, precision, rapidity, and repeatability heretofore unknown in the art, as well as provide data heretofore inaccessible or unknown in the art, by employment of a temperature-scanning technique.
BACKGROUND TO THE INVENTION
I. In General
Standard Scanning Brookfield techniques are well known in the field of viscometry and rheology. See, e.g., ASTM D 5133-96. In general, the standard Scanning Brookfield technique (SBT) is a method in viscometric testing for determining certain characteristics and parameters of fluids, for example, engine oils. Many of the standard runs vary the temperature from zero to minus forty degrees C, with small incremental changes in temperature over two to three days. Some, however, expand the temperature range, say, from +25 to −70 degrees C. See, Savant, Inc.,
Lubrication Technology
, May, 1998, pages 1, 2 and 4. Note, Selby et al., U.S. patent application Ser. No. 09/032,661 (abandoned) which discloses how the jet fuels and the like low viscosity liquids can be analyzed. In the standard techniques, however, very high viscosity liquids are found to be poor candidates for the techniques, if they can be considered to be effectively characterized at all. In fact, the ASTM D 5133 method cannot provide all data necessary for engine lubrication fluids under all operating conditions. For example, in internal combustion engine operation, fluid operation characteristics concerning the region of fluid operation in the so-called “Third Zone,” i.e., from the pump to the lubrication site, are being recognized as a critical area of concern in lubricant performance.
Nevertheless, in the ever more sophisticated art of lubricant characterization and employment, very high viscosity liquids come more and more under consideration. High viscosity and gelation of lubricating oil, for example, can be of critical concern not only when exposed to very low temperature environments but also in higher temperature environments when the engine oil is highly loaded with engine soot, when the engine oil is highly oxidized, or both. And yet, efficient test methodology is lacking in this critical area, which can be employed to predict lubrication fluid performance—before engine breakdown may occur as a result of the use of an inadequate lubricant.
Actually, engine oils which show classic gelation in sensitive bench test devices developed to correlate with field-failing oils show little or no evidence of gelation effects in fairly recent ASTM cold-room pumpability work. In addition to raising questions about the meaning of the pumpability results, this has led to difficulty in developing correlations between results from the engines and the bench-test sources of low-temperature data.
Brookfield-type rotational viscometer heads having low, medium, high and very high sensitivities are known. See, TABLE 1, infra. The medium, high and very high sensitivity models, in particular, are heretofore known to be employed in set, single-temperature settings, and data and correlations obtained therefrom are limited.
II. Brief History
Pumpability of engine oils at low temperatures has been an ongoing concern for a number of years, particularly for engine manufacturers who have seen pumpability problems as increasing their burden of warranty costs. See, Appeldoorn, “Motor Oil Viscosity and Cold Starting,” API Mtg., Chicago, November, 1948; SAE PT-10, pp. 1-6; Selby, “Viscosity and the Cranking Resistance of Engine Oils at Low Temperatures,” 6th World Petroleum Congress Proceedings, Section VI, Frankfurt, June, 1963, pp. 241-258; McMillan et al., “The Relationship of Low-Temperature Rheology to Engine Oil Pumpability,” SAE Paper No. 730478 (SP-382), Viscosity and Its Application to Automotive Lubricants, SAE National Automobile Engineering Meeting, Detroit, May 14-18, 1973; Groh, “Pumpability—Tempus Fugit,” Proceedings of the 1982 International Conference on the Viscometry of Automotive Lubricants, pp. 57-64, published 1983 by Savant, Inc., and Bierylo, “Low-Temperature Deficiencies in Marketed Engine Oils,” Proceedings of the 1982 International Conference on the Viscometry of Automotive Lubricants, pp. 65-68, published 1983 by Savant, Inc. While either the engine oil or the engine design (or a combination of both) may be the primary cause, the extensive damage that can ensue from a lack of sufficient oil supply to highly loaded lubrication sites in the engine often obscures any role of the oil. Oil-induced pumpability failure thus places warranty costs on the engine manufacturer unless there is an epidemic of failures identifying a common oil linkage.
An emphasis has been placed on lower SAE W-Graded engine oils
For several years engine manufacturers have encouraged the use of lower viscosity, multi-grade engine oils such as SAE 5W30 and 10W30. Reasons given have been a quicker supply of oil to lubrication sites at low temperature as well as fuel efficiency benefits. This direction of technical development would seem to also improve rapidity of lubricant flow in the engine on start-up at low temperatures.
Highly refined, hydro-treated base stocks have aided such development but also brought about the need to treat the increased paraffinic content of these highly refined mineral oil base stocks carefully with pour-point depressants. Such oils can be very sensitive to type and concentration of the pour-point depressant and thus require careful monitoring in production to avoid misblends having significant gelation. See, Kinker et al., “Evaluation of the Low Temperature Performance of Engine Lubricants Using the Scanning Brookfield Viscometer,” 11th International Colloquium on Tribology, Stuttgart, Jan. 13-15, 1998.
Additionally, it has been shown that even mixing brands of engine oils can produce gelation as a result of the interaction of viscosity index (VI) Improvers in one lubricant with the pour-point depressant and paraffinic content of another oil. See, Rhodes, “Low-Temperature Compatibility of Engine Lubricants and the Risk of Engine Pumpability Failure,” SAE Paper No. 932831 (SP-996), SAE Fuels and Lubricants International Fall Conference, Philadelphia, Oct. 18-20, 1993; Rhodes, “Assessment of the Low-Temperature Incompatibility Risk of Commercial Engine Oils,” SAE Paper No. 941976 (SP-1055), SAE 1994 Transactions, Journal of Fuels & Lubricants, Section 4, pp. 1342-1351.
III. Heretofore Known Status of Pumpability Studies
At low ambient temperatures, the importance of rapidly supplying engine oil to lubrication sites in the engine has led to incorporating pumpability limits in SAE J300 as well as the establishment of firm specifications by automotive engine manufacturers limiting the level of engine oil gelation as measured by the so-called Gelation Index. These specifications have been applied to engine oils used both internally (factory fill) and internationally. See, Ford Motor Co., Inc., Ford Engineering Material Specification WSB-M1C241-A, 1993; Chrysler Corp., Engineering Standard No. MS-9767, June, 1995; Cummins Engine Co., Inc., Material Specification No. 20,057-00, May, 1985; Engine Oil Licensing and Certification System, “ILSAC GF-2 Minimum Performance Standard for Passenger Car Engine Oils,” Nov. 6, 1995.
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