Method of measuring the effect of fine filtration conditions on the defoaming retention properties of lubricants

Abstract

A test method for evaluating lubricant performance, including defoaming and filterability, is disclosed. The method involves using a filter testing apparatus comprising a heated tank equipped with a temperature sensor, wherein the heated tank is fluidly connected to a circulation pump and a filter housing equipped with a filter having a pore size equal to or less than 25 micrometers. The heated tank is then filled with lubricant to at least 50% capacity and heated to at least 80°C. The lubricant is then circulated through the filter testing apparatus using the circulation pump, such that the lubricant passes through the 25-micrometer (or smaller) filter at least 5,000 times. A sample of the filtered lubricant is then obtained, and its defoaming properties are measured using ASTM D892.

Description

Technical Field

[0001] The present invention relates to methods for measuring the defoaming properties of lubricants after simulating turbulent or fine filtration conditions. These methods are particularly suitable for simulating field conditions of industrial gear oils. Background Technology

[0002] Foaming in industrial gear oils (“IGO”) can cause gearbox problems, including excessive wear, overheating, and oxidation. Foaming exacerbates wear because air displaces the lubricant between gears and other metal parts in the gearbox, leading to direct metal-to-metal contact. The air in the foam can also form a thermal barrier, hindering effective heat dissipation throughout the gearbox. Overheating can cause the various components in the industrial gear lubricant to decompose, reducing its effectiveness. Entrained air can also cause excessive oxidation of the lubricant and its components, further reducing their effectiveness.

[0003] Several industry-recognized testing methods exist for evaluating the performance of IGOs ​​under laboratory conditions, including defoaming and filtration properties. However, these methods do not always correlate well with or predict the actual performance of IGOs ​​in field or "real-world" applications. Therefore, a laboratory testing method that better predicts the actual field performance of IGOs ​​is needed. Summary of the Invention

[0004] The disclosed test methods are better predictors of IGO field performance. Therefore, test methods for evaluating lubricant performance, including defoaming and filterability, are disclosed. These methods involve utilizing a filtration test rig comprising a heated tank equipped with a temperature sensor, wherein the heated tank is fluidly connected to a circulation pump and a filter housing equipped with a filter having a pore size equal to or less than 25 micrometers. The heated tank is then filled with lubricant to at least 50% capacity and heated to at least 80°C. The lubricant is then circulated through the filtration test rig using the circulation pump, such that the lubricant passes through the 25-micrometer (or smaller) filter at least 5,000 times. A sample of the filtered lubricant is then obtained, and its defoaming properties are measured using ASTM D892.

[0005] In some embodiments, the filter may have a pore size equal to or less than 10 micrometers. In some embodiments, the lubricant may contain at least one polyacrylate defoamer and / or at least one silicone-containing defoamer.

[0006] In some embodiments, the lubricant is circulated through the filter test apparatus at a flow rate of 1 liter / min to 15 liters / min. In some embodiments, the lubricant aliquots may be tested using ASTM D892 before adding them to the filter test apparatus and / or before circulating them through the filter housing to establish a baseline for defoaming performance. These baseline results can then be compared with results obtained after the lubricant has circulated through the filter housing. In other embodiments, the filter test apparatus may be flushed with aliquots of the lubricant before circulating the lubricant through the filter housing.

[0007] The heating tank can be heated by a jacket, heat exchanger and / or direct immersion heater. Attached Figure Description

[0008] Figure 1 A schematic diagram of the filtration testing apparatus is shown. Detailed Implementation

[0009] The preferred features and implementation schemes will now be described in a non-restrictive manner.

[0010] Test methods for evaluating lubricant performance, including defoaming and filterability, are disclosed. These methods include the use of a filter testing apparatus comprising a heated tank equipped with a temperature sensor, wherein the heated tank is fluidly connected to a circulation pump and a filter housing equipped with a filter having a pore size equal to or less than 25 micrometers.

[0011] Filtration testing device

[0012] Filter testing equipment can be like Figure 1 The configuration is shown. The filtration test apparatus (10) may include a heating tank (12) equipped with a heat source and a temperature sensor (not shown). The heating tank is filled to at least 50% capacity with the lubricant to be tested through the filling port (14) or other opening (which may be submerged). The lubricant can then be heated in the tank to at least 80°C. The heating tank may be heated by any means known to those skilled in the art, including jackets, heat exchangers, and / or direct immersion heaters. The lubricant may also be gently agitated with blades or impellers to promote heating, provided that excessive air is not introduced into the lubricant, which may affect the defoaming test results.

[0013] Once the lubricant reaches the set temperature, it is circulated from the heating tank (12) to the circulation pump (18) via a first delivery line (16). The lubricant then travels through the circulation pump (18) through a second delivery line (20) to the filter housing (22). The filter housing is equipped with a filter with a pore size of 25 micrometers or smaller. After passing through the filter housing, the lubricant is circulated back to the heating tank (12) via a third delivery line (24). The tank inlet from the third delivery line (24) can be submerged. In some embodiments, the various parts of the filtration testing apparatus (tank (12), delivery lines, etc.) may be thermally insulated to help maintain a constant temperature and prevent the test lubricant from cooling significantly as it flows through the filtration testing apparatus.

[0014] Suitable filtration testing equipment includes commercially available filtration testing equipment or other testing equipment, such as suitably modified clutch testing equipment, for example, equipment available from Siemens Aktiengesellschaft (Munich, Germany) or ZF Friedrichshafen AG (Friedrichshafen, Germany). ZF filtration testing equipment can be based on the ZF SSP180, ZF GK1, or ZF GK2 clutch testing equipment, which have been modified into filtration testing equipment. However, the inventors of the methods disclosed herein have found that the recommended test procedures accompanying these devices are not always well-related to or predictive of the defoaming and filtration performance of lubricants in the field. This can lead to the approval of new lubricants using known test methods, which may perform poorly under actual or field conditions, resulting in field problems.

[0015] However, the filtration test methods disclosed herein correlate more accurately with actual or field conditions, and are therefore better suited for approving new lubricants than known test procedures recommended by testing equipment suppliers. Without limiting the disclosed techniques to a single operational theory, it is believed that some types of defoamers form droplets that are easily sheared as they pass through the filter, resulting in smaller defoamer droplets throughout the lubricant. Smaller droplets may be less effective at reducing foaming. The test methods disclosed herein are believed to more accurately simulate these shearing effects that occur in the field.

[0016] The test method disclosed herein includes heating the lubricant to at least 80°C and circulating the lubricant through a filter of a filtration test apparatus at least 5,000 times. A sample of the filtered lubricant is then obtained, and its defoaming properties are measured using ASTM D892.

[0017] The filter in the filter housing may have a pore size of 25 micrometers or less. In some embodiments, the filter may have a pore size of 10 micrometers or less (fine filtration). Exemplary filters are not overly limited and may include any commercially available inline filter having the required pore size and compatible with the selected filter housing. HYPAC and MAHLE are well-known online filter suppliers. In some embodiments, the lubricant may contain at least one polyacrylate defoamer and / or at least one silicone defoamer. Fine filtration or filters having at least 10 micrometers may be used with lubricants containing acrylate defoamers. When using silicone defoamers, filters with a pore size of 25 micrometers are generally preferred.

[0018] In some embodiments, the lubricant is circulated through the filter test apparatus at a flow rate of 1 liter / min to 15 liters / min. In some embodiments, aliquots of the lubricant may be tested using ASTM D892 before adding or circulating through the filter housing (and the filter) to establish a baseline for defoaming performance. These baseline results can then be compared with results obtained after the lubricant has been circulated through the filter housing. In other embodiments, the filter test apparatus may be flushed with aliquots of the lubricant before circulating through the filter housing.

[0019] The test methods disclosed herein include heating the lubricant to at least 80°C and circulating the lubricant through a filter of a filtration test apparatus at least 5,000 times or cycles. Table 1 below shows some operating conditions for various commercially available test apparatuses that would result in 5,000 cycles. The filtration level can be adjusted by changing the pore size of the filter.

[0020] Table 1

[0021]

[0022] Then, a sample of the filtered lubricant was obtained, and its defoaming properties were measured using ASTM D892.

[0023] Therefore, in some embodiments, the filtration testing apparatus is a Siemens filtration testing apparatus equipped with a 25-micron or 10-micron HYPAC filter. In the Siemens embodiment, the volume of lubricant in the tank can be 1.5 liters, and the flow rate can be 1 liter / minute. The lubricant is circulated through the Siemens testing apparatus for 125 hours (or 5,000 cycles). After 5,000 cycles, a sample of the filtered lubricant is obtained, and its defoaming properties are measured using ASTM D892.

[0024] In some implementations, the filtration test apparatus is a ZF SSP180 clutch test apparatus equipped with a 25-micron or 10-micron MAHLE filter. In the ZF SSP180 implementation, the lubricant volume in the tank can be 10 liters, and the flow rate can be 9 liters / minute. The lubricant is circulated through the ZF SSP180 test apparatus for 144 hours (or 5,000 cycles). After 5,000 cycles, a sample of the filtered lubricant is obtained, and its defoaming properties are measured using ASTM D892.

[0025] In some embodiments, the filtration test apparatus is a ZF GK1 or GK2 clutch test apparatus (collectively referred to as "GK") equipped with a 25-micron or 10-micron MAHLE filter. The GK1 and GK2 test apparatuses are similar, differing in that the GK1 test apparatus uses a test lubricant as the hydraulic fluid for operating the clutch, while the GK2 has a separate circuit. However, the procedures disclosed herein can be applied to both apparatuses. In the ZF GK1 embodiment, the lubricant volume in the tank can be 14 liters, the flow rate can be 15 liters / minute, and the circulation time is 75 hours (or 5,000 cycles). The ZF GK2 apparatus is equipped with a bypass line with a valve connecting from the filter housing to the heated tank to bypass the test head housing the friction disc (when the valve is open), thereby reducing the surface area of ​​the apparatus. The bypass outlet to the tank is immersed in the lubricant. The lubricant can be subjected to low-turbulence conditions (through the bypass) or high-turbulence conditions (through the test head). In the ZF GK2 implementation, the volume of lubricant in the tank can be 13 liters, the flow rate can be 15 liters / minute, and the circulation time is 72 hours (or 5,000 cycles). After 5,000 cycles, a sample of the filtered lubricant is obtained, and its defoaming properties are measured using ASTM D892.

[0026] The test methods disclosed herein can be used to simulate the conditions that lubricants will experience in the field, which can be better understood with reference to the following examples.

[0027] Example

[0028] The defoaming properties of aquilots of commercially available lubricant samples (Examples 1 and 2) were tested in a laboratory setting. Examples 1 and 2 are different commercial lubricant products containing the same base oil but different additive packages, including a polyacrylate defoamer. First, a subset of the samples was tested prior to filtration using ASTM D892 – Standard Test Method for Foaming Properties of Lubricating Oils (hereinafter referred to as “D892”).

[0029] For the D892 test, the fluid is heated to 49°C to remove any thermal history. A portion of the fluid (190 mL) is then transferred to a clear 1000 mL graduated cylinder and allowed to cool to 24°C. Once the fluid reaches 24°C, air is blown through the sample at a rate of 94 mL / min for 5 minutes. After 5 minutes, the air source is turned off, and the foam volume (mL) is recorded immediately. The sample is then allowed to stand for 10 minutes, and the foam volume (mL) is recorded again. This is referred to as Sequence I in the ASTM D892-18 test.

[0030] Simultaneously, the second portion of fluid (180 mL) was transferred to a transparent 1000 mL graduated cylinder and heated to 93.5 °C. When the fluid reached thermal equilibrium, air was blown through the sample at a rate of 94 mL / min for 5 minutes. After 5 minutes, the air source was turned off, and the foam volume (mL) was immediately recorded. The sample was then allowed to stand for 10 minutes, and the foam volume (mL) was recorded again. This is referred to as Sequence II in the ASTM D892-18 test.

[0031] The same sample used for Sequence II was then cooled back to 24°C. Once the fluid reached 24°C, air was blown through the sample at a rate of 94 mL / min for 5 minutes. After 5 minutes, the air source was turned off, and the foam volume (mL) was recorded immediately. The sample was then allowed to stand for 10 minutes, and the foam volume (mL) was recorded again. This is referred to as Sequence III in the ASTM D892-18 test.

[0032] A portion of the commercial lubricant was then loaded into a Siemens filtration test apparatus to test its filterability using the Flender procedure (FFT 7300_3rd edition, hereinafter referred to as "FFT7300") for testing the filterability of oils / fluids used in Flender gear units, and to test its foaming properties using Flender ISO 12152 - Lubricants, industrial oils and related products - Determination of foaming and outgassing characteristics of industrial gear oils using a spur gear test apparatus - Flender foam test procedure (hereinafter referred to as "Flender foam"), as specified in FFT 7300. All steps in the FFT 7300 procedure were followed. The Siemens filtration test apparatus has a sealed viewing window equipped with graduations (in ml) on the front of the gearbox housing. For the Flender foam test, the gear motor was turned on for 300 (+ / - 5) seconds and then stopped. The volume of foam was observed using the viewing window and scale and recorded at different time intervals (potentially up to 90 minutes). A foam volume of 15 ml at 1 minute was considered a failure. A foam volume of 10 ml at 5 minutes is considered a failure. Laboratory results of defoaming tests for commercial lubricants are shown in Table 2.

[0033]

[0034] As shown in Table 2 above, the two commercial lubricants, Example 1 and Example 2, did not exhibit any foaming tendency in a laboratory environment before filtration using the D892 test and passed Siemens filtration using the known FFT 7300 test method. However, Example 1 exhibited a foaming tendency in the field. Example 2 showed no known foaming tendency or other problems in the field.

[0035] Although Example 1 passed the known D892 and FF 7300 defoaming tests in the laboratory, it lost its defoaming tendency in the field. Four field samples of Example 1 (field discharges 1 to 4) were obtained and subjected to D892 defoaming tests. The defoaming properties of a lubricant are permanently affected by its use in practical applications in ways that cannot be detected or predicted using the known D892 and FFT 7300 laboratory tests.

[0036] A fresh sample of a commercial lubricant was obtained (Example 1), and the filtration and D892 test methods disclosed above were performed using a Siemens testing apparatus. Another aquilot was then subjected to filtration in the Siemens testing apparatus, and the defoaming properties of the aquilot were measured at 25°C as specified in the FFT 7300 test.

[0037] The D892 tests for field and laboratory samples using the known FFT 7300 test and the filtration and foaming test methods disclosed herein are shown in Table 3 below.

[0038] Table 3: Correlation between Example 1 - Method of the Invention and On-site Drainage

[0039]

[0040] As shown in Table 3 above, compared to the known laboratory testing methods shown in Table 2 for Example 1, the test results using the method of the present invention disclosed herein are more closely correlated with field-discharged samples. Furthermore, the modified Siemens filter testing device alone (and the FFT7300 test) is not a good predictor of field performance; however, when combined with the D892, the modified Siemens filter device correlates very well with field performance. Therefore, the method of the present invention disclosed herein is a better predictor of lubricant field performance than known laboratory testing methods prior to this disclosure.

[0041] The same filtration and foam testing methods disclosed herein are also applied to other laboratory filtration testing apparatuses. The defoaming test results of Examples 1 and 2 using the disclosed methods in different testing apparatuses are shown in Table 4 below.

[0042] Table 4: Correlation between test devices

[0043]

[0044] Example 1 showed poor performance among all test apparatuses using the method of the present invention disclosed herein, which is also related to the defoaming performance of Example 1 observed in the field effluent as shown in Table 3. Note that, for ease of reference, the Siemens test apparatus results in Table 3 have been copied to Table 4.

[0045] There are no known problems with the defoaming performance of Example 2 in the art. Example 2 also showed good performance in all test apparatuses using the method of the present invention disclosed herein.

[0046] The data in Table 4 show that the method of the present invention disclosed herein produces similar results for all types of testing equipment. Furthermore, the data in Table 4 correlates well with the performance observed in the field for Examples 1 and 2. The data shows that Example 1 failed in a laboratory environment using the testing method of the present invention, which was observed in the field, rather than using known laboratory testing methods prior to the present invention. Example 2 demonstrates good performance using the method of the present invention, and there are no known defoaming problems in the field. Therefore, the testing method of the present invention disclosed herein can well predict the field performance of lubricant formulations regardless of the type of testing equipment used.

[0047] Each of the foregoing references is incorporated herein by reference, including any prior application claiming priority thereto, whether or not specifically listed above. Any reference to any reference is not an admission that the reference conforms to the prior art or constitutes general knowledge of a person skilled in the art in any jurisdiction. Unless expressly stated in the examples or otherwise, all numerical quantities of matter, reaction conditions, molecular weight, number of carbon atoms, etc., specified in this specification should be understood to be modified by the word “about.” It should be understood that the upper and lower limits of the quantities, ranges, and proportions described herein can be combined independently. Similarly, the ranges and quantities of each element of the invention can be used in conjunction with the ranges or quantities of any other element.

[0048] As used herein, the transitional term “comprising,” synonymous with “comprising,” “containing,” or “characterized in,” is inclusive or open-ended and does not exclude additional, unlisted elements or method steps. However, in every use of “comprising” herein, it is intended that the term also cover the phrases “consistently composed of” and “composed of” as alternative embodiments, wherein “composed of” excludes any elements or steps not specified, and “consistently composed of” allows for the inclusion of additional, undescribed elements or steps that do not materially affect the essential and novel characteristics of the composition or method under consideration.

[0049] While certain representative embodiments and details have been shown to illustrate the purpose of this invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention. In this regard, the scope of the invention is defined only by the following claims.

Claims

1. A method for evaluating the defoaming properties of a lubricant, the method comprising: a) Using a filter testing device, wherein the filter testing device (10) includes a heating tank (12) equipped with a heat source and a temperature sensor, and wherein the heating tank is fluidly connected to a circulation pump (18) and a filter housing (22) equipped with a filter with a pore size equal to or less than 25 micrometers. b) Fill the heating tank with the lubricant to at least 50% of its capacity; c) Heat the lubricant to at least 80°C; d) Using the circulating pump, the lubricant is circulated through the filtration test device, so that the lubricant passes through the filter 5,000 times to obtain filtered lubricant; e) Obtain a sample of the filtered lubricant; as well as f) The defoaming properties of the obtained filtered lubricant sample were measured using ASTM D892 to obtain the results after filtration.

2. The method of claim 1, wherein the filter has a pore size equal to or less than 10 micrometers.

3. The method according to claim 1 or 2, wherein the lubricant comprises at least one polyacrylate defoamer.

4. The method according to any one of claims 1 to 3, wherein the lubricant comprises at least one silicone-containing defoamer.

5. The method according to any one of claims 1 to 4, wherein the lubricant is circulated through the filter testing device at a flow rate of 1 liter / minute to 15 liters / minute.

6. The method according to any one of claims 1 to 5, wherein prior to the filling step b) or the cycling step d), equidistant samples of the lubricant are tested using ASTM D892 to obtain pre-filtration results, and the pre-filtration results are compared with the post-filtration results of step f).

7. The method according to any one of claims 1 to 6, wherein, prior to cyclic step d), the filter test apparatus is rinsed with an equal sample of the lubricant.

8. The method according to any one of claims 1 to 7, wherein the heating tank is heated by a jacket, a heat exchanger and / or a direct immersion heater.

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