Method for indirectly evaluating working life of filter based on test data

Abstract

According to the method for indirectly evaluating the working life of the filter under the actual working condition, the working life of a filter element of the filter is indirectly evaluated through conversion calculation of test time on the basis of test data of the filter of the same type in a laboratory and in combination with parameters of working conditions of the actual working condition; according to the method, the application range is expanded, and the use limitation is reduced, so that engineering maintenance personnel can be helped to carry out scientific maintenance on the hydraulic system.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic system filters, and in particular to a method for indirectly evaluating the service life of a filter based on test data. Background Art

[0002] The filter is the "guardian" of oil working medium pollution control in the hydraulic system. Under actual working conditions, as the working time continues to increase, the pollutants inherent in the system and the new pollutants caused by the wear of the actuator components are constantly filtered and intercepted by the filter to maintain the normal purification function of the oil medium and stabilize the pollution control level of the hydraulic system, thereby ensuring the working performance and reliability of the hydraulic system. As the number of pollutants intercepted by the filter increases, the flow pressure difference of the filter will gradually increase. When the pressure difference increases to the allowable limit pressure difference, the working life of the filter reaches the end. That is to say, the working life of the filter is the time when the filter filters and intercepts pollutants until the oil working medium fails to meet the minimum requirement for effective working flow. The minimum flow requirement time and the process of increasing flow pressure difference are a linear function.

[0003] The process of increasing the flow pressure difference of the filter is formed naturally with the extension of working time under actual working conditions, and can also be achieved by artificially adding test dust under test conditions. The blocking time corresponding to the increase of the flow pressure difference under actual working conditions is the working time, that is, the working life; the time corresponding to the minimum requirement of effective working flow under test conditions is the test time, that is, the test life.

[0004] Therefore, if the test conditions in the laboratory are exactly the same as the working conditions in the actual working conditions, then the test time and working time corresponding to the same blocking pressure difference will be equal. As we all know, due to the limited conditions, the working conditions under the actual working conditions cannot be completely simulated in the laboratory, so the test time cannot be completely equal to the working time. However, for the same type of filter, assuming stable working and test conditions, there must be a corresponding functional relationship between its working blocking time and the test blocking time under the same set pressure difference.

[0005] Based on the basic principles of fluid mechanics, under relatively ideal conditions, there are three main factors that affect the filter clogging pressure difference: flow rate, temperature and medium contamination. In addition to these three influencing factors, other unknown factors such as pressure shock, flow pulsation, mechanical vibration, type of pollution, etc. are assumed to be negligible. A large number of statistical results show that the degree of contamination is inversely proportional to the test life and working life. Regarding this conclusion, a relatively scientific discussion was made in the scientific paper "Solution to the Actual Life of Engineering Machinery Hydraulic Filters" published in "Mechanical and Electrical Engineering Technology" in May 2022. The theoretical basis for the functional relationship between working life and test life in the paper "Solution to the Actual Life of Engineering Machinery Hydraulic Filters" is shown in formula (1):

[0006] T=2 n-N ×t(1)

[0007] Wherein: T - actual working life of the filter element (h);

[0008] N——The contamination level of the oil under actual working conditions (ISO 4406);

[0009] t——test life of filter element (h);

[0010] n——The contamination level of the oil under the test conditions (ISO 4406); the nN in the formula is the minimum value of the difference between the three contamination levels corresponding to ISO 4406;

[0011] The oil temperature in laboratory tests is controlled according to the temperature of actual working conditions.

[0012] Furthermore, from formula (1), it can be seen that the working life T of the filter (filter element) depends only on the test life t, the pollution level n of the test oil and the pollution level N of the system oil under actual working conditions. This is a model established under the premise that the flow rate and temperature are the same, which is an ideal mathematical relationship. Obviously, this idealized model has great application limitations, and its operability in specific engineering practice is subject to many restrictions.

[0013] Therefore, in order to provide scientific guidance and timely and accurate maintenance of the hydraulic system to ensure stable operation, the evaluation of the service life of the filter in the hydraulic system is very important. Indirect evaluation of the filter service life through test data can solve the above problems. Summary of the invention

[0014] In order to solve the deficiencies in the prior art, the present invention provides a method for indirectly evaluating the service life of a filter based on test data, so as to ensure that the filter works stably in a hydraulic system during its effective service life.

[0015] The technical solution of the present invention is a method for indirectly evaluating the service life of a filter based on test data, comprising the following steps:

[0016] Step 1: Based on the above background technology, the flow rate is inversely proportional to the test life and the working life. Two influencing parameters, test flow rate q and working flow rate Q, are introduced into formula (1);

[0017] Step 2: Based on the above background technology, the viscosity is inversely proportional to the test life and working life. Introduce the test oil viscosity v into formula (1): t and the oil viscosity v T Two influencing parameters;

[0018] Step 3: Based on the changes caused by flow rate, viscosity, and the difference in the types of dust used in the plugging test, a variation coefficient K is introduced into formula (1);

[0019] Step 4: A method for indirectly evaluating the service life of a filter (filter element) based on test data is invented, which is explained by a new mathematical model established, as shown in formula (2):

[0020]

[0021] Wherein: T——working life (h);

[0022] N——The contamination level of the oil under actual working conditions (ISO 4406);

[0023] t——test life (h);

[0024] n——Contamination level of the test oil (ISO 4406).

[0025] q——test flow rate (L / min);

[0026] Q——actual working flow rate (L / min);

[0027] v t ——Viscosity of the test oil (mm 2 / s);

[0028] v T ——Viscosity of the oil actually used (mm 2 / s);

[0029] K——coefficient of variation;

[0030] Wherein: n and N are both the solid particle contamination level of 4μm (c) particle size corresponding to ISO 4406 or GB / T 14039.

[0031] When formula (2) is used to indirectly evaluate the service life of the filter (filter element), since the actual working condition is intermittent non-continuous operation, the actual working flow, oil viscosity and contamination level are all taken from the rated flow, rated working oil temperature viscosity and constant stable contamination level during the working process.

[0032] The beneficial effects of the present invention are as follows: the present invention overcomes the limitations of idealized assumptions, opens up new ideas and provides new methods for studying the actual working life of filters under different working conditions, and its operability is more in line with the actual application of filters, and has important guiding significance for the selection and system maintenance of filters in engineering machinery hydraulic systems. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to specific embodiments.

[0034] The present invention provides a method for evaluating the service life of a filter, comprising:

[0035] Step 1) Obtain the contamination level of the oil passing through the filter under test conditions. Specifically, refer to the provisions of ISO16889 "Multiple-pass method for evaluating the filtration performance of filter elements" to purify and adjust the test system, do a good job of consistency verification of the upstream and downstream automatic particle counting systems, and use test dust (fine test dust ISO-FTD, medium fine test dust ISO-MTD or other standard dust) to prepare the concentrate of the pollution injection system (generally higher than ISO 4406 / 21 grade -4μm(c))n;

[0036] Step 2) Obtain the contamination level of the oil passing through the filter under actual working conditions. Specifically, collect the working oil contamination level N (generally ISO 4406 / 14-17 level -4μm(c)) of the same type of filter in actual use;

[0037] Step 3) Collect the test flow rate of oil through the filter under test conditions.

[0038] Specifically, the temperature of the test oil is controlled within the range of 33°C-37°C, and the initial pressure difference of the filter element is measured at a set flow rate q (generally 30L / min-200L / min);

[0039] Step 4) Collect the actual working flow rate of the oil through the filter under actual working conditions. Specifically, collect the working flow rate Q of the same type of filter when it is actually used;

[0040] Step 5) Collect the viscosity of the oil passing through the filter under test conditions.

[0041] Specifically, the temperature of the test oil is controlled within the range of 33°C-37°C, and the viscosity v of the test oil is measured. tand experimental life t;

[0042] Step 6) Collect the viscosity of the oil passing through the filter under actual working conditions.

[0043] Specifically, the viscosity v of the oil used by the same type of filter at the actual working temperature is collected. T ;

[0044] Step 7) Create a model to estimate the filter service life:

[0045]

[0046] Where: T is the working life of the filter;

[0047] N is the contamination level of the oil under actual working conditions;

[0048] t is the test life of the filter, which is a known value obtained from the test;

[0049] n is the contamination level of the oil under the test conditions;

[0050] q is the test flow rate of oil through the filter under test conditions;

[0051] Q is the actual working flow rate of oil through the filter under actual working conditions;

[0052] v t is the viscosity of the oil passing through the filter under the test conditions;

[0053] v T It is the viscosity of the oil passing through the filter under actual working conditions;

[0054] K is a coefficient of variation, which is an empirical value.

[0055] Step 8) Using the model for evaluating the service life of the filter, as well as the contamination level of the oil obtained under the test conditions, the contamination level of the oil obtained under the actual working conditions, the test flow rate collected under the test conditions, the actual working flow rate collected under the actual working conditions, the viscosity of the oil collected under the test conditions, and the viscosity of the oil collected under the actual working conditions, the service life of the filter can be indirectly obtained through calculation.

[0056] Specifically, the obtained relevant parameters are input into the model. Since the test life t and the coefficient of variation K of the filter are known values, the working life T of the filter can be calculated.

[0057] The above embodiment is only one of the preferred embodiments of the present invention, and is not intended to limit the scope of implementation of the present invention. Therefore, all equivalent changes made according to the principles and calculation methods of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for indirectly evaluating the service life of a filter based on test data, comprising: Obtain the contamination level of the oil passing through the filter under test conditions; Obtain the contamination level of the oil passing through the filter under actual working conditions; Collect the test flow rate of oil passing through the filter under test conditions; Collect the actual working flow rate of oil passing through the filter under actual working conditions; The viscosity of the oil passing through the filter is collected under test conditions; Collect the viscosity of the oil passing through the filter under actual working conditions; Create a model to indirectly estimate the filter service life: Where: T is the working life of the filter; N is the contamination level of the oil under actual working conditions; t is the test life of the filter, which is a known value obtained in the laboratory for this type of filter; n is the contamination level of the oil under the test conditions; q is the test flow rate of oil through the filter under test conditions; Q is the actual working flow rate of oil through the filter under actual working conditions; v t is the viscosity of the oil passing through the filter under the test conditions; v T It is the viscosity of the oil passing through the filter under actual working conditions; K is the coefficient of variation; The model for evaluating the service life of the filter is used, as well as the contamination level of the oil obtained under test conditions, the contamination level of the oil obtained under actual working conditions, the test flow rate collected under test conditions, the actual working flow rate collected under actual working conditions, the viscosity of the oil collected under test conditions, and the viscosity of the oil collected under actual working conditions. The test life is used to extrapolate the service life of the filter under the same pressure difference.

2. The method for indirectly estimating the service life of a filter based on test data according to claim 1, wherein the method for obtaining the contamination level of the oil passing through the filter under test conditions comprises: Purify and adjust the test system, verify the consistency of the upstream and downstream automatic particle counting systems, and prepare the test concentrate of the pollution injection system with test dust (fine test dust ISO-FTD, medium fine test dust ISO-MTD or other standard dust). The contamination level n of the concentrate corresponding to particles with a particle size of 4μm (c) is higher than level 21 of ISO 4406.

3. The method for indirectly evaluating the service life of a filter based on test data according to claim 1, wherein the method for obtaining the contamination level of the oil passing through the filter under actual working conditions comprises: Collect the contamination level N of the working oil corresponding to the particle size of 4μm(c) of the same type of filter in actual use.

4. The method for indirectly evaluating the service life of a filter based on test data according to claim 1, wherein the method for collecting the test flow rate of oil passing through the filter under test conditions comprises: The temperature of the test oil was controlled within the range of 33°C-37°C, and the initial pressure difference of the filter element was measured at a set flow rate q of 30L / min-200L / min.

5. The method for indirectly evaluating the service life of a filter based on test data according to claim 1, wherein the method for collecting the actual working flow rate of the oil passing through the filter under actual working conditions comprises: Collect the working flow Q of the same type of filter during actual use.

6. The method for indirectly estimating the service life of a filter based on test data according to claim 1, wherein the method for collecting the viscosity of the oil passing through the filter under test conditions comprises: The temperature of the test oil is controlled within the range of 33℃-37℃, and the viscosity v of the test oil is measured. t and experimental lifetime t.

7. The method for indirectly estimating the service life of a filter based on test data according to claim 1, wherein the method for collecting the viscosity of the oil passing through the filter under actual working conditions comprises: Collect the viscosity v of the oil used by the same type of filter at the actual working temperature T .

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