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Analysis of Performance Evaluation Criteria for Filter Element (ISO16889 、ISO19438、ISO4548)
- Jan 14, 2019 -

In recent decades, China has gradually acquired a profound understanding and Research on the hazards of pollution in hydraulic, fuel and oil systems. It has been found that the main pollutants are solid pollutants, water, air, bacteria and colloidal substances. However, the most serious hazards of solid pollutants are generally metal particles, oxides, dust and rubber powder. The main sources of pollution are: internal parts and components of the system. Wear, failure of sealing structure, invasion of external pollutants, oil itself, filter itself and so on. How to control these pollutants can improve the performance of parts, rationality of sealing structure, working environment and quality of oil, mainly by installing filters to purify the system and improve the cleanliness of working system media. Whether the design of the filter itself can meet the requirements of the working system needs an evaluation method. This paper mainly focuses on the three standards: ISO16889, ISO19438 and ISO4548.


1 Provisional Content

Hydraulic system has a wide range of applications, and the harm of pollutants is the most serious. The research and development of pollution control technology for hydraulic system is also good. The evaluation method of hydraulic filter ISO16889 is the earliest implementation and application. The evaluation methods of fuel and oil filters were born according to the evaluation method of hydraulic filter ISO16889: ISO19438,ISO4548-12.The three evaluation methods have the following similarities and differences in the prescribed scope:


1.1 Same:

(a)The on-line particle counting method is used for many passes under the condition of constant test flow and continuous injection of pollutants.

(b)Procedures for determining the capacity of filters for contamination, the characteristics of particle removal and pressure drop;

(c)Provide for a test method that is not affected by static changes and that the test data are reproducible;

(d)Test powder: ISOMTD, test circulation meson: YH-10 aviation hydraulic oil.

From the above four points of view, all of them use fixed flow rate to inject contaminants continuously: in order to better simulate the actual working conditions; using online particle counting method: monitoring and recording the test data at all times, reducing the intermediate error, and the test results are more accurate.


1.2 Differences:


Standard number

Scope of   application

Applicable Rated Flow Rate

Applicable particle size range

Applicable filtration characteristics


Filter element of hydraulic transmission filter



Average filtration ratio β≥75


Diesel Filter for Internal Combustion Engine

And gasoline   filters



Total efficiency of filter η=99%


Full Flow Oil Filter for Internal Combustion Engine





From the table, it is not difficult to find that the three standards are the relevant verification standards for the three types of filters. Because the pollution source of the lubricating oil system is similar to that of the hydraulic system. An additional source of pollution is the oxide of the coke-oil. Some data show that the formation of sediments, such as cokes, increases in the presence of fine metal particles, so in addition to the well-known reasons for filtering out fine particles in the lubricating oil system (such as small particles entering the gap wear elements on the working surface), another advantage of removing these small particles from the filter is to control the coking.Therefore, the applicable particle size range stipulated by the two relevant test standards is similar. Hydraulic system has a wide range of applications and complex system principles. Its particle size range is suitable for 4 to 25 microns. In terms of filtration mechanism, the mechanism applicable to hydraulic system is also applicable to lubricating oil system. The only big difference is that the oil system is an open system.This characteristic is also created, and the two standards are very similar in the range of rated flow.:4L/min~1600L/min,The flow range of fuel system is smaller according to its principle requirement:50L/h~800L/h(0.83L/min~13.3L/min). ISO16889 uses average filtration ratio in terms of applicable filtration characteristics β,ISO19438 and ISO4548-12 apply to total efficiency η,Why are they different?The working principle of the hydraulic system is mainly that it has a circulating system, that is, the working medium is recycled repeatedly. The oil of the system is purified through the hydraulic filter, and the cleanliness of the working medium is always in line with the working conditions of the hydraulic components. Its main pollutant source is the fine particles produced by the friction of hydraulic components. There are many kinds of hydraulic valves in the system and many levels of accuracy.Therefore, the performance index of hydraulic filters is higher, and the filtering characteristics are clear. The average filtration ratio of 10, 20, 75, 100, 200, 1000 and so on can indicate the corresponding filtering particle size.The working principle of fuel system is mainly a one-time combustion system, that is, the working medium does not recycle repeatedly, and filters clean before the working medium enters the engine. Its main pollutant source is brought into the fuel tank by the outside. The filter mainly protects the nozzle from working normally. According to the diameter of the nozzle, the contaminated particles controlled by the fuel filter are controlled by the fuel filter. Diameter is ≥10 microns, which is more suitable expressed by total efficiency η value: 75%, 85%, 90%, 99.9%, 99.99%. With the development of science and technology, it is possible to use average filtration ratio beta to evaluate the performance of fuel and lubricating oil systems.


2. Requirements for test equipment and materials

2.1 similarities

(a)The whole structure includes: test system, fouling injection system, particle counter/system and dilution system, and the required functions of each system are the same; for example, the test system has an oil tank with an angle not greater than 90 degrees, a pump that can not change the size of contaminated particles in the oil, and a purifying filter that can purify the oil in the test system to achieve the required accuracy of the test. The pressure measuring points in accordance with GB/I17486 and the sampling parts in the upper and lower parts of the tested filters in accordance with GB/17489 require the pipeline size to ensure turbulent mixing in the whole filter test circuit, that is to say, the designed pipeline can not change the initial pollution concentration of the test tank, and so on. The requirements for many functions are the same.

(b)Contamination injection system: There is an oil pump with an angle not more than 90°, which can not change the particle size distribution of pollutants. The size of the pipeline is required to ensure turbulent mixing in the whole filter test circuit.

(c)Particle counter and dilution system: In terms of calibration requirements, they are calibrated in accordance with GB/T18854.

The requirements and principles of the three standards for the whole structure of the experimental equipment are basically the same, but ISO16889 requires more detail.

(d)Test impurities and preparation of impurities: they all conform to ISO12103-A3, and are dried for one hour at 105℃±5℃ within 200 g by weight. But ISO16889 requires more detail, and I think the other two standards can also be used.

(e)The variation range of instrument accuracy and test conditions is basically the same.


2.2 Differences:

At the beginning, we also said to you that the different working environment of the three filters stipulated by the three standards has resulted in their corresponding design according to their own characteristics when they pass the test-bed many times.

(a)The contamination degree of the upstream basic weight of the test oil in the test system: ISO16889 requires test conditions of 3±0.3mg/L, 10 ±1.0mg/L,15±1.5mg/L, ISO19438 requires test conditions of 5 mg/, and ISO4548 requires the same as ISO19438.

(b)Systematic purification filters: Because the basic upstream weights mentioned above have different pollution concentrations, but they are guaranteed by purification filters, which also leads to their differences.

(c)Dilution system: This standard has been mentioned, but this is based on whether the particle counting function can meet the contamination level in the test system.

(d)Layout of test-bed: Most of them are the same. ISO 16889 has not drawn out the dilution system, discharged the external tank circuit, purification system. The symbols of the valves drawn by the test system are ordinary two-way ball valves. The tested filters have no through-line pipelines. The symbols of the valves drawn by the test system are three ball valves, while the ones marked by ISO 19438 and ISO 4548 are dilution systems. The symbols of the valves drawn by the test system are three ball valves. The filter has a straight-through pipeline. We think that the expression of ISO19438 and ISO4548 is more reasonable. The volume requirement of the test system and the sewage injection system is more accurate and it is convenient to replace the filter core of the tested filter.

There must be many other differences. Generally speaking, these three standards are based on the characteristics of the three filters themselves. Specific details should be referred to according to the performance characteristics of the filters themselves.


2.3 Verification of Test Bed Test System

(a)The purpose of verification is the same: to reveal whether the filter performance test circuit can effectively prevent the deposition of pollutants and the change of pollutant size;

(b)The minimum flow rate is used in the test system, and the straight tube is used instead of the tested filter.

(c)The relationship between flow rate and volume in the validation of the test system is the same as that of the hydraulic filter and the oil filter because of their similar working principle and wide flow range. The relationship between flow rate and volume is the same when they are validated: adjusting the total volume of oil in the test system (excluding the circuit of the purifying filter) to make it between 1/4-1/2 of the volume per minute under the minimum flow rate. If the flow rate is less than or equal to 60L/min, it is recommended that the total volume of oil in the verification system be equal to 50% of the flow volume per minute at the minimum flow rate. If the flow rate is greater than 60 L/min, it is suggested that the total volume of oil in the verification system be equal to 25% of the flow volume per minute at the minimum flow rate. ISO 19438 does not require either of them.

( d ) Verify the qualified indicators of the test system.

ISO16889 requirements meet the following conditions, considered qualified:

① The number of particles of a given size within each sampling interval must not deviate from 15% of the average number of particles of that size within all sampling intervals;

② The cumulative average of all size particles per milliliter should be within the allowable range of Table 3.

ISO4548 is considered qualified if it meets the following requirements:

① The difference between the particle counts measured at 10um and 20um each time and the average particle counts of the corresponding particle sizes shall not exceed 10%.

② The average number of particles measured in channels larger than 10um is not less than 750 per milliliter and not more than 1000;

③ The average number of particles measured in channels larger than 20um is not less than 70 per milliliter and not more than 120;

ISO19438 requires the following qualifications to be met:

① The measured particle counts of 5um, 10um and 20um cannot exceed 10% of these average counts.

② The average number of particles per milliliter in channels greater than or equal to 5um is not less than 6000, nor more than 7000;

③ The average number of particles per milliliter is not less than 815, not more than 1015, for channels greater than or equal to 10um.

④ The average number of particles per milliliter is not less than 77, nor more than 106.

It is possible to say from the above statement that the three standards have different qualifications for the test system, but let's take a closer look at the corresponding values of test condition 2 in Table 3 of ISO16889. I think the other two standards are included. It can also be said that the qualified conditions for the test system are the same. But ISO16889 is more detailed.

In terms of verification test system, the three standards are basically the same. The minor differences are as follows:

① ISO16889 is upstream in particle counting position, while ISO19438 and ISO4548 are downstream in particle counting position;

② The upstream and G80 sampling positions stipulated by ISO16889 are more rigorous than those stipulated by ISO19438 and ISO4548. We believe that these minor differences are based on the repeated validation of the test system to meet the requirements of their respective test benches.


2.4Verification of Pollutant Injection System in Test Bed

(a)In terms of flow rate and quality of pollutants, maximum flow rate and maximum weight of pollutants are used, which require sufficient time for mixing to make the pollutants fully mixed, and the mixing time is 15 minutes;

(b)In terms of time, it takes two hours, and the samples are extracted once in 30 minutes to analyze the oil samples. At the same time, the sampling flow should be verified.

(c)The impurity concentration of each sample oil is required to be within ±5% of the average value of the four samples, and the deviation between the injected flow measurements does not exceed ±5% of the average value.


2.5. Operational procedures for tests

2.5.1 Preparations for the experiment

(a) In terms of the tested filters, it is required to ensure that the test solution can not bypass the tested filters. The integrity test of the tested filters can not be done many times if the integrity pressure of the tested filters does not meet the requirements agreed by the manufacturer and users.

(b) In terms of test time, the calculation formulas prescribed by the three standards are the same, but as we mentioned above, because their upstream basic impurity concentration is different, the calculated values are different, so the recommended time of ISO16889 is 1h-2h, and the recommended time of ISO19438 and ISO4548 is more than 30 minutes.

(c) In calculating the minimum volume Vmin, the preset weight pollution concentration Gi, and the injected pollution quality M, the formulas are the same. However, in the specific experiment, because the performance indicators of the filters we choose are different, the results are different.

(d) The temperature of the test system is required to be stable in order to ensure that the viscosity of the test oil is consistent.

In summary, the requirements of the three criteria are basically the same before the experiment. The difference is that when doing the experiment, we should collect the performance indicators of the tested filters well, then count the corresponding values through the prescribed calculation formula, and then do the experiment.


Test system for test filters

(a) In terms of assembly, ISO16889 requires that the filter case (without test filter element) be installed in the filter test system and the air is exhausted, while ISO19438 and ISO4548 require that the straight tube be installed on the test bed instead of the filter. From the surface, it is different, but it is not difficult to find in the actual operation. In the later operation, the oil contamination degree of the purification test system meets the respective test requirements, and the flow rate of the adjustment test meets the respective prescribed values. Before each experiment, the conductivity of the oil must be measured, and the prescribed values of the conductivity are the same. We think that the results obtained by the operation are the same.

(b) In terms of temperature, the three standards all require temperature stability in order to ensure consistency of oil viscosity and record the pressure difference of the empty filter shell.

(c) In setting the channel diameter of particle counter:

ISO16889 requires that it correspond to the selected particle size, and ISO4548 requires that:

(1) 5-(6) Channel Counter,10,15,20,30,40;

(2)16-channel counter:5,(5)6,7、8、9、10、11、13、15、17、20、25、30、35、40、50;

ISO4548 requires that:

(1)5-(6) Channel Counter:,5,10,15,20,30;

(2)16-channel counter:4,5,6,7、8、9、10、11、13、(4)15、17、20、25、30、40、50;

Looking carefully, there are some differences, but we can go back to the three filters we mentioned: hydraulic filter, oil filter, fuel filter. The filtering accuracy tested is different. We can analyse the difference between the above values and say nothing.

2.5.2 Formal Performance Test of Filter

In terms of the test procedure, we think it is the same. The key points are to adjust the test temperature to ensure the oil viscosity in the range of 15mm2/s±1.0mm2/s, record the pressure difference of the clean filter assembly, calculate the pressure difference of the clean filter element, G80 value, measure the injection flow, the volume of the test system at the end of the test, the volume of the sewage injection system, the integrity of the filter element after the test, and get the test report.


2.6 Expression Of Experimental Results (Evaluation Method Of Products)

2.6.1 computing

(a) The whole calculation method:

ISO16889 calculates the filtration ratio (different particle sizes) at 10 different times in the whole test period.

ISO 19438 and ISO 4548 calculate the intermediate efficiency of different time periods in 5 minutes or 10 minutes.

They are calculated at different time points, the same is that the first three minutes do not require calculation, we think the purpose is to reflect the filter in different periods of life filter filtration ratio and filtration efficiency more refined, clearer evaluation process.

(b) In terms of evaluation accuracy.

ISO16889 uses β = upstream average particle number ÷ downstream average particle number, while ISO19438 and ISO4548 use total efficiency = (upstream average - downstream average) ÷ upstream average×100%. ISO19438 has an additional original efficiency and minimum efficiency. The original efficiency is the efficiency of the first 4, 5 and 6 minutes (the purpose is to test the filtration accuracy of clean filter element). ISO4548 is in total efficiency. Include maximum efficiency and minimum efficiency (the purpose is to compare maximum efficiency, minimum efficiency and average value to estimate whether the performance of the filter element is stable or not, the smaller the better).The three criteria are to understand the filter performance changes in the early, middle and late stages of the filter more clearly, intuitively and in more detail by understanding the filter efficiency or filter ratio calculation in each period. We think the evaluation in this respect is the same.

(c)On the calculation of pollutant carrying capacity:ISO16889 is the same as ISO19438:GR=Mi-G80×Vf/1000-qd×tf×(G80-Gb)/1000-qd×tf×(G80+Gb)/2000,ISO4548 is simpler GR=Mi-G80×Vf/1000. It is not difficult to see in formula that ISO16889 subtracts the estimated value of pollutants discharged from the downstream sampling port of the tested filter and the estimated value of pollutants discharged from the upstream sampling port more than ISO4548. This shows that ISO16889 and ISO19438 are more detailed. Perhaps ISO4548 thinks that this value is too small to be considered. We do find that this value is very small in the calculation process, such as If the final value is rounded, the latter two values are even more insignificant.

Others will not give more examples, because these three standards are all rules for measuring the capacity of pollutants, particle filtration characteristics and pressure drop characteristics. They are expressed in different forms and calculation ideas, so their basic ideas are the same.


3 Summary

From the above description, we can see that there are many similarities and differences among the three standards. According to the three standards, we have made many different shapes through the test bench, but they also meet different filter performance indicators (different from other designers, different customer requirements, different selection of electrical components, etc.). There are many changes in this field: the particle counting method is used to evaluate the filter separation characteristics (filtration accuracy, filtration level), the gravimetric analysis method is used to determine the service life of the filter (pollution capacity, dust capacity), and the pressure loss (flow pressure drop) of the filter in different life periods to reflect the influence of the product oil permeability characteristics on the matching system. We can think that from the point of view of pollution control test, the three standards are essentially the same, and the difference is only to meet the pollution control needs of their supporting systems. This proves that many times the test method is scientific and advanced in evaluating the performance of filters, and it is worth popularizing.

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