The hydraulic filters are important components of the hydraulic system used to control oil pollution, its role is to filter out the oil in the solid particle contaminants, oil pollution control in key hydraulic components that can withstand the limit to guarantee the reliability and extend the life of components of the hydraulic system. In general, people think that the hydraulic system has a filtering device is safe, In fact, this is often caused by a mistake to judge the hydraulic system failure, you can not ignore the filter quality system. In the hydraulic system to correct choice of the pollution control element in order to achieve the system goals cleanliness can directly improve the system performance, prolong the life of the components and fluids, and reduced maintenance, and can prevent the failure of the hydraulic system in the more than 80%.
With the improvement in the level of industrial automation, performance requirements of pollution control hydraulic systems as indispensable components - filter - also increasing. Therefore, the International Organization for Standardization constant introduction of new technical standards and product testing standards, in order to meet the filter manufacturers manufacturing needs and user needs.
A hydraulic filtration products standard and status quo
Hydraulic filters and filter filtration products. The filter press installation location, the filter can be divided into: Suction filter back to the oil filter, pressure line filter. (1) Suction filter: filter installed in the inlet line. (2) back to the oil filter: filter installed in the fuel tank back to the oil port and return pipe on the road. ③ pressure line filter: filter pressure pipeline.
Filter according to the location of the installation, the filter can be divided into: oil filter, oil filter back pressure line filter. (1) oil filter: the filter installed in the suction port or oil filter in the fuel tank. (2) the oil filter back: back to the oil port installed in the fuel tank or back to the oil filter element filter. (3) pressure pipe filter: the filter installed in the pressure line filter.
Optional filter, the filter can be divided into: inorganic fiber composite filter, paper filter, metal mesh filter. ① inorganic fiber composite filter: filter material for inorganic fiber composite filter. The ② paper filter: filter material for the vegetable fiber filter paper. (3) metal mesh filter: filter material for wire braid.
Currently, our hydraulic filtration products and the technical requirements of the standard 3.
Since the early 1980s and, with the introduction of hydraulic pollution control technology, hydraulic filtration products in China increasing production. In recent years, due to the more serious problems of quality filtration products exposure, in particular, the filter element, a large gap between the industrial countries products, and therefore the problem is caused by the majority of users and the attention of plant technical requirements of filtration products.
As can be seen from Table 1, China in 1996, developed by the aviation industry an industry standard HB5825-1996, may also have each their own corporate standards in the production plant, and our filter requires national standard GB/T20079-2006 and GB/T20080-2006 devised in 2006.
1.1GB/T20079-2006 "hydraulic filter technology conditions"
The GB/T20079-2006 main filter requirements: from the technical requirements, testing requirements, inspection requirements, logos, packaging, storage, etc.
(1) of the filter mainly made from the basic parameters, material, performance, design aspects proposed technical requirements, wherein:
1) Basic parameters: the filtering accuracy rated flow, nominal pressure, dirt holding capacity, the sender drop, bypass valve open pressure drop, the bypass valve sealing performance, bypass valve to close the pressure drop, drop versus flow bypass valve filter initial pressure drop, filter pressure drop versus flow curve.
2) performance requirements: low pressure sealing, high pressure sealing, blasting pressure and flow characteristics.
(2) Test requirements 12 Test: filtration accuracy test, the capacity of the nano scale test, the sender drop test, the bypass valve opening pressure drop test, bypass valve closed drop test, pressure drop flow test of the bypass valve, The filter initial pressure drop test, compatibility test, pressure tightness test filter low pressure tightness test, filter, filters, burst pressure test, the filter flow characteristics test.
1.2GB/T20080-2006 "hydraulic filters Conditions
The GB/T20080-2006 main requirements from the technical requirements, testing requirements, inspection requirements, signs, packaging, storage and other aspects of the filter:
(1) the filter from the basic parameters of materials, performance, design and manufacturing aspects of the proposed technical requirements, including:
1) of the basic parameters of the hydraulic filter requirements are: filtering accuracy, the capacity of the nano scale, filter rated flow, clean the filter pressure drop, ultimate filter pressure drop, the bypass valve opening pressure drop, the bypass valve sealing performance, a bypass valve closing pressure drop, pressure drop flow from the bypass valve, the structural integrity.
2) the performance requirements of: filter structural strength: (axial strength, crushing strength), flow characteristics, flow fatigue characteristics.
(2) The test requirements
11 test: the filtering accuracy test nano scale capacity test, test flow characteristics, the structural integrity of the test, structural strength test, flow fatigue test, compatibility test, bypass valve open pressure drop test, bypass valve to close the pressure drop test, the bypass valve pressure drop flow test, clean filter pressure drop test.
1.3HB5825-1996 "aviation hydraulic filters General technical conditions"
The standard for general aviation hydraulic filters technical requirements, test methods and inspection rules, an industry standard proposed in 1996 by the aviation industry. From the the standard content point of view, this standard is not only a product standard, is a test method standards. Due to the special nature of the aviation system, the standard makes provision for aviation hydraulic filters and filter at the same time have the the harsher technical requirements and test methods.
(1) the technical requirements
The technical requirements from the material, surface treatment, marking, design and structure, reliability, maintainability, performance, and environmental requirements detailed provisions.
Among them, in the performance of the filter with the requirements of 11: structural integrity, maximum aperture, the initial filter than the average specific filtration and dirt holding capacity, compatibility, cold start, flow fatigue cycle, media migration, axial strength, The squashed strength.
The filter requirements of 28: Appearance, bypass valve airtightness, the opening pressure, closing pressure, pressure drop and lifetime of the puncture device leakage and life, the differential pressure indicator indicates a pressure difference, the working temperature, life, pressure pulse, mechanical shock, filter low pressure tightness, high pressure tightness, pressure drop, pollution, the impact of high temperature pressure, extreme pressure, NW, environmental requirements are high temperature, low temperature, temperature shock, vibration, shock, heat and humidity, salt spray, mold.
(2) Test method
The test method is based on the product technical requirements of each performance requirements corresponding test procedures and methods for each one, a total of 39 trials.
2 hydraulic filtration products inspection standards and the status quo
Hydraulic filters should have high filtration efficiency, and pressure loss is small and the dirt holding capacity and other characteristics, and these properties need be through a certain test method to assess.
In the sixties and seventies of the 20th century, some developed countries proposed test methods to assess the performance of hydraulic filters, and to develop appropriate national or industry standards, then gradually adopted by the International Organization for Standardization and converted to international standards, a wide range of world various national hydraulic filters used in product testing.
2.1ISO2941 and GB/T14041.3 hydraulic filter burst resistance
The purpose of this test is the ability to assess the pressure difference filter structure. When the hydraulic system in the low-temperature start or filter by pollutants completely blocked and traffic impact at both ends of the filter will produce a lot of pressure differential will destroy the structure of the filter element, therefore, to carry out the inspection of this project .
During the test, the system flow to be maintained at the rated flow of the filter element, and then added in the system contaminants, so that the the filter ends differential pressure gradually increases, until a predetermined resistance to rupture pressure value; remove the filter, through the ISO2942 filter structure integrity test, the filter qualified.
2.2ISO2942 and GB/T14041.1 hydraulic filters structural integrity testing methods
The purpose of this standard test test may cause damage to the filter in the defects in the processing, storage and transportation, such as filter media rupture, end cap bonding defects and cracks.
The test method is cleaning filter is installed in the test apparatus, immersed in isopropyl alcohol under the surface 12.5mm at 360 ° rotation around the axis to pass into a given pressure compressed air filter, the filter surface should be continuous visible bubbles that the filter qualified structural integrity.
2.3ISO2943 test methods and GB/T14041.2 hydraulic filter material compatibility with fluids
This test is used to assess the temperature of the working fluid filter materials, the filter material to become brittle, swell softens decomposition performance changes.
The tests specified in this test temperature to be higher than the filter specified by the manufacturer, the maximum operating temperature of 15 ℃, but pay attention to safety, shall not exceed the flash point of the working fluid. Burst resistance test 72h after the ISO2941 filter must be qualified.
The hydraulic filter 2.4ISO3723 and GB/T14041.4 end load test method
In use, the fluid pressure of the filter end portion and installation force is applied, and thus need to pass the test to test filter under load will occur in the end to the permanent deformation or damage.
The trial in the filter after the compatibility test, finally burst resistance by ISO2941.
2.5ISO3724 and GB/T17488 hydraulic filter flow fatigue characteristics
The filter is often in the role of the pressure and flow fluctuations in the hydraulic system, and thus prone to fatigue of the filter material and cause damage and rupture. This fatigue damage generally occurs in the root of the folding cylinder line filter, pressure and flow fluctuations folding roots repeated bending fatigue damage.
This test is the analog filter cyclical pressure changes occur in the work, and the test filter medium anti-bending fatigue capability. Trials, to maintain the maximum differential pressure is controlled at less than 10% of the limit pressure difference of the filter, is a cyclical change in the test flow rate between zero and a maximum burst resistance to a predetermined number of cycles after the request by the ISO2941 filter, filter qualified.
2.6ISO11170 hydraulic power - Filter elements - procedures for verifying performance characteristics
Filter is the main function of the hydraulic filter element, and its performance is obtained through a series of tests measured, the standard provides for a reasonable, effective use of existing standard test methods to test the performance characteristics of the filter program steps, and the use of filter least the minimum number of tests the best permutations completed 8 fully reflect the performance of the filter structure and properties, filtering will do the test content.
2.7ISO3968 and GB/T17486 hydraulic filters assessment of the flow characteristics
The oil flow through the filter, due to the resistance of the filter medium on the oil and produce a certain pressure loss, thereby to produce a certain pressure difference between the oil inlet and outlet of the filter. According to the principles of fluid mechanics, the pressure loss generated when the fluid flows through the filter medium through flow, the viscosity of the fluid, and the filter medium of the physical structure factors. Therefore, in order to select the correct filter, the filter in the hydraulic system of least resistance under the rated flow, on the need assessment of the flow characteristics of the filter.
The test is the actual use state of the analog filter, the selected 10 points in the premise of a certain viscosity of the test medium, the test flow from zero to 10% of the rated flow between the differential pressure measurement, and to find the best work area.
2.8ISO16889, ISO4572 GB/T18853, GJB
3820 hydraulic transmission filter many times through many times through the test oil cycle assessment of filter performance test dust from the upstream test system continuously, not test filter to filter test dust back to test the fuel tank within circulating within the test system, and repeatedly passed through the filter, and thus its upstream pollutant concentration is varied.
Repeatedly through the actual working conditions of the test method of the analog filter in the hydraulic system, the contaminants continuously from outside is immersed in the internal generated, filter continuously filter out some pollutants, while the portion not filtered off is circulating in the system and many times through the filter. Therefore, the actual working conditions closer to the filter several times by law, and the International Organization for Standardization adopted.
Repeatedly through the contents of the test comprising: assessment of the filter for different particle sizes of the filter ratio, pressure characteristics, and dirt holding capacity. Test system flow test to maintain a certain contaminants continuously injected to test the fuel tank, the pressure difference across the filter differential pressure gauge monitoring and oil samples taken from both upstream and downstream of the filter, the oil samples online liquid automatic particle counters particle count analysis, the statistics of the specified time, the number of particles in the specified differential pressure calculated filter than filtering accuracy, dirt holding capacity, assessed the filtration performance of the filter.
The filter pilot project and the relationship of the standard applications
Series of tests for assessing the performance of hydraulic filtration products and product quality control, filtration products, as shown in Figure 1, the reference test items required by the new national standards GB/T20079 and GB/T20080 corresponding The method of choice criteria are shown in Table 4. HB5825 the harsh technical requirements and test conditions, so the standard is mainly used for aviation hydraulic filtration products. If necessary, other industries also can be implemented by reference.
Part of the standard is to refer to each other to apply these inspection standards. Such as structural integrity test (GB/T14041.1, ISO2942) in a number of test methods to be used: in several times before and after the test (GB/T18853, GJB3820, ISO16889, ISO4572), compatibility test (GB/T14041. 2, ISO2943), to flow fatigue test (GB/T17488, ISO3724), structural strength test anti-rupture test (GB/T14041.3, ISO2941) and end load test (GB/T14041.4 ISO3723). Can see the importance of structural integrity test (GB/T14041.1, ISO2942) standard is the most basic test items.
For rational and efficient use of these standard test methods to test the performance of the filter element, ISO11170 specifies the filter test procedure, as shown in Figure 1. The standard requirements determine the need for a comprehensive examination of a batch of filter performance characteristics, develop a need to select at least three filter can complete the entire test program.
Therefore, in the inspection of the filter, can refer to the method of the program. Currently, the standard is being transformed into the GB.
The development of international and domestic standards
The development of international standards in 4.1
With the improvement in the level of science and technology industrial automation, hydraulic transmission technology in the international arena has been a wide range of applications, in order to more secure, reliable, efficient, critical components - filter production - the technical requirements of the product of the work of the hydraulic drive system and inspection standards continue to push Chen updated. March 2006, the International Organization for Standardization ISO/TC131/SC6N441 discussed at the Orlando meeting 37 standards, which has identified 12 standards valid in the future, the have six current standard, six being discussed, other proposals did not pass or deleted. The standard drafting the schedule shown in Table 5.
The development of domestic standards in 4.2
With the recent development of the domestic hydraulic pollution control and detection technology, as well as testing equipment, instruments, constantly updated, in the organization of the National Standardization Technical Committee of hydraulic and pneumatic widely promoted and made amendments to the many hydraulic pollution control standards, and filter material testing standards.
At present, the existing domestic hydraulic pollution standards 20, 17 national standards (15 3 ISO standards); industry standards. 6 being revised standard, 4 GB, 2 line marked. There are four plans of adoption, its standard GB/T14041.3-1993 "hydraulic filter burst resistance" has been revised scheme, so not to implement its revision of the ISO standard ISO2941. Proposed industry standard developed hydraulic filters filter acceptance plan reporting has been completed by the end of November 2006, plans to launch in 2007. Development of domestic standards with the standard adoption, as shown in Table 6.
Filter in a hydraulic system, guarantee system purify and improve the reliability of the system, a key part to extend the useful life of equipment. How to properly design, select the hydraulic system filter needs according to their actual work status, such as the installation location, role type, the use of appropriate technical standards for products designed to create a proper filtration products to meet the system requirements. Complete design and manufacturing, product testing process, according to the different types of products also need to select the appropriate test standards, a comprehensive evaluation of its performance.
Therefore, in order to promote the our filtration products technology development, the need to constantly learn from the international state-of-the-art science and technology, with reference to international standards, take people long to make up our own short, the preparation of a suitable for China's national conditions, scientific, advanced, can operational technical standards and inspection standards to achieve both improve our filtration product quality, technical indicators and filtration products with international standards purposes. The limit alarm device.
1.3 function tests
Pumping hydraulic oil due to the first attempt to directly drive the mercury mobile compatibility study of mercury and hydraulic oil, it is necessary to confirm that the two can be separated from the good; addition, to ensure that the system safety of operation, it is necessary to the actual assessment of mercury will be pumping too far into the oil system.
Static compatibility test results show that: the hydraulic oil and mercury can be well separated from the mercury than a small proportion of the material below, hydraulic oil in the above.
Dynamic security test results show that: when all the mercury in a jar, to continue pumping hydraulic oil, hydraulic oil through the mercury goes up, goes up the hydraulic oil with mercury beads, mercury is not mixed into the oil system to system security. Pumping stopped, still about 2h, mercury liquid level can be maintained is maintained, proved trim attitude of the robot can adjust after a good stability is maintained.
Through the above experiment, confirmed that the hydraulic pumps to send the mercury-vertical tilting the feasibility and safety regulation system, the system can meet the needs of the underwater robot attitude adjustment, the overall performance of the system to meet the requirements.
2 Summary and Outlook
The topics, the hydraulic pumps to send the Mercury trim conditioning system design and research, and compatibility testing of the static and dynamic security testing. The study results show that: the posture conditioning system using hydraulic pumps to send the mercury is completely feasible; configuration of mercury by weight of mercury tank volume design, system security guarantee.
In fact, both the hydraulic oil system or mercury system, underwater use can not guarantee that it is completely isolated with seawater, there is no absolute zero leakage. The same time, liquid mercury is difficult to seal, and another leak of highly toxic mercury cause environmental pollution and damage to the human body. To eliminate such adverse effects have been carried out directly to the large flow of seawater hydraulic system research and development work underwater robot attitude adjustment. However, with the increased working depth of the sea water pump pressure requirements increase, to ensure that the large flow of sea water pump is still quite difficult subject.
According to reliable sources, the the the domestic sea water pump mature technology has reached 14MPa, 100L/min. Being developed by the United States "NewAlvin" No. 6500m deep-sea manned submersibles will use seawater hydraulic system to achieve substantial buoyancy and attitude adjustment.
The development of materials science in China is very rapidly emerging new engineering materials (such as engineering ceramics, polymer materials and corrosion resistant alloys, etc.), precision machining progress of technology, and the seawater hydraulic technology matures, water hydraulic system will be water in the future the robot to be more widely used.