In-depth analysis of excavator hydraulic oil filter: the loyal guardian of the hydraulic system
Posted: Apr 7th, '25, 23:12
In-depth analysis of the hydraulic oil filter element of the excavator: the loyal guard of the hydraulic system
In the complex structure of the excavator, the hydraulic system can be called the core "power source", driving the bucket, boom and other key components to operate flexibly. The hydraulic oil filter element, as the "loyal guard" of the hydraulic system, bears the heavy task of filtering impurities and purifying hydraulic oil. Its performance is directly related to the operating stability and service life of the hydraulic system and even the whole machine.
1. The key role of the hydraulic oil filter element
Hydraulic oil circulates in the hydraulic system of the excavator, just like human blood nourishes the whole body. However, during the operation, the hydraulic oil is easily contaminated, and dust in the air, debris generated by the wear of metal parts, and colloidal substances generated by the oxidation of the hydraulic oil itself, etc., will be mixed in. At this time, the hydraulic oil filter element stands up and plays a key filtering role. It can accurately intercept these impurities, prevent them from circulating in the system, avoid scratching the precision hydraulic pump plunger, jamming the control valve spool, and aggravating the wear of the cylinder seals and other serious problems, ensure that the hydraulic oil is always in a clean state, and lay the foundation for the efficient and stable operation of the hydraulic system. For example, in dusty and harsh working conditions such as mines, the filter element effectively blocks dust invasion, maintains the purity of hydraulic oil, and ensures that the excavator can continue to work at high intensity.
2. Type subdivision and installation layout
(I) Suction filter element
Usually "stationed" on the suction line of the hydraulic pump, it is like the "first line of defense" of the hydraulic system. Its main responsibility is to remove impurities in the oil tank and dirt that sneaks into the oil tank with the air inlet, and fully protect the hydraulic pump from damage. In order to prevent cavitation in the oil pump, the suction filter element is designed with low resistance and is mostly made of 100-200 mesh wire mesh or finer wire materials. However, this type of filter element has limited control over particulate contamination, and its main function is to coarsely filter large particles of impurities, reducing the burden on subsequent filtration links.
(II) High-pressure pipeline filter element
Located in the outlet pipeline of the hydraulic pump, where the hydraulic oil pressure is high and the flow rate is fast. The high-pressure pipeline filter element is like an "elite force" that can effectively remove dirt that "slips through the net" from the suction port and maintain the cleanliness of the system. Given that its working environment is subject to high-pressure pulsation and pressure shock, the strength of the filter element must strictly meet the requirements of the ISO3724 test standard. For hydraulic components such as slide valves and servo valves that are highly sensitive to pollutants, a higher-precision filter must be installed in front of them. The particle size of the filter element β value should be less than 75, and the filter material selection must be extremely cautious. At the same time, the filter element itself must be kept clean to prevent fiber shedding.
(III) Return oil filter element
Installed on the system return oil pipeline, it is responsible for intercepting newly generated or externally invaded dirt so that it can be filtered before returning to the oil tank. Although the pressure of the return oil filter element is relatively low, the system operating state is changeable and may also be affected by pulsation or pressure shock. Therefore, its quality requirements are equally strict, and it needs to be carefully designed in accordance with relevant standards to ensure that the filtering effect is stably exerted under complex working conditions, and to prevent dirt from flowing back to the oil tank and polluting the entire hydraulic oil circulation system.
(IV) Circulation filter element
It is often found in systems with almost stringent cleanliness requirements and is often arranged on the oil tank circulation loop. Its uniqueness lies in that it can continue to work even if the system stops operating temporarily, silently reducing the degree of system pollution. If the system is equipped with a cooler, the circulating filter element can also work together to reduce the system temperature, create favorable conditions for system maintenance, and extend the service life of each component.
(V) Air filter element
Installed on the top of the oil tank, it is like the "respiratory tract" of the hydraulic system. It can effectively prevent dirt from entering the oil tank as the oil volume changes. With the large filter element capacity, it prevents micropores from clogging and causing negative pressure inside the oil tank, causing cavitation. When working outdoors or in harsh environments, the role of the air filter element is particularly critical and requires key protection to ensure its normal operation and create a clean storage environment for hydraulic oil.
III. Interpretation of key performance parameters
(I) Filtration accuracy
As a core parameter, filtration accuracy clarifies the minimum particle size that the filter element can effectively block, in microns (μm). Different types of excavators and hydraulic systems have significantly different requirements for filtration accuracy. For example, an excavator equipped with a high-precision servo system may require a filter element with a filtration accuracy of less than 1μm to ensure accurate valve core movement and avoid the jamming of tiny particles; while for ordinary hydraulic systems, a filtration accuracy of about 10μm or 25μm can meet basic needs. Selecting a filter element with a suitable filtration accuracy is a key step to ensure the normal operation of the hydraulic system.
(ii) Dirt capacity
It refers to the total amount of pollutants that the filter element can accommodate before reaching the specified pressure difference. The larger the dirt capacity, the greater the "belly" of the filter element to accommodate impurities, the longer the service life, and the lower the replacement frequency. Under conditions where the excavator operates continuously for a long time and the risk of hydraulic oil contamination is high, the advantages of high dirt capacity filter elements are fully demonstrated, which can reduce the downtime caused by frequent filter element replacement and improve operating efficiency.
(iii) Pressure loss
When hydraulic oil flows through the filter element, pressure drop, that is, pressure loss, is inevitable. Excessive pressure loss will consume hydraulic system energy, reduce work efficiency, affect system performance, and even cause the system to fail to work properly in severe cases. Therefore, under the premise of satisfying the filtering effect, the filter element with small pressure loss should be preferred to ensure the efficient and energy-saving operation of the hydraulic system.
(IV) Flow characteristics
The flow characteristics reflect the filtering performance and pressure loss of the filter element at different flow rates. High-quality filter elements should have good flow characteristics, and always maintain stable filtering effects and low pressure losses within the system working flow range, to ensure smooth passage of hydraulic oil and meet the hydraulic oil flow requirements of the excavator under different working conditions.
IV. Reasonable selection and maintenance points
(I) Filter element selection
1. Applicable equipment model: Be sure to accurately select the appropriate filter element based on the brand, model and specific parameters of the hydraulic system of the excavator. There are differences in the design of hydraulic systems of excavators from different manufacturers and different series, and the requirements for the size, interface and filtering performance of the filter element are different. Only the appropriate filter element can perfectly fit the system and exert the best filtering efficiency.
2. Consider the working environment: If the excavator often works in harsh environments such as dust, high humidity, and high temperature, you should choose a filter element with high filtration accuracy, large dirt holding capacity, high temperature resistance, and corrosion resistance, and shorten the replacement cycle appropriately. For example, in a mining operating environment, it is recommended to use a glass fiber filter element with a high-efficiency protective shell to enhance the filtering and protection capabilities.
(II) Maintenance
1. Regular inspection: During daily operations, regularly check the appearance of the filter element to check for signs of damage, deformation, and blockage. At the same time, use the pressure difference monitoring device to pay attention to the pressure difference changes of the filter element in real time. When the pressure difference exceeds the specified value, it indicates that the filter element may be blocked and needs to be replaced in time to avoid affecting the normal operation of the system.
2. Correct replacement: When replacing the hydraulic oil filter element, first drain the original hydraulic oil, and fully check the return oil, oil suction, pilot and other filter elements to check for iron filings, copper filings or other impurities. If so, there may be a hydraulic component failure, which needs to be repaired and eliminated and the system cleaned before replacing the filter element. When replacing, be sure to replace all related hydraulic oil filter elements at the same time, and it is strictly forbidden to mix hydraulic oils of different grades and brands. Install the oil suction filter element before refueling, and drain the main pump air in time after refueling to ensure the normal startup and operation of the system.
3. Cleaning points (partially washable filter elements): For some filter elements that are allowed to be cleaned, such as metal mesh filter elements, be careful when cleaning. Use a suitable cleaning agent, such as a special hydraulic oil filter element cleaning agent or clean diesel, and a soft brush to gently remove impurities on the surface of the filter element to avoid damaging the filter element structure. After cleaning, use compressed air to blow dry from the inside of the filter element to the outside to ensure that no impurities remain. It can only be reinstalled and used after passing the test. However, it should be noted that paper filter elements and other filter elements that are not resistant to cleaning should not be tried to clean to avoid damaging the filter medium and losing the filtering function.
Although the hydraulic oil filter element is small, it plays an irreplaceable and key role in the hydraulic system of the excavator. By having a deep understanding of its functions, types, and performance parameters, and by selecting and maintaining it rationally, this "loyal guardian" can continue to safeguard the efficient and stable operation of the excavator, extend the service life of the equipment, reduce maintenance costs, and improve the efficiency of engineering operations.
In the complex structure of the excavator, the hydraulic system can be called the core "power source", driving the bucket, boom and other key components to operate flexibly. The hydraulic oil filter element, as the "loyal guard" of the hydraulic system, bears the heavy task of filtering impurities and purifying hydraulic oil. Its performance is directly related to the operating stability and service life of the hydraulic system and even the whole machine.
1. The key role of the hydraulic oil filter element
Hydraulic oil circulates in the hydraulic system of the excavator, just like human blood nourishes the whole body. However, during the operation, the hydraulic oil is easily contaminated, and dust in the air, debris generated by the wear of metal parts, and colloidal substances generated by the oxidation of the hydraulic oil itself, etc., will be mixed in. At this time, the hydraulic oil filter element stands up and plays a key filtering role. It can accurately intercept these impurities, prevent them from circulating in the system, avoid scratching the precision hydraulic pump plunger, jamming the control valve spool, and aggravating the wear of the cylinder seals and other serious problems, ensure that the hydraulic oil is always in a clean state, and lay the foundation for the efficient and stable operation of the hydraulic system. For example, in dusty and harsh working conditions such as mines, the filter element effectively blocks dust invasion, maintains the purity of hydraulic oil, and ensures that the excavator can continue to work at high intensity.
2. Type subdivision and installation layout
(I) Suction filter element
Usually "stationed" on the suction line of the hydraulic pump, it is like the "first line of defense" of the hydraulic system. Its main responsibility is to remove impurities in the oil tank and dirt that sneaks into the oil tank with the air inlet, and fully protect the hydraulic pump from damage. In order to prevent cavitation in the oil pump, the suction filter element is designed with low resistance and is mostly made of 100-200 mesh wire mesh or finer wire materials. However, this type of filter element has limited control over particulate contamination, and its main function is to coarsely filter large particles of impurities, reducing the burden on subsequent filtration links.
(II) High-pressure pipeline filter element
Located in the outlet pipeline of the hydraulic pump, where the hydraulic oil pressure is high and the flow rate is fast. The high-pressure pipeline filter element is like an "elite force" that can effectively remove dirt that "slips through the net" from the suction port and maintain the cleanliness of the system. Given that its working environment is subject to high-pressure pulsation and pressure shock, the strength of the filter element must strictly meet the requirements of the ISO3724 test standard. For hydraulic components such as slide valves and servo valves that are highly sensitive to pollutants, a higher-precision filter must be installed in front of them. The particle size of the filter element β value should be less than 75, and the filter material selection must be extremely cautious. At the same time, the filter element itself must be kept clean to prevent fiber shedding.
(III) Return oil filter element
Installed on the system return oil pipeline, it is responsible for intercepting newly generated or externally invaded dirt so that it can be filtered before returning to the oil tank. Although the pressure of the return oil filter element is relatively low, the system operating state is changeable and may also be affected by pulsation or pressure shock. Therefore, its quality requirements are equally strict, and it needs to be carefully designed in accordance with relevant standards to ensure that the filtering effect is stably exerted under complex working conditions, and to prevent dirt from flowing back to the oil tank and polluting the entire hydraulic oil circulation system.
(IV) Circulation filter element
It is often found in systems with almost stringent cleanliness requirements and is often arranged on the oil tank circulation loop. Its uniqueness lies in that it can continue to work even if the system stops operating temporarily, silently reducing the degree of system pollution. If the system is equipped with a cooler, the circulating filter element can also work together to reduce the system temperature, create favorable conditions for system maintenance, and extend the service life of each component.
(V) Air filter element
Installed on the top of the oil tank, it is like the "respiratory tract" of the hydraulic system. It can effectively prevent dirt from entering the oil tank as the oil volume changes. With the large filter element capacity, it prevents micropores from clogging and causing negative pressure inside the oil tank, causing cavitation. When working outdoors or in harsh environments, the role of the air filter element is particularly critical and requires key protection to ensure its normal operation and create a clean storage environment for hydraulic oil.
III. Interpretation of key performance parameters
(I) Filtration accuracy
As a core parameter, filtration accuracy clarifies the minimum particle size that the filter element can effectively block, in microns (μm). Different types of excavators and hydraulic systems have significantly different requirements for filtration accuracy. For example, an excavator equipped with a high-precision servo system may require a filter element with a filtration accuracy of less than 1μm to ensure accurate valve core movement and avoid the jamming of tiny particles; while for ordinary hydraulic systems, a filtration accuracy of about 10μm or 25μm can meet basic needs. Selecting a filter element with a suitable filtration accuracy is a key step to ensure the normal operation of the hydraulic system.
(ii) Dirt capacity
It refers to the total amount of pollutants that the filter element can accommodate before reaching the specified pressure difference. The larger the dirt capacity, the greater the "belly" of the filter element to accommodate impurities, the longer the service life, and the lower the replacement frequency. Under conditions where the excavator operates continuously for a long time and the risk of hydraulic oil contamination is high, the advantages of high dirt capacity filter elements are fully demonstrated, which can reduce the downtime caused by frequent filter element replacement and improve operating efficiency.
(iii) Pressure loss
When hydraulic oil flows through the filter element, pressure drop, that is, pressure loss, is inevitable. Excessive pressure loss will consume hydraulic system energy, reduce work efficiency, affect system performance, and even cause the system to fail to work properly in severe cases. Therefore, under the premise of satisfying the filtering effect, the filter element with small pressure loss should be preferred to ensure the efficient and energy-saving operation of the hydraulic system.
(IV) Flow characteristics
The flow characteristics reflect the filtering performance and pressure loss of the filter element at different flow rates. High-quality filter elements should have good flow characteristics, and always maintain stable filtering effects and low pressure losses within the system working flow range, to ensure smooth passage of hydraulic oil and meet the hydraulic oil flow requirements of the excavator under different working conditions.
IV. Reasonable selection and maintenance points
(I) Filter element selection
1. Applicable equipment model: Be sure to accurately select the appropriate filter element based on the brand, model and specific parameters of the hydraulic system of the excavator. There are differences in the design of hydraulic systems of excavators from different manufacturers and different series, and the requirements for the size, interface and filtering performance of the filter element are different. Only the appropriate filter element can perfectly fit the system and exert the best filtering efficiency.
2. Consider the working environment: If the excavator often works in harsh environments such as dust, high humidity, and high temperature, you should choose a filter element with high filtration accuracy, large dirt holding capacity, high temperature resistance, and corrosion resistance, and shorten the replacement cycle appropriately. For example, in a mining operating environment, it is recommended to use a glass fiber filter element with a high-efficiency protective shell to enhance the filtering and protection capabilities.
(II) Maintenance
1. Regular inspection: During daily operations, regularly check the appearance of the filter element to check for signs of damage, deformation, and blockage. At the same time, use the pressure difference monitoring device to pay attention to the pressure difference changes of the filter element in real time. When the pressure difference exceeds the specified value, it indicates that the filter element may be blocked and needs to be replaced in time to avoid affecting the normal operation of the system.
2. Correct replacement: When replacing the hydraulic oil filter element, first drain the original hydraulic oil, and fully check the return oil, oil suction, pilot and other filter elements to check for iron filings, copper filings or other impurities. If so, there may be a hydraulic component failure, which needs to be repaired and eliminated and the system cleaned before replacing the filter element. When replacing, be sure to replace all related hydraulic oil filter elements at the same time, and it is strictly forbidden to mix hydraulic oils of different grades and brands. Install the oil suction filter element before refueling, and drain the main pump air in time after refueling to ensure the normal startup and operation of the system.
3. Cleaning points (partially washable filter elements): For some filter elements that are allowed to be cleaned, such as metal mesh filter elements, be careful when cleaning. Use a suitable cleaning agent, such as a special hydraulic oil filter element cleaning agent or clean diesel, and a soft brush to gently remove impurities on the surface of the filter element to avoid damaging the filter element structure. After cleaning, use compressed air to blow dry from the inside of the filter element to the outside to ensure that no impurities remain. It can only be reinstalled and used after passing the test. However, it should be noted that paper filter elements and other filter elements that are not resistant to cleaning should not be tried to clean to avoid damaging the filter medium and losing the filtering function.
Although the hydraulic oil filter element is small, it plays an irreplaceable and key role in the hydraulic system of the excavator. By having a deep understanding of its functions, types, and performance parameters, and by selecting and maintaining it rationally, this "loyal guardian" can continue to safeguard the efficient and stable operation of the excavator, extend the service life of the equipment, reduce maintenance costs, and improve the efficiency of engineering operations.