Introduction to Hydraulic Oil Filter Elements and Their Application Scope

　　Hydraulic oil filter elements are used in various hydraulic systems to remove solid contaminants that either enter from external sources or are generated internally during system operation. They are typically installed in the suction line, pressure line, return line, bypass line, and standalone filtration systems. During operation, industrial hydraulic oil can become contaminated with various impurities due to a range of factors; the primary contaminants include particulate matter, water, and air. Such contaminants accelerate corrosion, increase mechanical wear, reduce operational efficiency, degrade oil quality, shorten equipment service life, and, in severe cases, cause blockages in the hydraulic lines, leading to production accidents. Applications include hydraulic oil filtration for concrete delivery pumps, construction machinery, and hydraulic power units.

　　Main Parameters and Features

　　It is used to protect specific components in a hydraulic system and is installed upstream of the component to be protected in the medium-pressure pipeline, where it filters out solid particles and colloidal substances from the working fluid, effectively controlling the level of contamination and ensuring the normal operation of the component. Hydraulic oil filter elements are primarily made from stainless steel woven mesh, sintered mesh, and iron-woven mesh; their filter media, meanwhile, mainly consist of glass fiber filter paper, synthetic fiber filter paper, and wood pulp filter paper.

　　Therefore, it features high concentricity, excellent pressure resistance, superior straightness, and is made of stainless steel with no burrs, ensuring a long service life. Its structure consists of single- or multi-layer metal mesh combined with filter media; the number of layers and the mesh count of the wire screen are determined based on specific operating conditions and application requirements.

　　Scope of Application for Hydraulic Oil Filter Elements

　　1. Used for filtration in the hydraulic systems of rolling mills and continuous casting machines, as well as for filtration in various lubrication equipment.

　　2. Petrochemical Industry: Separation and recovery of products and intermediate products in oil refining and chemical manufacturing; liquid purification; purification during the production of magnetic tapes, optical discs, and photographic film; and particulate filtration of injection water and natural gas in oilfields.

　　3. Textiles: purification and uniform filtration of polyester melt during the drawing process, protective filtration for air compressors, and oil- and water-removal from compressed gases.

　　4. Electronics and pharmaceuticals: pretreatment filtration for reverse osmosis water and deionized water, as well as pretreatment filtration for cleaning solutions and glucose.

　　5. Machining equipment: lubrication systems and compressed-air purification for paper-making machinery, mining equipment, injection-molding machines, and large-scale precision machinery; dust-collection filtration for tobacco-processing equipment and spray-coating equipment.

　　6. Internal combustion engines and generators for railways: filtration of lubricating oil and engine oil.

　　7. Various hydraulic oil filters for automobile engines, construction machinery, ships, and heavy-duty trucks.

　　8. Thermal and nuclear power: purification of lubricating oil for gas turbines, boiler lubrication systems, speed control systems, and bypass control systems; as well as purification of feedwater pumps, fans, and dust-collection systems.

　　9. Various lifting and handling operations: from construction machinery such as cranes and loaders to specialized vehicles for fire-fighting, maintenance, and material handling; shipboard cargo-handling gear and anchor windlasses; blast furnaces and steelmaking equipment; ship locks and ship-gate opening-and-closing mechanisms; orchestra pits and stage lifts in theaters; and various automated conveyor systems, among others.

　　10. Various operating devices that require applied forces, such as pushing, squeezing, pressing, shearing, cutting, and excavating: hydraulic presses; die-casting, forming, rolling, calendering, drawing, and shearing equipment for metal materials; plastic injection molding machines, plastic extruders, and other chemical processing machinery; tractors, harvesters, and other agricultural and forestry machines used for felling and mining; tunnel-, mine-, and surface-excavation equipment; and steering gear for various types of vessels, among others.

　　11. High-response, high-precision control: systems for gun-tracking drives, turret stabilization, ship roll damping, attitude control of aircraft and missiles, high-precision positioning systems for machine tools, drive and control of industrial robots, thickness control in metal-sheet rolling and leather-slicing operations, speed regulation for power-generator sets, high-performance vibration tables and testing machines, multi-degree-of-freedom large-scale motion simulators, and entertainment…

　　Leisure facilities, etc.

　　12. Automatic operation and control through the combination of multiple working programs: such as modular machine tools and automated machining lines.

　　13. Specialized Work Environments: Operational equipment for use in underground, underwater, and explosion-proof environments, among others.

　　Hydraulic Oil Filter Element Testing Standards

　　(1) ISO 2941 Filter Elements – Test Method for Burst Strength of Filter Elements

　　(2) ISO 2942 Filter Elements—Test Method for Structural Integrity of Hydraulic Filter Elements

　　(3) ISO 2943 Filter Elements—Test Method for Compatibility of Hydraulic Filter Element Materials with Fluids

　　(4) ISO 3723 Filter Element – End-Flow Compliance Test

　　(5) ISO 3724 Filter Element – Fatigue Property Determination

　　(6) ISO 3968 Filter Elements – Pressure Differential–Flow Characteristics

　　(7) ISO 4572 Filter Elements—Multi-Pass Method for Determining Filtration Characteristics

　　Hydraulic Oil Filter Maintenance Methods

　　The maintenance procedure for hydraulic oil filters is as follows:

　　1. Before replacement, drain the existing hydraulic oil, inspect the return-line filter element, suction-line filter element, and pilot-line filter element for iron filings, copper shavings, or other contaminants. If such contaminants are present, it may indicate a failure in one or more hydraulic components; after troubleshooting and rectifying the issue, flush and clean the entire hydraulic system.

　　2. When changing the hydraulic oil, all hydraulic oil filters (return-line filter, suction-line filter, and pilot filter) must be replaced simultaneously; otherwise, the oil change is effectively meaningless.

　　3. Identify the hydraulic oil grade; do not mix hydraulic oils of different grades or brands, as this may cause a chemical reaction, leading to degradation and the formation of flocculent precipitates. It is recommended to use the hydraulic oil specified for this excavator.

　　4. Before refueling, the suction filter element must be installed first. The pipe opening covered by the suction filter element leads directly to the main pump; if impurities enter, they can at best accelerate wear on the main pump and at worst cause it to fail.

　　5. Refuel to the specified level; hydraulic oil tanks are typically equipped with an oil-level gauge—refer to the gauge to check the level. Pay attention to the parking procedure: generally, all cylinders should be fully retracted, meaning the boom and bucket are fully extended and resting on the ground.

　　6. After refueling, be sure to bleed the air from the main pump; otherwise, at a minimum the entire machine will temporarily become inoperative and the main pump will emit abnormal noises (air-cavitating sounds), and at worst cavitation could damage the pump. To bleed the air, simply loosen the pipe fitting at the top of the main pump and fill the system completely.