Hydraulic oil filter element

Why do hydraulic systems need filters

In our life, hydraulic systems can be found everywhere. The hydraulic system provides necessary support for the production of enterprises and the operation of large machinery. The hydraulic system relies on hydraulic oil to provide continuous power for enterprises. If the hydraulic oil is contaminated, it may cause damage to the equipment. Serious damage will affect the production of the enterprise, which is a situation we do not want to see. Therefore, we need to install a filter in the hydraulic system. The hydraulic filter can adsorb the impurities entering the system from the outside world and the particles generated inside the system on the medium, keep the hydraulic oil clean, and ensure that the hydraulic system can work normally for a long time.

Three common types of hydraulic filter elements

Oil suction filter

The oil suction filter must be installed at the position below the oil level of the oil tank in the pump suction pipeline. The oil suction filter is the basic protection of the pump to avoid the wear caused by large particles. The oil suction filter element is very important to the pump.

Pressure line filter

The pressure line filter is installed after the pump of the hydraulic system and is installed in the hydraulic component attachment to protect the hydraulic component from wear. The pressure line filter element is very important, so you must pay attention to regular maintenance and replacement.

Oil return filter

Return line filters can be found on almost every hydraulic system. It mounts directly on the fuel tank cap. So you can easily replace the filter element when needed and maintenance is easy. Choose your return line filter based on the maximum flow of your hydraulic system.
 

Hydraulic oil filter element structure

In general, the main structure of hydraulic oil filter element includes end cap, rubber ring, skeleton and filter material. Of course, some hydraulic oil filter element is also equipped with bypass valve or pull ring. 1. End cap.
The end caps of hydraulic oil filter elements are mainly divided into machine end caps, stamping end caps, nylon end caps and PU end caps. Among them, the material of the stamping end cap is generally iron with galvanized surface, commonly known as galvanized sheet, which can effectively prevent oxidation and rust through the galvanizing process. The stamping end cap needs to make a mold. After the mold is made, it is stamped by the machine at one time, and the shape is relatively thin. In contrast, the machined end caps are made by machining, and the material is generally aluminum, iron or steel. The machined end caps are characterized by thicker thickness and high pressure resistance. Due to the raw materials and unique processing technology, the machined end caps are The price of the cover is higher. Both nylon (commonly known as plastic) and PU end caps are molded by casting, but PU end caps are softer and nylon is harder.
2. Rubber ring
The function of the rubber ring is like the function of the rubber ring in the thermos cup. They all play a sealing effect. The rubber ring is responsible for the sealing of the joint between the filter element and the filter. Rubber rings are generally divided into fluorine rubber rings and nitrile rubber rings. Fluorine rubber rings are commonly found in purple, red, green and black, which are corrosion-resistant. Some filters use gaskets.
3. Skeleton
The skeleton plays the role of supporting the corrugation of the filter material, connecting the end cover, and avoiding the corrugation bump in the hydraulic oil filter element. Generally, the material of the skeleton is stainless steel, aluminum plate and plastic. According to the purpose, it can be divided into inner skeleton, middle The skeleton, the outer skeleton and the spiral skeleton can be divided into round hole skeleton, square hole skeleton, diamond skeleton and rectangular hole skeleton according to the shape of the hole. Some hydraulic oil filter elements will be included in the ultra-high pressure working environment in order to improve the pressure resistance of the filter element. A support ring is installed in the skeleton to improve the compressive capacity.
4. filter material
The filter material is the core part of the hydraulic oil filter element. All oil products need to be filtered through the filter material. The filtration accuracy and filtration effect of the filter element completely depend on the quality of the filter material. Therefore, we cannot be polluted by dirt in the process of making filter material, otherwise it will affect the filtering effect. The filter element can be divided into metal, filter cloth, glass fiber, paper and polypropylene according to the categories. Among them, metal filter materials mainly include stainless steel mesh, sintered felt and sintered mesh. Paper filter media include chemical fiber filter paper and wood pulp filter paper.
5. pull ring
The lifting ring is generally mainly installed on the upper end cover, mainly made of metal material, and its function is to facilitate installation and disassembly.
6. Bypass valve
When the engine is severely mechanically worn for some reason, which causes the filter element to be blocked, the bypass valve will automatically open at this time to ensure the smooth flow of oil and prevent the engine from locking. The material of the bypass valve is generally nylon, but not all hydraulic oil filter elements are equipped with a bypass valve.

Filter Media Types for Hydraulic Filter Cartridges

For hydraulic oil filter elements, the filter medium is an important factor that affects the efficiency and performance of the filter element. You must choose a suitable material as the filter medium. The correct filter element will allow the filter to perform at its best.
Materials commonly used as filter media in enterprises include wire mesh, stainless steel, microglass, paper, and cellulose. Hydraulic filter elements generally have multiple layers of filter media, and different filter media play different roles. wire mesh filter
This material is usually used for surface filtration, because of structural limitations, fine particles cannot be filtered out. However, the material can be cleaned and reused, so it has a longer lifespan.

Where can you find filters

The installation positions of hydraulic filter elements in the hydraulic system are usually as follows:
1. Installed at the suction port of the pump:
Generally, a surface oil filter is installed on the suction road of the pump to filter out large impurity particles to protect the hydraulic pump. In addition, the filtering capacity of the oil filter should be more than twice the flow rate of the pump, and the pressure loss should be less than 0.02MPa.
2. Installed on the outlet oil road of the pump: the purpose of installing the oil filter here is to filter out the pollutants that may invade the valve and other components. Its filtration precision should be 10 ~ 15μm, and it can withstand the working pressure and impact pressure on the oil circuit, and the pressure drop should be less than 0.35MPa. At the same time, a safety valve should be installed to prevent the oil filter from being blocked.
3. Installed on the oil return road of the system: This installation acts as an indirect filter. Generally, a back pressure valve is installed in parallel with the filter. When the filter is blocked and reaches a certain pressure value, the back pressure valve opens.
4. Installed on the branch oil circuit of the system.
5. Separate filtration system: A hydraulic pump and an oil filter can be specially set up for a large hydraulic system to form an independent filtration circuit.

The maintenance method of hydraulic oil filter

1. Drain the original hydraulic oil before replacing, check the oil return filter element, oil suction filter element and pilot filter element to see if there are iron filings, copper filings or other impurities. .
2. When changing hydraulic oil, all hydraulic oil filter elements (oil return filter element, oil suction filter element, pilot filter element) must be replaced at the same time, otherwise it is equivalent to not changing.
3. Identify the hydraulic oil labels. Do not mix hydraulic oils of different labels and brands, which may react and deteriorate to produce floccules. It is recommended to use the specified oil for this excavator.
4. The oil suction filter element must be installed before refueling. The nozzle covered by the oil suction filter element directly leads to the main pump. The impurity entering will accelerate the wear of the main pump in light, and the pump will be hit in heavy.
5. Refuel to the standard position. There is generally an oil level gauge on the hydraulic oil tank, see the level gauge. Pay attention to the parking method, generally all cylinders are fully retracted, that is, the forearm and bucket are fully extended and landed.
6. After refueling, pay attention to the main pump to exhaust air, otherwise the whole vehicle will not move temporarily, the main pump will make abnormal noise (air sonic boom), and the cavitation will damage the main pump. The air exhaust method is to directly loosen the pipe joint on the top of the main pump and fill it up directly.

When should the hydraulic oil filter be replaced?

Like other equipment, the hydraulic system needs regular maintenance to ensure that it is always in the best condition. Many people who use the hydraulic system know that the hydraulic filter element needs to be replaced, but they do not know when it is the best time to replace the hydraulic oil filter element. Improper filter replacement cycle may increase business costs, or cause contamination of system components. Replacing filter elements too early or too late are all issues that need attention.
You look online for answers, and different people will give you different answers, some will tell you to change them regularly, some will tell you to wait for the filter to get clogged and replace it.
In fact, you can follow the manufacturer's advice, the manufacturer is more familiar with the system than everyone, so they can better understand the problems with the system.
A better way to determine when to replace a filter element is to use a monitoring device. Instead of strictly following a schedule, you monitor the fluid pressure to see if the filter element has reached the end of its life. This method ensures that the filter element is replaced at the right time and avoids downtime due to unnecessary maintenance.
Of course, you can also extend the filter change interval by adding more filters, and adding offline filters is an effective way to reduce wear and tear.