What is hydraulic filtration?

Hydraulic parts are expensive and valuable parts in all industries.Failure of any of the hydraulic parts causes the failure of the hydraulic system and, in many cases, the failure of the production line of a factory.Today, the protection of the hydraulic system and parts is one of the main priorities of device manufacturers and industrial owners.One of the ways to increase the lifespan of parts is to protect hydraulic fluid and parts against impurities. Hydraulic filters that are installed in different parts of the hydraulic system are responsible for this task.

A hydraulic filter (in English: Hydraulic Filter), which is usually called an oil filter in a car, is a part of an industrial hydraulic system that has the task of cleaning the hydraulic fluid from contaminating particles so that the contaminated fluid does not damage the system. Hydraulic filters come in different sizes and are named according to the size of their screens. Filters are easily replaceable.

The hydraulic strainer and filter is a part of hydraulic systems that prevents contamination and additional substances in hydraulic oils from entering the device.This filter is produced in two types, low pressure and high pressure, and each of them is installed in different parts of hydraulic systems.

How the hydraulic filter works

In hydraulic filters, the suction or return of the hydraulic fluid is from the top of the filter and the inlet port, and the outlet of the filter is below it so that the refined oil returns to the tank from under the filter.A return path to the pump with a safety valve is also placed next to the inlet port so that if the filter is removed from the circuit, the pump circuit will not be without fluid.In line filters, the oil inlet and outlet pressure are both above the filter and opposite each other, that is, the hydraulic fluid enters the filtration chamber from the inlet opening and collects around the filter element, and after passing through the paper layer of the filter element and being purified, It moves from inside the filter element to the outlet opening and leaves the filtration chamber and filter.

Hydraulic filter components

Each filter consists of a main body that includes the inlet and outlet ports, the filtration chamber, and inside the body, the filter element that is responsible for the main job of filtering or purifying the fluid is placed along with the bypass valve.Of course, as mentioned, the filter status indicators can also be installed on the filter body. The filter element can be periodically replaced and there is no need to replace the entire filter.In addition, according to the existing standards, the filter element in different brands and manufacturers is produced with the same standard, which makes it easier to replace it, and the filter element can be replaced by any brand if the sizes and standards are met.

The importance of hydraulic filters in the system

Modern hydraulic systems work with increasingly high pressures and faster cycle times. By increasing both characteristics, the sensitivity of the system to pollution also increases.Fluid contamination is the main cause of hydraulic system failure and can cause many problems, including:

• Unwanted mixing of incompatible fluids causes fluid breakdown and leads to acid corrosion
• Internal leakage, reduction of parts (pump, motor, valve), efficiency and accuracy
• Accumulation of particles in critical areas leads to sludge that causes parts to stick
• Accumulation of particles in close tolerance areas leads to seizure of components

The obvious solution to prevent these problems is to prevent the pollutant particles from circulating in the system.Therefore, a clean and efficient filter is very important for the hydraulic system.

Hydraulic filter selection criteria

Before selecting the type of filter as described below, an engineer must determine the specifications and details of the hydraulic system. Some important variables are:

• Type of hydraulic fluid and working pressure
• Fluid flow in each cycle
• Ideal filter resistance
• The amount of pollutant that the filter is expected to have for a certain period of time
• Ideal liquid cleanliness

Types of hydraulic oil filters

Hydraulic filters are divided into several parts based on their pressure level and the position where they are absorbed. Hydraulic filters are divided into different forms:

• Hydraulic suction filter   

The main task of the suction filter is to prevent particles from entering the pump inlet.The size of suction filters can reach 150 microns or even more than that,                  that’s why this filter is also known as suction strainer.

• Hydraulic pressure filter

This filter must be clean to be used. The amount of pressure tolerance in pressure filters in industrial activity reaches 420.The size of particle and pollutant          absorption in pressure filters has reached four to twelve microns. These filters are usually placed either in a linear form or in a block form in the hydraulic chamber.

• Hydraulic return filter

These filters are used when particles have entered the oil and there is a possibility of their entering the system.The purpose of these works is to prevent particles from entering the system by absorbing them.Of course, the presence of a cartridge filter inside this filter determines the size of the particles, which should be between 21 and 40 microns. From those mentioned, it can play a role in their size, but this filter has no role in the cleanliness of the hydraulic oil filter.

A hydraulic filter system usually has two oil filters, but today’s hydraulic filters that engineers make can have several filters and these filters can be stored in different parts.
In some cases, pressure filters and return filters can be installed in parallel or double in the system. In this case, the filters are installed in the hydraulic system with the same filtration action.
One of the advantages of installing in this way is that when one of the filter ducts is blocked, other ducts can be used so that the passage of oil is not delayed. For a hydraulic filter, tasks such as opening, cleaning, replacing, closing the assembly and reinstalling have very important roles. And these actions must be done according to the necessary orders and requirements.

Hydraulic oil filter in 3 different structures
Hydraulic oil filter can be divided into three parts based on the type of structure and characteristics they have:

1. Filter with metal mesh

2. Keono type filter

3. Micron filter

As their name suggests, mesh filters have a metal structure that is woven together with small metals. This filter plays an important role in oil cleaning, since this filter has a filter device that is protected by a metal shield.

These filters have the ability to be cleaned, removed and replaced. After the oil enters the filter through a cylindrical metal tube, particles and sediments are trapped inside the mesh and with this method, the oil can be away from pollutants. be and be erased.

Of course, it should be noted that in these filters there is a device called a crossroads, if the filter is blocked due to the accumulation of sediments and particles, this crossroads can allow the oil to come out after cleaning, of course, the main purpose of this crossroads is that this oil can pass through the hydraulic system, which will prevent the production line from stopping.

We said that another type of hydraulic oil filter is Kiuno type filter. This filter is not very effective and its name is less used in the hydraulic oil filter. One of the advantages of this Kino type filter is that in case of clogging or sedimentation, it can be fully serviced before being opened or replaced.

Hydraulic oil filter structure

The equipment of this hydraulic oil filter is made of a completely basic body and an oil outlet duct and a separate duct located on it. The hydraulic oil filter inside the system has different types, which include:

Side suction filters

One of the side suction filters is only to protect the pump against the pollution that is inside the hydraulic oil and it is very harmful for it. These filters are usually installed before the hydraulic pump.

Tank breathing filters

But another type of this filter is the tank breathing filter, which is usually installed on the tank to eliminate the entry of pollution and humidity caused by the entry of oil.

Separate filters

These filters are usually used independently of the filter system, which are used to clean the oil before entering the hydraulic system.