Most of the mobile and industrial hydraulic applications contain precision machined components that are sensitive to wear and causes damages. Contaminated hydraulic fluids are the primary reason for premature failure and low performance of the hydraulic system. The particle and chemical contaminants present in the hydraulic oil will result in accelerated component wear, orifice blockage, corrosion, oil degradation, etc.. Contaminants enter into the system as a result of manufacturing defects, low quality/cleanliness of fluid and filling process, and poor maintenance. How do you remove these contaminants and protect your hydraulic system?
Filters and strainers are the two important equipment’s used commonly in every hydraulic system for removing insoluble contaminants from the hydraulic oil. Both have the same function, but the construction and filtration capacity will differ. Strainers are constructed of a fine wire mesh screen and are suitable for removing large particles. Filters are commonly used filtration media containing fabricated steel housing with an inlet and an outlet. The maximum foreign particle accumulating capacity of filters made it highly adaptable in hydraulics. So, more details on hydraulic oil filters and filtration are discussed here.
Filtration is the process used by the hydraulic industry to remove contaminants from the hydraulic fluid circulating through the system. The filters installed in this system will pass fluid through it by blocking the contaminants and passing filtered hydraulic oil. The clear fluid obtained after passing through the system is called the filtrate and the contaminants collected are called residue.
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The performance of a hydraulic system is measured by its dirt holding capacity. There are three methods to understand the efficiency of a filter. It includes nominal rating, absolute rating and beta rating. Nominal rating is the value assigned by the manufacturer and the absolute rating is based on the size of the largest particle that can pass through the system. The hydraulic industry widely uses beta testing, based on the multipass method. It is necessary to change the filters after a certain time period for removing the contaminated particle collected by the filter. Otherwise, a damaged filter can block fluid passage or the filtration media will damage.
Hydraulic Oil Filter Types
Hydraulic oil filters have numerous advantages in the hydraulic industry. They are available in different types based on the applications. The hydraulic oil filters can be classified according to the filtering method, size of pores, location of the filter and the amount of oil filtered. To select a suitable filter that matches with your system you need to consider pressure, fluid type, flow rate, resistance, percentage of contaminants, and ideal cleanliness. Suction filters, pressure filters, off-line filters, return filters, etc.. are some important classifications.
These filters are placed in the suction life before the pump to filter oil entering the pump. It uses higher micron rated filtering media such as wire screen. This filter provides a low-pressure drop and protects the pump from large-sized contaminants.
Pressure filters are placed between the pump output and the other component. It filters minute fluid contaminants and protects the sensitive components like valves and actuators. This filter is capable to withstand full system pressure and this pressure helps to push fluid through the filter material.
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This is a self-contained filter system placed independent from the hydraulic system, inside the reservoir. It filters the fluid before entering the pump by pulling oil from the reservoir through the filter. In short, this filter cleans the fluid stored in the reservoir and return it to the reservoir itself.
Continuous operations of hydraulic system causes wear. The return filters placed in between the control valve and reservoir will collect this wear debris and prevent these particles to enter back to the reservoir. Return filters are available in different assembly styles.