Contamination is the reason why more than 80 percent of all hydraulic system failure occurs. You can keep downtime to a minimum if you properly maintain your hydraulic systems and maintain a recommended cleanliness level and oil temperature. 120°F is the ideal oil temperature for industrial hydraulic systems. When the temperature reaches 140°F, oil starts to break down. 15°F rise in the temperature above 140°F will cut the oil life in half.

When it comes to mobile hydraulic systems, they are designed to function at higher temperatures. Relatively smaller reservoir size limits the amount of heat dissipating into the atmosphere. Therefore, oils with high viscosity are used in mobile systems to control the higher temperature. A common practice is to measure contaminant particles in hydraulic systems in microns.

How small is a micron? A grain of salt is 100 microns or 0.0039 inch. The clearance inside most valves and pumps is approximately 0.0004 inch. The naked human eye can’t see that small particles but these small particles can irreparably damage a hydraulic system. This is why it’s important to protect hydraulic systems with reliable filters. Once you identify the desired cleanliness level, the next step is to figure out where you should locate the filters. Here are four locations where you can remove the contaminants.

1. Pump suction filter

A suction filter helps you prevent large particles from entering the pump. Pump suction filter can be used as a strainer situated underneath the fluid level. These filters typically have a 149-micron rating.

2. Pressure line filters

A pressure filter can be mounted in the pump outlet line when the pressure exceeds 2,200 psi in a system. It will filter metal particles and keep the system clean. It’s important to install the pressure line when a variable displacement pump is utilized on pressures higher than 1,500 psi.

3. Reservoir breathers

Atmospheric air flows through the breather when oil levels drop in a reservoir. When hydraulic systems come with a low-quality breather that doubles as a fill cap, unfiltered oil must not be added to the system.

4. Pressure line filter

It is necessary to mount a pressure filter in the pump outlet line when the displacement pump is utilized at a pressure level higher than 1,200 psi in a system. Using a pressure switch is the right way to monitor the element conditions.


There is no one-size-fits-all rule when it comes to determining the number of filters that should be used in a system. The more filters you have in a system, the more time you will spend on maintaining them. If the equipment in your facility doesn’t meet the ISO cleanliness levels, make sure to put the filters in the proper locations. This will help you minimize hydraulic downtime.

About Micro Lube

Micro Lube is a leading lubrication and maintenance company where we help industries maintain their hydraulic systems through proper maintenance and using high-quality filtration systems. We offer a broad range of Harvard filtration solutions ranging from standard filter elements and housings to fully customized systems. Browse through our website or contact us for more information!