Hydraulic systems & components


Hydraulic components need protection!

Second Quarter 2007 Hydraulic systems & components

Fluid power circuits are designed in all shapes and sizes, both simple and complex in design, and they all need protection from damaging contamination. Abrasive particles enter the system and, if unfiltered, damage sensitive components like pumps, valves and motors.

It is the job of the hydraulic filter to remove these particles from the oil flow to help prevent premature component wear and system failure. As the sophistication of hydraulic systems increases, the need for reliable filtration protection becomes even more critical.

How contamination damages precision parts

The cutaway view in Figure 1 is of a simple hydraulic valve and illustrates how particles damage components. In normal operation, the spool slides back and forth in the valve body, diverting oil to one side of the valve or the other. If a particle lodges between the spool and valve body, it will erode small flakes from the metal surfaces. As these flakes are moved back and forth by the action of the spool, they can roll into a burr that jams the spool and disables the valve.

Figure 1.  Spool valve cutaway view
Figure 1. Spool valve cutaway view

Types of contaminant

Many different types of contamination may be present in hydraulic fluid, causing various problems. These include:

* Particulate (dust, dirt, sand, rust, fibres, elastomers, paint chips).

* Wear metals, silicon, and excessive additives (aluminium, chromium copper, iron, lead, tin, silicon, sodium, zinc, barium, phosphorus).

* Water.

* Sealant (Teflon tape, pastes).

* Sludge, oxidation, and other corrosion products.

* Acids and other chemicals.

* Biological, microbes (in high water-based fluids).

Typical factors in component life

Studies show that most (typically 70%) of hydraulic component replacement is necessary because of surface degradation, and most of that is due to mechanical wear. Proper filtration of hydraulic fluids can lengthen component life.

Figure 3. Causes of hydraulic component failure.
Figure 3. Causes of hydraulic component failure.

Donaldson is a leading worldwide provider of air and liquid filtration systems and replacement parts. The company is technology-driven and works to satisfy customers' needs for diesel engine equipment and industrial filtration solutions through innovative research and development and global presence.

For more information contact Donaldson Filtration Systems, +27 (0)11 997 6000, [email protected], www.donaldson.co.za





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