Hydraulic Fluids

A hydraulic fluid that takes the form of oil is used as a medium for the transmission of power.  It also functions to lubricate and cool engine components.

In principle, fluids can be gas or liquid.  As this unit discusses about hydarulics, we will discuss on the characteristics of oil.

In application, hydraulic fluid functions as:

  • Power transmission
  • Lubricant
  • Seal
  • Coolant
  1. Power Transmission

One of the functions of a hydraulic fluid is to transmit power.  In this case, it is obvious that a fluid must flow smoothly through its passage.  Any obsruction in the lines can cause a loss of power, resulting in an inefficient system.

  1. Lubricant

Most of the components in a hydraulic system are lubricated by liquid fluid, the oil itself.  The contact points of moving components in a pump where frictions may occur must be applied with oil film to avoid direct contact of the moving components so that the life span of the hydraulic components can be maintained.

  1. Seal

In some cases, a fluid functions only to seal the pressure in a hydraulic component (see Figure 2-7).  It is showed that there is no seal between the spool and the valve body for eliminating leakage from higher pressure paths to lower pressure paths.  The average leakage is determined by both the oil viscosity and the mechanical tightness between the spool and the spool body.

  1. Coolant

Circulation in hydraulic systems takes place through pipes or hoses, and the entire wall of the reservoir absorbs the heat generated in the hydraulic system.  In addition to the main functions as mentioned above, a hydraulic fluid should meet several requirements, including:

  • It should be able to prevent corrosion or contamination.
  • It should be able to prevent deposit from building up.
  • It should not easily generate oil bubbles
  • It should be able to remove water content.

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