Functions of hydraulic fluids

HYDRAULIC FLUIDS

FUNCTIONS OF HYDRAULIC FLUIDS

• Hydraulic fluid is the medium by which energy is transferred in a hydraulic system.

• The hydraulic fluid, besides its basic purpose of transmitting power, it must also lubricate, cool, protect from corrosion, sealing and other functions depending on the system design.

• The various functions of hydraulic fluids are listed in Fig.2.1 and are presented in Table 2.3.

Table 2.3. Functions of hydraulic fluids

1. Power transmission: 

• The primary function of the hydraulic fluid is to transmit power from the pump to the hydraulic actuator (hydraulic cylinder or motor).

• In order to perform this primary function efficiently, the hydraulic fluid must be incompressible and flowable to respond to every minute change in applied force.

2. Lubrication: 

• The hydraulic fluids lubricate the moving parts.

• Lubrication is required in most hydraulic components to protect internal parts from friction wear. The hydraulic fluid provides full-film lubrication between moving parts.

• Without the lubricating properties of hydraulic fluid, hydraulic systems would be unreliable with a very short life for many components.

3. Sealing: 

• The hydraulic fluids provide sealing in gaps and clearances. 

• It is practically difficult to provide perfect mechanical sealing at all. places in hydraulic system, hence the hydraulic fluid should be thick enough to form a strong film to seal the close clearances against leakage.

4. Cooling (Heat transfer): 

• The hydraulic fluids carry and dissipate the heat generated due to various frictional losses in the system to keep the temperature of system under control.

• In other words, the hydraulic fluids act as coolants to dissipate the heat generated by internal friction.

5. Prevention of rust and corrosion: 

• The hydraulic fluids should also prevent rust and corrosion of system components.

• This can be done (i) by selecting the fluid which is compatible with component materials, and (ii) by adding proper additives with the fluid. 

6. Contaminants removal:

• The hydraulic fluids also remove unwanted and harmful impurities from the system.

• The presence of contaminants will damage the system or reduces productivity. The contaminants can be solid particles or water content. The hydraulic fluids carry all the foreign particles towards the filter.