A hydraulic oil is the medium by which power is transferred in hydraulic machines.Hydraulic oil consists of oils and additives designed to transmit power while acting as a lubricant and coolant. The oil is effective in a wide range of temperatures and reduces wear, rust and corrosion in equipment. Hydraulic oil is used for many of the same reasons as oil but has wider use in automobile systems like automatic transmissions, as well as power brakes and steering. Aircraft systems also require hydraulic fluids. Viscosity is of paramount importance in choosing such oil.
Hydraulic
system mainly consists of five main parts:
1. Pump
2. Valve
3. Piston
4. Filtering system
5. Cooling system
Why Hydraulic Oils are used instead of air?
|
TYPES |
PRESSURE |
COMPRESSABILITY |
CONTROL |
|
Air |
Low (10~14 bar) |
Compressible |
Not easy to control |
|
Oil |
High (10~560 bar) |
Not compressible |
Controlling is easy |
3 Hydraulic Rules
1. Pump - Pouring the oil (It means, it just pours the oil only and does not provide any
pressure to the system)
2. Pressure - By resistant
3. Oil Flow - Flows where the resistance is low
Hydraulic Pressure
|
PRESSURE |
BAR |
PUMP USED |
|
|
Low |
~ 14 |
Inner gear pump |
|
|
Medium |
14 ~ 35 |
Screw pump |
|
|
Medium - High |
35 ~ 84 |
Screw pump |
|
|
High |
84 ~ 210 |
Outer gear pump |
|
|
High - High |
Low |
210 ~ 270 |
Vane pump |
|
Medium |
270 ~ 350 |
Axial piston pump |
|
|
High |
350 ~ |
Radial piston pump |
|
Vane pump & Piston pump are used widely in Industries. Vane pump is used in CNC machines & Die casting machines. Piston pumps are used in Die-casting & Rolling machines.
ISO Standard Viscosity Grades
Below mentioned viscosity is measured at 40 degree C.
|
VISCOSITY GARDE |
USAGE |
|
2 |
Used for manufacture of Spindle type oils. |
|
7 |
|
|
10 |
|
|
15 |
|
|
22 |
Mostly used in the manufacture of Hydraulic oils. |
|
32 |
|
|
46 |
|
|
68 |
|
|
100 |
Mostly used in the manufacture of Gear oils. |
|
150 |
|
|
220 |
|
|
320 |
|
|
460 |
Types of Oils
1. Hydraulic oil
2. Slide oil
3. Generator oil
4. Turbine oil
5. Compressor oil
6. Spindle oil
7. Gear oil, etc
Almost all the above oils are of same type but varies in there working characteristics & Viscosity. According to the working characteristics & Viscosity, their additives changes slightly.
Hydraulic Sealing
Sealing is a very important factor when hydraulics are concerned. Mostly rubber type sealing are used in Hydraulics.
Main raw materials of Hydraulic Oil
1. Mineral oil
2. Anti-wear agent
3. Anti-oxidant
4. Rust preventives
5. Pour point decreaser
6. Viscosity index improver
7. De-emulsifier
8. Anti-foam agent
Tank Cleaning Method
While using a new oil in a Hydraulic system, it is must to clean the system. There is a procedure to be followed in cleaning the tank of the hydraulic system as given below,
Remove the old oil
Clean the tank manually to remove the sludge & other waste particles
Flush the tank with a low grade oil
Top-up new oil