LUBRITA hydraulic oils and basic principles


Pascal in the seventeenth century produced a fundamental law of hydraulics: “The pressure applied
to a confined fluid is transmitted undiminished in all directions and acts with equal force on equal
areas and at right angles to them”

Hydraulics is one of the oldest branches of science and can be defined as “The transmission of force
from one point to another using a fluid as a transmitter of force.” Hydraulics is used to transmit
force in order to, for example, change direction in a hydraulic excavator or change the magnitude of
force (braking). It uses a special circulating system in which a pump drives an oil to move actuators.

Hydraulics offers major advantages over mechanical pulleys, levers, and gears:

• High power to weight ratio.
• Infinitely variable speeds.
• Eliminates complex, expensive, mechanical linkages.
• Easily rerouted and disconnected.
• Can serve many actuators/applications.
• Fluid does not break.
• Forces can be transmitted over a great distance.
• Allows large loads to be moved by small forces.
• Able to transfer large forces over distances with relatively small space requirements.
• Operations can commence from rest while the system is at full load.
• Speed can be easily controlled.
• Smooth adjustments to speed, torque, and force.
• Simple protection against system overloading.
• Suitable for both quick and slow controlled sequences of movements.
• Simple centralized drive systems available (several machines can be operated off one hydraulic system).

Hydraulic systems are subject to the laws of hydromechanics. This means that balances within the hydraulic system are subject to both hydrostatic and hydrodynamic forces.

Hydrostatic force is the pressure that exists in a system. This is created by a combination of gravity, the height of the fluid in the reservoir, and the fluid density. The height of the fluid in a reservoir and its density determine the static pressure at any point within a given system, and the static pressure at the bottom of the reservoir will always be higher than the pressure at the top. Note that volume has no effect on static pressure.
Hydrostatics is important in the design and application of hydraulic systems. Hydrostatic considerations that should be recognized include: higher density fluids need more energy to pump, the location of pump suctions is critical relative to fluid levels, and the impact of how far and to what height fluids are needed to perform work. For example, pumps designed with a positive static head at their suctions are much less susceptible to cavitation than pumps with suctions located above fluid levels.
Hydrodynamics, or hydrokinetics, involves the energy of fluids in motion, and there are specific areas where they are important. Fluids in motion contain an energy component above that indicated by pressure and flow. This energy level is related to mass and acceleration. The instantaneous pressure rise generated by the sudden stoppage of motion can be very high, leading to a “shockwave.” These shockwaves can be severe enough to cause failure of system components. Where these conditions exist, accumulators (hydraulic shock absorbers) should be installed at appropriate locations within the system to minimize the negative effects of these shock waves.

In service, properly selected hydraulic fluids enable effective pressure transmission and controlled flow, reduce wear and friction, improve system efficiency, provide cooling, prevent rust and corrosion, and help keep the system components free of deposits. High-quality hydraulic oils are able to maintain their initial characteristics and provide satisfactory service for long periods—often years in well-designed and well-maintained hydraulic systems.

Lubrita hydraulic oils are engineered to resist thermal and oxidative breakdown, provide extended drain intervals, protect against equipment wear and also minimize sludge and varnish deposits for smoother hydraulic equipment performance. And these advantages reduce maintenance costs significantly.

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