Transmission and control of power can achieved in different ways: Mechanical, pneumatic, hydrodynamic and hydrostatic. Hydrodynamic systems rely on the momentum of a fluid to transmit power smoothly through the vanes of a turbine. Hydrostatic refers to the transmission of power using the flow and pressure of a fluid. Hydraulic fluid power is used just about anywhere on land, sea or in the air (and even in space). There are many applications such as tractors, forklifts, presses, agricultural machines, cranes, aerial platforms, mobile lifts, construction machines such as excavators and more.
For example; in an excavator, hydraulic cylinders operate the boom, arm and bucket. Hydraulic motors are commonly used to swing the body of the machine and also to drive the tracks, wheels and auxiliary attachments.
Many functions in an excavator use hydraulic power
Industrial applications such as plastics and die-casting machines again make us the rapid and accurate control capability of hydraulic power, while presses benefit from the almost limitless amount of force that can be both generated and precisely controlled. Currently the largest hydraulic press in the world is an 80000 ton die forging press in China.
80000 ton press in China
Advantages of hydraulic power transmission:
- Large amounts of power from small components
- Linear or rotary output movement
- Simple bi-directional output
- Infinitely variable speed control
- Force/torque, speed and power limiting easily achieved
- Multiple outputs from single-input power source
- Manual, eletrical or electronic control inputs
- Self lubricating
- Ability to cope with difficult working environments
- Relatively simple, well-understood technology
Beside these advantages, there are a few disadvantages as following:
- Generally less efficient than mechanical transmission
- Requirement for fluid cleanliness
- Fluid leakage may create pollution, fire risk or health hazard
Part of this article is from the book “An Introduction to Practical Hydraulic System Maintenance”
Photos are used for training purpose only