Harnessing Fluid Power: The Pros and Cons of Hydraulic Systems

Hydraulic systems provide the basis for heavy lifting in various scenarios, whether that be in car brakes, large excavators, or airplane landing gear. These machines supply tremendous amounts of force by using the pressure of an incompressible fluid (usually oil) in a sealed system. 

But like any technology, hydraulics come with trade-offs, which are important to consider before designing the next great machine. Here are the main advantages and disadvantages of fluid power.

Key Benefits (The Pros)

Hydraulic systems are employed for high-force applications because they provide power and control that other systems can’t.

1. Amazing Power Density

Hydraulics are the kings of force multiplication. Based on Pascal's Law, a small force applied to a small piston can create a great force on a larger piston. Hence, a relatively small, compact hydraulic component can provide an incredible amount of power, especially important in heavy machinery applications with limited space.

2. Precise and Variable Control

Utilizing incompressible fluid allows for smooth, precise, and rapid movement control.

• Speed Control: Hydraulic systems can provide infinitely variable speed control without a complex gearing system, and operators can match speed and force easily and accurately to the task.
• Constant Force: They will provide constant force or torque with speed changes, as important in applications like pressing and clamping or lifting and moving heavy and unpredictable loads.

3. Simplicity and Reliability

Although having considerable power, core operating components (e.g. pumps, valves, cylinders) tend to be less complex than mechanical or electric equivalent technologies for the same power output. 

• Less Complexity: In general, hydraulics use fewer moving components which means also less wear and tear and longer life. 
• Self-Lubrication: The hydraulic fluid is also a lubricant to the internal components, which again contributes to the longevity of the hydraulic system. 

4. Overload Protection

Hydraulic systems are naturally protected from excessive force damage. If the load becomes too great, the hydraulic system's relief valves open to allow the hydraulic fluid to bypass the actuator, thereby preventing damage or complete failure of the hydraulic system.

Drawbacks in Fluids (The Cons) 

While hydraulic, as a method of actuation, has advantages, the disadvantages involve upkeep, cleanliness and the fluid nature itself.

1. Potential leak and contamination 

This is hydraulics' Achilles heel. A single small leak will not only destroy efficiency, it will create a working mess and an even bigger issue to the environment if petroleum-based fluid is used. Additionally, the system is extremely sensitive to contamination (dust, dirt, and/or water), which can damage high precision parts such as pumps and valves.

2. Maintenance demands 

Hydraulic systems are tough, but they do require constant attention and maintenance of systems detailed attention:

• Periodic checks: Seals, hoses, and filters must be checked, repaired or replaced periodically, to avoid any leakage or contamination.
• Fluid Replacement: The hydraulic fluid must also be checked for quality and be replaced periodically, thus adding to an operating cost.

3. Temperature sensitive

System performance is directly linked to the properties of the hydraulic fluid.

• Viscosity: The thickness, or viscosity, is changed at temperature. If fluid is too cold it will become sluggish. Conversely, too hot will become too thin thus reducing efficiency and creating an increase in internal leakage.

4. Increased Initial Investment

Hydraulic components cannot be manufactured to a lower cost because they must be produced to higher tolerances to accommodate high operating pressures and reduce internal leakage. As a result, the requirement for high-tolerance hydraulic components will usually result in a higher initial system design and installation cost than a pure mechanical or pneumatic system.

The Final Decision: When Is Hydraulics The Right Choice?

Even with the drawbacks, the unique power-density and precision of hydraulics make hydraulics the only solution for applications with substantial sustained force land heavy-weight applications meaning construction, aerospace, heavy manufacturing, and material handling industries.

If it is heavy-duty and reliable under load, then the benefits of hydraulic power easily justify the costs and maintenance issues!