The Power Behind the Force: Understanding the Core Components of a Hydraulic System

Have you ever wondered how an excavator can easily lift tons of dirt, or how a dump truck cab be lifted at a really high angle? The secret is hydraulics which applies Pascal's Law that says that if a pressure is applied to a fluid in a closed system, it will transmit that pressure equally throughout the entire system. 

This force transmitted electively will allow a smaller force applied to one part of the system to create a much larger force at some other part of the system so it is a perfect option for applications that need an incredible amount of force with extraordinary precision. Of course, for this powerful technology to even work, it must contain the right components, and each of those components serves as an important role. 

The Five Elements and Functionality

A hydraulic circuit is a simple closed loop made up of four major parts: the pump, control, actuator and reservoir. This circuit will be very similar to your body's circulatory system, where the hydraulic fluid will then become the blood, which carries the energy. 

1. The Reservoir

• Function: The Storage and Condition System

The reservoir is not only a storage tank for hydraulic fluid (normally oil), it also is a reservoir that conditions clean cool fluid to the pump. Reservoirs allow returning fluid to settle, allowing the air bubbles to escape, and allowing solid contaminants to settle at the bottom of the reservoir. Reservoirs also help cool the hydraulic fluid by allowing the hydraulic system to utilize the oil for cooling.

2. The Pump

• Purpose: The Core of The System

The pump will convert mechanical energy (produced from an engine or electric motor) into hydraulic energy by moving the fluid within the system. The pump does not generate pressure: it generates flow. Pressure is created when the fluid has resistance from other components, valves, or even the workload itself, (i.e. lifting a very heavy load). Some common pumps are gear, vane and piston.

3. The Valves (Control System)

• Purpose: The Traffic Controllers

The valves are responsible for controlling the flow, pressure, and direction of the hydraulic fluid around the entire circuit. Valves are the component that will allow an operator to have direct control of the movement of the machine.

Directional Control Valves: Determine the path the fluid travels in, switching the flow to extend and retract a cylinder.

Pressure Control Valves: Protect the system from overload on the system by routing the excess pressure back to the reservoir. (For example, Relief Valves.)

Flow Control Valves: Regulate the flow rate of the fluid, which in turn regulates the actuator speed.

4. The Actuators

• Function: The Muscle That Does the Work

Actuators are the end-effectors. They take the pressurized hydraulic fluid and change it back into mechanical motion do the work.

Hydraulic Cylinders: Change fluid pressure into linear motion (straight-line motion) for pushing (or pulling or both) or lifting (think of the arm of an excavator).

Hydraulic Motors: Change fluid pressure into rotary motion (continuous spinning) to drive wheels, conveyors, drills, etc.

5. Hydraulic Fluid (The Medium)

• Function: The power transmitter and lubricant

This is the incompressible medium (normally oil) that transmits power throughout the system according to Newton's Law. The fluid doesn't just transmit force, but it also lubricates all the moving parts and helps cool the system. The filters are necessary to keep the fluid as pure as possible for the entire life of the hydraulic system.

Why This Is Important:

The first step in maintaining any hydraulic equipment is knowing how the core parts work. Because hydraulic systems work at enormous pressure, a malfunction of one small component, such as a clogged filter or a bad valve, can bring down the whole system. 

The next time you see a crane lift the steel beam of a skyscraper or a bulldozer push a mountain of earth, you will know it's not just brute strength; it is a carefully perfected dance between the pump, the valves, and the actuator, all actuated by the clean, non-compressible power of hydraulic fluid.