A Review of the Basics of Hydraulics

Equipment in the automotive, construction, and manufacturing sectors – among others – relies on the transmission of power from one place to another. For a large portion of the components, this power is conducted through the use of a liquid (hydraulics) or gas (pneumatics), to which certain physical laws or principles apply. 

Since our business is dedicated to remanufactured hydraulic pumps, motors, and valves, naturally, we’re focused on hydraulics.

Our company is built around providing value and quality service to our customers with education and knowledge as our foundation. In this article, we’ve provided a review of the basics of hydraulics. This information is meant to be a primer for someone new in the field or a refresher for those more experienced but who do not work with hydraulics every day.

Incompressible Fluid: The Essence of Hydraulics

Essentially, hydraulics is all about the transmission of power using liquids, specifically incompressible fluids, which are defined as fluids where the volume or density does not change with pressure. 

Here are a few key facts to know about hydraulic fluids.

• Key Fact #1: Hydraulic fluids have a fixed volume, but since they take on the shape of their containers, they have no fixed shape.
• Key Fact #2: Since hydraulic liquids won’t compress, they transmit applied pressure in every direction, and as a result, they accelerate the workforce.
• Key Fact #3: There are three varieties of hydraulic fluids that are most common. They are water-based, petroleum-based, and synthetic. In certain applications, water is used, but typically it’s emulsified with oil. So, currently, the most standard type of hydraulic fluid is made from refining mineral oil.

Pascal’s Law and Hydraulic Fluids

The science of hydraulics was established by French scientist Blaise Pascal in 1653. 

Essentially, the fundamental law upon which the science is based states that when a confined liquid has pressure applied to it, the pressure transmits – undiminished – in all directions and acts with equal force on all equal areas.

An interesting example of a confined liquid in another application is blood, with the body being the container that confines the liquid. Another example is brake fluid – which is the confined liquid in a vehicle’s hydraulic braking system.

Pascal’s law states that the shape of the container (i.e., confined area) doesn’t matter – any force applied to the confined liquid will be transmitted in all directions throughout the liquid as long as the passage isn’t obstructed.

Output Force = Pressure x Area

• Output Force = Force exerted on an object to do work. Usually exerted by an actuator
• Pressure = Continuous physical exerted force. Hydraulic pressure is created by the resistance to flow
• Area = Square units of a shape

As the basis for hydraulic transmission, hydraulic devices, and hydraulic systems, Pascal’s Law tells us that a small force at point 1 can push a heavy object at point 2.

In effect, many large-capacity and high-pressure machinery solely rely upon hydraulic pressure to increase mechanical strength. Example below:

To learn more about Pascal’s Law and its relevance to understanding hydraulics and fluid-pressure transmission, read our previous article, Pascal’s Principle and the Origin of Hydraulics.

Hydraulics: Important Talking Points

The next time you’re involved in a hydraulics conversation, here are some of the talking points you should know:

• Talking Point #1 - Hydraulics refers to fluids, specifically, the fluid transmission of power – as opposed to pneumatics, the gas transmission of power
• Talking Point #2 - Hydraulics is a science first developed by Blaise Pascal. Simply put, it is based upon the principle that the intensity of the pressure applied on an incompressible liquid is the same in all directions. Basically, this allows for the generation of a large force with minimal effort
• Talking Point #3 - Hydraulic power propels the majority of automotive and construction equipment – from airplanes and backhoes to bulldozers and brakes. This is done through the employment of hydraulic systems, which are made of hydraulic pumps, motors, and valves, which happen to be Hydraulics Parts Source’s areas of expertise

Eager to Learn? Rely on Our Library

The Hydraulic Parts Source blog features dozens of articles on the fundamentals of fluid power, hydraulic troubleshooting topics, hydraulic parts specifics, and more. Make sure to bookmark & return to this knowledgebase as we’re always building it to bring more value to you – and as a result – your end-users.