Basic Hydraulics


Hydraulics systems are all about transmitting power.

They do this by applying force at one point in the system. It’s then transmitted to another point in the system using a fluid that cannot be compressed – typically an oil of some type.

For a basic hydraulic system, imagine a pipe filled with oil that has two pistons connected at each end. Pushing one piston down sends pressure through the pipe that then pushes up the second piston.

Sounds simple, but how about a real-world example of hydraulic systems and hydraulic system design?

Think of a conveyor belt, and how power can be transmitted from the electric motor up to the conveyor’s drive gear, which turns the belt and moves the load along.

Activating the electric motor gets the motor shaft turning, and drives the hydraulic pump. As the pump activates, hydraulic fluid sitting in the reservoir is pushed up.

With the pump operating, hydraulic fluid is then sent into the piping.

The piping is its own circuit, and the hydraulic fluid is pushed into three places more or less at the same time. This happens because of one basic principle behind any hydraulic system is that pressure applied at any point in a body of fluid results in force transmitting in all directions equally.

So the fluid goes to the pressure relief valve, the pressure gauge and the hydraulic manifold.

The pressure relief valve acts as a safety device. If the pressure becomes too high, it can trigger a line break or a fitting split – bad news for a hydraulic system. To prevent this, the valve controls the pressure in the system by diverting the hydraulic fluid back into the reservoir tank if the pressure enters into the danger zone.

The pressure gauge shows the level of pressure in the hydraulic system. It tracks this in psi – pounds per square inch, a standard measurement of pressure – using a display with a needle indicator.

Then there is the manifold. The manifold is a large block drilled through with internal passageways. Think of these as a plumbing system, which route the hydraulic fluid to the return line – back into the reservoir – and the pressure line which powers our conveyor belt’s drive gear.

One other principle of hydraulic systems is hydraulic multiplication. Unlike mechanical systems, where force is traded for distance, in hydraulic systems can multiply the force by using differently sized pistons and cylinders.

For example, a piston with a small surface area connected to a piston with a larger surface area will move more units of force than its original surface area. If the ratio is 1:9, if you apply 100 pounds of downward force to the piston the left, you’ll get 900 pounds of upward force on the right piston.

But if you go the other way, you’ll have to apply 900 pounds of downward force to the right piston to generate 100 pounds of upward force on the left piston.

In short, hydraulic systems make it easy to add or divide force multiplication.