How Does a Hydraulic Crane Work? A Brief Guide

The Ancient Greeks invented cranes in the 6th century or earlier. Since then, we have relied on cranes to build our most significant structures.

And the hydraulic crane is the most efficient of all. You can apply constant torque at any speed. And they are simple to control and maintain.

Let’s take a look at how hydraulic cranes work.

The Basics of Hydraulics

Hydraulic systems change mechanical energy into hydraulic energy, then back to mechanical again. They use pistons, cylinders, and pressure to do this.

Oil is the most common hydraulic fluid. It is hard to compress, which makes it ideal for this purpose. Its viscosity is vital, as is its availability and cost.

The first piston pushes this fluid down. This displacement puts pressure on a piston at the other end of the cylinder. The second piston then moves up or out. This movement drives the crane’s lifting system.

Hydraulics avoid the heat generated by mechanical means. They bypass the friction of metal-on-metal systems giving them an advantage.

They are quieter and easier to maintain. They can generate more lifting power with less wasted energy than mechanical systems. 

Parts of a Hydraulic Crane System

Both hydraulic truck cranes and fixed cranes use a boom and jib to lift loads. The boom can extend on most models. The jib attaches to the end of the boom,  increasing reach.

A counterweight sits at the opposite end to the jib. This balances the upper parts of the crane while it lifts loads.

Most hydraulic truck cranes have outriggers. These beams extend out to the ground stabilizing the crane.

Then there is the hydraulic lifting system and its pump.

Types of Hydraulic Crane Pumps

There are two main types of hydraulic pumps: gear pumps and variable-displacement pumps.

The gear pump is the most common. But the precision of variable-displacement pumps suits some projects. So let’s take a look at how both work.

Gear Pumps

Most cranes use gear pumps to displace hydraulic fluid between pistons. These are the more affordable options, and their simplicity can make repairing cranes easier. 

Two interlocking gears move a piston to put pressure on hydraulic fluid. This pressure moves the opposite piston.

They are simple to operate. More engine power equals more hydraulic pressure and greater lifting capacity.

Variable-Displacement Pumps

Variable-displacement pumps have piston cylinders joined to a ring within a barrel. This barrel spins, rotating the cylinders. A swashplate drives the first pistons in and out.

This motion displaces fluid in the cylinders. This pressure moves the opposite pistons out, driving the lifting mechanism.

The crane operator can change the fluid flow rate and outlet pressure giving them more precision when lifting. 

This control comes at a cost. Variable-displacement pumps are more expensive and harder to repair than gear pumps. 

Need Hydraulic Crane Parts or Repairs? 

Hydraulic cranes are invaluable tools for efficient lifting. Maintenance helps keep them that way.

But components wear with use. So to keep your hydraulic crane at its best, you might need new parts from time to time.

At Kor-Pak, we stock a huge selection of parts for various cranes. And if you need a professional to fit them, we can service your crane for you.

Contact us today to find what you need.


Posted in Crane.