Cranes have been used for thousands of years. In fact, the first known crane, thought to be from 3000BC, was the Shaduf or Shadoof, a water lifting contraption from ancient Mesopotamia. This was originally used to retrieve water from deep wells.
But cranes have changed a lot since then. This article gives you basic information on what cranes are and how they work.
What is a crane?
Cranes are machines that lifts items that are too heavy for humans, usually to places that humans can’t carry them.
Cranes can be static, where they’re fixed in one position, like tower cranes, or they can be mobile, where they can move around on wheels or tracks, like crawler cranes
How do cranes work?
Cranes work using pulley systems. Steel cable gets anchored onto to a winch at one end of the system, then runs along a series of pulleys, in the form of sheaves, to the crane hook at the other end. Pulleys are an ancient tried and tested system that alloys items to be lifted easier.
The cable that is wrapped around a drum on the winch gets fed in and out using a motor.
This system can also be used to raise and lower luffing/derricking jibs. But sometimes, hydraulics are used instead for this purpose.
The more sheaves used, and the more times the cable runs to and from the hook and crane, the more weight the crane can lift.
Cranes use a balancing system to stop them from tipping over. Counterweights are at the rear of the crane to counteract the weight that gets lifted at the front.
In some cases, cranes get controlled in cabs using levers or joysticks. In other cases, they’re controlled from the ground using control panels or remote-control units.
Cranes can be powered by diesel engines or electricity. Some modern cranes are even battery powered.
Types of cranes
There are 16 main types of cranes. They all have their various uses and are used in different industries.
Here some examples of cranes and what they’re often used for:
- Tower cranes – Construction industry
- Gantry cranes – Warehouses and industrial units
- Crawler cranes – Energy sector and construction
- Wheeled telescopic cranes – Construction, energy sector, contract lifts, domestic use
- Aerial cranes – Sea rescue, logging, floods, wildfires
Parts of a crane
Because there are many different styles of cranes, their parts will also differ. But the main parts are:
- Jib/boom
- Slew ring
- Hook
- Trolley
- Counterweight
Jib/boom
A jib or boom is the arm that extends from the main body of a crane, with the hook at the other end to lift the loads.
Booms are telescopic arms that get used on machines like mobile cranes, telehandlers, and such like. Jibs are fixed arms that are used on machines like tower cranes, and floor cranes, etc. A jib can be put onto the end of a boom to give it more length. These are called fly jibs.
Slew ring
A slew ring is a device that helps the main body of a crane to rotate.
Hook
A crane hook is what loads get attached to when being lifted. Large cranes usually have the hook attached to a hook block. This hook block houses the sheaves that feed the wire rope through the pulley system.
Trolley
A crane trolley is a device that moves along a jib (on saddle jib cranes) or beam (on gantry cranes). This trolley carries the hook, taking it to whatever destination a load is at.
Counterweight
As previously mentioned, counterweights use physics to keep the crane upright when the crane takes strain while lifting a load. The amount of counterweight should be far greater than the crane’s maximum lifting capacity.
If you were to look up at a tower crane that has no load on, the mast will sometimes be leaning backwards because of the counterweight at the back. Once the weight of a load gets put on the front end of the crane, if it’s heavy enough, it will straighten the mast up.
Conclusion
Understanding the basics of cranes is very important if you want to get into the industry, not only as an operator, but also as a slinger/signaller, crane supervisor or Appointed Person. But cranes are great for everyone to know about because they are amazing pieces of engineering.
The most important thing to keep in mind with cranes is safety. It’s a safety-critical industry, which is why cranes have lots of in-built safety features, and why there are lots of regulations and protocol to abide by.
As a bonus, to see all the parts of a tower crane and watch one in action, here is a YouTube playlist of a tower crane being disassembled.