It’s All About Hydraulics

The newer cranes rely on hydraulic systems. The hydraulic cranes have a simple working principle: a transmission of forces from point to point through a fluid. Most hydraulic cranes use a fluid with maximum density, which is known as incompressible fluid. The most commonly used fluid is the oil, an incompressible fluid that makes the hydraulic crane work perfectly. In the simple working principle of a hydraulic crane, a piston pressurizes the oil which transmits the whole amount of force to another piston. So, when the piston is pushed down, another one is pushed up.

The principle of the hydraulic crane is all about hydraulics. It uses a hydraulic pump that creates enough pressure to move the pistons. The pressure in the hydraulic system can be created by a gear pump or by a variable-displacement pump. Thanks to the hydraulics, the hydraulic crane is able to lift and move extremely heavy loads.

Many hydraulic cranes feature two-gear pumps with a pair of inter-meshing gears that pressurize the hydraulic fluid. To increase the pressure, the operator can push the foot throttle and run the pump faster. The only way to increase the pressure is to run the engine at full speed. For example, a hydraulic crane with lifting capacity of 70 tons features a 12.7-liter diesel engine that provides even 365 horsepower. This type of engine is connected to three two-gear pumps:

• Main Pump: The main pump can generate the most pressure, so it operates the piston rod that raises and lowers the boom (and all the telescopic sections that extend the boom). It generates more pressure than the other two pumps, mainly because it has the responsibility of lifting and moving more weight.
• Counterweight Pump: Any hydraulic crane has counterweights in the rear of the cabin, because reduce the risks of tipping over. The counterweights are added and removed by using a counterweight pump, as it generates a great amount of pressure.
• Steering Pump: The steering pump, or also known as outrigger pump, is the one that controls the steering and the outriggers. The outriggers increase the stability of the hydraulic crane during lifting operations and as the steering and outrigger operation are not performed in the same time, they can use the same pump.