High-Pressure Hydraulics Make Heavy Lifting
Look Easy
Ever wonder how big, heavy objects are moved from one spot to another?
When Jeanie-blinking fails, hydraulic truck cranes are often used to lift
thousand-pound objects. Such cranes are very simple by design but
can perform Herculean tasks in minutes. When watching one in action, it's
hard to believe just how much weight it's moving because it transports
multi-ton objects with relative ease.
From raising bridge beams on highways to moving heavy equipment in factories,
high-pressure fluid power system hydraulics have an enormous impact on
modern life.
Construction and Beyond
The cranes, backhoes, and bulldozers doing the heavy lifting at construction
sites aren't the only machines that take advantage of the power of
hydraulics. Hydraulics operate the control surfaces on large airplanes,
the machines that lift your vehicle at the service station, and even the
brakes on your car.
How They Work
Hydraulic machines rely on the transmission of forces from point to point
through a fluid. Most hydraulic machines use an incompressible fluid like
oil. In a simple hydraulic system, when a piston pushes down on the oil,
the oil transmits the original force to another piston, which is driven
up.
Two-Gear Pumps
A hydraulic pump creates the pressure that moves the pistons. Most hydraulic
truck cranes use two-gear pumps, which have a pair of inter-meshing gears
that pressurize the hydraulic oil.
For example, the 12.7-L diesel engine in a 70-ton hydraulic truck crane
is connected to three two-gear pumps:
- Main pump - This pump operates the piston
rod that raises and lowers the boom (the steel arm of the crane that
holds the load), as well as the hydraulic telescoping sections that
extend the boom. The main pump is able to generate 3,500 pounds per
square inch (psi) of pressure. It generates more pressure than the
other two pumps because it's
responsible for moving much more weight.
- Pilot pressure counterweight pump - A hydraulic truck crane
uses counterweights on the back of the cab to keep it from tipping
over. These are added and removed by a hydraulic lift that has its own
pump. The counterweight gear pump can generate 1,400 psi.
- Steering/outrigger pump - One pump that generates 1,600 psi
controls the steering and the outriggers. The outriggers are used to
stabilize the truck during lifting operations.
For more information about hydraulics parts, visit the www.pcc-aft.com. |
