A hydraulic forklift is a machine that uses hydraulic lifting devices to raise or lower heavy objects. Hydraulic pistons are cylinders that are filled with a liquid, usually some type of oil, that can be pressurized to expand or depressurized to contract. A hydraulic forklift will use more than one cylinder mounted on the machine to lift a fork mechanism, which generally features two blades or tines, which slide into a pallet. A forklift can lift objects without a pallet, though the pallet makes lifting more stable and safer.
Most hydraulic forklift models feature a drive system, and the driver will sit in or on the unit. Some models require the driver to walk behind the unit, controlling the hydraulic forklift using a hand yoke or lever. The tires of the lift can either be pneumatic tires filled with air or solid rubber tires. The type of tires used on the lift will depend on where the lift is most likely to be driven: a lift with solid rubber tires will usually only be used on flat surfaces such as warehouse floors, while pneumatic tires will be used outdoors or on uneven surfaces.
The design of the hydraulic unit of the forklift will vary depending on the size and function of the lift. Many hydraulic forklift models feature a vertical lift system that raises the forks straight up. Other models may feature a telescoping boom arm that extends upward and outward from the body of the machine. This latter model is often known as a telehandler, and it is used for lifting objects much higher or farther out than a standard vertical lift model can accommodate.
Forklifts can be powered in several ways: smaller models are often powered with electricity and will feature one or more batteries to control operations. Larger forklifts may feature gasoline powered engines for more power and torque. The largest versions of the hydraulic forklift will be diesel powered for the most power and torque. Diesel lifts are usually only used outdoors or in very well-ventilated areas, since diesel engines can produce a significant amount of exhaust; they also tend to be quite noisy, and can make working conditions quite difficult when used indoors. Narrow forklifts are often used in warehouses or even retail establishments that have narrow aisles; these are usually electric-powered, though some are gas-powered as well.