The hydraulic system of a forklift consists of connections of pipes and hoses through which high pressure oil is pushed in order to create a hydraulic force and provide movement from the use of mechanical parts such as cylinders and pistons. For a forklift this is obviously very important as a hydraulic lift, tilt and auxiliary functions will be used to manipulate a wide variety of heavy loads, all of which need to be maneuvered to ensure they do not get damaged and to load vehicles efficiently.
The hydraulic pump creates fluid pressure in the system. This pressure is controlled by many valves, ports and switches. The hydraulic fluid is pumped under pressure from a reservoir into a system of tubes, hoses, valves and cylinders. This flow is measured in gallons-per-minute. Since a liquid will not compress, the pressure is used to move a piston in a cylinder.
The cylinders are sealed tubes with an internal piston. As the hydraulic fluid pressurizes the cylinder, the piston is pushed out as the fluid pressure acts on it. The amount of work the piston can perform is governed by the laws of hydraulics discovered by Blaise Pascal. That is where we get the unit of measure- Pascals from.
The control valve is the heart of the system. It controls where and how much fluid is directed by using control levers that control spool valves.
Relief valves protect the entire system in case of pressure overload, restriction or other problem. Example- when a piston reaches the end of its travel inside the hydraulic cylinder pressure in the system will raise quickly. The relief valve senses excessive pressure build up and opens the fluid circuit allowing oil to flow back into the tank.
There are 3 main functions a forklift can perform- Lifting, tilting and auxiliary functions.
Auxiliary functions are used to help with the moving and shifting of loads. This can be adjustable forks, sideshifters, clamps or a number of other attachments. The side shifting function includes extra hydraulics to move loads to one side; this allows the driver to stay in the same position while getting a better view of the work he is performing. Without a side shifter, the operator in the cab of the forklift would have to lean out of the side of the truck to ensure he can see beyond the load, this could be dangerous for both the driver of the forklift and anyone in operation around it.
Hydraulics must be used carefully. Drivers need to be trained as all forklift act a little bit different. LP powered trucks act and feel much different that electric forklifts.
Basic forklift information, operation and functions.
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