A hydraulic pump can be a source of power for many different means. Hydraulic pumps can push large qualities of oil through cylinders or motors. There are usually three types of hydraulic pumps used. These are vane, piston, and gear pumps, but there are also dump pumps and clutch pumps, depending on the needs of the application. A hydraulic pump will either be bi-rotational or uni-rotational in design.
Vane pumps used to commonly be used on utility vehicles, but today they are less common for these types of systems and instead gear pumps are used. A vane pump works by an input shaft rotating to cause oil to be between the vanes of the pump, where it is then moved to the pump’s outlet side. The process is similar to how gear pumps work. With vane pumps, there is one set of vanes instead of a pair of gears. As the area between the vanes increases on the inlet side and decreases on the outlet side, oil is brought in through the supply port and leaves through the outlet.
Piston pumps are used when the application requires high operating pressure. Piston pumps will withstand higher pressure than other pumps, but there is a higher cost associated with the ability to withstand higher pressure. These pumps can be more complex, and they are not as resistant to contamination. The service technician and equipment designer need to understand the complexities of the pump, in order to make sure that it will work correctly. Piston pumps can often be used with truck mounted cranes, but they can also be used for other needs, such as ice and snow control, where it makes sense to not vary the engine speed but vary the system flow. Piston pumps work by having a cylinder block contain pistons that move out and in. It’s the movement of the pistons that draws oil from the support port and then forces it through the outlet. Both variable and fixed displacement designs are available.
The gear pump is the most common type of pump for a truck mounted hydraulic system. These don’t have as many moving parts, they are more tolerant of contamination than other designs, they are easy to service, and are cheaper than other options. Gear pumps are also fixed displacements, which means the same volume of flow is produced with each rotation. Gear pumps will be rated in terms of the pump’s maximum pressure rating. Gear pumps can be used in open center hydraulic systems. Gear pumps work by trapping oil between the teeth on the pump’s two gears and the body of the pump and transport it around the gear cavity. The pump then forces it through the outlet port.