For truck-mounted hydraulic systems, the most common design in use may be the gear pump. This design can 
be characterized as having fewer shifting parts, being simple to service, more tolerant of contamination than various other designs and relatively inexpensive. Gear pumps are set displacement, also called positive displacement, pumps. This means the same volume of circulation is created with each rotation of the pump’s shaft. Gear pumps are rated with regards to the pump’s maximum pressure rating, cubic inch displacement and maximum input speed limitation.
Generally, gear pumps are found in open center hydraulic systems. Gear pumps trap essential oil in the areas between the teeth of the pump’s two gears and your body of the pump, transport it around the circumference of the gear cavity and then push it through the store interface as the gears mesh. Behind the brass alloy thrust plates, or use plates, a little amount of pressurized essential oil pushes the plates tightly against the apparatus ends to boost pump efficiency.