For truck-mounted hydraulic systems, the most common design in use is the gear pump. This design is definitely characterized as having fewer moving parts, being simple to support, more tolerant of contamination than additional designs and fairly inexpensive. Gear pumps are fixed displacement, also called positive displacement, pumps. This means the same level of stream is created with each rotation of the pump’s shaft. Gear pumps are rated with regards to the pump’s optimum pressure rating, cubic in . displacement and maximum 
input speed limitation.
Generally, gear pumps are found in open center hydraulic systems. Gear pumps trap oil in the areas between the tooth of the pump’s two gears and your body of the pump, transportation it around the circumference of the apparatus cavity and then power it through the outlet slot as the gears mesh. Behind the brass alloy thrust plates, or put on plates, a small amount of pressurized essential oil pushes the plates tightly against the apparatus ends to improve pump efficiency.