Hydraulic pumps


Gear pumps are used as hydraulic generators in hydrostatic circuits.

Description and use

HP pumps are divided into four dimensional groups. They are pumps with constant geometric volume and single, simple, double or multiple drive direction. The suction fluid flow rate must be max. 2.5 m/s; in this case, the pumps can work continuously with a suction pressure between (-0,2) and (0,5) bar and a discharge pressure according to the leaflets. The pumps can be equipped with flow and pressure controllers upon request. They are used in hydraulic systems or groups and in hydraulic circuits of machinery, agricultural machinery, machine tools etc.

Working fluid

It is recommended to use hydraulic oil that retains its viscosity characteristics. During operation, the viscosity must not fall below 15 cSt; optimal operation is at a viscosity of 25-100 cSt. In continuous mode, the viscosity must not exceed 250 cSt. For cold start, at low pressure, a viscosity of 2000 cSt is admitted for a limited time. The oil filtration fineness shall be 30 μm and the impurity concentration shall be below 0.05%; abrasive particles are not allowed.
Working temperature
The pumps can operate continuously between -10 and 80°C.It is allowed to start at (-15)°C.
pompe hidraulice


The most common types of vane pumps are with fixed flow which generate flow with a set of vanes that slide radially inside a rotor provided with channels. They rotate in an elliptical chamber. The elliptical chamber is named a ring and, due to its shape, it produces volume differences between the adjacent vanes that create the pumping action when the rotor is started. Most new models of vane pumps form the pressure chamber with two pressure plates that fit the rotating group on the sides. This assembly bears the name of cartridge and makes it easier to repair it.

hydraulic vane pump


Axial piston pumps are another variant of piston pumps in which the pistons are axially disposed, so they are parallel to the axis of rotation of the rotor (the block), the active movement of the pistons being made either by an inclined or fixed disc, or by a frontal cam. Thus, the pistons have the great advantage of greatly reducing the gauge of the pump and at the same time achieving a constant moment of inertia through the symmetry of the rotating masses, which allows their operation at angular speeds superior to other types. In view of these qualities, to which the good stability of the movement to low speeds as well as the ease of adjusting the active volume are added, priority is given to them, being the most common types of volumetric machines used in hydraulic drive, which also applies to the driving systems of machine tools. The main parameters of these types of pumps are: pressures between 150 and 500 bar, even higher, moments up to 800 – 900 daN × m, powers up to 3500 kW, flows up to 900 l/min, maximum speeds to pumps up to 3000-4000 revs/min.htdraulic axial piston pumps

Radial piston pumps are high flow and high-pressure pumps, and the motors have high torque and powers. They are used for pressures up to 300 bar, flow rates up to 8000 l/min, moments up to 5000 daNm, powers up to 4000 kW, multiple drive motors operating at steady speeds below 1 rpm. It should be noted that this type of pumps was the subject of the first models of hydraulic rotary piston machines, that in the meantime axial piston pumps have emerged as an improved version of the first ones and which have expanded more than radial piston pumps. At present, however, there is a revival of these ones, not only to high powers and large couples, where the basic methods remain, but also for the usual parameters. The causes of these reconsiderations are the emergence of new improved models, especially with reduced gauges (small inertia), with multiple drive, with cylindrical or spherical pistons.hydraulic radial piston pumps