How Does a Servo Hydraulic System Work?

Hydraulic energy is used as a power source for hydraulic systems. This energy comes from a combination of potential, hydrostatic, and hydrodynamic energy (Bernoulli’s equation). Here, in addition to hydrostatic energy as a function of pressure, the effects of potential energy as a function of the liquid’s weight or height and hydrodynamic energy as a function of flow rate are minimal.  


Therefore, the hydrostatic energy generated by the hydraulic system’s pressure effect is considered. Hydraulic power is obtained by driving a hydraulic pump by an electric motor or an internal combustion engine. For this hydraulic power to perform its intended function, it must be controlled by control elements (pressure, directional and flow control valves) and directed to the necessary elements (hydraulic cylinders or hydraulic actuators).


Servo-hydraulic testing machine can control the pressure, flow and direction of a fluid with an incompressible fluid and uses this hydraulic energy to produce linear, circular and angular movements that are precise and controllable. Each element in the circuit is represented by a standard symbol and connected by a pipe connection.


Several hydraulic system functions can be seen on the diagram. For large schemes, motion and control charts can be used to determine the exact timing of action sequences. If you look closely at the circuit diagram, it looks big and complicated. For this reason, servo hydraulic system circuits are easy to construct, and any circuit problems that may arise can be easily overcome with a good knowledge of the essential elements of the course.

servo hydraulic universal testing machine

Hydraulic pump

Devices that convert the power received by the motors that drive them into hydraulic power are called hydraulic pumps. The pumping process for all pumps is based on the same principle. Pumping is done by increasing the volume with the suction nozzle and decreasing the volume with the outlet nozzle. There are many pumps, but the most common are vane pumps, gear pumps and piston pumps.


Vane pump

The vane pump consists of a rotor, vanes, rings and a distribution plate with inlet and outlet ports. The rotor of a vane pump moves in slots from a motor shaft to which it is attached. The rotating vanes are thrown out by centrifugal force and follow the walls of the non-rotating ring. Therefore, as the rotor rotates, the blades form a volume along the ring that gradually increases and decreases. The intake ports through the distribution panel have a shape corresponding to an increase in size, and the exhaust ports have a shape corresponding to a decrease in size. 


Gear pump

It consists of a body with inlet and outlet holes, a rotating gear and a rotating gear connected to the drive motor. Engaging and disengaging gears increases or decreases the volume. Thus the pumping process is carried out.


Piston pump

The piston pump consists of a cylinder block, piston and shoe inclined plate. The pistons are arranged around the circumference parallel to the axis of the pump. The piston pump’s pumping is done by back and forth movement of the piston inside the cylinder. The movement of the piston is provided by an inclined rocker plate attached to the bearing shaft. As the shaft rotates, the piston moves away from the cylinder block’s centre of rotation, creating more volume (thrust). Later in the revolution, volume decreases as the piston approaches the cylinder block.