The servo valve, also called electro-hydraulic converter, converts the control output signal into a hydraulic signal. It is one of the core components of the EH oil system. It consists of a torque motor and two-stage hydraulic expansion and mechanical feedback system as shown in the figure below. When there is electric signal input, there will be a current passing through the electromagnet coil in the servo valve torque motor, generating a certain rotating torque to rotate the armature, and driving the baffle connected therewith to rotate. The baffle extends into the middle of two nozzles. Under normal circumstances, the distance between the two sides of the baffle and the nozzle is equal, so that the oil discharge area of ​​the nozzles on both sides is equal, and the oil pressure on both sides of the nozzle is equal. When an electric signal is input, the armature moves the baffle and the baffle moves close to a nozzle, so that the oil discharge area of ​​this nozzle becomes smaller, the flow rate becomes smaller, the oil pressure before the nozzle becomes higher, and the opposite is the opposite, so that it will The electrical signal is converted into a mechanical displacement signal that eventually translates into an oil pressure signal and the signal is amplified by the nozzle flapper system. The oil pressure on the two sides of the baffle is the same as the two chambers of the lower slide valve. The difference in oil pressure between the two ends causes the slide valve to move, and the oil port controlled by the shoulder on the slide valve opens or closes to control the flow of high pressure oil to the oil. Motive piston lower chamber, open the valve against the spring force, or lead the lower chamber of the piston to return oil, close the small valve. A feedback spring is also provided in the servo valve, and a mechanical zero is set. When the electric signal is lost, the slide valve is biased to one side and the valve is closed. 
Servo valve structure
Servo valve main fault
The main fault of the servo valve is jamming and electrochemical corrosion. The main manifestation is that the oil motive is always in the fully open or fully closed position and cannot be controlled. The gap between the spool and valve sleeve of the servo valve is only about 2μm, which may easily cause jam. Once it is stuck, it will cause the control process to be unable to control; in addition, the nozzle and the baffle of the servo valve are also prone to jam, and the servo valve nozzle is The gap between the baffles is around 0.03mm. When particles in the oil get stuck in it, the baffle will always be close to a nozzle and the feedback lever cannot pull it back. The pressure difference at both ends of the main spool is always present. The spool opens in one direction and the oil motive is in a fully open or fully closed position and cannot be controlled. When it is stuck, it's best to give it to a professional manufacturer for repair.
When the chlorine ion content in the EH oil is high, a large amount of chloride ions will accumulate at the valve opening of the servo valve to cause electrochemical corrosion, resulting in leakage of the servo valve, lowering of the EH oil pressure, and increase of the return oil temperature and pressure. Servo valve through the adjustment of the valve opening to control the output flow, when the servo valve reaches full flow 63L/min, the spool's stroke does not exceed 1mm, visible flow rate at the valve port is quite high, the servo valve is zero open spool valve, The zero seal is ensured by the sharp angle of the valve core step. When the valve core is corroded by 0.1mm, the internal leakage may reach about 10L/min. The normal should be less than 2.4L/min. It is impossible to realize the steam turbine. Precise control can not even open the oil motive. After electrochemical corrosion of the servo valve, the valve plug and the valve sleeve must be replaced. During the operation, the chlorine ion content in the anti-fuel oil must be strictly controlled to prevent electrochemical corrosion. If the chloride content exceeds the standard, the EH oil system must be thoroughly cleaned and replaced with oil.
Reed Switch Fuel Level Sensor, also called float fuel level senosr, it is done by sealed reed switches positioned inside the main shaft of the sensor. A float with built-in magnets then triggers the reed switch relays, generating a potential-signal with resistance, current, or voltage value that increases or decreases according to the fluid level, then give the signal to the gauge via wires, which shows the right level reading by pointer. In the whole reed switch level sensors,the float is the only moving part of the sensor,thereby minimizing potential mechanical failures to get the precision measurement.
Reed Switch Fuel Level Sensor,Fuel Float Sensor,Fuel Tank Float Sensor,Float Level Sensor, Float fuel level sensor
Xi'an Gavin Electronic Technology Co., Ltd , https://www.gamicos-meas.com