Internal leakage is a key index for servo valve repair. Radk Hydro sets technical standards for electro-hydraulic servo valve maintenance. If internal leakage exceeds 15% of the rated flow, we recommend replacing the servo valve with a new unit.
What is hydraulic servo valve internal leakage?
Internal leakage means the flow out of the return port when load flow equals zero. The unit is L/min.
Internal leakage changes with input current. It reaches the maximum value at the null position.
For two-stage servo valves, total internal leakage includes pilot stage leakage qp0 and power stage leakage qc.
Null leakage shows spool manufacturing quality for new valves. For used valves, it tells the degree of spool wear.
What causes high internal leakage?
Electro-hydraulic servo valves are precision components. They need very clean hydraulic oil.
Poor oil cleanliness is the main cause of heavy internal leakage. Tiny solid particles enter the servo valve.
High-speed oil carries these micro particles and hits the sharp edges of the valve port.
The original sharp valve edges turn rounded after erosion. This makes internal leakage worse.
Can we fix servo valve internal leakage?
You can monitor servo valve performance in real time. Software can activate spool displacement compensation.
This method partly fixes null drift caused by erosion.
If leakage goes over 15% of rated flow, valve replacement is required.
Why retire a servo valve when internal leakage exceeds 15% rated flow?
If you keep running the valve above this limit, you will face these problems:
- The servo valve overheats.
- It can still drive loads, but control accuracy and force output drop.
- The valve becomes slow and has poor response.
Conclusion
Internal leakage is an important performance index of electro-hydraulic servo valves. Keep hydraulic oil clean during operation and maintain oil quality regularly.
Contact us for servo valve maintenance. Send valves back to our factory for cleaning and service to extend their service life.
