| In the Power Generation Industry, it is imperative that all EHC components function flawlessly during their full-service period. Servovalves are critical to ensure proper operation on Steam or Hydraulic Systems.
The technical staff at United Servo rebuilds hundreds of Parker Abex and Moog Servovalves annually and finds varying degrees of damage caused by heat, vibration, fluid contamination, electrical erosion, and acid formation in phosphate ester-based hydraulic fluids. Such circumstances cause Abex or Moog servovalve failure and the operation of the valve is determined by the severity of these problems.
For example, a system with excessive heat and contamination can cause the valve to stick or freeze. Valves which have been attacked by the acid formed in unmaintained phosphate ester-based fluids are eroded on the critical metering edges and the nozzles, causing excessive internal leakage and lack of response. Both of these can occur within a few months or less when the fluid is not properly maintained; therefore, it is essential to regularly monitor your phosphate ester-based fluid.
Generally, when heat, contamination, and acid content are controlled and restricted to less than specified levels, the Parker Abex or Moog Servos show little wear, even over a period of years. However, we find there are always some contaminants deposited on the filter and the bushing and spool assembly during normal service.
United Servo recommends the following periodic maintenance on all servovalves to maximize service life:
- Monitor EHC fluid very closely. Samples should be analyzed monthly.
- Monitor and regulate EHC fluid temperature at the reservoir. Keep in mind, many times the servovalves are hotter than that at the reservoir.
- Send all Abex servovalves in for reconditioning at first available outage. This will give you a baseline to begin monitoring and tracking system performance. Then recondition the Parker Abex or Moog Servovalves at 24-36 month intervals. Reconditioning would include parts cleaning, new Viton seals, parts inspection and replacement, if needed, a new strainer, and functional testing. United Servo will also provide a service report with each valve for trending.
We recommend maintaining spares of each component in your warehouse in case of emergencies. If this is not possible, call United Servo for any emergencies, as we have stock items which can be expedited for emergencies.
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