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Parker Jet-Pipe® EHSVs have a “single inlet” first stage, making them a fail-to-center design. There is no risk of unbalance from contamination because there is only a single source of fluid for the first stage. Our second stage spool design can generate anywhere from 100 pounds of chip shear force (Model 410) to 2,000 pounds of chip shear force (Model 450) with a nominal 3,000 psi system.
Parker EHSVs offer a first to second stage gap that is four times larger than that of the nearest competitor. The large gap allows particulates up to 500 microns to easily pass through the valve. By allowing larger particulates to pass through the system, Parker EHSVs can then use a coarser filter that helps prevent clogging of the filter assembly in a dirty fluid environment.
With a fully welded torque motor, Parker EHSVs provide superior strength compared to the bolted torque motor construction provided by the competition. In addition, Parker uses armature straps to dampen the effect of vibration on the system. Our first stage is balanced and supported along all three axes, eliminating helicopter mode rotation of the armature and flexure tube. As a result of these improvements, acceleration and vibration tests show almost no effect on load output from 0 to 3,000 Hz.
Our highly stable valve is capable of holding absolute position, ensuring maximum efficiency of fuel flow. Stability is gained through use of a single inlet momentum transfer device, precise tolerance of spool overlap, diametral fit, and tightly controlled torque motor construction and set-up.
While many things can affect the electro-magnetic null of a servovalve, Parker goes to great lengths to prevent valves from shifting. The rugged construction of the torque motor prevents coils and magnets from physically shifting. Plus extensive stabilization of the valve during manufacturing and testing helps to ensure no residual stresses.
Simplicity of design allows for a near maintenance-free solution. While we recommend periodically inspecting and changing the filter assembly, EHSVs are designed to function as an “on condition” device requiring no periodic maintenance while providing years of service life.
Parker’s Jet-Pipe® valves exceed the ARP 490 standard for external leakage by incorporating a two-piece endcap design that prevents leaks as well as seeping fluid. What’s more, Parker valves are very responsive to input commands due to our tight manufacturing standards that prevent internal leakage.
Parker Jet-Pipe® servovalves offer power generation customers the clear advantages of longer life and fewer unscheduled trips within the system, resulting in an overall lower life-cycle cost as well as unsurpassed reliability when compared to other designs. Parker also provides service solutions for EHSV MRO that provide extended life of the Jet-Pipe® solution.