Parker Abex – Jet Pipe Servos
Electrohydraulic Servovalves
• Nuclear, Steam and Gas Power Plant Applications
• Unique Jet Pipe® First Stage Design
Presentation Abstract
 Pedigree – Parker Non-Incendive Jetpipe Electro-
Hydraulic Servovalve Design
 Hydraulic Design Features & “Varnishing”
 Special note on A160 varnishing
 Performance of Jetpipe Design Versus Flapper
Style Servovalves
 “Intrinsically Safe” vs “Non-Incendive” Designs
 Open Questions
Presentation Abstract (cont.)
 Goal is 20 minutes ppt, 25 minutes questions/open




discussion
Single task is to show how Jetpipe Servo design is
more robust/fail resistant in harsh oil
environments (i.e. A160 lube skid)
Presenter is Sr. Engineer at Electro Hydraulic
Servovalve Division
Asst. will be handy to help with more specific 7FA
related questions
Following Slides Give a Flavor of ppt
Servo Controls Division
 Uniquely positioned for the powergen market
 Over 40 years as a supplier to the Power Gen
Market
 EHSV’s specified on over 40 GE drawings
 Unique Jet-Pipe® construction
– 5-70 GPM
 1, 2 or 3 coil models available
 Factory Mutual Approved Intrinsically Safe
Models by 2Q ‘04
 Complete R & O facilities-to OE requirements
 Single sourcing within Parker enables access to
over 500,000 parts
SERVO CONTROLS DIVISION
JET-PIPE OPERATION
Figure 1 — Servovalve at null
High pressure filtered fluid flows to
the flexible feed pipe attached at the
base of the torque motor, to the top of
the jet pipe, and out the projector jet.
Fluid from the projector jet impinges
upon the receiver. Two small orifices
are connected hydraulically to the
ends of the second-stage spool.
With the servovalve at null, the projector jet is centered over the
receiver holes and equal pressures are developed at each end
of the spool.
SERVO CONTROLS DIVISION
JET-PIPE OPERATION
Figure 2 — Actuation
Input current is applied to the torque motor. A
magnetic torque is produced causing the
armature and the attached jet pipe with projector
jet to rotate through a very small angle. The
polarity will cause the jet pipe to move left or right..
The projector jet movement causes differential pressure
across the second-stage spool causing movement. As t
he spool moves, the feedback spring pulls the jet pipe
back against the magnetic torque toward the center of
the receiver.
When the feedback spring force is equal to the magnetic
force, the projector jet will again be centered over the
receiver generating equal pressure at each end of the
spool, and spool movement stops at the new position.
Fluid will now flow from the second stage pressure port to the cylinder port C2, through the
actuator, and back through cylinder port C1 to return.
A reversal of the input current results in an opposite motion of the spool, changing
the direction of the flow to the actuator.
SERVO CONTROLS DIVISION
JET-PIPE SERVO VALVES
 Excellent contamination resistance.
 Jet-Pipe allows larger particulate passage than nozzles.
Additionally, high spool-driving forces and long powerstage strokes help our Jet-Pipe servovalves deliver
premium contamination resistance – the highest in the
industry.
 The reliability leader.
 Rugged servovalve design and construction combine with
excellent contamination resistance to make Parker’s JetPipe servovalve the industry leader in performance and
reliability.
 Low life-cycle costs.
 High reliability minimizes servovalve and actuator
maintenance, significantly reducing life-cycle costs