Flowserve XL90 Series - Manual (Page 2)

Supply air biases the pilot-valve in an upward direction. As
the capsule moves up, it will close the exhaust seat of the upper
pilot poppet and open the supply seat, which applies increased
air pressure to the bottom cylinder port. At the same time, the
pilot-valve capsule will open the exhaust seat for the lower pilot
poppet; thus, decreasing pressure to the top cylinder port.
This difference in pressure will drive the piston outward, rotate
the pinion and stretch the feedback spring until the spring ten-
sion exactly opposes the force resulting from the instrument sig-
nal pressure. At this point, the flapper will be moved toward the
detecting nozzle to restore the pressure above the pilot-valve
capsule to its equilibrium value. As a force-balanced condition
is approached, the pilot-valve capsule will be forced back to a
neutral position where the pilots are neither supplying air to, nor
exhausting air from, their respective sides of the piston.
A decrease in instrument signal pressure reverses the described
actions and causes a proportional inward movement of actuator
pistons and a reversal in pinion direction.
Installation of XL90 Series Positioner on Actuators
The XL90 can be installed on most sizes of rotary and linear
actuators. Actuators can be either double acting or spring return.
Cams can be used for direct acting or reverse acting directions.
These instructions apply to rotary actuators only. For linear actu-
ator mounting instructions, consult the factory.
NOTE: For retrofitting to an actuator equipped with an Apex
positioner, the same bracket and bolting may be used.
NOTE: NAMUR mounting is available with the XL90 position-
er. When retrofitting the XL90 positioner to an actuator
equipped with another positioner, remove the existing posi-
tioner, tubing and associated bolting. See tubing instructions
in Connecting XL90 Positioner Ports section.
48-2 Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
Figure 1: XL90 Positioner Schematic for Air-to-Open
Figure 2: Positioner Mounting with NAMUR shaft
Figure 3: Positioner Mounting with Double D Shaft
and Linkage
Supply Seat
Upper Pilot
Poppet
Exhaust Seat
Port No. 1
Restriction
Supply
Pilot Valve
Capsule
Exhaust Seat
Port No. 2
Lower Pilot
Poppet
Supply Seat
Piston
Cylinder
Balance Adjustment Feedback Spring Zero Adjustment
Range Adjust
Screws
Cam
Feedback
(shaft)
Instrument Signal
Upper Diaphragm
Lower Diaphragm
Flapper
Detecting
Nozzle
Input Capsule