48-6
Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
FLOWSERVE
ZE
R
O
M
PC
SP
AN
N
O
S
ER
VIC
EA
BL
E
IN
TE
R
N
AL
P
AR
TS
Gain Adjustment Procedure
The unique gain adjustment on the XL90 positioner
provides a means to increase or decrease responsive-
ness of the valve / actuator / positioner system. Increas-
ing gain makes the valve more responsive and faster,
while decreasing gain makes the system less sensitive
and slower to respond (with increased damping).
The gain is infinitely adjustable between its highest and
lowest settings. For convenience, three marks indicate
(H) high, (M) medium and (L) low gain. Most sizes of
actuators will respond well to a (M) setting. Unique
actuator / valve configurations may require a gain
adjustment at the factory or in the field.
1. Before adjusting the gain, place controller on manual
and isolate the valve from the process.
2. Turn off supply air to control valve actuator.
3. Using a
5
/
64
-inch allen wrench,
loosen both upper
and lower lock screws about one half turn. Do not
loosen the spacer nut. (See Figure 8.)
4. By grasping adjust lever, carefully rotate gain ad-
just assembly to desired position.
CAUTION: To avoid damaging gain adjust con-
necting spring mechanism. Make sure both up-
per and lower gain adjust plates rotate together.
When they are rotated to the new position, the
connecting spring should be perpendicular to the
plates.
5. When the gain is set to the desired position, firmly
tighten both lock-down screws.
6. Turn on supply pressure. Check actuator respon-
siveness by providing a step signal to positioner.
When gain is set as desired, check valve zero and
span calibration and re-calibrate if needed.
7. Return valve to service.
Calibrating I/P Module Zero and Span
Settings
NOTE: Although calibration can be accomplished
using output pressure gauge on I/P module, its
accuracy is
±
3 percent. The standard gauge should
be removed only for calibration and more accu-
Figure 8: Gain Adjustment
Upper
Lock Screw
Lower
Lock Screw
Adjust Lever
Spacer Nut
Figure 7: Close-up of Gain Adjustment
Figure 9: NT 3000 Circuit Board Module
(housing cover removed)
Current Loop (+)
Termination
Current Loop (-)
Termination
Circuit Board
Mounting Screws
Grounding Screw
Zero Adjustment
Span Adjustment
Minimum Pressure
Cutoff Adjustment
RFI Can
Terminal Block
Spacer Nut
(
Do not loosen)
