WARNING: Be certain power to I/P module is disconnected
before removing housing cover in explosive atmospheres;
otherwise personal injury may occur.
3. Before adjusting the zero and span, be certain the MPC fea-
ture is disabled. Refer to Step 7 in the ‘Adjusting the
Minimum Pressure Cutoff Feature’ section.
4. Connect a current source to the terminal block on circuit
board.
NOTE: The zero and span adjustments are multi-turn potentio-
meters (pots) that have no stops on the ends of their travel;
however, they have a slip clutch to prevent damage from over-
adjustment. The pots also make a clicking noise when they
have reached adjustment limits.
5. Apply a 4.0 mA signal to the input. Locate and adjust zero
trim pot to achieve a 3.0 psi output. The output will increase
with clockwise rotation of the zero trim pot. If calibrating an
I/P module with a 10-50 mA input signal, apply a 10.0 mA
signal to input.
6. Increase input signal to 20.0 mA (50 mA for 10-50 mA
units). Locate and adjust span trim pot to achieve a 15.0 psi
output. The output will increase with clockwise rotation of
the span.
7. Recheck zero setting by repeating Step 5. The span adjust-
ment may affect zero setting.
8. Repeat Steps 5, 6 and 7 until proper adjustments are
obtained.
Adjusting the Minimum Pressure Cutoff Feature
The XL90 positioner with I/P Transducer has a “Minimum
Pressure Cutoff” (MPC) feature, which allows the user to set
the positioner. When the input signal falls below a user-
adjustable current, the pressure output falls rapidly to approxi-
mately 1.7 psi, causing the valve to move to the failure position.
This feature is generally used when the service requires a tight
shut off or to prevent throttling near the valve seat. To adjust this
feature, refer to Figure 9 and perform the following :
NOTE: The following procedure applies only when the mini-
mum pressure cutoff feature will be used.
NOTE: The zero and span settings of both the positioner and
I/P transducer should be verified as accurate before the min-
imum pressure cutoff feature is enabled and adjusted.
1. Connect the I/P module to a 30 to 150 psi air supply
pressure.
48-6 Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
Figure 7: Close-up of Gain Adjustment Figure 8: Gain Adjustment
(69 páginas)
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