Flowserve 2000 Series Digital Positioner - Manual (Page 7)

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Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
• Power supply: 24 VDC, 300 mA
• Digital volt meter with 4 - 20 mA range
• Air supply: 50 psig minimum, 80-100 psig preferred
• Gauges or the ability to accurately determine pro-
cess pressures and valve air supply pressures
• 4 - 20 mA command source
• Thermocouple calibrator or simulator with 0 to 500
°
Celsius range
Mechanical Subsystem Maintenance
Refer to the appropriate Valtek Installation, Operation &
Maintenance (IOM) instructions for details on repair and
maintenance of the control valve actuator components.
Please refer to the manufacturers’ manuals for mainte-
nance and operation instructions for non-pneumatic
actuators, e.g., electric or electro-hydraulic actuators.
WARNING: The process line must be depressurized
and drained of process fluid and decontaminated
prior to working on internal valve components. Fail-
ure to do so may cause serious injury to personnel.
1. Depressurize the line, decontaminate the valve (if
needed) and shut off the air supply to the valve
positioner.
2. Disconnect the actuator air tubes from the unit.
3. Disconnect the two mounting bolts that attach the
StarPac II / Logix 2000 system bracket.
4. Disconnect the follower arm from the unit base.
This is done by removing the follower arm nut and
washer and pulling the arm off the shaft. Notice that
this shaft connection is keyed and that the shafts
are slightly spring loaded.
5. The actuator subassembly is now isolated and is
removed by loosening the bonnet bolts and lifting
the actuator away from the body.
The tubing holds the StarPac II / Logix 2000 base in
place, eliminating the need to disconnect wiring or
air connections.
6. Standard valve maintenance may now be done on
the actuator or valve body components. Refer to
the Valtek IOM instructions for details on such
things as trim or packing replacement. If you have
to replace the trim, use the same trim number and
characteristic as the original trim so the flow calcu-
lations are not affected. If a trim size change is
needed, contact your Valtek representative to find
out about flow characterization options.
7. Reassemble the system by reversing the above
steps. Be sure to follow the procedures outlined in
the Valtek IOM instructions for valve reassembly.
When reconnecting the follower arm, make sure
that the arm fits correctly on the keyed shaft and has
a positive spring action.
8. Turn on the air supply to the valve and check for
leaks in the reattached actuator tubing lines.
9. Turn on power to the unit. Check the system
calibration and perform a Valve Stroke Calibration
to reset the position feedback. Refer to the Calibra-
tion section of the StarPac II / Logix 2000 manual.
StarPac II / Logix 2000 Positioner
Overview
The StarPac II / Logix 2000 is double-acting, capable of
supplying air to either side of the actuator piston while
exhausting the other side to the atmosphere. Also, the
positioner can be mounted on either Valtek linear or
rotary actuators without modification to the actuator.
The positioner is pending non-incendive for class I,
division II, groups A, B, C, and D; class II, groups E,
F, and G. Since the positioner is insensitive to supply
pressure changes and can handle supply pressures
from 30 to 150 psig, a supply regulator is usually not
required; however, an air filter is required due to the
close tolerances of the spool assembly.
NOTE: The air supply should conform to ISA
Standard S7.3 (a dew point at least 18
°
F below
ambient temperature, particle size below 5 microns,
oil content not to exceed 1 part per million).
Positioner Operation
The StarPac II / Logix 2000 Positioner is an electric
feedback instrument. Figure 6 shows a StarPac II
installed on a double-acting actuator for air-to-open
action. Positioning is based on a balance of two signals:
one proportional to the modulator input signal and the
other proportional to the stem position.
The supply pressure for the positioner modulator is
tapped off the main supply and is filtered as it passes
through a field-replaceable, coalescing filter element in
the module. Next it passes through an internal pressure
regulator that regulates it to approximately 22 psig. The
air then goes through an orifice that restricts the flow
and air consumption (refer to Figure 6).
The air is further controlled to 6-12 psig using a spring-
diaphragm flapper that is attracted by an electromagnet
to a nozzle. A temperature compensated hall effect
sensor mounted on a circuit board senses the spool
valve position. The hall effect sensor and circuitry
create a feedback loop, which determines how much
current to send to the electromagnet for a desired spool
valve position. The electromagnet in the feedback loop
varies the nozzle-flapper spacing, which regulates the
output pressure to 6-12 psig proportional to the com-
mand input signal.
When these opposing signals are equal, the system will
be in equilibrium and the stem will be in the position
called for by the command signal. If these opposing