Instruction Manual
Form 1837
November 1992
3570 Series
357
0 S
erie
s P
neumati
Contents
Introduction
Scope of Manual 2.
Description 2
Valve Positioner Type Numbers 2.
Specifications 4
Installation, Mounting, and
Connections
Installation 4
Diagnostic Test Connections (Optional) 4.
Connections:
Piping Sizes 4.
Vent 4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Supply Pressure Connections 6.
Cylinder Connections 7.
Instrument Connection 7.
Operating Information
Initial Adjustments 7.
Signal Range Codes 8.
Frequency Response 8.
Adjustment Procedures 8.
Changing Positioner Action 12.
Split Range Operation 13.
Initial Range Spring Extension Procedure
for Type 3570P and 3570PC Positioners 13.
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c V
2.
4.
7.
alv
e P
ositioners
W5566*/IL
Figure 1. T
ype 3570 Positioner Mounted
on T
ype 470 Actuator
Principle of Operation
Type 3570, 3570C, 3570P, 3570PC, and
3571 Valve Positioners 14.
Type 3572 and 3576 Valve Positioners 15.
Type 3573 and 3577 Valve Positioners 16.
Relay Operation 16.
Maintenance
Troubleshooting 18
Converting a Type 3570 Valve Positioner to a
Type 3570C Valve Positioner 18.
Range Spring 19.
Disassembly 19
Assembly 20
Bias Spring 20.
Disassembly 20
Assembly 20
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14.
Parts Ordering
17
Parts Kits
Positioner Repair Kits 20.
Diagnostic Test Connection Kits 20.
Parts List
Positioner Common Parts 21.
Relay Assembly Parts 23.
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D200137X012
3570 Series
Introduction
Scope of Manual
This manual provides installation, operation, adjustment, maintenance, and parts ordering information for
the 3570 Series pneumatic valve positioners. The various product types within this series are described later
in this manual. Please refer to figure 1 for a typical
mounting of a Type 3570 positioner. Refer to separate
instruction manuals for information concerning the actuator, valve, and accessories.
Note
Only personnel qualified through train-
ing or experience should install, oper-
ate, and maintain these positioners. If
there are any questions concerning
these instructions, contact your Fisher
sales representative or sales office be-
fore proceeding.
Description
The 3570 Series pneumatic valve positioners are used
with control valve assemblies to provide an accurate
valve stem position that is proportional to the input
signal received from a control device. The input signal
range can be 3 to 15 psig (0.2 to 1.0 bar), 6 to 30 psig
(0.4 to 2.0 bar), or another pneumatic input signal
range, as required.
These posit ioner s are normally used with pneumatic piston actuators . However, product types within the 3570
Series can be used with pneumatic, long-stroke, cylinder
actuators or with pneumatic diaphragm actuators .
Valve Positioner Type Numbers
Type 3570 — Pneumatic valve positioner with two
relays for use with Fisher 470 and 480 Series pneumatic piston actuators. See figure 2. The positioner
includes three pressure gauges for input signal, for
relay output pressure to the top of the actuator cylinder, and for relay output pressure to the bottom (piston
underside) of the actuator cylinder.
The Type 3570 positioner is mounted on the top of the
actuator cylinder. The actuator stem position feedback
is provided through extension of the range spring attached to the actuator piston rod.
Type 3570C — Pneumatic valve positioner with automotive tire valves instead of pressure gauges. Tire
valves can be used for clip-on test pressure gauges.
The relay nozzles are locked in place with locknuts to
resist unwanted nozzle movement due to vibration.
Type 3570P — Pneumatic valve positioner with two
relays for use with Fisher 490 Series pneumatic piston
actuators. The positioner includes three pressure
gauges for input signal, for relay output pressure to
the top of the actuator cylinder, and for relay output
pressure to the bottom (piston underside) of the actuator cylinder.
The Type 3570P positioner is mounted alongside the
actuator cylinder. Actuator stem position feedback is
provided from the actuator-valve stem connector
through a cable and spool assembly.
Type 3570PC — Pneumatic valve positioner with automotive tire valves instead of pressure gauges. Tire
valves can be used for clip-on test pressure gauges.
The relay nozzles are locked in place with locknuts to
resist unwanted nozzle movement due to vibration.
Type 3571 — Pneumatic valve positioner with two
relays for use with long-stroke cylinder actuators. The
positioner includes three pressure gauges for input
signal, for relay output pressure to the top of the actuator cylinder, and for relay output pressure to the
bottom (piston underside) of the actuator cylinder.
The Type 3571 positioner is bracket-mounted to the
side of the actuator. Actuator stem position feedback
is provided through a wire from the actuator-valve
stem connector.
Type 3572 — Pneumatic valve positioner with one
relay. The Type 3572 positioner is normally used on
the Fisher Type 472 pneumatic piston actuator
mounted on valve bodies having push-down-to-open
(PDTO) action. The positioner includes two pressure
gauges. The pressure gauges monitor input signal
pressure and relay output pressure to the top of the
actuator cylinder.
The Type 3572 positioner is mounted on the top of the
actuator cy linder. Actuator st em position feedback is provided through an extension of the actuator piston rod.
Type 3573 — Pneumatic valve positioner that is similar
to Type 3572 positioner with the relay output pressure
piped to the bottom (piston underside) of the actuator
cylinder. The Type 3573 positioner is normally used on
the Fisher Type 473 pneumatic pist on actuator with
valve bodies hav ing push-down-to-close (P DT C) action.
Type 3576 — Pneumatic valve positioner with one relay
for use on direct-acting pneumatic diaphragm actuators
that requir e high operating pressures. The Type 3576
positioner includes two pressure gauges. The pressure
gauges monitor input signal pressure and relay output
pressure to the top of the act uator diaphragm.
2
Table 1. Specifications
PRESSURE
ST
ANDARD GAUGE
POSITIONER
3570 Series
Available Configurations
See the positioner type number descriptions given
above.
Input Signal
(1)
Standard Ranges: 3 to 15 psig (0.2 to 1.0 bar) or
6 to 30 psig (0.4 to 2.0 bar)
Optional Ranges: As desired, within the limits of
the bellows
Split Ranges: Use one-half of either standard
range when two control valves are operated by one
output signal form a single control device
Output Signal
(1)
Type: Pneumatic pressure as required to maintain
the correct valve stem position and seat load
Action: Field-reversible between direct and reverse
Resolution
(1)(2)
0.2% of instrument pressure span
Repeatability
(1)(2)
0.3% of total stroke or instrument pressure span
Frequency Response
(1)(2)
See figure 5
Pressure Indications
Type 3570C and 3570CP Positioners: Tire valves
accept standard pressure gauge chucks (gauges
not supplied)
All Other Types: Gauges supplied per table 2
Bellows Pressure Rating
Standard Bellows: 50 psig (3.4 bar)
Optional Bellows: 90 psig (6.2 bar)
Supply Pressure
Maximum: 150 psig (10.4 bar)
Minimum: 35 psig (2.4 bar)
Steady-State Air Consumption
(3)
20 scfh (0.54 normal m3/h) with 100 psig (6.9 bar)
supply pressure
Operative Ambient Temperature Limits
(1)(2)
With Nitrite O-Rings and Diaphragms: –30 to
160°F (–34 to 71°C)
With Fluoroelastomer O-Rings and Polyacrylate
Diaphragms (Optional): 0 to 220°F (–18 to 104°C)
Options
Type SS-52 clip-on chuck (with or without gauge)
for Type 3570C positioners; restrictor (high-frequency filter for bellows)
Pressure Connections
Vent: 3/8-inch NPT
All others: 1/4-inch NPT
1. These terms are defined in ISA Standard S51.1:1979.
2. For a Type 3570 or 3570C positioner mounted on a Type 470 or 480 actuator. Values do not apply to other constructions or actuator-valve combinations.
3. Scfh at 60°F, 14.7 psia (m3/h at 0°C, 1.01325 bar, absolute).
Table 2. Pressure Indications
NUMBER OF
PRESSURE
MONITORED
Positioner
input signal
pressure
Cylinder
(relay output)
pressure
1. For gauges marked in other units and ranges, consult your Fisher sales
representative or sales office.
GAUGES SUPPLIED
Two-Relay
Positioner
One-Relay
Positioner
1 1
2 1 0-160 psi/0-1.1 MPa/0-1
ST
ANDARD GAUGE
RANGE
0-30 psi/0-0.2 MPa/0-2 bar or
0-60 psi/0-0.4 Mpa/0-4 bar
(1)
1 bar
Approximate Weight
6 pounds (2.7 kg) without optional mounting bracket
or actuator/valve assembly
Table
3. Action Under Normal Operating Conditions
POSITIONER
ACTION
Direct-acting
Reverse-acting
1. Supply pressure is routed through relays to piston.
Increasing input signal
pressure to bellows
Decreasing input signal
pressure to bellows
DESIRED PISTON MOTION
Down Up
Type 3577 — Pneumatic valve positioner that is simi-
lar to Type 3576 positioner with the relay output pressure piped to the underside of the actuator diaphragm
on reverse-acting pneumatic diaphragm actuators.
The Type 3576 positioner is bracket-mounted to the
actuator yoke. Actuator stem position feedback is provided through a wire from the actuator-valve stem connector.
Specifications
Specifications for the 3570 Series positioners are
listed in table 1.
(1)
Decreasing input signal
pressure to bellows
Increasing input signal
pressure to bellows
3
3570 Series
Installation,
Mounting, and
Connections
Installation
The positioner is usually mounted on the actuator at
the Fisher Controls’ factory. However, if the positioner
and actuator are ordered separately, it is necessary to
mount the positioner on the actuator. Before mounting
the positioner, be certain the O-ring (key 33, figure 11)
is in place in the cylinder (top connection) in the base
of the positioner.
For appropriate actuator/positioner combinations, refer
to the positioner type number descriptions given earlier in this instruction manual.
D For Type 3570, 3570C, 3572, and 3573 posi-
tioners, mount the positioner with two cap screws
(key 32, figure 11). If the range and bias springs are
not installed in the positioner, refer to the range spring
and bias spring procedures in the Maintenance section.
Insert the threaded end of the spring retainer (key 19,
figure 3) into the center of the range spring (see figure
3). Then, insert a screwdriver into the center of the
range spring and extend the spring until the spring retainer can be screwed into the top of the actuator piston rod extension. Tighten the spring retainer into the
top of the actuator piston rod extension. If the range
spring and/or bias spring is not installed in the positioner, refer to the procedures for either spring in the
Maintenance section.
To support diagnostic testing of the control valve assembly, the connectors, piping, and other hardware
can be installed between the 3570 Series positioner
and the actuator. A typical connector installation is
shown in figure 4. For connectors, please refer to the
FlowScannert Diagnostic Connection kit listing in the
parts list.
The hardware used includes 3/4-inch NPT pipe nipple,
pipe tee, and pipe bushings with a 1/8-inch NPT pipe
bushing for the connector. The connector consists of
1/8-inch NPT body and body protector (see figure 4).
1. Before assembling the pipe nipple, pipe tee, pipe
bushings, actuator piping, and connector body, apply
sealant to all threads.
2. Position the pipe tee, connector body, and body
protector for easy access when doing diagnostic testing.
Connections
Piping Sizes
All pressure connections on the 3570 Series positioners are 1/4-inch NPT (female). Use 3/8-inch pipe or
tubing for supply, cylinder (bottom connection), and
instrument (input signal) connections. For the remote
vent pipe, if one is required, use 3/4-inch (19 mm)
(minimum inside diameter) pipe for runs up to 20 feet
(6.09 meters). For vent piping runs from 20 to 100 feet
(6.09 to 30.5 meters), use 1-inch (25.4 mm) (minimum
inside diameter) pipe. Refer to figure 2 for the locations and sizes of connections.
D For Type 3570P and 3570PC positioners, at-
tach the positioner extension and positioner to the cylinder mounting plate with the two cap screws (key
100, figure 13). Make the required pressure connections as described in the following procedure. Go to
the initial range spring extension procedures for Type
3570P and 3570PC positioners.
D For Type 3571, 3576, and 3577 positioners,
insert two cap screws through the holes in the mounting bracket (key 55, figure 14) to attach the positioner
to the actuator mounting boss. Attach the hex drive
stud to the actuator-valve stem connection. Attach the
end bearing (key 56E, figure 14) to the hex drive stud.
Diagnostic Test Connectors (Optional)
Diagnostic test connectors are available from the factory, when the unit is ordered, or they can be installed
on an existing control valve assembly in the field.
These connectors are especially useful for ‘‘quick’’
connections when using the FlowScannert. The
FlowScannert is a portable, microprocessor-based
diagnostic and calibration system specifically designed
for use with pneumatically-operated control valves.
Vent
WARNING
If a flammable, toxic, corrosive, or reactive gas is to be used as the supply
pressure medium, personal injury or
property damage could result from fire
or explosion of accumulated gas or
from contact with toxic, corrosive, or
reactive gas. The positioner/actuator assembly does not form a gas-tight seal,
and when the assembly is enclosed, a
remote vent line, adequate ventilation,
and necessary safety measures should
be used. A remote vent pipe alone cannot be relied upon to remove all hazardous gas. Vent line piping should comply
with local and regional codes and
should be as short as possible with adequate inside diameter and few bends to
reduce case pressure buildup.
4
FlowScanner is a mark owned by Fisher Controls International, Inc.
3570 Series
RANGE SPRING
(SPAN ADJUSTMENT)
CYLINDER
BOTTOM
PRESSURE
INSTRUMENT
PRESSURE
VENT CONNECTION
3/8-INCH NPT
BIAS SPRING SEAT
BIAS SPRING SEAT
(ZERO ADJUSTMENT)
(ZERO ADJUSTMENT)
W4025*/IL
NOTES:
1
ON SOME CONSTRUCTIONS, TWO NOZZLES AND ADJUSTMENTS ARE REQUIRED.
CLEAN-OUT
PLUNGER
CYLINDER
TOP PRESSURE
HORIZONTAL
RELAY
CYLINDER
(TOP
CONNECTION)
(O-RING,
KEY 33)
Figure 2. Typical Locatiion of T
RELAY NOZZLE
(OUTPUT PRESSURE
ADJUSTMENT )
W4027*/IL
1
BELLOWS
POSTS
CYLINDER
(BOTTOM CONNECTION)
(1/4 INCH NPT)
ype 3570 Positioner Parts and Adjustments
BELLOWS
VERTICAL
RELAY
SUPPLY
CONECTION
(NOT SHOWN)
(1/4-INCH NPT)
INSTRUMENT
CONECTION
(INPUT SIGNAL)
(1/4-INCH NPT)
AJ7270-C
1H8907-C
1J2233-C
B2402/IL
Figure
3. Bias and Range Springs for Zero
and Span Adjustments
12B8044-A
A6112/IL
Figure 4. Diagnostic Test Connections
5
3570 Series
CAUTION
When installing a remote vent pipe, take
care not to overtighten the pipe in the
vent connection. Excessive torque will
damage the threads in the connection.
Note
The vent connection is always plugged
with a pipe plug for Type 3570P and
3570PC positioners when mounted on
Fisher 490 Series actuators.
The connection marked VENT (see figure 2) should be
left open if the actuator is installed in the vertical position. However, the vent must be protected against the
entrance of any foreign material that could plug it.
Check the vent periodically to be certain it is not
plugged.
If the actuator is mounted in other than the vertical
position, be sure there is a vent and drain at the lowest point of the positioner. To do this, remove the pipe
plug (key 36, figure 10) from the cover. Then, position
the cover in such a way that the hole in the cover is at
the lowest point. Plug the vent connection because the
positioner is now vented through the cover.
influences can have on pneumatic
equipment, Fisher Controls has no
technical basis to recommend the level
of filtration equipment required to
prevent performance degradation of
pneumatic equipment. A filter or filter
regulator capable of removing particles
40 microns in diameter should suffice
for most applications. Use of suitable
filtration equipment and the
establishment of a maintenance cycle to
monitor its operation is recommended.
WARNING
To avoid personal injury or property
damage resulting from the sudden release of pressure, do not install the
valve assembly where service conditions could exceed the limits given in
this manual or on the appropriate nameplates. Use pressure-relieving devices
as required by government or accepted
industry codes and good engineering
practices.
CAUTION
Note
A remote vent is not possible with Type
3570P, 3570PC, 3571, 3576, and 3577 po-
sitioners.
If a remote vent is required, the vent line must be as
short as possible with a minimum number of bends or
elbows. Vent line piping should have a minimum inside
diameter of 3/4 inches (19 mm) for runs up to 20 feet
(6.09 meters) and a minimum inside diameter of 1-inch
(25.4 mm) for runs from 20 to 100 feet (6.09 to 30.5
meters).
Supply Pressure Connections
WARNING
Personal injury or property damage may
occur from an uncontrolled process if
the supply medium is not clean, dry,
oil-free, or non-corrosive gas. Industry
instrument air quality standards
describe acceptable dirt, oil, and
moisture content. Due to the variability
in nature of the problems these
If the supply pressure medium is corrosive, make sure the tubing and instrument components that contact the corrosive medium are of suitable corrosionresistant material. The use of unsuitable
materials might result in personal injury
or property damage due to the uncontrolled release of the corrosive media.
The connection marked SUPPLY (see figure 2) must
be provided with clean, dry air or a non-corrosive gas.
Install a 40-micron filter and suitable equipment to dry
the supply medium. Establish a maintenance cycle to
ensure that the regulator and filter are working
correctly.
The maximum allowable supply pressure to prevent
damage to the components of the positioner, actuator,
and valve is normally stamped on the actuator nameplate. Use a suitable supply pressure regulator to reduce the supply pressure source to the value stamped
on the nameplate.
If this maximum supply pressure value is not available,
use a supply pressure that does not exceed any of the
following:
D The maximum supply pressure for the positioner
as shown in table 1.
6
3570 Series
D The maximum pressure rating of the actuator,
from the appropriate actuator instruction manual.
D The maximum allowable valve plug stem load for
the specific valve body assembly being used. Contact
your Fisher sales representative or sales office for
valve plug stem load information, if required.
D For diaphragm actuators, refer to the actuator
instruction manual for the recommended supply pressure and use the larger value of the range listed.
The recommended supply pressure for use with piston
actuators is the highest available supply pressure between 50 psig (3.4 bar) and the maximum limit determined by the actuator and positioner specifications.
Selecting the highest pressure within the limits will minimize load error and will maximize stroking speed and
thrust. For the lowest supply pressure that will assure
satisfactory performance, the factors of valve plug unbalance force, valve plug seating force, and frictional force
must be considered in the following relat ionship:
(Frictional
+
force,
kg)
]
+ 0.7 bar
Supply
pressure, = 98
bar
unbalance,
[
(Valve
kg)
(Area of the actuator piston,
(Seating
+
force,
kg)
in square mm)
3570P, 3570PC, 3571, 3576, and 3577 positioners, a
mounting bracket (key 55, figure 13) is required. This
mounting bracket connects to the bottom of the base.
An O-ring (key 33, figure 10) is placed between the
base and mounting bracket. This mounting bracket
provides a 1/4-inch NPT connection for the positioner
output. This connection is made at the factory if the
positioner is ordered mounted to the actuator or if the
mounting bracket is installed.
Instrument Connection
The connection marked INSTRUMENT (see figure 2)
connects to the output signal connection of the control
device. The positioner operates only on a pneumatic
input signal; the input signal range is marked on the
nameplate (key 23, figure 10). The maximum allowable input signal for positioners with standard or optional bellows is in table 1 (bellows pressure rating).
The instrument connection is made at the factory
when a complete control valve assembly with a valvemounted control device is ordered. Otherwise, make
field connections to the positioner from an appropriate
control device. Refer to table 1 and the nameplate for
input signal pressure ranges.
Operating Information
or
(Valve
Supply
pressure, =
psig
Consult your Fisher sales office or sales representative for the appropriate values for specific actuators,
valves, and service conditions. The 10 psig (0.7 bar) is
added to the equation to account for an approximate
10 psi (0.7 bar) differential pressure loss in the positioner. For spring-return piston actuators, the pressure
required to compress the actuator spring completely
must also be considered.
unbalance,
[
pounds)
(Area of the actuator piston,
(Seating
+
force,
pounds)
in square inches)
(Frictional
+
pounds)
force,
]
+ 10 psig
Cylinder Connections
1. The connect ion mark ed CYLI NDER (see figure 2) is
connected at the fac t ory to the lower part of the cylinder
(bottom) or to the lower diaphragm casing if the
positioner is used with a pneumatic diaphragm actuator.
2. The cylinder top connection is a pressure passage
located in the bottom of the positioner base (key 1,
figure 10). On Type 3570 and 3570C positioners, an
O-ring (key 33, figure 10) is used between the bottom
of the positioner and the top of the actuator. On Type
Initial Adjustments
Normally, no adjustments are necessary upon initial
installation. The positioner is set at the factory for the
travel, input signal range, and action specified in the
order. Adjustment is necessary when operating
conditions are changed, when the unit has been
dismantled and reassembled, or when the control
valve travel does not correspond to the desired input
signal range. If the operating conditions have not
changed but the positioner requires adjustment, refer
to the adjustment procedures in this section. If the
operating conditions have changed, first, refer to the
signal range code descriptions, then, refer to the
adjustment procedures.
Signal Range Codes
The range spring and the bias spring are matched to a
specific input signal range and length of travel. Also,
the spring retainer length is matched to the application
on the Type 3570, 3570C, 3572, and 3573 positioners.
Refer to figure 3 for location of parts.
The signal range codes in table 4 are based on the
following applications:
D Codes for valve travels up to and including
2 inches (50 mm) are used for actuators that have a
7
3570 Series
2-inch (50 mm) maximum travel. If the actuator maximum travel is greater than 2 inches (50 mm), an additional retainer spacer (key 235, see figure 3) is required. Refer to the parts list for the additional spring
retainer spacer (key 235) part number.
D Codes for valve travels greater than 2 inches
(50 mm), up to and including 4-1/8 inches
(105 mm), are used for actuators that have a
4-1/8 inch (105 mm) maximum travel, except the
Types 480-12 or 480-15 Size 20 actuators which have
a 2-1/8 inch (54 mm) maximum travel. If the actuator
maximum travel is greater than 4-1/8 inches (105
mm), two an additional retainer spacer are required.
Refer to the parts list for the additional spring retainer
spacer (key 235) part numbers.
D Codes for valve travels great er than 4-1/ 8 inch-
es (105 mm), up to an d in cl u di n g 8-1/ 8 in ch es (206
mm), are for actuators that have a 8-1/8 inch (206 mm)
maximum travel. If the valve travel is 4-1/8 inches (105
mm) or les s , two additional spring retainer spac er s are
required. Refer to the parts list for the additional spring
retainer spacer (k ey 235) part numbers.
If the input signal range and travel do not match any of
the selections in table 4, consult your Fisher sales office or sales representative for information. To change
the springs, refer to the range and bias spring procedures in the Maintenance section.
From table 4, select the signal range that matches
your application. Find the travel length for the application under the signal range selected, then use the
code (from the direct or reverse column) that matches
the direct or reverse operation of the positioner.
The first number in the code is used to identify the
range spring, the letter in the code is used to identify
the bias spring, and the second number (after the letter) is used to identify the spring retainer. For example, from table 4, for a signal range of 0 to 15 psig
(0 to 1.0 bar), an actuator travel of 9/16-inch (14.3
mm), and direct action, the signal range code from
table 4 is 6G3. The ‘‘6’’ indicates the range spring. The
‘‘G’’ indicates the bias spring. The ‘‘3’’ indicates the
spring retainer.
extension type spring to a compression type spring, it
is necessary to add the bias spring seat (key 8). Refer
to the appropriate procedures in the Maintenance section of this manual.
In some cases, it is necessary to add an additional
spring retainer spacer or change from the standard
bellows to the optional high pressure bellows. Table 4
footnotes indicate the use of an additional spring retainer spacer or high pressure bellows.
Use the code from table 4 while referring to tables 5,
6, and 7 to determine the part numbers for the range
spring, bias spring, and spring retainer. Unless otherwise specified, use the standard bellows. Also, no
spring retainer spacer is required unless the spacer is
specified in the footnotes of table 4.
Frequency Response
Figure 5 shows how a Type 3570 or Type 3570C positioner with Type 470 or Type 480 actuator responds
when the input signal pressure is cycled at a small amplitude (3 to 5 percent), and at an increasing frequency. Assume the cycling input signal and the movement
of the actuator rod are represented by sine waves. As
the actuator rod is forced to move faster, its motion
begins to fall behind the input signal in both time
(shown as phase lag) and amplitude (shown as
normalized gain).
Adjustment Procedures
Refer to figure 3. The 3570 Series positioners have
three adjustments:
D The bias spring. It is the zero adjustment which
determines the starting point of the valve plug travel.
D The range spring. It is the span adjustment
which determines the full valve plug travel for a given
input signal range.
D The relay nozzle adjustment. This adjustment
determines the steady- stat e positioner output pressur e.
Note
It is necessary to add the bias spring
seat (key 8) to a unit when changing
from an extension type spring (key 9) to
a compression type spring (key 48).
When planning to change the bias spring in an existing
unit, inspect the unit first to determine if the current
bias spring is an extension type spring (key 9) or a
compression type spring (key 48). To change from an
8
To illustrate the use of the various adjustments, assume that the positioner has been repaired or has become completely out of adjustment. Assume also that
the input signal range is 3 to 15 psig (0.2 to 1 bar).
Proceed as follows:
1. Make sure the input signal range and the valve
travel stamped on the nameplate agree with the present operating conditions.
2. Loosen the four thumb screws on the underside of
the positioner base and remove the cover.
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