Emerson Fisher 657, Fisher 667 Installation Instructions

Instruction Manual

D100310X012

Fisherr 667 Diaphragm Actuator
Sizes 30-76 and 87

667 Size 30-76 and 87 Actuators

November 2013

Contents

Introduction 1...................................

Scope of Manual 1.............................

Description 2.................................

Specifications 3...............................

Educational Services 3.........................

Maximum Pressure Limitations 3................

Installation 4

Mounting the Actuator on the Valve 5............

Discussion of Bench Set 6.......................

Spring Verification 7...........................

Installing the Stem Connector Assembly 9.........

Friction Discussion 10..........................

Deadband Measurement 11.....................

Loading Connection 12.........................

Maintenance 12

Actuator 13..................................

Top-Mounted Handwheel Assembly

(Adjustable Down Travel Stop) 15.............

Side-Mounted Handwheel Assembly for

Size34through60Actuators 19...............

Side-Mounted Handwheel Assembly for

Size 70, 76, and 87 Actuators 20...............

Casing-Mounted Travel Stops 22.................

Parts Kits 24

Side-Mounted Handwheels Retrofit Kits 24........

Top-Mounted Handwheel Retrofit Kits 24.........

Actuator Repair Kits 24.........................

....................................

.................................

.....................................

Figure 1. Fisher 667 or 667-4 Actuator Mounted on
easy-e™ Valve

W1916-1*

Parts List 24.....................................

Actuator Assembly 24..........................

Top-Mounted Handwheel 25...................

Side-Mounted Handwheel (34-60) 33...........

Side-Mounted Handwheel (70, 76, and 87) 33....

Casing Mounted Travel Stops 35.................

Introduction

Scope of Manual

This instruction manual provides information on installation, adjustment, maintenance, and parts ordering for the
Fisher667actuatorinsizes30through76andsize87.The667-4 actuator in sizes 70 and 87 is also covered. Refer to
separate instruction manuals for information about the valve positioner and other accessories used with these
actuators.

Do not install, operate, or maintain a 667 actuator (see figure 1) without being fully trained and qualified in valve,
actuator, and accessory installation, operation, and maintenance. To avoid personal injury or property damage, it is
important to carefully read, understand, and follow all the contents of this manual, including all safety cautions and
warnings. If you have any questions about these instructions, contact your Emerson Process Management sales office
before proceeding.

www.Fisher.com

667 Size 30-76 and 87 Actuators

November 2013

Instruction Manual

D100310X012

Table 1. Specifications

SPECIFICATION

Nominal Effective Area

Yoke Boss Diameter

Acceptable Valve Stem Diameter

Maximum Allowable Output Thrust

Maximum Travel

Maximum Casing Pressurefor Actuator

Maximum Excess Diaphragm

Maximum Diaphragm Casing

Approximate Weight

Material

Temperature

Capabilities

1. These values also apply tothe 667-4 actuator construction.

2. Actuator travel may be less than the value listed after connected to the valve.

3. Maximum actuator travel for667-4 is 102 mm (4 inches).

4. See also the Specificationsportion of the introduction section.

5. Additional pressure may be added when the actuator is at full travel. If the Maximum Excess Diaphragm Pressure is exceeded, damage to the diaphragm or diaphragmcasing might result.
SeetheMaximumPressureLimitationsection.

6. Maximum diaphragm casing pressuremust not be exceeded and must not produce a force on theactuator stem greater thanthe maximum allowable actuatoroutput thrust or the maxi
mum allowable stem load. See the Maximum Pressure Limitation section.

7. This maximum casing pressure is not to be used for normal operating pressure. Its purpose isto allow for typical regulator supply settings and/or relief valve tolerances.

Sizing

Pressure

Pressure

(4,6)

(4,5)

(4,6,7)

(1)

Sq cm 297 445 445 667 1006 677 1006 1419 1006 1419

Sq Inch 46 69 69 105 156 105 156 220 156 220

mm 54 54 71 71 71 90 90 90 90 125
Inch 2-1/8 2-1/8 2-13/16 2-13/16 2-13/16 3-9/16 3-9/16 3-9/16 3-9/16 5
mm 9.5 9.5 12.7 12.7 12.7 19.1 19.1 19.1 19.1 25.4
Inch 3/8 3/8 1/2 1/2 1/2 3/4 3/4 3/4 3/4 1

(4)

(2)

Nitrile Elastomers -40 to 82_C (-40 to 180_F)

Silicone Elastomers -54 to 149_C (-65 to 300_F)

N 10230 10230 12010 25131 33582 25131 30246 39142 30246 39142

LB 2300 2300 2700 5650 7550 5650 6800 8800 6800 8800
mm 19 29 38 51 51 51 51 76
Inch 0.75 1.125 1.5 2 2 2 2 3

Bar 3.8 4.8 4.8 4.5 3.8 4.5 3.8 3.4 3.4 3.4

Psig 55 70 70 65 55 65 55 50 50 50

Bar 3.8 1.4 1.4 0.7 0.7 0.7 0.7 0.7 0.7 0.7

Psig 55 20 20 10 10 10 10 10 10 10

Bar 7.6 6.2 6.2 5.2 4.5 5.2 4.5 4.1 4.1 4.1

Psig 110 90 90 75 65 75 65 60 60 60

Kg 15 22 23 41 55 43 55 115 86 118

Pounds 34 48 50 90 121 94 122 254 190 260

30 34 40 45 46 50 60 70

ACTUATOR SIZE

(1)

76 87

(3)

(3)

51 76

2 3

(1)

(3)

(3)

Description

The 667 actuator (figure 1) and the 667-4 actuator are reverse-acting, spring-opposed diaphragm actuators. They
provide automatic operation of control valves. The 667 actuator provides 76 mm (3 inches) maximum actuator travel.
The 667-4 actuator provides 102 mm (4 inches) maximum actuator travel. Both actuators position the valve plug in
response to varying pneumatic loading pressure on the diaphragm. Figure 2 shows the operation of these actuators.

A 667 or 667-4 actuator can be furnished with either a top-mounted or a side-mounted handwheel assembly. A
top-mounted handwheel assembly is normally used as an adjustable down travel stop. (A down travel stop limits
actuator travel in the down direction [when the stem is traveling out of the actuator]. Travel in the up direction is when
the stem is traveling into the actuator.) A side-mounted handwheel assembly is normally used as an auxiliary manual
actuator. The side-mounted handwheelcanalsobeusedasanadjustableupordowntravelstop.Casing-Mounted
adjustable up or down travel stops are also available on this actuator.

Note

If repeated or daily manual operation is expected, the actuator should be equipped with a side-mounted handwheel rather than a
casing-mounted travel stop or top-mounted handwheel. The side-mounted handwheel is designed for more frequent use as a
manual operator.

2

Instruction Manual

D100310X012

Figure 2. Schematic of Fisher 667 and 667-4 Actuators

667 Size 30-76 and 87 Actuators

November 2013

AIR LIFTS
STEM UP

A6759

SPRING PUSHES
STEM DOWN

STEM
SEAL

STEM

Specifications

Refer to table 1 for Specifications of the 667 and 667-4 actuators. See the actuator nameplate for specific information
foryouractuator.

Educational S ervices

For information on available courses for Fisher 667 diaphragm actuators, as well as a variety of other products,
contact:

Emerson Process Management
Educational Services, Registration
P.O. Box 190; 301 S. 1
Marshalltown, IA 50158-2823
Phone: [phone] or
Phone: [phone]
FAX: [phone]
e-mail: [e-mail]

st

Ave.

WARNING

To avoid personal injury or damage to equipment that may result in the malfunction of the control valve or loss of control
of the process caused by excessive pressure, do not exceed the Maximum Pressures listed in table 1. Refer to the Maximum
Pressure Limitations section.

Maximum Pressure Limitations

The casing and diaphragm of 667 actuators are pressure operated. This air pressure provides energy to compress the
spring, to stroke the actuator, and to seat the valve. The following explanations describe the maximum pressure limits
for an actuator. Refer to the nameplate or table 1 for maximum values for your actuator.

3

667 Size 30-76 and 87 Actuators

November 2013

D Maximum Casing Pressure for Actuator Sizing: This is the maximum pressure that can be applied at less than full

travel of the actuator. If this stroking pressure is exceeded before the upper diaphragm plate contacts the travel
stop, damage to the stem or other parts might result.

D Maximum Excess Diaphragm Pressure: Additional pressure may be added when the actuator is at full travel. If the

Maximum Excess Diaphragm Pressure is exceeded, damage to the diaphragm or diaphragm casing might result.

Because the actuator has traveled its specified travel, and the diaphragm head is physically stopped from movement,
the energy from any additional air pressure is transmitted to the diaphragm and diaphragm casings. The amount of air
pressure that can be added once the actuator has traveled to the stops is limited by the resultant adverse effects that
may occur. Exceeding this limiting factor could result in leakage or casing fatigue due to the deformation of the upper
diaphragm casing.

D Maximum Diaphragm Casing Pressure: If the Maximum Diaphragm Casing Pressure is exceeded, damage to the

diaphragm, diaphragm casing, or actuator might result.

Instruction Manual

D100310X012

Installation

WARNING

Always wear protective gloves, clothing, and eyewear when performing any installation operations.

Check with your process or safety engineer for any other hazards that may be present from exposure to process media.

If installing into an existing application, also refer to the WARNING at the beginning of the Maintenance section in this
instruction manual.

Key number locations are shown in figures 6, 7, and 8, unless otherwise noted. Also, refer to figure 3 for location of
parts.

CAUTION

To avoid parts damage, do not use an operating pressure that exceeds the Maximum Diaphragm Casing Pressure (table 1)
or produces a force on the actuator stem greater than the Maximum Allowable Output Thrust (table 1) or the Maximum
Allowable Valve Stem Load.

D Valve/Actuator Assembly: If the actuator and valve are shipped together as a control valve assembly, it has been

adjusted at the factory, and may be installed in the pipeline. After installing the valve in the pipeline, refer to the
Loading Connection procedures.

D Actuator Mounting: If the actuator is shipped separately or the actuator has been removed from the valve, it is

necessary to mount the actuator on the valve before placing the valve in the pipeline. Refer to the following
actuator mounting procedures before placing the valve in service. It is recommended that you perform the Bench
Set Spring Adjustment procedures in this section to confirm that the actuator is adjusted correctly for the valve
travel.

D Positioner: If a positioner is installed, or is to be installed on the actuator, refer to the positioner instruction manual

for installation. During the adjustment procedures, it will be necessary to provide a temporary loading pressure to
the actuator diaphragm.

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Instruction Manual

D100310X012

667 Size 30-76 and 87 Actuators

November 2013

D Handwheel Cap: If the handwheel cap (key 247, figures 9, 11, or 17) is not in place, install the cap by pushing i t on

by hand until it snaps into place.

Mounting the Actuator on the Valve

CAUTION

The 667 actuator spring load pushes the stem down out of the actuator yoke (see figure 2), and it can come in contact with
the valve stem during actuator mounting.

If the valve stem is allowed to remain in the up position (towards the actuator) during actuator mounting, it can interfere
with the actuator stem during mounting. It is possible to damage valve stem threads or bend the valve stem. Be sure the
valve stem is pushed down (into the valve body), away from the actuator while mounting.

It may be necessary to apply a temporary loading pressure to the actuator to move the actuator stem away from the
valve during installation.

If it is not possible to provide a temporary loading pressure, be very careful when lowering the actuator over the valve
stem to prevent damage to valve stem and threads.

WARNING

When moving the actuator stem with loading pressure applied, exercise caution to keep hands and tools out of the
actuator stem travel path. If the loading pressure is accidently disconnected, personal injury and property damage may
result if something is caught between the actuator stem and other control valve parts.

1. Provide a vise or some other method of supporting the valveandtheweightoftheactuatorduringassembly.For
direct or reverse acting valves, push the valve stem down away from the actuator while mounting the actuator.

2. Screw the stem locknuts all the way onto the valve stem. With the concave side of the travel indicator disk (key 34)
facing the valve, install the travel indicator disk on the valve stem. (Note: The travel indicator disk is not used with
size 87 actuators.)

3. Lift or hoist the actuator onto the valve bonnet:

a. For size 87 actuators: Slowly lower the actuator down onto the valve while guiding the valve stem into the

opening in the end of the actuator stem (see figure 4). Once the actuator is in place, insert the cap screws and
tighten the hex nuts, securing the actuator to the bonnet.

b. Forallothersizeactuators:

D Slowly lower the actuator down onto the valve. As the yoke passes over the end of the valve stem, place the yoke

locknut over the valve stem. (Note: On small size actuators, it may be necessary to remove the indicator disk and
re-installitwhileloweringtheactuatorontothevalvebecausethediskwillnotgothroughtheactuatoryoke
opening).

D Continue to lower the actuator while guiding the valve stem into the opening in the end of the actuator stem u ntil

the actuator is in place (see figure 4).

D Screw the yoke locknut onto the valve bonnet and tighten the locknut.

4. Do not connect the actuator stem to the valve stem at this time. Whenever the actuator is installed on the valve, it
is recommended that you perform the Bench Set Spring Adjustment procedures below, to verify that the actuator is
still adjusted correctly.

5

667 Size 30-76 and 87 Actuators

November 2013

Figure 3. Actuator-Mounting Components for Size 30 through 70 Actuators

VENT ASSEMBLY

DIAPHRAGM CASINGS

DIAPHRAGMAND STEM
SHOWNINDOWNPOSITION

DIAPHRAGM
PLATE

LOADING AIR
PRESSURE CONNECTION

ACTUATOR SPRING

ACTUATOR STEM

SPRING SEAT

SPRING ADJUSTOR

STEM CONNECTOR

YOKE

TRAVEL INDICATOR DISK

INDICATOR SCALE

W0364-1

Instruction Manual

D100310X012

VALVE STEM

YOKE LOCK NUT

YOKE BOSS DIAMETER

BONNET

TYPICAL VALVE
(REFER TO
VALVE MANUAL)

W6199-1

MATCH LINE
FOR
ACTUATOR

Discussion of Bench Set

The bench set pressure values are used to adjust the initial compression of the actuator spring with the valve-actuator
assembly “on the bench.” The correct initial compression ensures that the valve-actuator assembly will function
properly when it is put into service and the proper actuator diaphragm operating pressure is applied.

The bench set values are established with the assumption that there is no packing friction. When attempting to adjust
the spring in the field, it is very difficult to ensure that there is no friction being applied by “loose” packing.

Accurate adjustment to the bench set range can be made during the actuator mounting process by making the
adjustment before the actuator is connected to the valve (see the Spring Verification Procedure).

6

Instruction Manual

D100310X012

Figure 4. Bench Set Adjustment

SPRING
ADJUSTER

ACTUATOR STEM

UPPER BENCH
SET LOADING
PRESSURE

LOWER BENCH
SET PRESSURE
MARK

3

4

RATED VALVE
TRAVEL MEASURE

667 Size 30-76 and 87 Actuators

November 2013

NOTES:

1

THE LOWER PSIG LOADING PRESSURE (MARKED
ON NAMEPLATE) WHERE THE FIRST MOVEMENT OF
ACTUATOR STEM IS DETECTED.

2

MARK THIS POINTWITH TAPE OR AMARKER.

3

THE UPPER PSIG LOADING PRESSURE RETRACTS
ACTUATOR STEM.

MEASURE DISTANCE OF TRAVEL. IT SHOULD EQUAL

4

THE TRAVEL SHOWN ON THENAMEPLATE.

VALVE STEM

50A8379-C
B2429-1

4

MARK VALVE
STEM HERE

LOWER BENCH SET

2

1

LOADING PRESSURE

Spring Verification

Ensure that the actuator diaphragm is at the bottom of its travel as shown in figure 4 and not connected to the valve.
(Note: Some spring compression is required to move the diaphragm to the bottom of its travel.)

Also, provide a certified pressure gauge that will accurately read the diaphragm pressure from 0 through 0.3 bar (5
psig) above the upper operating range pressure marked on the nameplate. Apply loading pressure to the diaphragm.

Stroke the actuator a few times to ensure that the pressure gauge is working correctly, and that the actuator is
functioning properly.

CAUTION

Topreventactuatordamage,itisimportanttoensurethatthe actuator stem is stroking smoothly and not exhibiting
binding or excessive friction between the actuator stem and the bushing (key 7). Binding or excessive friction could be an
indicator of incorrect assembly or damaged parts.

Keynumbersareshowninfigures6,7,and8.

Note

For 667 actuators installed on push-down-to-close (direct acting) valves with f ail-close action, the valve plug seat is the limit for
downward travel and the actuator is the limit for upward (away from the valve) movement.

For 667 actuators installed on push-down-to-open (reverse acting) valves with fail-open action, the actuator down stop is the limit
for downward movement, and the valve seat is the limit for upward (away from the valve) movement.

Ensure the correct Spring Verification procedure is followed for the type of valve on which the 667 actuator is installed.

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667 Size 30-76 and 87 Actuators

November 2013

Instruction Manual

D100310X012

For Push Down to Close (Direct Acting) Valves

1. If not already accomplished, push the valve stem down away from the actuator to the closed position.

2. Set the diaphragm loading pressure to 0.3 bar (5 psig) over the upper operating range pressure. The travel stop cap
screw (key 12) should be contacting the upper diaphragm casing.

3. Slowly decrease the pressure towards the upper bench set pressure, a s indicated on the nameplate, while checking
for the first linear movement of the actuator stem.

Note

Before turning the spring adjuster on size 70, 76, or 87 actuators, assemble the stem connector around the actuator stem and the
anti-rotating lug on the yoke. Mark the actuator stem as a visual reference to verify that stem rotation does not occur. Remove the
stem connector before rechecking the bench set.

4. If movement occurs before or after the upper bench set pressure is reached, adjust the spring adjuster (see figure

4). Thread the adjuster up or down on the actuator stem until the actuator stem movement is first detected at the
upper bench set pressure. (Note: You may need to lower the loading pressure to reduce spring compression,
allowing the spring adjuster to turn.)

5. Be sure the spring adjuster is adjusted to meet the requirements of step 4 above.

6. Slowly decrease diaphragm loading pressure to the lower bench set pressure, as indicated on the nameplate. This
will extend the actuator stem toward the valve. Mark the end of the actuator stem on a nearby surface using tape or
some other method.

7. Slowly increase the diaphragm loading pressure until the upper bench set pressure is reached. Again, the travel stop
cap screw (key 12) should be against the upper diaphragm casing.

8. Measure the distance between the mark or tape to the end of the actuator stem. This distance should match the
rated travel indicated on the nameplate.

9. If the measured travel matches the nameplate travel, bench set is complete. Proceed to the Installing the Stem
Connector Assembly subsection.

10. If the measured travel is not exact, consider the spring free-length and spring rate tolerances may produce a
slightly different bench set than specified. Contact your Emerson Process Management sales office for assistance.

ForPushDowntoOpen(ReverseActing)Valves

1. If not already accomplished, push the valve stem down away from the actuator to the open position. Later, when
installingtheconnector,pullupthevalvestemtotheclosedposition.

2. Set the diaphragm loading pressure to a value less than the lower bench set pressure, as indicated on the
nameplate, or near zero. The down travel stops (key 77) should be contacting the yoke.

3. Slowly increase the pressure towards the lower bench set pressure while checking for the first linear movement of
the actuator stem.

Note

Before turning the spring adjuster on size 70, 76, or 87 actuators, assemble the stem connector around the actuator stem and the
anti-rotating lug on the yoke. Mark the actuator stem as a visual reference to verify that stem rotation does not occur. Remove the
stem connector before rechecking the bench set.

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Instruction Manual

D100310X012

667 Size 30-76 and 87 Actuators

November 2013

4. If movement occurs before or after t he lower pressure is reached, adjust the spring adjuster (see figure 4). Thread
the adjuster up or down on the actuator stem until the actuator stem movement is first detected at the lower bench
set pressure.

5. Apply the upper bench set pressure indicated on the nameplate to the diaphragm. This will retract the actuator
stem away from the valve. Mark the end of the actuator stem on a nearby surface using tape or some other method.

6. Slowly decrease the diaphragm pressure until the lower bench set pressure is applied. Again, the down travel stops
(key 77) should be against the yoke.

7. Measure the distance between the mark or tape to the end of the actuator stem. This distance should match the
rated travel indicated on the nameplate.

8. If the measured travel matches the nameplate travel, bench set is complete. Proceed to the Installing the Stem
Connector Assembly subsection.

9. If the measured travel is not exact, consider the spring free-length and spring rate tolerances may produce a slightly
different bench set than specified. Contact your Emerson Process Management sales office for assistance.

Installing the Stem Connector Assembly

When installing the stem connector assembly (key 31), theactuatorandvalvestemthreadsshouldengagethe
threads of the stem connector by a distance equal to the diameter of the stem.

WARNING

Install the stem connector securely before a positioner is mounted to the actuator and pressurized, using only a
regulator-controlled air supply, not the positioner, to move the actuator stem.

To avoid personal injury or property damage, keep hands and tools out of the actuator stem travel path while applying
loading pressure to move the actuator stem in the following steps.

CAUTION

To avoid damaging the seating surfaces, do not rotate the valve plug while it is seated. Exercise care while installing the
stem connector assembly to a void damage to the valve plug stem and valve stem threads.

Note

Replacement stem connectors are an assembly of two stem connector halves, cap screws, and a spacer between the connector
halves. Remove the spacer and discard it, if present, before clamping the actuator and valve stems together. Use only a mated pair
of stem connectors.

1. Ifnecessary,pushthevalvestemdownsothatthevalveplug is touching the seat ring on direct-acting valves. For
reverse-acting valves, pull the stem up to the closed position. Always start with the valve plug on the seat.

2. If necessary, screw the valve stem locknuts down, away from the connector location. For all actuators except size
87, ensure that the travel indicator disk (key 34) is on top of the locknuts.

3. Adjust the diaphragm pressure to the lower bench set pressure (or, the upper bench set pressure for reverse-acting
valves.) This should be the same pressure used in the Spring Verification steps, and it is marked on the nameplate.

4. Place the stem connector half with the threaded holes approximately half way between the actuator and valve
stems, and align the actuator stem and valve stem with threads from both stems mated root-to-crest with the stem
connector. If the threads from one of the stems do not fully align with the stem connector, a slight change to

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667 Size 30-76 and 87 Actuators

November 2013

Instruction Manual

D100310X012

loading pressure may be necessary to align the threads. Refer to figures 6, 7, and 8 to help locate the connector
position.

CAUTION

Incomplete engagement of either the valve stem or actuator stem in the stem connector can result in stripped threads or
improper operation. Be sure that the length of each stem clamped in the stem connector is equal to or greater than one
diameter of that stem. Damage to threads on either stem or in the stem connector can cause the parts to be replaced
prematurely. Do not loosen the cap screws when the stem connector has spring or loading pressure force applied.

5. Install the other half of the stem connector and insert the cap screws and tighten them while ensuring even spacing
between the stem connector halves on all sides. If installing a positioner, also attach the feedback bracket at the
same time.

CAUTION

Over-tightening the valve stem locknuts can make disassembly difficult.

6. Screw the valve stem locknuts up against the stem connector for the size 87 actuator. For all other actuator sizes,
screw the valve stem locknuts up until the indicator disk contacts the bottom of the stem connector. Do not
overtighten the locknuts.

7. Slowly stroke the valve from fully open to fully closed and verify full rated travel is achieved.

Be sure that the valve is in the closed position. Loosen the screws on the travel indicator scale (key 32), and align it with
the travel indicator disk (key 34). Stroke the valve full travel to ensure that the travel matches the rated valve travel on
the nameplate. If valve travel is not correct, repeat the stem connector procedure.

Friction Discussion

If you are attempting to adjust the bench set after the actuator is connected to the valve and the packing tightened,
you must take friction into account. Make the spring adjustment so full actuator travel occurs at the bench set values
(a) plus the friction force divided by the effective diaphragm area with increasing diaphragm pressure or (b) minus the
friction force divided by the effective diaphragm area with decreasing diaphragm pressure.

If the stem connector assembly has been installed, the valve friction may be determined by the following procedure:

1. Install a pressure gauge in the actuator loading pressure line that connects to the actuator diaphragm casing.

Note

Steps 2 and 4 require that you read and record the pressure shown on the pressure gauge.

2. Increase the actuator diaphragm pressure and read the diaphragm pressure as the actuator reaches a travel
position in the rated travel of the valve that does not contact a travel stop. Make a reference mark on the travel
indicator scale using tape or some other method at this point.

3. Increase the actuator diaphragm pressure until the actuator is at a travel position greater than the position
referenced in step 2 using the reference point to identify first movement.

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Instruction Manual

D100310X012

667 Size 30-76 and 87 Actuators

November 2013

4. Decrease the actuator d iaphragm pressure and read the diaphragm pressure as the actuator returns to the position
referenced in step 2.

The difference between the two diaphragm pressure readings is the change in the diaphragm pressure required to
overcome the friction forces in the two directions of travel.

5. Calculate the actual friction force:

Friction
Force, = 0.5
pounds

Difference
in pressure
readings, psig

Effective
diaphragm area,

¢

inches

2

Refer to table 1 for the effective diaphragm area.

It is difficult to rotate the spring adjustor (key 74, figures 6, 7, and 8) when the full actuator loading pressure is applied
to the actuator. Release the actuator loading pressure before adjusting. Then re-apply loading pressure to check the
adjustment.

Figure 5. Typical Valve Response to Deadband

UPPER
BENCH SET
PRESSURE

LOWER

DIAPHRAGM PRESSURE, PSIG

BENCH SET
PRESSURE

NOTE:

1

A6763-2

15

BENCH SET BENCH SET

9

3

0

OPEN

MID RANGE

VALVE TRAVEL

DIRECT ACTING VALVE REVERSE ACTING VALVE

DEADBAND IS CAUSED BY FRICTION.

CLOSING
VALVE

OPENING
VALVE

RANGE OF
DEADBAND

CLOSED

1.0

0.6

1

0.2

DIAPHRAGM PRESSURE, BAR

UPPER
BENCH SET
PRESSURE

LOWER

DIAPHRAGM PRESSURE, PSIG

BENCH SET
PRESSURE

15

9

3

0

CLOSED

OPENING
VALVE

CLOSING
VALVE

MID RANGE

VALVE TRAVEL

RANGE OF
DEADBAND

OPEN

1.0

0.6

1

0.2

DIAPHRAGM PRESSURE, BAR

Deadband Measurement

Deadband is caused by packing friction, unbalanced forces, and other factors in the control valve assembly. Deadband
is the range a measured signal can vary without initiating a response from the actuator (see figure 5). Each actuator
spring has a fixed spring rate (force divided by compression). You have verified that the right spring was installed in the
actuator by completing the Spring Verification steps.

Deadband is one factor that affects the control valve assembly operation during automatic loop control. The control
loop tolerance for deadband varies widely depending on the loop response. Some common symptoms of the
deadband being too wide are no movement, a “jump” movement, or oscillating movements of the actuator during
automatic loop control. The following steps are provided to determine the span of deadband. The percent of
deadband is helpful in troubleshooting problems with the process control loop.

1. Start at a pressure near the lower bench set pressure, slowly increase pressure until the valve is approximately at
mid-travel. Note this pressure reading.

11