Samson 3761 Service manual

Type 3761
Pneumatic or Electropneumatic Positioner
for Rotary Actuators
Mounting and Operating
Instructions
EB 8386 EN
Edition July 2007
Fig. 1 · Type 3761 Positioner

Note!
Devices with a CE marking fulfil the requirements of the Directives 94/9/EC and
89/336/EEC.
The declaration of conformity can be viewed and downloaded on the Internet at
http://www.samson.de.
2EB 8386 EN
Contents
Contents Page
1 Design and principle of operation . . . . . . . . . . . . . . . . . . . 4
1.1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Attachment to rotary actuators . . . . . . . . . . . . . . . . . . . . . 7
2.1 Determining the operating direction . . . . . . . . . . . . . . . . . . . 9
2.2 Selecting and aligning the cam disc . . . . . . . . . . . . . . . . . . 10
3 Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Pneumatic connections. . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1.1 Pressure gauges. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Operation – Adjustment. . . . . . . . . . . . . . . . . . . . . . . . 16
4.1 Starting point and reference variable. . . . . . . . . . . . . . . . . . 16
4.2 Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2.1 Spring-return actuator: valve CLOSED without supply air . . . . . . . . 17
4.2.2 Spring-return actuator: valve OPEN without supply air . . . . . . . . . 18
4.2.3 Double-acting actuator: valve opens counterclockwise and clockwise . . 18
5 Adjusting the limit switch . . . . . . . . . . . . . . . . . . . . . . . 20
6 Servicing explosion-protected devices . . . . . . . . . . . . . . . . . 21
7 Dimensions in mm . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Test certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4
The device is to be assembled, started up or operated only by trained and ex-
perienced personnel familiar with the product.
According to these mounting and operating instructions, trained personnel is
referred to as individuals who are able to judge the work they are assigned to
and recognize possible dangers due to their specialized training, their knowl-
edge and experience as well as their knowledge of the applicable standards.
4
Explosion-protected versions of this device are to be operated only by person-
nel who has undergone special training or instructions or who is authorized to
work on explosion-protected devices in hazardous areas.
4
Any hazards that could be caused in the control valve by the process medium,
the operating pressure or by moving parts are to be prevented by means of
the appropriate measures.
If inadmissible motions or forces are produced in the pneumatic actuator as a
result of the supply pressure level, it must be restricted using a suitable supply
pressure reducing station.
4
Proper shipping and storage are assumed.
Safety instructions Versions
EB 8386 EN 3
Positioner versions Type 3761– xxxxxx
Explosion protection Without 0
EEx ia IIC T6 1
Design Pneumatic 10
Electropneumatic 2
Tight-closing function Without 0
At a reference variable of 0 % 1
At a reference variable of 100 % 2
Type of function Single output 1
Double output 2
Accessories Without electric limit switch 0
With electric limit switch 1
Pneumatic connections ISO-228/1 – G ¼ 1
¼-18 NPT 2

1 Design and principle of opera-
tion
The pneumatic or electropneumatic
positioner ensures the assignment of the
valve position (controlled variable) to the
control signal (reference variable).
The input signal received from a control unit
is compared to the control valve's angle of
rotation and a corresponding pneumatic
signal pressure (output variable) is pro-
duced.
The positioner mainly consists of a pneu-
matic unit including a tension spring (4), di-
aphragm lever (5) and the amplifier (8) with
double plug (7). The electropneumatic
positioner is additionally equipped with an
electropneumatic converter (10).
Any change of the valve position (controlled
variable) is transmitted as a rotary motion of
the actuator over the cam disc (2), the
pick-up lever (1) and the tension spring (4)
to the pneumatic system.
The control signal (positioner's input signal)
from the control unit, if it is a pneumatic sig-
nal, is applied as a pressure signal pedirectly
to the measuring diaphragm (6). A DC input
signal e.g. from 4 to 20 mA, is directly
passed on to the electropneumatic converter
(i/p converter) where it is converted into a
proportional pressure signal pe.
The pressure signal pecreates a force on the
measuring diaphragm (6), which is bal-
anced by the force of the tension spring (4).
The movement of the measuring diaphragm
is passed on to the double plug (7) of the
amplifier (8) through the lever (5) so that a
corresponding signal pressure pst is pro-
duced.
The positioner's principle of operation is de-
termined by equipping it with either one
(single-acting) or two (double-acting) ampli-
fiers.
The operating direction of the signal pres-
sure with increasing << or decreasing <> in-
put signal can be changed by relocating the
amplifier for single-acting positioners. For
double-acting positioners, the signal pres-
sure connections need to be reversed.
Zero is corrected on an adjustment screw.
The angle of rotation is determined by the
cam disc.
Tight-closing function: For electropneumatic
positioners with tight-closing function, the
rotary actuator is completely vented or filled
with air (depending on the operating direc-
tion) as soon as the reference variable falls
below or exceeds a given value.
For Type 3761-x21x, the deactivation func-
tion is initiated when the switching point of
4.08 mA is not reached. The actuator is
completely vented.
For Type 3761-x22x, the activation function
is initiated when 19.92 mA are exceeded.
The actuator is completely filled with air.
4EB 8386 EN
Design and principle of operation

EB 8386 EN 5
Design and principle of operation
5
6
7
8
43
1
2
910
i
Input
27
pi
Supply
9
pst1
pst2
A
pe
I
N
Fig. 2 · Functional diagram
Fitting position
marked
Position 2
Output 238
Position 1
Output 138
Output 238
Output 138
1 Pick-up lever
2 Cam disc
3 Zero point adjuster
4 Tension spring
5 Diaphragm lever
6 Measuring diaphragm
7 Double plug
8 Amplifier
9 Fastening screw
10 i/p converter
(in electropneumatic version)

1.1 Technical data
Type 3761 Positioner
Angle of rotation 55° / 70° / 75° / 90°
Reference variable Electric 4 to 20 mA (min. 3.6 mA), must be operated on current source
Load: 300 Ωat 20 mA (350 Ωat 20 mA with tight-closing
function and explosion protection)
Reverse polarity protection
Static destruction limit 60 mA or 6.4 V (without explosion
protection) or 7.6 V (with explosion protection)
Pneumatic 0.2 to 1 bar (3 to 15 psi)
Supply air pressure 1.4 to 6 bar (20 to 90 psi)
Signal pressure 0 to 6 bar (0 to 90 psi)
Characteristic Cam discs Linear, deviation from terminal-based conformity ≤2 %
Standard: 90° linear; others: see table on page 10
Operating direction Reversible
Principle of operation Single-acting or double-acting
Hysteresis ≤1 %
Variable position ≤7 %
Tight-closing function
(can be deactivated) Type 3761-x21x: Type 3761-x22x: Deactivated when reference variable ≤4.08 mA
Activated when reference variable ≥19.92 mA
Air consumption in steady state Supply air 1.4 bar 6 bar
Single-acting
Double-acting 80 ln/h
150 ln/h 200 ln/h 350 ln/h
Air supply 3000 ln/h at 2 bar 6000 ln/h at 6 bar
Permissible ambient temperature –20 to +70 °C, –30 to +70 °C with metal cable entry
For explosion-protected versions, the specifications in the decla-
ration of conformity apply additionally
Degree of protection IP 54 (optionally IP 65)
Weight Approx. 0.9 kg
Electrical accessories (optional) Electric limit switch (microswitch with gold-plated contact, SPDT),
250 V AC, 3 A
6EB 8386 EN
Design and principle of operation

2 Attachment to rotary actua-
tors
Accessories Order no.
VDI/VDE 3845, level 1 mounting kit
Additionally, a bracket (2) included in
the actuator's scope of supply is re-
quired
1400-7595
Mounting kit for SAMSON
Type 3278 including
bracket
160 cm² 1400-7615
320 cm² 1400-7616
The mounting kit consists of a follower plate,
coupling wheel, scale plate and coupling lever
as well as a hose clamp and clamping screw.
For SAMSON Type 3278 Rotary Actuators,
mount the spacer delivered with the actuator
to the free shaft end of the rotary actuator.
1. Fasten mounting bracket (2) to the
positioner using 4 screws (2.1).
2. Push follower plate (5) onto the slotted
actuator shaft or the spacer (7).
3. Push coupling wheel (4) with its flat side
facing towards the actuator onto the fol-
lower plate (5). Make sure to position
the oblong hole of the coupling wheel
such that the clamping screw (3.1) of the
coupling lever (3) can easily be ac-
cessed when the valve is in closed posi-
tion.
4. Firmly fasten coupling wheel and fol-
lower plate to the actuator shaft using
the pan head screw (6) and disc
spring (6.1)
EB 8386 EN 7
Attachment to rotary actuators
2.1
6
1
6.1
5
2
3.1
3
4
7.1
7
Fig. 3 · Attachment to rotary actuator
1 Positioner
2 Mounting bracket
2.1 Fastening screws
3 Coupling lever
3.1 Clamping screw
4 Coupling wheel
4.1 Scale plate
5 Follower plate
6 Pan head screw
6.1 Disc spring
7 Actuator shaft / spacer
7.1 Screws

5. Place coupling lever (3) including hose
clamp and clamping screw (3.1) loosely
onto the coupling wheel (4) so that its
contact stud slides into the oblong
hole (3.2).
6. Carefully place positioner with mounting
bracket (2) onto the rotary actuator.
Make sure the positioner axis slides into
the coupling lever (3). Observe direction
for arranging the connections.
7. Screw the mounting bracket (2) to the
actuator using four screws (7.1).
8. Fix scale plate (4.1) to the coupling wheel
so that the arrow tip indicates closed po-
sition and can easily be identified when
the valve is installed (see Fig. 4).
9. Leave the coupling lever, which is fas-
tened with the clamping screw (3.1),
loosened at first. Align the cam disc (see
section 2.2, page 10). Clamp the lever
onto the positioner axis.
8EB 8386 EN
Attachment to rotary actuators
4
44.1
3.1 3.2 3
4
4.14
3.1 3.2 3
Fig. 4 · Aligning the scale plate
Control valve opens counterclockwise
Control valve opens clockwise
3 Coupling lever
3.1 Clamping screw
3.2 Oblong hole
4 Coupling wheel
4.1 Adhesive scale plate

2.1 Determining the operating di-
rection
Important!
The positioner with either single-acting or
double-acting output is fixed and cannot be
changed by subsequently adding or remov-
ing an amplifier.
Single-acting positioners:
The operating direction of the positioner is
determined by the mounting position of the
amplifier. When the input signal (reference
variable) increases, the signal pressure pst
can either increase (direct operating direc-
tion) or decrease (reverse operating direc-
tion).
The same applies when the input signal de-
creases. For direct operating direction, the
signal pressure decreases whereas it in-
creases for reverse operating direction.
For direct operating direction, screw the am-
plifier in mounting position 1(Fig. 2); for re-
verse operating direction, screw the ampli-
fier in mounting position 2. Screw the cover
plate onto the unoccupied position so that
the associated supply air bore is sealed.
Note!
When relocating the amplifiers, make abso-
lutely sure that both O-rings remain in the
base of the housing.
Double-acting positioners:
The operating direction is determined by the
assignment of the signal pressure out-
puts 138 and 238 to the two connections
(y1 and y2) of the rotary actuator.
Note!
The designation of the signal pressure con-
nections on the rotary actuator varies de-
pending on the manufacturer.
In Figs. 5 and 6, y1 and y2 have been as-
signed the following functions:
Single-acting actuator
Increasing the signal pressure at y1 opens
the valve if the closure member rotates coun-
terclockwise.
Double-acting actuator
Increasing the signal pressure at y1 and de-
creasing the pressure at y2 opens the valve
if the closure member rotates counterclock-
wise; or
increasing the signal pressure at y2 and de-
creasing the pressure at y1 opens the valve
if the closure member rotates clockwise.
EB 8386 EN 9
Attachment to rotary actuators

2.2 Selecting and aligning the
cam disc
The positioner is delivered with a 90° linear
cam disc. If a different control characteristic
is required, replace the existing cam disc
with a cam disc listed in the table below.
The default setting of the cam disc depends
on the valve design (butterfly valve, ball
valve, etc.) and rotary actuator version used.
For proper assignment refer to Figs. 5
and 6.
Fig. 5 shows how to adjust the cam disc for
control valves with rotary actuators that are
equipped with spring-return mechanism. The
fail-safe action "valve CLOSED" or "valve
OPEN" without supply pressure is deter-
mined by how the actuator is attached to the
valve.
For example, SAMSON's Type 3278 Actua-
tor can be mounted on a butterfly valve with
the shaft attached to either the left or the
right actuator flange.
Fig. 6 shows how to adjust the cam disc
when a double-acting, springless rotary ac-
tuator is used. The direction of rotation, ei-
ther counterclockwise or clockwise (looking
from the positioner onto the actuator shaft),
depends on how the rotary actuator is
mounted on the valve and how the two sig-
nal pressure outputs 138 and 238 are as-
signed to the connections y1 and y2 of the
rotary actuator.
Depending on the rotary actuator's direction
of rotation (counterclockwise or clockwise),
the starting point of the cam section that
must be passed through is either on the
front Aor the back Bof the cam disc.
10 EB 8386 EN
Attachment to rotary actuators
Cam discs Order no.
Linear cam disc, 90° 0050-0093
Equal percentage cam disc, 90° 0050-0095
Linear cam disc, 70° for butterfly valves 0050-0108
Equal percentage cam disc, 70° for butterfly valves 0050-0110
Linear cam disc, 75° for VETEC rotary plug valves 0050-0102
Equal percentage cam disc, 75° for VETEC rotary plug valves 0050-0104
Linear cam disc, 90° for Type 3310 Segmented Ball Valves 0050-0114
Equal percentage cam disc, 90° for Type 3310 Segmented Ball Valves 0050-0116
Linear cam disc, 70° for Type 3310 Segmented Ball Valves with reverse flow 0050-0126
Equal percentage cam disc, 70° for Type 3310 Segmented Ball Valve with reverse flow 0050-0128
Linear cam disc, 55° for Type 3310 Segmented Ball Valve with reduced opening angle 0050-0118
Equal percentage cam disc, 55° for Type 3310 with reduced opening angle 0050-0120

EB 8386 EN 11
Attachment to rotary actuators
Pos.2 Pos.1 Pos.2 Pos.1
N
N
B
I
I
A
N
Pin Starting position I Pin Starting position N
Pos.2 Pos.1
N
B
I
Pos.2 Pos.1
I
A
N
Pin Starting position N Pin Starting position I
Single-acting actuator with spring return mechanism
Valve opens counterclockwise, linear cam disc (standard)
Fail-safe position "valve CLOSED" without supply pressure
Orientation of cam disc when control valve is closed
Direct operating direction Connection: Output 138 Reverse operating direction Connection: Output 238
Ref. variable Signal pressure Valve Cam Ref. variable Signal pressure Valve Cam
Increases Increases Opens ADecreases Increases Opens B
Fail-safe position "valve OPEN" without supply pressure
Orientation of cam disc when control valve is closed, additionally apply max. signal press. to actuator
Direct operating direction Connection: Output 138 Reverse operating direction Connection: Output 238
Ref. variable Signal pressure Valve Cam Ref. variable Signal pressure Valve Cam
Decreases Decreases Opens BIncreases Decreases Opens A
Fig. 5 · Aligning the cam disc for single-acting rotary actuators with spring return mechanism

12 EB 8386 EN
Attachment to rotary actuators
N
N
B
I
I
A
N
Pin Starting position N Pin Starting position I
I
N
B
N
I
A
N
I
Pin Starting position N Pin Starting position I
Double-acting actuator with spring return mechanism
Linear cam disc (standard)
Orientation of cam disc when control valve is closed, additionally apply max. signal press. to actuator
Control valve opens counterclockwise (increasing pressure to y1, decreasing pressure to y2)
Direct operating direction Reverse operating direction
Ref. variable Signal pressure Valve Cam Ref. variable Signal pressure Valve Cam
Increases Output 138 to y1
Output 238 to y2 Opens ADecreases Output 138 to y2 Output 238 to y1 Opens B
Control valve opens clockwise (increasing pressure to y2, decreasing pressure to y1)
Direct operating direction Reverse operating direction
Ref. variable Signal pressure Valve Cam Ref. variable Signal pressure Valve Cam
Increases Output 138 to y2
Output 238 to y1 Opens BDecreases Output 138 to y1 Output 238 to y2 Opens A
Fig. 6 · Aligning the cam disc for double-acting rotary actuators

Aligning the cam disc:
Important!
Close the control valve before aligning the
cam disc as illustrated in Figs. 5 and 6.
For actuators with fail-safe action "valve
OPEN" without supply pressure and for
springless actuators, apply the max. signal
pressure to the actuator before aligning the
cam disc so that the valve is moved to closed
position.
4Slightly loosen clamping screw (3.1,
Fig. 4) so that the cam disc can be ro-
tated together with the positioner shaft.
4Turn cam disc with the selected cam (A
or B) so that the fulcrum of the cam disc,
the marking point and the black pin form
a line (Figs. 5 and 6).
4Hold cam disc in place and tighten
clamping screw (3.1).
To flip the cam disc over, insert an Allen key
into the positioner shaft to hold it stationary.
Loosen the fastening nut and remove the
cam disc.
Turn the cam disc over and remount it.
The default setup is shown in the top left of
Figs. 5 and 6 (valve closed in fail-safe posi-
tion, opens counterclockwise and closes
clockwise).
3 Connections
3.1 Pneumatic connections
Depending on the cover plate, the pneu-
matic connections are either ¼-18 NPT or
ISO 228/1- G ¼ tapped holes.
The supply input (Supply 9) is fitted with a
sintered metal filter (order no. 1400-6897).
The other connections are fitted with filters
(order no. 0550-0213) to prevent dirt from
collecting in the device. Remove the cover
plate to clean or replace the filters, if neces-
sary.
Commonly available male connections for
metal and copper pipes or plastic hoses can
be used for connection.
Caution!
The supply air must be dry and free of oil or
dust. Always observe the maintenance in-
structions of upstream pressure reducing sta-
tions. Thoroughly purge all pneumatic lines
before connecting them.
Important!
Adjust the supply pressure to 0.2 bar above
the upper bench range value of the actuator
(see nameplate).
EB 8386 EN 13
Connections

3.1.1Pressure gauges
To control the supply air (Supply) and signal
pressure (Output), pressure gauges as well
as a gauge mounting block are required.
Replace the included connecting plate with
the gauge mounting block.
Accessories Order no.
Gauge mounting block:
G ¼
¼ NPT 1400-7611
1400-7612
Pressure gauge (st. steel/brass):
1x supply, 1x output for single-acting
1x supply, 2x output for double-acting 1400-6950
1400-7613
3.2 Electrical connections
Electropneumatic positioner
Connect the wires for the reference variable
to terminals +11 and –12 using the hous-
ing's cable glands.
For versions with limit switch, additionally
connect the limit switch wires to
terminals 41, 42 and 43.
For electrical installation, you are
required to observe the relevant
electrotechnical regulations and the
accident prevention regulations that
apply in the country of use. In Ger-
many, these are the VDE regula-
tions and the accident prevention
regulations of the employers’ liabil-
ity insurance.
The following regulations apply to
installation in hazardous areas:
EN 60079-14:2003; VDE 0165
Part 1:1998.
The data specified in the certificate
of conformity and the EC type ex-
amination certificate apply to the
connection of intrinsically safe cir-
cuits.
Warning!
Switching the assignment of the
electrical terminals for the control
signal and the limit switch may
cause the explosion protection to
become ineffective!
Do not loosen enameled screws in
or on the housing.
14 EB 8386 EN
Connections

Note on selecting cables and wires
To run several intrinsically safe circuits in
one multi-core cable, observe section 12 of
EN 60079-14 and VDE 0165, Part 1.
Note especially that, for commonly used in-
sulating materials, such as polyethylene, the
radial thickness of the conductor insulation
must be at least 0.2 mm. The diameter of a
single wire of a flexible conductor must not
be smaller than 0.1 mm.
The conductor ends must be protected
against unlaying, e.g. by using wire-end
ferrules.
When two separate cables are used for con-
nection, an additional cable gland can be
installed.
Cable entries left unused must be sealed
with plugs.
Accessories Order no.
M20x1.5 cable gland
Black
Blue 1400-6985
1400-6986
Metal cable gland
for temperatures below –20 °C 1890-4875
M20x1.5 to ½ NPT adapter
Powder-coated aluminum 0310-2149
Plug connector acc. to DIN 43650
For the reference variable
For the microswitch 1400-7603
1400-7604
Limit switch (retrofit kit) 1400-7602
Conversion kit to IP 65 1790-7408
EB 8386 EN 15
Connections
[phone]
Fig. 7 · Electrical connection
4 to 20 mA
control signal
Electropneumatic
version only
Optional
limit switch

4 Operation – Adjustment
4.1 Starting point and reference
variable
Note!
The positioner is delivered with the default
settings adjusted by the manufacturer.
The pre-determined fitting position of the
tension spring (4) is marked by a dot of
paint and should not be changed.
If the reference variable is, e.g. 4 to 20 mA
(0.2 to 1 bar), the angle of rotation for
opening or closing the valve determined by
the cam disc causes the valve to travel
through its full range.
The starting point is 4 mA (0.2 bar); the up-
per range value is 20 mA (1 bar).
Note!
Zero adjustment is always based on the
valve's closed position. As a result, zero ad-
justment depends on the actuator version
used, e.g. for an actuator with reverse oper-
ating direction, zero must be set to 20 mA
(1 bar) instead of 4 mA (0.2 bar).
The exact starting point is adjusted using
the zero adjuster (3; Fig. 2).
The upper range value is automatically de-
termined by the cam disc's angle of rotation.
If it should be necessary to correct the upper
range value, only slight changes can be
made using the potentiometer span of the
electropneumatic positioner. Turn the poten-
tiometer counterclockwise to reduce the
span and clockwise to increase it.
Note!
Electropneumatic positioners with tight-clos-
ing function are equipped with a slide
switch on the printed input circuit board to
activate or deactivate the function.
Important!
Switch off the activation/deactivation func-
tion while adjusting zero. Do not activate
the relevant function on the switch before
zero has been adjusted.
16 EB 8386 EN
Operation – Adjustment
N
I
ANN
I
AN
Fig. 8 · Adjuster
Version without tight-closing function
Version with
tight-closing function OFF
ON
Potentiometer span
Potentiometer span

Connection
4For electropneumatic positioners, con-
nect an ammeter to terminals +11
and –12.
4For pneumatic positioners, connect con-
trol signal input (Input 27) to a com-
pressed air source providing
max. 1.4 bar using a pressure trans-
ducer and pressure gauge.
4Apply compressed air to the supply input
(Supply 9).
4.2 Adjustment
4.2.1Spring-return actuator: valve
CLOSED without supply air
Important!
To ensure that the full closing force can be
effective in the control valve, the actuator
must be completely vented when either the
lower (direct operating direction) or upper
(reverse operating direction) range value of
the reference variable is reached.
As a result, set the input signal to a slightly
higher starting point of 4.5 mA (0.225 bar)
for direct operating direction and to a
slightly lower starting point of 19.5 mA
(0.975 bar) for reverse operating direction.
This applies in particular to controllers and
control systems whose output signal is lim-
ited to 4 to 20 mA.
For electropneumatic positioners with
tight-closing function, the starting point and
upper range value can be set to 4 or
20 mA. The activation/deactivation function
ensures that the valve's closed position is
reached.
Example:
With direct operating direction, the control
valve is expected to travel through an angle
of rotation of 90° (90° cam disc must be in-
stalled) with a reference variable of 4 to
20 mA (0.2 to 1 bar).
The valve opens when the reference variable
increases.
Starting point (zero) 4 mA (0.2 bar)
1. Set input signal to 4.5 mA using the am-
meter or set the pressure adjuster to
0.225 bar.
2. Turn zero adjuster (3) until the closure
member of the valve just starts to move
from its rest position.
3. Switch off the input signal and slowly in-
crease it again. Check whether the clo-
sure member starts to move at 4.5 mA
(0.225 bar).
4. Correct any deviations by turning the
zero adjuster (3).
Note on adjustment with reverse operating
direction
With reverse operating direction (Fig. 5, top
right), set the starting point (valve CLOSED)
to 20 mA (1 bar). The upper range value
(valve OPEN) will then be 4 mA (0.2 bar)
EB 8386 EN 17
Operation – Adjustment

4.2.2Spring-return actuator: valve
OPEN without supply air
Note!
For this fail-safe action, a signal pressure
that is high enough to tightly close the valve
regardless of the plant's upstream pressure
must be applied to the actuator at the upper
range value of the reference variable
(20 mA or 1 bar) for direct operating direc-
tion and at the lower range value of the ref-
erence variable (4 mA or 0.2 bar) for re-
verse operating direction.
The required signal pressure should be
approx. 1 bar above the upper bench range
value of the actuator.
Example:
With direct operating direction, the control
valve is expected to travel through a rota-
tional angle of 90° (90° cam disc must be
installed) with a reference variable of 4 to
20 mA (0.2 to 1 bar).
The valve closes when the reference variable
increases.
Starting point (zero) 20 mA (1 bar)
1. Set input signal to 20 mA using the am-
meter or set the pressure adjuster to
1 bar.
2. Turn zero adjuster (3) until the closure
member of the valve just starts to move
from its initial position.
3. Increase the input signal and slowly re-
duce it again. Check whether the closure
member starts to move at 20 mA
(1 bar).
4. Correct any deviations by turning the
zero adjuster (3).
Note on adjustment with reverse operating
direction
With reverse operating direction (Fig. 5,
bottom right), set the starting point (valve
CLOSED) to 4.5 mA (0.225 bar). The upper
range value (valve OPEN) will then be
20 mA (1 bar)
4.2.3Double-acting actuator: valve
opens counterclockwise and
clockwise
Example:
With direct operating direction, the control
valve is expected to travel through a rota-
tional angle of 90° (90° cam disc must be
installed) with a reference variable of 4 to
20 mA (0.2 to 1 bar).
The valve opens when the reference variable
increases.
Starting point (zero) 4 mA (0.2 bar)
1. Set input signal to 4.5 mA using the am-
meter or set the pressure adjuster to
0.2 bar.
2. Turn zero adjuster (3) until the closure
member of the valve just starts to move
from its rest position.
3. Switch off the input signal and slowly in-
crease it again. Check whether the clo-
sure member starts to move at 4.5 mA
(0.225 bar).
4. Correct any deviations by turning the
zero adjuster (3).
18 EB 8386 EN
Operation – Adjustment

Note on adjustment with reverse operating
direction
With reverse operating direction (Fig. 6,
right), set the starting point (valve CLOSED)
to 19.5 mA (0.975 bar). The upper range
value (valve OPEN) will then be 4 mA
(0.2 bar).
Important!
After adjusting the positioner, close it by re-
mounting the cover. Make sure that the vent
plug in the housing points down when the
control valve is installed in the plant. This
helps prevent condensed water from collect-
ing in the positioner.
EB 8386 EN 19
Operation – Adjustment

5 Adjusting the limit switch
Versions equipped with a limit switch can is-
sue signals to indicate the travel end posi-
tions.
The rotary motion of the closure member is
transmitted to the limit switch over the actua-
tor, positioner shaft and cam disc (1).
The limit switch can be adjusted to issue a
signal when the valve has reached either of
its end positions, i.e. OPEN or CLOSED po-
sition.
Adjusting the switching point:
Adjust the starting point and upper range
value before adjusting the limit switch.
1. Adjust the reference variable so that the
valve moves to the desired end position
where the switching function is to be ac-
tivated.
2. Loosen screw (3) and turn plate (2) so
that the roll (4) of the limit switch (5) trig-
gers the switching contact at the respec-
tive cam (1.1) of the cam disc.
3. Tighten screw (3) and check switching
point again.
20 EB 8386 EN
Adjusting the limit switch
1
1.1
2
3
4
5
41
41
42
43
42
43
A
I
N
Fig. 9 · Limit switch activation using the cam disc
1 Cam disc
1.1 Switching cams
2 Plate
3 Screw
4 Roll
5 Limit switch
Switching contact