Samson 4765 Service manual

Pneumatic Positioner
Type 4765
Fig. 1 · Type 4765 Positioner
Mounting and
Operating Instructions
EB 8359-1 EN
Edition April 2008

Contents
1 Design and principle of operation. . . . . . . . . . . . . . . . . . . . 6
2 Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Attachment to valves with cast yokes . . . . . . . . . . . . . . . . . . . 8
2.2 Attachment to valves with rod-type yokes . . . . . . . . . . . . . . . . 9
2.3 Cover of the positioner housing . . . . . . . . . . . . . . . . . . . . . 9
3 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Pneumatic connections. . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1.1 Pressure gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1.2 Supply pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4 Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1 Combining positioner and actuator. . . . . . . . . . . . . . . . . . . 11
4.1.1 Determining/reversing the operating direction . . . . . . . . . . . . . 11
4.2 Starting point and input signal (reference variable) . . . . . . . . . . . 12
4.3 Setting the positioner at the valve. . . . . . . . . . . . . . . . . . . . 14
4.3.1 Setting the air delivery (volume restriction Q) and proportional band XP . 14
4.3.2 Setting actuator version “Stem extends” . . . . . . . . . . . . . . . . 15
4.3.3 Setting actuator version “Stem retracts”. . . . . . . . . . . . . . . . . 15
4.4 Exchanging the range spring. . . . . . . . . . . . . . . . . . . . . . 16
5 Converting a pneumatic positioner. . . . . . . . . . . . . . . . . . . 17
6 Accessories, mounting parts and conversion kits . . . . . . . . . . . . 19
7 Dimensions in mm. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2EB 8359-1 EN
Contents

EB 8359-1 EN 3
Safety instructions
General safety instructions
4
The positioner is to be mounted, started up or operated only by trained and
experienced personnel familiar with the product.
According to these Mounting and Operating Instructions, trained personnel
refers to individuals who are able to judge the work they are assigned to
and recognize possible dangers due to their specialized training, their
knowledge and experience as well as their knowledge of the applicable
standards.
4
Any hazards that could be caused by the process medium, the operating
pressure, the signal pressure or by moving parts of the control valve are to
be prevented by means of the appropriate measures.
4
If inadmissible motions or forces are produced in the pneumatic actuator as
a result of the supply pressure, the supply pressure must be restricted by a
suitable supply pressure reducing station.
4
Proper shipping and appropriate storage are assumed.

4EB 8359-1 EN
Versions
Pneumatic Positioner Type 4765- 01x00x 1 xxxx0
Range spring
Range spring 1, travel = 15 mm 1
Range spring 2, travel = 30 mm,
split-range 15 mm 2
Range spring 3, travel = 60 mm,
split-range 30 mm 3
Pneumatic connections
ISO 228/1 G ¼ 1
¼-18 NPT 3
Temperature range
Standard 0
Low temperature down to –50 °C 1
Special version
None 000
For oxygen as the operating medium 001

EB 8359-1 EN 5
Type 4765 Positioner
Travel range 7.5 to 60 mm, with 90 mm lever extension
Reference variable
Split-range 0 to 50 %
and 50 to 100 %
(up to 50 mm travel)
0.2 to 1 bar
0.2 to 0.6 bar and 0.6 to 1 bar
Range spring See table on page 13
Supply air 1.4 to 6 bar (20 to 90 psi)
Output signal pressure pst Max. 0 to 6 bar (0 to 90 psi)
Characteristic Linear · Deviation from terminal-based conformity: £1.5 %
Hysteresis < 0.5 %
Sensitivity < 0.1 %
Operating direction Reversible
Proportional band Xp
(at 1.4 bar supply air) 1 to 3 % with spring 1 or 2 1 to 1.5 % with spring 3
Air consumption in
steady state, Xp= 1 % With 1.4 bar supply air: 0.13
mn³/h With 6 bar supply air: 0.33 mn³/h
Air output capacity At Dp 1.4 bar: 3.0 mn³/h At Dp 6 bar: 8.5 mn³/h
Transit time for Type 3271 Actuator
“Stem extends” 240 cm²: £1.8 s · 350 cm²: £2.5 s · 700 cm²: £10 s
Permissible ambient temperature –20 to +80 °C · Extended temperature range on request
Influences Temperature < 0.02 %/1 K
Supply air < 0.2 %/0.1 bar
Effect when turned by 180°: < 3.5 %
Degree of protection IP 54 · Special version IP 65
Weight Approx. 1.1 kg
Materials Housing: Die-cast aluminum, chromated and plastic-coated
External parts: Stainless steel

1 Design and principle of
operation
The pneumatic positioner is used for the cor-
relation between the valve stem position
(controlled variable x) and the input signal
(reference variable w).
In this case, the input signal issued by a con-
troller is compared to the travel (valve stem
position) of the control valve, and a pneu-
matic signal pressure (output variable y) is
delivered.
The positioner consists of a lever with at-
tached shaft and range spring, diaphragm
and the pneumatic control system compris-
ing nozzle, flapper plate and booster.
In addition, a pressure gauge can optionally
be attached for the instrument input signal
and the positioner output signal.
The positioner operates according to the
force-balance principle. In this way, the
stroke of the actuator stem or the plug stem
(controlled variable x) is transmitted to the
lever (1) and the range spring (6) by the
plate (20). This action twists the range
spring and varies the torsional force.
The input signal (pe) supplied by the up-
stream controller produces a positioning
force on the diaphragm (8). This force is
compared with the force of the range spring
(6). At the same time, the motion (deflection)
of the diaphragm is transmitted to the flap-
per plate (10.2) by the feeler pin (9.1),
causing pressure to be released from the
nozzle (10.1).
Supply air is supplied to the pneumatic
booster (12) and flows through the Xpre-
striction (13) and the nozzle (10.1) until it
hits the flapper plate (10.2).
6EB 8359-1 EN
Design and principle of operation
10.21314
3
1
15
7
8
4 5 6.1 6
Fig. 2 · Positioner with cover removed

Any changes of the input signal peor the
valve stem position cause the pressure up-
stream and downstream of the booster to
change. The air released by the booster (sig-
nal pressure pst) flows to the pneumatic actu-
ator over the volume restriction (14), caus-
ing the plug stem to take on a position cor-
responding to the reference input variable.
The adjustable tuning restrictions (13 and
14) are used to optimize the control loop.
The range spring (6) corresponds to the
rated valve travel and the nominal reference
input span. It can be exchanged.
EB 8359-1 EN 7
Design and principle of operation
1.1 122.1 20
4
6
8
9
9.1
10.2
10
10.1
11
pst
Output 36
Supply 9 pe
Input
27
6
8
9
9.1
12.2
10.1
10
12
14
13
Fig. 3 · Functional diagram
Legend for Figs. 2 and 3
1 Lever for valve travel
1.1 Shaft
2 Pin
2.1 Nut
3 Sleeve
4 Zero adjustment screw
5 Mounting screw
6 Range spring
6.1 Bracket
7 Mounting screw
8 Measuring diaphragm
9 Diaphragm lever
9.1 Feeler pin
10 Nozzle block
10.1 Nozzle
10.2 Flapper
11 Cover plate
12 Booster
13 Xp restriction
14 Volume restriction Q
15 Hole for mounting screw
20 Plate
Arrangement of nozzle/flapper for
reverse operating direction <>
Travel

2 Attachment
To attach the positioner to valves with cast
yokes, mounting parts (order no.
1400-5745) are used. For valves with
rod-type yokes (pillars), the mounting kit (or-
der no. 1400-5745) and additionally the
mounting kit (order no. 1400-5342) are
necessary (see also Table 2 on page 19).
Since the positioner can be attached on ei-
ther side of the valve, the physical location
(left or right attachment) should be deter-
mined before actual attachment (see corre-
sponding Figs. 6 to 9 in section 4.1).
2.1 Attachment to valves with
cast yokes
1. Fasten the plate (20) to the stem connec-
tor clamps (22) of the valve using the
screws (21).
2. Unscrew the positioner cover, and secure
the device to the valve yoke using the
mounting screw (15). The O-ring in-
cluded in the mounting kit is not required
for this device. Make sure that the pin (2)
is routed inside the wire strap and there-
fore clamped against the plate (20).
8EB 8359-1 EN
Attachment
Legend for Figs. 4 and 5
1 Lever
2 Pin
2.1 Nut
15 Mounting screw
20 Plate
21 Screw
22 Stem connector
23 Plug stem
24 Travel indicator
26 Clamping plate
27 Valve rod (pillar)
28 Support
15 1 20 2 2.1 21 22 23
Fig. 4 · Attachment to valves with cast yokes (NAMUR rib)

2.2 Attachment to valves with
rod-type yokes
1. Screw the plate (20), off-centered, to the
travel indicator (24) of the plug stem (23)
using the screws (21).
2. Place both the support (28) and the
clamping plate (26) on the rod (27) and
lightly fasten. Move the support until both
the center of the plate (20) and the sup-
port (28) are aligned at half the valve
travel.
3. Screw tight the support and clamping
plate.
4. Mount the positioner to the support using
the mounting screw (15). Make sure that
the pin (2) is led inside the wire strap
and therefore clamped against the plate
(20).
2.3 Cover of the positioner
housing
After attaching the positioner, make sure
that the vent plug on the cover of the
positioner housing points downwards after
the valve has been installed.
EB 8359-1 EN 9
Attachment
151282726202.12 212423
Fig. 5 · Attachment to valves with rod-type yokes

3 Connections
3.1 Pneumatic connections
The pneumatic connections are designed as
tapped holes with ¼ NPT or ISO 2228/1-
G ¼ thread. The conventional male connec-
tions for metal and copper pipes (or plastic
hoses) can be used.
Note:
The supply air must be dry and free of any
oil and dust. Always observe the mainte-
nance instructions applicable to the con-
nected pressure reducing stations. Blow out
air lines thoroughly before connecting them.
3.1.1Pressure gauges
We recommend attaching pressure gauges
for the supply air and signal pressure in or-
der to monitor the positioner. The parts are
listed as accessories in Table 2 on page 19.
3.1.2Supply pressure
The required supply pressure is determined
by the bench range and the operating direc-
tion (fail-safe action) of the actuator.
The bench range is written on the nameplate
as spring range or signal pressure range
depending on the type of actuator. FA (actu-
ator stem extends) or FE (actuator stem re-
tracts) or a symbol indicates the operating
direction.
Actuator stem extends (FA)
Fail-safe position Valve CLOSED
(for globe and angle valves)
Required supply pressure =
Upper bench range value + 0.2 bar,
minimum 1.4 bar.
Actuator stem retracts (FE)
Fail-safe position Valve OPEN
(for globe and angle valves)
The required supply pressure for a
tight-closing valve is roughly estimated from
the maximum signal pressure pstmax:
pstmax = F + dp
A
2
4
××
×
pD [bar]
d = Seat diameter [cm]
Dp = Differential pressure across valve [bar]
A = Actuator diaphragm area [cm²]
F = Upper bench range of actuator [bar]
In the absence of such specifications, pro-
ceed as follows:
Required supply pressure =
Upper bench range value + 1 bar
The signal pressure (output) is routed to the
top or bottom diaphragm case of the actua-
tor as shown in Figs. 6 to 9.
10 EB 8359-1 EN
Connections

4 Operation
4.1 Combining positioner and
actuator
The arrangement of the actuator, input sig-
nal, operating direction and mounting loca-
tion is schematically represented in Figs. 6
to 9.
Each subsequent change such as reversal of
the operating direction or field reversing the
actuator version from direct "Actuator stem
extends" to reverse "Actuator stem retracts"
or vice versa also involves changing the
mounting location of the positioner.
4.1.1Determining/reversing the
operating direction
When the input signal (reference variable w)
increases, the signal pressure pst can either
be increasing (direct operating direction <<)
or decreasing (reverse operating direction
<>).
The same applies to a decreasing input sig-
nal; the output pressure either decreases (di-
rect operating direction <<) or increases (re-
verse operating direction <>).
Symbols are located on the flapper plate
(10.2) which identify the respective operat-
ing directions (direct << or reverse <>).
EB 8359-1 EN 11
Operation
Actuator: Stem extends (FA)
Actuator: Stem retracts (FE)
1
20
pst
w
Fig. 6 · Operating direction << Left attachment
1
20
pst
w
Fig. 7 · Operating direction <> Right attachment
pst
w
Fig. 8 · Operating direction << Right attachment
pst
w
Fig. 9 · Operating direction <> Left attachment
Lever (1) on top of plate (20) Plate (20) on top of lever (1)

If the operating direction of the required
function does not match the symbol or if the
operating direction is to be changed,
proceed as follows:
1. Remove both screws of the cover plate,
and lift off the nozzle block (10) along
with the cover plate.
2. Reinstall the nozzle block turned 180° to-
gether with the cover plate and fasten.
Make sure that the nozzle block and flapper
are correctly located above or below the
feeler pin (9.1) as shown in Fig. 10.
If the operating direction is to be changed
after the initially determined arrangement of
positioner and actuator, note that the
positioner must be mounted in a different lo-
cation and the nozzle block must be turned.
Always consider the location of the lever (1)
and the plate (20), "lever on top of plate" or
reversed "plate on top of lever" as shown in
Figs. 6 to 9.
4.2 Starting point and input
signal (reference variable)
The attached lever and the installed range
spring of the positioner correspond to the
rated valve travel and the reference variable
(input signal) according to Table 1.
In standard operating mode, the reference
input span is 100 % = 0.8 bar. A narrower
span of, for example 50 % = 0.4 bar, is
only required in split-range operation.
This span can be changed by subsequently
replacing the range spring (see section 4.4).
On adjusting the positioner, the travel must
be adjusted to the reference variable and
vice versa.
With a reference input span from 0.2 to
1 bar, the valve must have passed full travel
from 0 to 100 % where the starting point
then begins at 0.2 bar and the span ends at
1 bar.
12 EB 8359-1 EN
Operation
Fig. 10 · Position of nozzle block, cover plate removed
Nozzle block
Feeler pin
Cover plate
Range spring
Marking Flapper
Operating direction increasing/increasing (direct <<)
feeler pin on top of flapper Operating direction increasing/decreasing (reverse <>) flapper on top of feeler pin

In split-range operation, the controller output
signal is split to operate two control valves in
such a way that each valve moves through
its entire travel at half the input signal each
(e.g. first control valve is set from 0.2 to
0.6 bar, the second valve from 0.6 to
1 bar). To avoid overlapping, consider a
dead band (hysteresis) of +/–0.05 bar ac-
cording to Fig. 12.
The starting point (zero) is adjusted using
the zero adjustment screw (4). The reference
input span and the final value is adjusted by
the pin (2).
EB 8359-1 EN 13
Operation
Fig. 11 · Standard operation
Reference variable
Input signal
Closed
Travel
Open
Fig. 12 · Split-range operation, two valves
operating in opposite directions
Open
Travel
Closed Valve 2 Valve 1
Dead band
Table 1
Rated travel [mm] Min./max. travel [mm] Reference variable (input signal) Range spring
Standard travels for SAMSON valves with lever I (40 to 127 mm long)
15 7.5 to 15 100 %
50 % 1 2
30 14 to 32 100 %
50 % 2 3
60 30 to 70 100 % 3
Additional travel ranges with lever I and lever extension (40 to 200 mm long)
20 7.5 to 26 100 %
50 % 1 2
40 14 to 50 100 %
50 % 2 3
> 60 30 to 90 100 % 3

4.3 Setting the positioner at the
valve
4Connect the control signal input to a
compressed air source of max. 1.5 bar
using a remote adjuster and a pressure
gauge.
4Connect the supply air to the supply in-
put (supply 9).
4.3.1Setting the air delivery
(volume restriction Q) and
proportional band XP
1. Close the volume restriction (14) as far
as the required speed of response al-
lows.
You can check the speed of response by
pressing the range spring (6) as far as it
will go.
2. Set the input signal to approximately
50 % of its range. Then, turn the zero
adjustment screw (4) until the valve is at
approximately 50 % valve travel.
On setting the Xp restriction, observe the re-
lationship with the supply air pressure as in-
dicated in Fig. 13. The preset value of Xp
should read approximately 3 %.
3. Check the plug stem's tendency to oscil-
lation by pressing the range spring (6)
briefly as far as it will go.
Xp should be set to a value as small as
possible, however, without causing no-
ticeable overshoot.
Note:
Always determine the Xp setting prior to ad-
justing the starting point. Subsequent modifi-
cation displaces the zero point!
The zero can also be shifted by altering the
adjusted supply air pressure.
If necessary, check the zero adjustment un-
der operating conditions of the plant and,
readjust, if need be.
14 EB 8359-1 EN
Operation
Zul. Supply Alim.
Xp
[%]
5
4
3
2
1
0
6 bar 3 bar 1.4 bar
90˚ 0˚180˚270˚
270˚90˚
180˚
0˚
360˚
Fig. 13 · Setting the XP restriction

4.3.2Setting actuator version
“Stem extends”
Note:
To ensure that the total closing force of the
actuator can be effective in the control valve,
the diaphragm chamber must be completely
vented at the lower range value of the refer-
ence variable (operating direction <<) and
at the upper range value (operating direc-
tion <>).
When the operating direction is direct <<,
the input signal is therefore set to a slightly
higher starting point of 0.23 bar and when
the operating direction is reverse <>, to a
slightly lower starting point of 0.97 bar.
Starting point (zero) e.g. 0.23 bar
1. Turn the zero adjustment screw (4) until
the plug stem just begins to move from
the resting position (observe plug stem
with travel indicator).
2. Reduce the input signal on the ammeter
and increase again slowly. Check
whether the plug stem starts moving at a
starting point of 0.23 bar and, if neces-
sary, correct.
Upper range value (span) e.g. 1 bar
3. After the starting point has been ad-
justed, increase the input signal. The plug
stem must be motionless at an upper
range value of exactly 1 bar and there-
fore already moved through 100 % of its
travel range (watch the travel indicator at
the valve!). If the upper range value is in-
correct, the pin (2) must be moved as fol-
lows in order to correct the signal:
4. Move pin to:
End of lever –> to increase travel
Pivot –> to reduce travel
If the span is corrected, the zero must be
recalibrated. Afterwards, the span must also
be checked.
Keep repeating the procedure until the two
values match.
If a pressure gauge is available, check
whether the actuator is completely vented at
an instrument input signal of exactly 0.2 bar
(operating direction <<), i.e. 1.0 bar (oper-
ating direction <>).
4.3.3Setting actuator version
“Stem retracts”
Note:
For actuators with "Actuator stem retracts",
a signal pressure which is high enough to
tightly close the valve - even with existing
upstream plant pressure - must be applied to
the diaphragm chamber. For direct operat-
ing direction <<, the upper end value of the
reference variable is 1 bar. For reverse op-
erating direction <>, the lower end value of
the reference variable is 0.2 bar.
The required signal pressure is indicated on
the adhesive label on the positioner or is
roughly estimated as in section 3.1.2.
Starting point (zero) e.g. 1 bar
1. Adjust the instrument input signal to
1 bar.
Turn zero adjustment screw (4) until the
control valve just begins to move from
the resting position.
EB 8359-1 EN 15
Operation

2. Increase the instrument input signal and
gradually decrease again to 1 bar,
checking whether the control valve be-
gins to move at exactly 1 bar.
Correct the deviation using the zero ad-
justment screw (4). Turn it counterclock-
wise to move the control valve earlier
from its final position and clockwise to
move it later.
Upper range value (span) e.g. 1 bar
3. Once the starting point has been ad-
justed, set the instrument input signal to
0.2 bar. When the final value reaches
exactly 0.2 bar, the plug stem must be
motionless and therefore have passed
100 % travel (watch travel indicator).
4. If the final value does not match, slide the
pin (2) to correct. Set to 1 bar again and
turn the zero adjustment screw (4), until
the pressure gauge indicates the re-
quired signal pressure (see also section
3.1.2).
In case there is no pressure gauge avail-
able, set the starting point to 0.97 bar
instead.
4.4 Exchanging the range spring
If the range is to be altered or changed to
split-range operation, replace the range
spring as shown in Fig. 3 as follows:
1. Remove screw (7) on the range spring.
Pull out hexagon socket screw (5) and
the lever together with shaft.
2. Exchange range spring. Slide lever with
shaft through sleeve (3), positioner hous-
ing and bracket (6.1).
3. Secure range spring with the screw (7).
4. Move bracket and shaft until the screw
(5) sits on the flattened part of the shaft.
Tighten screw (5). Allow for a play from
0.05 to 0.15 mm between the lever (1)
and the sleeve (3) as well as between the
range spring (6) and the positioner
housing.
16 EB 8359-1 EN
Operation

5 Converting a pneumatic
positioner
The pneumatic positioner can be converted
to a Type 4763 Electropneumatic Positioner
using a corresponding conversion kit.
A conversion kit is required for each
Type 6109 or Type 6112 i/p converter
module (see Table 3), which contains the
printed circuit boards, the cable gland and
the mounting screws.
For the Type 4763 Electropneumatic
Positioner, refer to the Mounting and Oper-
ating Instructions EB 8359-2 EN.
1. Undo the connecting plate (6) and re-
move along with sealing element (7). Pull
off the hose (5).
2. Twist the connecting nipple (4) from the
housing.
Type 6109 i/p converter module:
3. Push the i/p module over the plug con-
nection onto the printed circuit board.
4. Insert the sealing element (7), on the bot-
tom, in the opening of the printed circuit
board so that the restriction and the filter
(8) are situated on the right side above
the innermost of the two housing holes
(supply air) when the module (dashed
line in Fig. 14) is installed.
5. Secure the module and the printed circuit
board in the housing (two screws for the
module, one screw for the printed circuit
board). Subsequently assemble the cable
gland (1) along with the sealing ring.
Type 6112 i/p converter module:
3. Place the i/p module on the plug of the
printed circuit board, and tighten the
side terminal screws.
4. Check whether the hose seals (10, 11)
are properly inserted on the bottom side.
When the module (dashed line in
Fig. 14) is installed, the seal with throttle
and sieve must be situated on the right
side above the innermost of the two
housing holes (supply air).
5. Secure the module and the printed circuit
board in the housing (two screws for the
module, one screw for the printed circuit
board): Subsequently assemble the cable
gland (1) along with the sealing ring.
EB 8359-1 EN 17
Converting a pneumatic positioner

18 EB 8359-1 EN
Converting a pneumatic positioner
Fig. 14 · Converting the positioner
1 Cable gland
2 Printed circuit board
3 i/p module
4 Connecting nipple
5 Hose
6 Connecting plate
7 Sealing element

6 Accessories, mounting parts and conversion kits
EB 8359-1 EN 19
Accessories, mounting parts and conversion kits
Table 2
Accessories – Mounting parts Order number
Range spring 1
Range spring 2
Range spring 3
Lever I
Lever extension
Pressure gauge attachment
Pressure gauge attachment, free of copper
1190-0736
1190-0737
1190-0738
1690-6469
1400-6716
1400-6950
1400-6951
Mounting kit for valves with cast yoke acc. to NAMUR
Mounting kit for valves with rod-type yokes acc. to NAMUR for 18 to 35 mm
rod diameters
1400-5745
1400-5745 and
1400-5342
Spare parts assortment with seals and diaphragms 1400-6792
Spare parts assortment with seals, diaphragms and pneumatic components
(for model index .02 or higher) 1042-0040
Conversion kit to upgrade to degree of protection IP 65
(refer to SAMSOMATIC print Z 900-7 for more details) 1790-7408
Table 3
Required input signal
(reference variable)
Required i/p module
(order no.)
Additional conversion kit
(index .03or higher)
Order no.
4 to 20 mA
0 to 20 mA
1 to 5 mA
6109-0010
6112-002110
6112-003110
1400-6797
1400-6798
1400-6798

7 Dimensions in mm
20 EB 8359-1 EN
Dimensions in mm
Useable lever length I: 40 to 127 mm (with 40 to 200 mm lever extension)
Pneum. connection: ISO-228/1-G ¼ or ¼-18 NPT
157
Tapped hole G 18
for G threaded connection or
18NPT for NPT threaded connection