Samson 42-34 Service manual

Self-operated Regulators
Differential Pressure Regulators with
Flow Limitation
Type 42-34 · Type 42-38
Mounting and
Operating Instructions
EB 3013 EN
Edition July 2009
Type 42-38
Type 42-34

Contents Page
1 Design and principle of operation . . . . . . . . . . . . . . . . . . . . . . 4
2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Mounting position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Strainer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Shut-off valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Pressure gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Control line, equalizing tank and needle valve . . . . . . . . . . . . . . . . 8
3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 Start-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Set point adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.1 Adjusting the differential pressure . . . . . . . . . . . . . . . . . . . . . . 10
3.2.2 Adjusting the flow restriction . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.3 Pressure conditions in the plant and regulator . . . . . . . . . . . . . . . . 12
3.3 Decommissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4 Maintenance · Troubleshooting . . . . . . . . . . . . . . . . . . . . . . 18
4.1 Replacing the operating diaphragm . . . . . . . . . . . . . . . . . . . . 19
5 Nameplates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6 Dimensions and weights. . . . . . . . . . . . . . . . . . . . . . . . . . 22
7 Customer service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8 Technical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2EB 3013 EN
Contents
WARNING!
WARNING indicates a hazardous situation
which, if not avoided, could result in death or
serious injury.
NOTICE
NOTICE indicates a property damage
message.
Note: Supplementary explanations, informa-
tion and tips
Definitions of the signal words used in these instructions

EB 3013 EN 3
Safety instructions
General safety instructions
4
The regulators must be installed, started up and serviced by fully trained and
qualified personnel only, observing the accepted industry codes and practi-
ces. Make sure employees or third persons are not exposed to any danger.
4
The regulator complies with the requirements of the European Pressure Equip-
ment Directive 97/23/EC. The declaration of conformity issued for a valve
bearing the CE marking includes information on the applied conformity as-
sessment procedure.
The declaration of conformity can be provided on request.
4
For appropriate operation, make sure that the regulator is only used in appli-
cations where the operating pressure and temperatures do not exceed the
operating values based on the sizing data submitted in the order.
4
Note that the manufacturer does not assume any responsibility for damage
caused by external forces or any other external factors.
4
Any hazards which could be caused in the regulator by the process medium or
operating pressure are to be prevented by means of appropriate measures.
4
Proper shipping and appropriate storage are assumed.
Note: Non-electric valve versions which do not have a valve body lined with an insulating coa-
ting do not have their own potential ignition source according to the ignition risk assessment sti-
pulated in EN 13463-1: 2001, section 5.2, even in the rare incident of an operating fault. The-
refore, they do not fall within the scope of Directive 94/9/EC.
For the connection to equipotential bonding, observe section 6.3 in EN 60097-14: 1977
(VDE 0165, Part 1)

1 Design and principle of
operation
The differential pressure regulators are used
to maintain the differential pressure between
the high-pressure and the low-pressure pipe
at a set point which is either fixed (Type
42-38) or adjustable (Type 42-34). The re-
striction built into the valve body allows for
limitation of the flow rate.
The regulators basically consist of a valve
with a seat, plug and restriction as well as a
closing actuator with an operating dia-
phragm. The valve and actuator are deliv-
ered in separate packaging and need to be
connected on site using the coupling nut (11).
The process medium flows through the valve
in the direction indicated by the arrow. The
free areas of flow released by the orifice (1.4)
and the valve plug (3) determine the flow rate
V
.and the differential pressure Δpplant across
the plant.
Fully balanced valves ensure that the up-
stream and downstream forces acting on the
valve plug are eliminated by a balancing bel-
lows (5) or a balancing diaphragm (5.1). The
principle of operation of the regulators with
valves balanced by a bellows or by a dia-
phragm only differ concerning their pressure
balancing. Valves balanced by a diaphragm
(DN 125 to 250 only) have a balancing dia-
phragm instead of a balancing bellows (5).
The pressure downstream of the orifice (1.4)
acts on the outer surface of the metal bellows
or balancing diaphragm and the down-
stream pressure on the inside of the bellows
or diaphragm. As a result, the forces created
by the upstream and downstream pressures
acting on the valve plug are equally bal-
anced.
The regulators in sizes DN 15 to 100 are
equipped with a connecting piece (10) for the
low-pressure control line between the valve
and the actuator.
In differential pressure control, the high pres-
sure (flow) of the plant is transmitted to the
bottom diaphragm chamber of the actuator
over the high-pressure control line. The pres-
sure downstream of the orifice (1.4) acts on
the top diaphragm chamber over the hollow
plug stem and the connected low-pressure
control line. The differential pressure is con-
verted into a positioning force at the dia-
phragm (13) and is used to change the posi-
tion of the valve plug according to the force of
the set point springs (16). Depending on the
version of the actuator, the set point springs
are installed in the actuator to provide a fixed
set point (Type 42-38), or they are located
outside to allow the set point to be adjusted as
required (Type 42-34).
The restriction (1.1) is used to adjust the flow
limitation.
The force limiter (20) as well as the internal
excess pressure limiter (21) are designed to
protect the seat (2) and plug (3) against over-
load in case of extreme operating conditions.
4EB 3013 EN
Design and principle of operation
Table 1 · Regulator configuration
Controller = Valve + Actuator
Type 42-34 with connecting piece (for DN 15 to 100) Type 2423 Balanced Type 2424 Adjustable set point
Type 42-38 with connecting piece Type 2423 Balanced Type 2428 Fixed set point

EB 3013 EN 5
Design and principle of operation
Fig. 1 · Schematic diagrams of regulator with valve balanced by a bellows
Type 42-34, Type 42-38 · Balanced by a bellows
Type 2423 Valve
balanced by a bellows
1 Valve body
1.1 Restriction (for flow rate
set point adjustment)
1.2 Lock nut
1.3 Cap
1.4 Orifice
2 Seat
3 Plug
4 Plug stem
5 Balancing bellows
7 Spring
8 Venting
(DN 125 and larger)
9 Low-pressure control line
(up to DN 100)
9.1 Low-pressure control line
connection (DN 125 and larger)
10 Connecting piece (up to DN 100)
11 Coupling nut
12 Diaphragm stem
13 Operating diaphragm
14 Actuator housing
15 Screws
16 Set point springs
17 Set point adjustment (screw)
18 Nut
19 Diaphragm plate
20 Force limiter
21 Internal excess pressure limiter
Type 42-34
DN 15 to 250
Type 42-38
DN 15 to 100
Type 2424
Actuator
Type 2428 Actuator

2 Installation
See Figs. 1 and 2
The regulator must be installed in the return
flow pipe as shown in the installation sche-
matic in Fig. 5.
When choosing the place of installation, en-
sure the regulator can be easily accessed af-
ter completion of the plant.
NOTICE
The regulator must be installed free of stress. If
necessary, support the piping near the con-
nections. However, do not attach supports to
the valve or actuator.
6EB 3013 EN
Installation
Fig. 2 · Schematic diagrams of regulator with valve balanced by a diaphragm
Type 42-34 · Balanced by a diaphragm · DN 125 to 250
1 Valve body
1.1 Restriction (for flow rate
set point adjustment)
1.2 Lock nut
1.3 Cap
1.4 Orifice
2 Seat
3 Plug
4 Plug stem
5.1 Balancing diaphragm
11 Coupling nut
12 Diaphragm stem
Type 2424
Actuator
Type 2423 Valve
balanced by a
diaphragm

Note: Install a strainer (e.g. SAMSON
Type 2 N/2 NI) upstream of the regulator to
prevent sealing particles, welding spatter or
other impurities carried along by the process
medium from impairing the proper function-
ing of the valve, especially tight shut-off.
2.1 Mounting position
See Fig. 3 for permissible mounting positions.
Standard installation · Install the valve with-
out the actuator in a horizontal pipeline with
the connection for the actuator facing down-
wards. Make sure the medium flows through
the valve in the direction indicated by the ar-
row. Then connect the actuator (and the con-
necting piece (10) for versions in sizes DN 15
to 100) to the valve using the coupling nut
(11).
NOTICE
Protect the regulator when it is used to control
freezing process media.
On shutting down the plant in areas not free
from frost, depressurize and empty the regu-
lator and remove it from the pipeline.
2.2 Strainer
A strainer installed in the flow pipe (Fig. 5)
prevents foreign matter and dirt particles in
the medium from entering the regulator. The
SAMSON product range includes the
Type 2 N/2 NI Strainer (refer to Data Sheet
T 1010 EN).
Install the strainer upstream of the regulator.
Make sure the direction of medium flow cor-
responds with the direction indicated by the
arrow on the strainer. The filter element must
be suspended downwards. Remember to
leave enough space to remove it.
2.3 Shut-off valve
We recommend installing a hand-operated
shut-off valve (Fig. 5) both upstream of the
strainer and at the outlet of the return flow
pipe to be able to shut down the plant for
cleaning and maintenance, and when the
plant is not used for longer periods of time.
2.4 Pressure gauge
To monitor the pressures in the plant, install a
pressure gauge both upstream and down-
stream of the regulator (Fig. 5).
EB 3013 EN 7
Installation
Fig. 3 · Permissible mounting positions
–Standard mounting position
– all versions –
–All versions
up to max. 80 °C
–Only versions with fixed
plug guide and
up to max. 80 °C

2.5 Control line, equalizing tank
and needle valve
Control lines · After mounting the actuator,
fasten the supplied high-pressure control line
to the regulator (standard: 8 mm pipe diame-
ter) routing it from the bottom diaphragm
chamber to the high-pressure line (flow pipe)
of the plant. Attach the low-pressure control
line to the regulator as shown in Figs. 1 and
2.
The control line to be installed on site for pres-
sure tapping at the pipeline must be at least
three times the nominal size (DN) away from
pipe fittings or instruments that cause flow tur-
bulence (e.g. pipe bends, manifolds, pressure
measuring points or other valves) (see Fig.
4.1). How the lines are routed generally de-
pends on the installation location. Preferably
connect the control line at the side of the main
pipeline (Fig. 4.4).
Do not change the pipe diameter of the main
pipeline so that it is off-center!
Control line kit · A control line kit for tapping
pressure directly at the valve body is avail-
able as an accessory from SAMSON. Refer to
Data Sheet T 3095 EN.
Equalizing tank · An equalizing tank is re-
quired for liquids above 150 °C. Install an
equalizing tank in the control line directly
downstream of the pressure tapping point.
The mounting position of the equalizing tank
is indicated by an adhesive label on the tank
itself as well as by an arrow and the word
"top" stamped onto the top of the tank. Ad-
here to the mounting position and distances
prescribed, otherwise the safe functioning of
the regulator cannot be guaranteed.
8EB 3013 EN
Installation
Fig. 4 · Control line connection
4.1 · Control line connection, depending on how
the pipeline is routed
4.3 · Connection at the top – incorrect
4.4 · Connection at the side – correct
4.2 · Connection at the bottom – incorrect
Correct!
DN = Nominal size
Incorrect!
Incorrect!

Needle valve · If the regulator tends to hunt,
we recommend installing a SAMSON needle
valve in the control line installed on site at the
actuator connection.
Note: Needle valves, equalizing tanks and
compression-type screw fittings can be sup-
plied as required. These accessories are listed
in the Data Sheet T 3095 EN.
3 Operation
See Figs. 1 and 2.
3.1 Start-up
CAUTION!
First start up the regulator after mounting all
the components, e.g. valve, actuator and con-
trol line.
Make sure the control line (and needle valve)
is open and correctly connected before
start-up.
For media temperatures above 150 °C, fill
the equalizing tank with the process medium
(water) before start-up.
Note: On filling the plant, make sure the
orifice (1.4) is open by unscrewing the restric-
tion (1.1) counterclockwise as far as it will go.
4Open all the valves on the consumer side.
Slowly open the shut-off valves starting on
the return flow pipe first. In case of valves
balanced by a bellows in DN 125 or
larger, vent the bellows housing at the
stopper (8) located at the side of the bel-
lows housing.
Rinsing the plant · After filling the plant, first
completely open the consumers. At the regu-
lator, open the restriction counterclockwise as
far as it will go and adjust the maximum dif-
ferential pressure by tensioning the set point
springs to the maximum. Rinse out the pipe-
line at full flow rate for several minutes. Check
the installed strainer (e.g. by measuring the
pressure drop) afterwards. Clean the strainer,
if necessary.
EB 3013 EN 9
Operation
Fig. 5 · Typical installation, Type 42-34/42-38
installed in the return flow pipe
1 Shut-off valve
2 Strainer
3 Differential pressure regulator
4 Equalizing tank (optional)
5 Pressure gauge
6 Needle valve (optional)
7 Motorized valve

NOTICE
When testing the pressure of the plant when
the regulator is already installed, the pressure
must not exceed the nominal pressure of the
valve by 1.5 times nor the maximum permissi-
ble differential pressure in the actuator (final
value of set point range by 1.5 times).
If higher test pressures are used, unscrew the
control lines connected to the actuator and
seal openings at the actuator and control lines
with stoppers.
3.2 Set point adjustment
3.2.1 Adjusting the differential
pressure
Type 42-34 only · Set the required differen-
tial pressure by turning the set point screw
(17) when the plant is almost closed and the
orifice (1.4) is completely open. Then adjust
the value for the flow restriction.
–Turn clockwise = Tensioning the springs→
To increase the set point
–Turn counterclockwise = Relieving the
springs of tension →To reduce the set
point.
How to proceed
4Close motorized valve!
4Unscrew cap (1.3) and undo lock nut
(1.2).
4Turn the restriction (1.1) counterclockwise
as far as it will go (completely opening it)
to deactivate the flow restriction.
4Relieve the set point springs (16) of ten-
sion.
4Open motorized valve slightly (approx.
10 % travel).
4Adjust the differential pressure by
tensioning the set point springs at the set
point screw (17).
3.2.2 Adjusting the flow restriction
Open control and shut-off valves as well as all
the consumers (minimum plant resistance) to
achieve the maximum flow rate.
Close the bypass, if applicable.
Adjust the desired flow limitation by turning
the restriction (1.1), monitoring the flow meter
in the heat meter (see Table 2 · Flow rate set
points for water).
Note: Always start the set point adjustment
based on a closed restriction.
–Turn clockwise to close the restriction →
Reduces the flow rate.
–Turn counterclockwise to open the restric-
tion →Increases the flow rate.
How to proceed
4Completely close the restriction (1.1) to
block the flow rate
4Completely open motorized valve.
4Open restriction (1.1), turning it counter-
clockwise, until the desired flow rate is
reached.
4Initially open the restriction by one turn at
a time, while monitoring the flow rate at
10 EB 3013 EN
Operation · Set point adjustment

the flow meter in the heat meter. Then ad-
just it in small steps until the required flow
rate is constant (generally, ±2 % devia-
tions are acceptable).
4If the required flow rate is not reached, the
differential pressure set point must be in-
creased (see section 3.2.1).
4When the required flow rate is reached,
secure the setting of the restriction (1.1)
with the lock nut (1.2). Screw back on cap
(1.3).
4Lead-seal the set point setting at the set
point adjuster (17) and cap (1.3).
If the pressure drop in the plant is known, the
adjustment diagrams for water in Figs. 7 to
10 (pages 14 to 17) can also be used.
Example:
Adjusting the flow restriction
Determining the adjustment values using the
adjustment diagram in Fig. 7.
AType 42-34 Regulator, DN 25,set point
range 0.25 to 3.5 m³/h, is to be used in a
plant to limit the flow rate to 3.0 m³/h.
The pressure drop across the plant is 0.4 bar.
To which value do you have to adjust the dif-
ferential pressure set point and how many
turns of the set point screw at the restriction
will be required?
Solution:
Follow the sequence from Ato Ein the dia-
gram in Fig. 7.
The pressure drop Δp across the plant serves
as a basis. This value must be known!
Assuming Δp = 0.4 bar, this value corre-
sponds to point A in the diagram. Add the
upper differential pressure across the restric-
tion Δprestriction, assumed to be 0.2 bar.
A horizontal line corresponding to this value
is drawn from Ato the right-hand side, result-
ing in point B. Point B is located on the
straight line associated with the differential
pressure Δp to be adjusted = 0.6 bar (see sec-
tion 3.2.1).
From point B, the line is further drawn verti-
cally downward to the desired limiting curve
for the flow rate (3.0 m³/h), resulting in point
C.
Then, plot the line from point C straight to the
curve associated with the nominal size and
you will reach point D.
The vertical line above point D which meets
point E shows the required number of turns of
the set point screw.
Result: approx. 1.9 times
Based on a closed restriction, the set point
screw must be turned counterclockwise
approx. 1.9 times.
EB 3013 EN 11
Operation · Set point restriction

3.2.3 Pressure conditions in the plant and regulator
When selecting the differential pressure set point or set point range, it is important to observe
that the differential pressure set point Δpset point is calculated from the known pressure drop
across the completely open plant Δpplant and the pressure drop directly at the orifice (restric-
tion) Δprestriction.
Table 2 list the flow rates with the known upper differential pressure value at the restriction for
Type 2423 Valves balanced by a bellows and balanced by a diaphragm.
Δpset point =Δpplant +Δprestriction
The minimum required differential pressure Δpmin between the flow pipe and return flow pipe
is calculated as follows:
Δpmin =Δpset point +
&
V
KVS
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
2
Fig. 6 shows a schematic diagram of the plant’s pressure conditions.
12 EB 3013 EN
Operation
p1p2
Δprestriction
Δpplant
Δpset point
Δpmin
Fig. 6 · Pressure conditions in the plant
Δpmin Minimum differential pressure between
flow and return flow pipes in bar
Δprestriction Pressure drop at restriction in bar
Δpset point Differential pressure set point adjusted
at the regulator in bar
Δpplant Differential pressure (pressure drop) across
a completely open plant in bar
&
VFlow rate adjusted in m³/h
KVS Valve flow coefficient in m³/h
Type 42-34
or
Type 42-38

3.3 Decommissioning
Preferably close the shut-off valves starting
from the flow pipe side and then return flow
pipe side.
EB 3013 EN 13
Operation
Table 2 · Flow rate set points for water in m³/h
Type 2423 Valve balanced by a bellows
Δpset p. Δpplant Δprestr. DN ... 15 20 25 32 40 50 65 80 100 125 150 200 250
0.2
bar 0.1 bar 0.1 bar V
.min 0.05 0.15 0.25 0.4 0.6 0.9 2 3.5 6.5 11 18 20 26
max 1.4 2.1 2.4 4.9 7.7 11.2 19 28 44 56 84 126 154
0.5
bar 0.3 bar 0.2 bar V
.max 2 3 3.5 7 11 16 28 40 63 80 120 180 220
1.0
bar 0.5 bar 0.5 bar V
.max 3 4.5 5.3 9.5 16 24 40 58 90 120 180 260 300
Max. perm. diff. pressure Δp25 bar 20 bar 16 bar 12bar 10 bar
Type 2423 Valve balanced by a diaphragm
Nominal size DN 125 150 200 250
Flow rate set points in m³/h with
Δprestriction = 0.2 bar 11 to 120 18 to 180 20 to 320 26 to 350
Max. perm. diff. pressure Δp12 bar 10 bar

14 EB 3013 EN
Operation
Fig. 7 · Adjustment diagram DN 15 to 25
V max
˚
m
3
/h
A
E
DC
B
321
DN 15
DN 25
0.2 0.4
5.4
4.8
4.2
3.6
3.0
2.4
1.8
1.2
0.6
DN 20
0.1
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.5
Turns of the set point adjuster
Upper diff. pressure Δp
Differential pressure set point
(fixed for Type 42-38, adjustable Type 42-34)
Δp (bar)
Pressure drop across the plant
Adjustment diagram based on water!

EB 3013 EN 15
Operation
0.1
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.5
642
DN 32
DN 50
0.2 0.4
27.0
24.0
21.0
18.0
15.0
12.0
9.0
6.0
3.0
DN 40
V
max
˚
m
3
/h
Fig. 8 · Adjustment diagram DN 32 to 50
Differential pressure set point
(fixed for Type 42-38, adjustable Type 42-34)
Turns of the set point adjuster
Adjustment diagram based on water!
Δp (bar)
Pressure drop across the plant
Upper diff. pressure Δp

16 EB 3013 EN
Operation
Fig. 9 · Adjustment diagram DN 65, DN 80 and DN 100
0.1
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.5
8765 32110 9 4
DN 65
DN 100
0.2 0.4
80
90
72
64
56
48
40
32
24
16
8
DN 80
V
max
˚
m3/h
Turns of the set point adjuster
Adjustment diagram based on water!
Differential pressure set point
(fixed for Type 42-38,
adjustable Type 42-34)
Δp (bar)
Pressure drop across the plant
Upper diff. pressure Δp

EB 3013 EN 17
Operation
Fig. 10 · Adjustment diagram DN 125 and DN 150
0.1
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.5
12 84
DN 125
DN 150
0.2 0.4
200
180
160
140
120
100
80
60
40
20
V
max
˚
m
3
/h
Turns of the set point adjuster
Differential pressure set point
(fixed for Type 42-38, adjustable Type 42-34)
Adjustment diagram based on water!
Δp (bar)
Pressure drop across the plant
Upper diff. pressure Δp

4 Maintenance ·
Troubleshooting
The regulators are maintenance free. Never-
theless, they are subject to natural wear, par-
ticularly at the seat, plug and operating dia-
phragm.
Depending on the operating conditions, the
regulator needs to be checked at regular in-
tervals to avoid possible malfunctions.
CAUTION!
On performing any work on the regulator,
make sure the relevant section of the pipeline
is depressurized and, depending on the pro-
cess medium, drained as well.
For high temperatures, allow the regulator to
cool down to ambient temperature before
starting any work on it.
Interrupt or shut off the control line to avoid
any hazards which could be caused by mov-
ing parts.
As valves are not free of cavities, remember
that residual process medium might still be
contained in the valve.
We recommend to remove the valve from the
pipeline after it has been depressurized and
drained. Make sure that all the plant sections
connected to the control line are also
depressurized. If this is not the case, shut off
the control line.
Details on malfunctions and the recom-
mended action can be found in the Ta-
ble 3 · Troubleshooting.
Proceed as described in section 4.1 if the op-
erating diaphragm is defective.
18 EB 3013 EN
Maintenance · Troubleshooting

4.1 Replacing the operating
diaphragm
See Figs. 1 and 2.
If just the operating diaphragm is defective, it
can be replaced without having to remove the
valve from the pipeline. Relieve the relevant
section of the pipeline of pressure and drain
it. Unscrew the control lines and separate the
actuator from the valve.
EB 3013 EN 19
Maintenance · Troubleshooting
Malfunction Possible reasons Recommended action
Flow rate or
differential
pressure
exceeds the flow
rate V
.or
differential
pressure set
point.
Seat and plug leak Remove valve from pipeline. Clean seat and plug. Replace plug, if necessary. Otherwise send the
regulator to SAMSON for repair.
Operating diaphragm defective Replace diaphragm (see section 4.1) or send the
regulator to SAMSON for repair.
Control line blocked Remove control line and clean it.
Check and clean the screw joint with orifice plate.
Valve too large to regulate the
flow rate or too small to regulate
the differential pressure
Recalculate KVS coefficient and contact SAMSON
for further action.
Flow rate or
differential
pressure does
not reach the
flow rate V
.or
differential
pressure set
point.
Wrong set point range selected Check set point range and contact SAMSON for
further action.
Safety equipment, e.g. pressure
limiter, has been triggered Check plant and unlock safety equipment.
Insufficient pressure drop across
the plant Δp
Compare existing differential pressure across the
plant with the plant’s drag:
Min. differential pressure across the plant
Δpmin =Δprestriction + (VK
.
VS
/)2+Δpplant.
Strainer blocked Drain and clean filter of the strainer.
Direction of flow, valve incorrect-
ly installed Install the valve so that the direction of flow is the same as indicated by the arrow.
Control loop
hunts
Valve too large for control task Recalculate KVS coefficient and contact SAMSON
for further action.
Restriction (or needle valve) is
missing in a control line to dam-
pen pulsation
Install a needle valve in the control line and start
to close it until the control loop becomes stable.
NOTICE Do not completely close needle valve.
Contact SAMSON if the malfunction cannot be remedied using the above table.
Table 3 · Troubleshooting

Type 2428 Actuator
1. Place actuator upside down.
2. Undo screws (15) at the actuator. Pull out
the top cover (+ chamber) together with
diaphragm plate (19) and diaphragm
(13) as well as the diaphragm stem (12).
3. Unscrew nut (18), while holding the dia-
phragm stem stationary using a suitable
tool.
4. Lift off diaphragm plate (19) and pull out
diaphragm (13).
5. Check the diaphragm stem (12) for scor-
ing and replace it with a new one, if nec-
essary.
NOTICE
The stem surface is roller-burnished. Never
regrind the stem!
6. Insert a new diaphragm.
7. Proceed in the reverse order to reassem-
ble the actuator. Secure nut (18) from
turning with suitable adhesive (e.g.
8121-0230 from SAMSON). Use lubri-
cant from SAMSON (8150-0111).
8. Check screw fittings for dirt and clean
them, if necessary.
Start up as described in section 3.1.
Type 2424 Actuator
1. Place actuator upside down.
2. Relieve set point springs (16) completely
of tension by turning the set point adjuster
(17) counterclockwise.
3. Take off set point springs (16) and set
point adjuster (17).
4. Undo screws (15) at the actuator. Re-
move top cover (+ chamber) and take out
inner springs in the + chamber.
5. Lift out diaphragm plate (19) together
with diaphragm (13), diaphragm stem
(12) and excess pressure limiter unit . Re-
move force limiter (20) together with stem
(12).
6. Check stem (12) for scoring and replace
it with a new one, if necessary.
NOTICE
The stem surface is roller-burnished. Never
regrind the stem! When exchanging the dia-
phragm stem, the nipple (guide bushing) in
the actuator cover must also be replaced.
7. Unscrew nuts (18) and pull out dia-
phragm stem.
8. Remove diaphragm (13) and insert a
new diaphragm.
9. Insert diaphragm stem. Tighten nuts (18)
to fix diaphragm, diaphragm plate and
washer into place. Secure nut (18) from
turning with suitable adhesive (e.g.
8121-0230 from SAMSON).
10. Proceed in the reverse order to reassem-
ble the actuator. Use lubricant
(8150-0111).
11.Check screw fittings for dirt and clean
them, if necessary.
Start up as described in section 3.1.
20 EB 3013 EN
Maintenance · Troubleshooting