Samson 3277, 3277-5 Mounting And Operating Instructions
Pneumatic Actuator
Type 3277
Mounting and
Operating Instructions
EB 8311 EN
Edition July 2006
Fig. 1 · Type 3277 Pneumatic Actuator
Fig. 2 · Type 3277-5 Pneumatic Actuator
1 Design and principle of
operation
The Type 3277 Pneumatic Actuators with an
effective diaphragm area of 240, 350 or
700 cm² are primarily mounted to control
valves from the Series 240, 250 and 280.
Type 3277-5 with a die-cast aluminum case
and an effective diaphragm area of
120 cm², is mounted to Type 3510 and Se
-
ries 240 Valves.
The actuator is made up of two diaphragm
cases, a rolling diaphragm and springs. The
lower diaphragm case is permanently fixed
to the yoke which allows the direct attachment of either a pneumatic or electropneumatic positioner or a limit switch.
Actuators with manual override (Fig. 5) additionally have a handwheel mounted on the
diaphragm case. The handwheel moves the
actuator stem over a spindle after the lock
-
ing mechanism (lock nut) has been disen
gaged. In addition, the actuator can be
equipped in a special version with a me
-
chanically adjustable travel stop.
The signal pressure creates a force at the di
aphragm surface which is balanced by the
springs (6) arranged in the actuator. The
number of springs and their compression
determine the bench range (signal pressure
range) while taking the rated travel into ac
count which is directly proportional to the
signal pressure. A maximum of 30 springs
can be installed, partly fitted inside one an
other.
The stem connector (16) connects the actuator stem (2) with the plug stem of the control
valve.
2 EB 8311 EN
Design and principle of operation
4
Assembly, start-up and operation of the device may only be performed by
trained and experienced personnel familiar with this product.
According to these mounting and operating instructions, trained personnel is
referred to individuals who are able to judge the work they are assigned to
and recognize possible hazards due to their specialized training, their
knowledge and experience as well as their knowledge of the relevant
standards.
4
Any hazards which could be caused by the signal pressure and moving
parts of the actuator are to be prevented by means of appropriate
measures.
4
Proper shipping and appropriate storage are assumed.
Fail-safe action
When the signal pressure fails, the fail-safe
action of the actuator depends on whether
the springs are installed in the top or bottom
diaphragm chamber.
Actuator stem extends
When the signal pressure is reduced or the
air supply fails, the springs move the actua
tor stem downwards and close the valve.
The valve opens when the signal pressure is
increased enough to overcome the force ex
-
erted by the springs.
Actuator stem retracts
When the signal pressure is reduced or the
air supply fails, the springs move the actua
tor stem upwards and open the valve. The
valve closes when the signal pressure is in
-
creased enough to overcome the force ex
-
erted by the springs.
EB 8311 EN 3
Design and principle of operation
Fig. 3 · Sectional diagram of Type 3277 with 240, 350 and 700 cm² effective diaphragm area
5
1.1
1
6
6.1
3
8
12
12.1
11
10
12.1
13
2
15
16
4
7
a
9
1 Nut
1.1 Nut
2 Actuator stem
3 Vent plug
4 Loading pressure
connection
5 Top diaphragm
case
6 Springs
7 Diaphragm plate
8 Diaphragm
9 Nuts and bolts
10 Yoke with bottom
diaphragm case
11 Loading pressure
connection
12 Stem seal
12.1Dry bearing
13 Wiper
15 Ring nut
16 Stem connector
Dimension a
350 cm² = 209 mm
700 cm² = 246 mm
Loading pressure connection
Type 3277 Actuator (Fig. 3)
In the Type 3277 Actuator with fail-safe ac
tion "Actuator stem extends", the loading
pressure is connected to the loading pres
sure connection (11) at the side of the yoke
to fill the bottom diaphragm chamber which
causes the actuator stem (2) to move up
-
wards. In an actuator with the fail-safe ac
tion "Actuator stem retracts", the loading
pressure is connected the loading pressure
connection (4) to fill the top diaphragm
chamber which causes the actuator stem to
move downwards.
Type 3277-5 Actuator (Fig. 4)
In the Type 3277-5 Actuator, the loading
pressure is connected to a borehole either at
the left or right of the yoke. A switchover
plate (14, accessories) directs the air to one
of the diaphragm chambers, depending on
the fail-safe action of the actuator ("Actuator
stem extends" or "Actuator stem retracts"),
which is determined by how the plate is
aligned with the mark (14.4).
4
Turn the switchover plate to align the
symbol (14.3) for the appropriate
fail-safe action with the mark (14.4). See
Fig. 4, bottom left. The operating direc
-
tion (>>) or (<>) of the positioner deter
-
mines whether the left or right attach
-
ment is to be used.
A connecting plate (accessories) is required
instead of the switchover plate if the actua
-
tor is operated without a positioner. The
loading pressure is directly connected to the
loading pressure connection (14.8) of the
connecting plate to fill the diaphragm cham
-
ber.
4
Turn the connecting plate to align the
symbol (14.3) for the appropriate
fail-safe action "Actuator stem extends"
or "Actuator stem retracts" with the mark
(14.4). See Fig. 4, bottom right.
4
Make sure that the flat gasket of the con
-
necting plate is correctly inserted.
4
The connecting plate has both NPT and
G threaded bores. Seal the bore not re
quired with a rubber gasket and square
plug.
Accessories: The switchover plate or con
necting plate must be ordered separately.
Please note that actuators with modification
index 01 e.g. 3277-531xxx20.01 (old =
.00) are equipped with new plates.
Old and new plates are not interchangeable.
In-
dex
Order no.
Switch-
over plate
New
Old
01001400-6822
1400-6819
Con-
necting
plate
New
Old: G thread
Old NPT thread
01
00
00
1400-6823
1400-6820
1400-6821
Note! The pneumatic actuators are designed
for a maximum supply pressure of 6 bar.
To prevent the actuator from being dam
aged, do not let the supply pressure exceed
the upper spring range value by more than
3 bar when the actuator is used for
flow-switching service (on-off valve) with the
fail-safe position "Actuator stem retracts".
Label actuators that have a reduced supply
pressure with a sticker "max. supply pres
-
sure limited to … bar".
Note! Refer to the operating instructions of
the corresponding valve on how to mount
and remove the actuator from the valve.
4 EB 8311 EN
Design and principle of operation
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