Samson 3730-0 - Mounting Versions; Device Overview and Operating Controls

EB 8384-0 EN 13
Design and principle of operation
The position of the valve stem is transmitted
as a linear travel motion over the pick-up le-
ver to the travel sensor (2) and supplied to
an analog PD controller (3). The PD control-
ler compares this actual value to the DC con-
trol signal coming from the control system,
e.g.a4to20mAsignal.
In case of a system deviation, the activation
of the i/p module (6) is changed so that the
actuator of the control valve (1) is pressur-
ized or vented accordingly over the down-
stream booster (7). This causes the valve
plug to move to the position determined by
the set point.
The supply air is supplied to the booster (7)
and the pressure regulator (8). An intermedi-
ateowregulator(9)withxedsettingsis
used to purge the positioner and, at the
same time, guarantees trouble-free operation
of the booster. The output signal pressure
supplied by the booster can be limited by
enabling the DIP switch setting S5.
The volume restriction (10) and the switch S6
are used to optimize the positioner by
adapting it to the actuator size and chang-
ing the gain factor.
Tight-closing function:
After activating the tight-closing function (see
section 7.4), the pneumatic actuator is com-
pletelylledwithairorventedassoonas
the set point falls below or exceeds the corre-
spondingdeactivatingpointof4.5mAor
19.5mA.
In the case of three-way valves, the function
allows the plug move to the end position
with full actuator thrust.
3.1 Mounting versions
TheType3730-0Positionerissuitableforthe
following types of attachment using the cor-
respondingaccessories(seesection3.3):
− DirectattachmenttoType3277Actuator
(seesection5.3):Thepositioneris
mounted on the yoke. The signal pres-
sure is connected to the actuator over a
connection block: internally over a hole
in the valve yoke for "actuator stem ex-
tends" fail-safe action and through an
external signal pressure line for "actuator
stem retracts" fail-safe action.
− Attachment to actuators according to
IEC60534-6(seesection5.4):Theposi-
tioner is mounted to the control valve us-
ing a NAMUR bracket.
− Attachment according to VDI/
VDE3847-1(seesection5.5):Attach-
mentaccordingtoVDI/VDE3847-1/-2
using the corresponding accessories al-
lows the positioner to be replaced quick-
ly while the process is running.
− AttachmenttoType3510Micro-ow
Valve(seesection5.6):Thepositioneris
attached to the valve yoke using a brack-
et.
3.2 Device overview and
operating controls
Seesection6onpage53.