5
external control system, interprets the signal as
an intended output shaft position, then runs the
motor until the output shaft matches that position.
The DCM-2 also contains most conguration
information, maintains statistics related to actuator
performance, and creates signals to send back to
the external control system.
A DCM-2 model is available that communicates
with Foundation Fieldbus (FF) networks, and a
model is available that communicates with HART
Communication Foundation (HART) networks. The
FF models communicate using digital signaling.
The HART models can receive and send analog
and/or digital signals. The HART models include
a local conguration interface for analog control
systems that do not use the HART protocol. All
models have an “RS 232” serial interface that can
be used for conguration and diagnostics.
Refer to DCM-2 OVERVIEW (page 18).
CONTROL END
The control end provides electronic and electro-
mechanical sensing of the output shaft position.
Electronic sensing is provided by the CPS-2
Contactless Position Sensor, which provides a
signal to the DCM-2. The DCM-2 uses this signal
to determine the actual position of the output shaft.
Electro-mechanical sensing is provided by sets of
cam-operated switches. Two of these switches
act as over-travel limit switches to ensure the
motor cannot drive the output shaft beyond the
desired range. Other switches are available to the
external control system for indication and interlock
functions. Refer to OUTPUT SHAFT POSITION
SENSING (page 36) for information related to the
DCM-2 interaction with the CPS-2 signal. Refer
to CONTROL END OVERVIEW (page 34) for
information on setting up the control end.
SERIAL NUMBER
The Beck serial number is important in several
respects. The serial number begins with Group
number, which is followed by the model number.
These numbers allow a person to determine the
specications of the actuator. The model number
is followed by the sales order number. Using the
sales order as an index, Beck maintains complete
build information for every actuator built.
The serial number is stamped into the
nameplate, which is xed to the outside of the
actuator housing.
The serial number is also useful to the DCM-2.
Using the serial number, the DCM-2 can determine
the Group and model numbers, and from these can
determine what product-specic congurations are
available.
The format of the serial number is:
GG MMM-SSSSSS-LL-XX
e.g., 14-109-113065-01-02
where GG is the Group number
MMM is the model number
SSSSSS is the sales order number
LL is the sales order line item number
XX is the sales order sequence number
When entering the serial number into the
DCM-2, use the dashes as shown. The Group and
model numbers are mandatory entries because
the DCM-2 identies model-specic conguration
information from these elds. The sales order
information is useful for documentation, but is not
needed by the DCM-2. For information on how the
DCM-2 uses the serial number information, refer to
OUTPUT SHAFT POSITION SENSING (page 28).
TIGHT-SEATER™
The Beck Tight-Seater™ assembly is a pre-
loaded coupling that is installed between the drive
output shaft and the valve stem. It produces a
controlled positive pressure against the valve
seat, independent of drive thrust.
The Tight-Seater™ consists of four parts: A
housing attached to the output shaft, linear thrust
discs contained in the housing, a anged coupling
attached to the valve stem, and a threaded ring to
contain the anged coupling in the housing and to
allow adjustment of the pre-load on linear thrust
discs.
The factory pre-load, by a threaded ring,
ensures that no relative motion occurs between the
anged coupling and housing during normal valve
operation until the pre-load thrust is exceeded in
the seated plug position of the valve.
When the seated plug position of the valve is
reached, the anged coupling on the valve stem
is stationary, and the output shaft exceeds the
pre-load pressure of the Tight-Seater™. When
the pre-loaded pressure is exceeded, the housing
will compress the linear thrust discs, maintaining
a controlled pressure on the valve seat, with the
shaft stationary.
Tight-Seater™
Cross-Section
Tight-Seater™