SIEMENS
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Siemens ST PCS 7 · 2017 (Preliminary edition)
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Function
(continued)
Engineering System
ES Software
Standard Engineering Software
Sequential function chart
Sequential function chart (SFC)
The SFC editor is used for the graphical configuration and com-
missioning of sequential controls for batch production opera-
tions. It possesses convenient editing functions as well as pow-
erful test and commissioning functions. An integrated graphical
formula editor for arithmetic operations, Boolean algebra and
mathematical functions enables calculations within the SFC.
Using a sequential control, basic automation functions usually
created using CFC are controlled and selectively processed by
means of changes in operating mode and status. Depending on
the subsequent use, the sequential controls can be created ei-
ther as a SFC plan or SFC type
SFC plan
The SFC can be used to implement sequence controls which
can be applied once and which access several partial areas of
the production plant. Each SFC plan contains standardized in-
puts and outputs for status information and for control by the
user program or the user. The SFC plan can be positioned and
linked as a block in the CFC. The required CFC block connec-
tions are selected by simple operations and connected to the
steps or transitions of the step chains. A status management
conforming to ISA 88 enables the configuration of up to 8 sepa-
rate sequencers within a single SFC, e.g. for states such as
RUNNING, HOLDING or ABORTING, or for different operating
modes.
SFC type
SFC types are standardized sequential controls which can be
applied repeatedly and which access one partial area of the pro-
duction plant. They can be organized in libraries, and handled
like normal function blocks, i.e. they can be selected from a cat-
alog and positioned, interconnected and configured as an in-
stance in a CFC plan.
Changes to the original automatically result in corresponding
changes in all instances. An SFC type may contain up to
32 sequences. Using the function "Create/update block sym-
bols", a block symbol is automatically positioned and intercon-
nected in the associated process display for all SFC instances
with HMI features.
I&C libraries
The use of library elements plays a major role in minimizing the
amount of engineering required and thus also the project costs.
Two process control libraries are integrated in the standard en-
gineering software of SIMATIC PCS 7:
•
Advanced Process Library (current standard, pre-installed)
•
PCS 7 Standard Library (former standard, can be installed
subsequently if required)
Pre-configured and tested blocks, faceplates and symbols are
organized in these libraries and form the basic elements for the
graphic configuration of automation solutions.
The comprehensive range of blocks can be categorized as fol-
lows:
•
Blocks for mathematical operations, analog and digital logic
•
Interlocking blocks
•
Technological function blocks with integral display, operation
and signaling functions, e.g.:
- Standard Control and Advanced Process Control blocks
- Motor and valve blocks
- Counter blocks
- Dosing block
•
Blocks for the integration of field devices
•
Operator control and monitoring blocks
•
Message and diagnostics blocks
Furthermore, pre-configured process tag types for process
equipment such as pumps, valves, dosing units and controllers
(cascade, spit-range) etc. extend the scope of library elements.
This is advantageous for adaptation of the user software follow-
ing a system upgrade so that multiple versions of a library can
exist side by side.
Examples of OS standard faceplates from the SIMATIC PCS 7 Advanced
Process Library, valves
Advanced Process Library
The Advanced Process Library (APL) based on many years of
experience of project engineers and plant owners takes into
consideration current NAMUR recommendations and PNO
specifications. Proven functions as well as visually attractive
GUIs for a high level of operator convenience facilitate and also
force interaction of operators with the plant.
© Siemens AG 2017