Design and Implementation of HC900 Control System - HC900 Safety configurations
48 HC900 Process & Safety Controller Safety Manual Revision 1.9
01/14
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Figure 15 – Series Relay for Analog Outputs
HC900 Safety configurations
HC900 configurations provide critical system monitoring blocks which the user may optionally use for
control and monitoring of the modular system in the configuration. Safety configurations should make use
of these blocks such as the startup control function outline in Figure 17. These blocks do not count against
the users function block count and are always operating in the background; however if the blocks are added
to a commissioned system for additional reporting or control a COLD START will be required.
The HC900 configuration is done in Designer using “Process” and “Safety” worksheets. The process
configuration is used for non-safety process control configurations (i.e. PID loops) and is fully accessible in
all modes of operation. The safety configuration is similar to the process configuration except it’s made
with a restricted set of function blocks on a safety worksheet and restricts changes when operating in the
RUN mode. Safety functions must be protected from outside influence to assure proper operation. The
HC900 controller ONLY operates as a safety application when it is running in the RUN MODE (also
known as RUN-LOCK MODE). Dataflow into the safety worksheet is only permitted from IO modules
operating in the RUN (SAFETY) MODE. Normal process type operations including communications
within the safety worksheet are only permitted during RUN/PROGRAM, PROGRAM or OFFLINE modes
of operation. The following data flow diagram for safety worksheets including data to/from other devices
is illustrated in the following diagram.
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