Safety Considerations Guide for Triconex General ... - ICEWeb

22 Chapter 2 Application Guidelines
• The receiving program must monitor the status of the TR_URCV and
TR_PORT_STATUS functions to determine if there is a network problem that requires
operator intervention.
For information on data transfer time and examples of how to use Peer-to-Peer functions to
transfer safety-critical data, see Appendix A, Triconex Peer-to-Peer Communication.
SIL2 Guidelines
For SIL2 applications, these guidelines should be followed:
• If non-approved modules are used, the inputs and outputs should be checked to verify
that they do not affect safety-critical functions of the controller.
• Two modes control write operations from external hosts:
— Remote Mode: When true, external hosts, such as Modbus master, DCS, etc., can
write to aliased variables in the controller. When false, writes are prohibited.
— Program Mode: When true, TriStation 1131 software can make changes including
operations that modify the behavior of the currently running application. For
example, Download All, Download Change, declaring variables,
enabling/disabling variables, changing values of variables and scan time, etc.
Remote mode and program mode are independent of each other. In safety applications,
operation in these modes is not recommended. In other words, write operations to the
controller from external hosts should be prohibited. If remote mode or program mode
becomes true, the application should include the following safeguards:
— When remote mode is true, the application should turn on an alarm. For example, if
using the SYS_SHUTDOWN function block, the ALARM_REMOTE_ACCESS
output could be used. Verify that aliased variables adhere to the guidelines
described in Maintenance Overrides on page 24.
— When program mode is true, the application should turn on an alarm. For example,
if using the SYS_SHUTDOWN function block, the
ALARM_PROGRAMMING_PERMITTED output could be used.
• Wiring and grounding procedures outlined in the Planning and Installation Guide for
Triconex General Purpose v2 Systems should be followed.
• Maintenance instructions outlined in the Planning and Installation Guide for Triconex
General Purpose v2 Systems should be followed.
• The operating time restrictions in this table should be followed.
Operating Mode
SIL 1
Operating Time
SIL 2
Operating Time
TMR Mode Continuous Continuous
Dual Mode Continuous Continuous
Single Mode Continuous Industry accepted MTTR
Safety Considerations Guide for Triconex General Purpose v2 Systems