Inputs - ABB Triguard SC300E Safety Manual

Note that during the change-over period the outputs of a HR partnership could be frozen for up
to 2 seconds.
The frequency of a main to standby, auto hot repair cycle for a HR partnership is calculated by:
number of HR partners + 1 * swap time (hours)
This period should not exceed the admissible repair times, see Appendix 2.
If the process time constraint is less than 30 seconds, or only single sensors are provided for
process measurement, then all input modules associated with safety loops must also be
configured with adjacent hot repair partner slots.
3.3.1

Inputs

Safety inputs to a Safety System will be either Normally Energised Digital Inputs (De-Energise
to Trip) or Analogue Inputs.
3.3.1.1 Digital Inputs
De-energise to trip inputs (usually termed fail-safe) will be used for all safety digital inputs. The
number of safety monitoring signals required for each safety parameter will depend primarily on
the safety integrity level (safety classification) required to be achieved, the 100% proof test cycle
required and the level of diagnostics available from the field device.
All safety digital inputs will be wired to a Digital Input Termination Card. Where the safety
integrity level requires that more than one field sensor monitoring a safety parameter, each of
these sensors should be, where practical, wired to separate Termination Cards. The Simplex
part of the termination card (eg fuses) must be considered for reliability analysis as part of the
field loop.
The Termination Card will be connected to the Triguard SC300E Input Module via a standard
system cable which connects to the socket on the appropriate Hot Repair Adapter Card (THR)
or chassis slot.
Through the hot repair adapter card, where required, and the chassis backplane connector the
input signal is connected to the configured digital input slot position where a Digital Input Module
would be located.
All the chassis slots and, where required, its hot repair partner slots configured for the Digital
Input Module must also have the coding blocks fitted and configured for this type of module as
specified in the Module and Chassis Users Manuals.
Where the safety integrity level requires that separate sensors are used to monitor the same
safety parameters they should be configured to separate Digital Input Modules where practical.
3.3.1.2 Analogue Inputs
Analogue transmitters are used to monitor safety parameters and inherently provide an
increased level of diagnostics with respect to a simple fail-safe digital input. Analogue signals
always provide values within a set operating range. For safety related transmitters this should be
4-20mA or 1-5 volts allowing for fault indication below say 3mA (0.75V) and 20mA (5V). If over-
range detection is required a 0-10V input module must be used. All monitored faults from the
analogue signals must be used by the application software to produce fail-safe results (eg failed
transmitter demands a shutdown).
The number of analogue transmitters used to monitor a safety parameter will be dependent on
the system integrity level (safety classification) requirement of the loop, the 100% proof test
cycle of the loop and the level of diagnostics available from the transmitter.
Issue 5 - September 2006
Page 13 of 65