85
Reference Manual
00809-0200-4728, Rev RA
Section 7: Safety Instrumented Systems (SIS) Certification
April 2015
Safety Instrumented Systems (SIS) Certification
7.5
Configuration
Use any HART capable configuration tool or the optional Local Operator Interface (LOI) to
communicate with and verify the initial configuration or any configuration changes made to the
644 prior to operating in Safety Mode. All configuration methods outlined in
are the
same for the safety certified 644 temperature transmitter with any differences noted.
Software lock must be used in order to prevent unwanted changes to the transmitter
configuration.
Note
Transmitter output is not safety-rated during the following: Configuration changes, Multidrop
operation, Simulation, Active Calibrator mode, and loop tests. Alternative means should be
used to ensure process safety during transmitter configuration and maintenance activities.
7.5.1
Damping
User-adjustable damping affects the transmitter’s ability to respond to changes in the applied
process. The
damping value
+
response time
should not exceed the loop requirements.
If using a thermowell assembly, make sure to also take into account the added response time
due to thermowell material.
7.6
Alarm and saturation levels
The 644 features software driven alarm diagnostics. The independent circuit is designed to
provide backup alarm output if the microprocessor software fails. The transmitter will go to a
high or low output current for internally detected failures. The connected PLC must monitor the
transmitter current for the high and low output current values beyond the normal range. The
alarm directions (HI/LO) are user-selectable using the failure mode hardware switch found on
the top face of the device. If failure occurs, the position of the switch determines the direction in
which the output is driven (HI or LO). The switch feeds into the digital-to-analog (D/A)
converter, which drives the proper alarm output even if the microprocessor fails. The values at
which the transmitter drives its output in failure mode depends on whether it is configured to
Standard, Custom, or NAMUR-compliant (NAMUR recommendation NE 43, June 2003)
operation.
shows the alarm ranges available for the device to be
configured to. The DCS, or safety logic solver, should be configured to match transmitter
configuration.
Setting the alarm values is a two step process:
1.
With a Field Communicator, select the alarm and saturation levels using the following
Fast Key sequence 1, 3, 4, 2.
2.
Position the Alarm switch to the required HI or LO position.
Summary of Contents for Rosemount 644
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