Emerson Rosemount - Page 193

183
Reference Manual
00809-0100-4021, Rev GC
Section 6: Certified Safety Instrumented System (Safety-Certified)
April 2014
Certified safety instrumented system (safety-certified)
Abbreviated proof test
Conducting the abbreviated proof test detects approximately 63% of transmitter DU failures,
and approximately 90% of temperature sensor(s) DU failures, not detected by the 3144P
safety-certified automatic diagnostics, for a typical overall assembly coverage of 67%.
1. Using Loop Test, enter the milliampere value representing a high alarm state.
2. Check the reference meter to verify the mA output corresponds to the entered value.
3. Using Loop Test, enter the milliampere value representing a low alarm state.
4. Check the reference meter to verify the mA output corresponds to the entered value.
5. Use a Field Communicator to view detailed device status to ensure no alarms or
warnings are present in the transmitter.
6. Check that sensor value(s) are reasonable in comparison to a basic process control
system (BPCS) value.
7. Document the test results per the plant’s requirements.
Extended proof test
Conducting the extended proof test, which includes the abbreviated proof test, detects
approximately 96% of transmitter DU failures and approximately 99% of temperature sensor(s)
DU failures, not detected by the 3144P safety-certified automatic diagnostics, for a typical
overall assembly coverage of 96%.
1. Execute the abbreviated proof test.
2. Perform a minimum two point sensor verification check. If two sensors are used, repeat
for each sensor. If calibration is required for the installation, it may be done in
conjunction with this verification.
3. Verify that the housing temperature value is reasonable.
4. Document the test results per the plant’s requirements.
Proof test intervals are based on typical sensor failure rates from the Electrical and Mechanical
Component Reliability Handbook Second Edition, exida.com, 2008. A low stress environment
without extension wire is assumed, with 30% of SIL 2 PFDavg limit budgeted for the transmitter
and sensor element. See the FMEDA report for additional details or references.
Table 6-1. Proof test interval guideline
Sensors
SFF
Abbreviated proof
test
Extended proof
test
Notes
4-wire RTD 90.8% 10 years 10 years
T/C 92.0% 10 years 10 years
Dual T/C 92.9% 10 years 10 years Using U3 Drift Alert & HotBackup
Dual 3-wire RTD 92.5% 10 years 10 years Using U3 Drift Alert & HotBackup
T/C & 3-wire RTD 91.2% 10 years 10 years Using U3 Drift Alert & HotBackup