ABB LLT100, Functional Safety Manual

Page: 24 / 32

24
User Guide
—
Figure 2 LLT100 current measurement
6
Set the transmitter output to a HIGH ALARM value by means of the HMI push buttons, HART
communication by using a DTM in combination with HART software, or with the Field Information
Manager (FIM-Tool) using simulation function (Menu: Diagnostics>Simulation Mode>Current Out).
7
Check whether the current output signal reaches the value set for high alarm value.
8
Set the output of the transmitter to a LOW-ALARM value by means of the push buttons of the HMI,
HART communication by using the LLT100 DTM or with the Field Information Manager tool (FIM-
Tool) using simulation function (menu:
Diagnostics>Simulation Mode>Current Out
).
9 Check whether the current output signal reaches this value.
10
Terminate the simulation mode after finishing the output simulation.
11
Activate the write lock (see section 4.4 Configuration) and wait for 10 seconds.
12
Restart the device by powering it down.
13 Check the measured distance or ullage against a secondary standard on an installed device which
could be a calibrated reference device, a mobile calibration rig or on a factory calibration rig. The
measured values of the secondary standard and the device under test (DUT) must be compared. The
amount of deviation between the measured distance, ullage and the set point must not exceed the
measured error specified for the safety function (±0.32 mA).
14
Remove the bridging of the safety DCS or restore normal operation in another way.
15
After the test has been performed, the results must be documented and stored in a suitable manner.
By using this test method at least 72 % (PTC = 0.72) of dangerous, undetected failures are detected. The
influence of systematic errors like e.g., medium properties, operating conditions, build-up or corrosion
on the safety function is not fully covered by the test.
If one of the test criteria from the test procedure described above is not fulfilled, the device may no
longer be used as part of a safety instrumented system.