Baker Hughes Masoneilan 12400 Series, Instruction Manual & Safety Manual

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48 | BHGE ® 2017 Baker Hughes, a GE company. All rights reserved.
8.4.4. C
HARACTERISTICS
Device Level (SIL) Unit type HFT

sd

su
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dd

du
SFF
12400 Series
Digital Level
Instrument
B 0 0 FIT 192 FIT 575 FIT 72 FIT
91.4
%
8.5. SAFETY FUNCTION
The Safety Function of the 12400 series Digital Level Transmitter must be to monitor the level or interface of a liquid and
transmit a 4-20 mA analog signal within the measurement safety accuracy. It includes the whole hardware and software
measurement chain from the displacer through the torque tube and the electronic board to the primary analog output signal
AO_1.
8.6. PROOF TEST
According to section 7.4.3.2.2 f of IEC 61508-2, proof tests must be undertaken regularly to reveal dangerous faults which are
undetected by diagnostic tests. This means that it is necessary to specify how dangerous undetected faults, which have been
noted during the FMEDA, can be detected during proof testing
The test intervals necessary for this purpose are defined in the calculation of the respective safety loop.
Tests must be conducted by the manufacturer or an authorised person duly trained on the instrument and SIS operations.
Recommend Proof test
Step Action
1
Bypass the safety function and take appropriate actions to avoid a false trip and any safe actions
against dangerous atmospheres.
2
Inspect the instrument for dirty or clogging parts, adequate wiring, correct mounting of end
connections and other physical damage.
3 Examine the torque tube and the displacer to detect corrosion or leaks (replace if necessary).
4 Observe the tightening torques for the nuts and studs.
5 Check the Bias spring position is correct.
5 Use HART communications to retrieve any diagnostics and take appropriate action.
6
Send a HART command to the transmitter to go to the high alarm current output and verify that the
analog current reaches that value.
This tests for compliance voltage problems such as a low loop power supply voltage or increased
wiring resistance.
7
Send a HART
®
command to the transmitter to go to the low alarm current output and verify that the
analog current reaches that value.
This tests for possible quiescent current related failures.
8
Perform a five-point calibration check of the displacer and transmitter over the full working range
using the process fluids(s).
If the calibration check is performed by any means other than the fluid(s) acting on the displacer, this
proof test will not detect any failures of the displacer.
9 Lock the settings by adjusting the hardware lock jumper position
10 Remove the bypass and otherwise restore normal operation.