Chemical Engineering October 2021 - 47

that the device has been correctly configured and
is correctly tracking the reflector echo. It also confirms
that the alarm loop is working, with a highlevel
alarm being displayed in the control room.
Because this automated testing function does
not require the device to be removed from the tank,
or the level in the tank to be manually raised, it
increases the safety of both the plant and workers.
Verification
reflector
functionality
reduces
the risk of accidental spills and enables the highlevel
alarm testing process to be completed more
quickly.
It also tests the loop from the device to
the distributed control system (DCS), as well as the
device itself.
Simulated reference reflectors. The high-level
alarm can also be verified using a simulated reference
reflector, whereby an artificial digital echo is
inserted into the radar signal. This artificial digital
echo triggers the high-level alarm when detected,
thus eliminating the need to have a physical reference
reflector. One benefit of this approach is to
avoid having a tank obstruction. Performing the
test with either a physical or simulated reference
reflector as part of a combination of partial prooftests
can achieve a proof-test coverage factor of
73%.
Reporting proof-test results
Both IEC 61511 and API 2350 require organizations
to provide written procedures, schedules
and documentation of proof-testing. This documentation
must include instructions for maintaining
safety during the proof-test, as well as actions
to be taken upon detection of a fault. Records
certifying that tests were completed must be
maintained. These should include descriptions
of the tests performed, the names of the people
that performed them, the dates when they took
place, and their results. By providing the reporting
functionality to support these requirements,
the latest smart level measurement devices and
their supporting software ensure compliance with
the standards, while simplifying the documentation
and auditing process.
n
Edited by Scott Jenkins
Author
AnnCharlott Enberg is the global functional safety
manager at Emerson (8000 Florissant Ave., St. Louis,
MO 63136; Phone: (314) 553-2000; Email: AnnCharlott.
Enberg@Emerson.com; Website: www.emerson.com/
proof-testing). Enberg began working in the functional
safety field 20 years ago, as chief executive for SILTECH
AB. She was then business unit director for DEKRA AB
and SRE site responsible process safety engineer for
Akzo Nobel AB. Enberg is now the global functional
safety manager at Emerson. Her focus has been to
work closely with the industry to ensure safe processes in engineering systems
through hazard and operability (HAZOP) studies, failure mode effects
analysis (FMEA) and layers of protection analysis (LOPA), to ensure risk reduction
and optimize personal human design processes. Enberg's goal is to
continue to make safety instrumented systems devices easier to implement,
and to increase safety globally. Enberg was selected as Global Manager of
the Year in 2020 by the International Association of Top Professionals
(IAOTP).
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