Hydrocarbon Processing - April 2022 - 70

Environment
and Safety
D. CHAUDHURI, P. V. SINGH and V. S. KUMAR,
Fluor, New Delhi, India
Raising the alarm: Understanding the operator's
perspective on refinery process alarms
As refineries and petrochemical complexes worldwide are
moving toward more automated operations, plant operators are
increasingly becoming dependent on process alarms for safe,
smooth and continuous operation. Process alarms also play an
important role in mitigating the risks during plant upsets.
During the early stages of a project, typically the front-end
engineering design (FEED) stage, the client's operations team
and the design engineering contractor outline the preliminary
alarm requirements to assess the vital process parameters that
require significant monitoring during plant operations. The
definition of an alarm not only includes the proper setting of
the alarm, but also consists of defining the correct priority and
operator actions for the respective alarm. To confirm these parameters,
an alarm management study is typically done in the
engineering, procurement and construction (EPC) phase of the
project. A proper study provides the operator with an appropriate
action plan after an alarm has been enunciated. This plan
includes steps to be taken, as alarm verification and safeguarding
actions, to mitigate the possibility of any subsequent hazard.
Various design practices are followed when determining
and defining process alarms for essential process parameters.
The guidelines outlined in these design practices explain the
steps involved in defining a process alarm. These design practices
also provide the necessary documentation needed for defining
the alarms, and typically vary from project to project, as
defined by the client.
Once a process alarm goes off, it is the responsibility of the
operator to take corrective actions in a timely manner to mitigate
a potential hazard. This requires a well-coordinated effort
between the panel operator and the field operator to address
an alarm successfully without tripping the plant. Therefore,
understanding an operator's perspective is of utmost importance
while developing alarm management documents during
the detailed engineering phase. It is beneficial to organize an
alarm management review meeting with plant operations personnel
to understand the operational and maintenance aspects
of a particular process unit. Such meetings may be conducted
over a few weeks, depending upon the number of alarms in
that specific process unit.
The lifecycle of an alarm begins with a proper definition
of the alarm. In the case of a licensed unit, this definition is
provided by the licensor in the process design package. For an
70 APRIL 2022 | HydrocarbonProcessing.com
open art unit, the FEED package should clearly define the required
alarms. Further additions or deletions of alarms typically
happen during safety reviews, such as in a hazard and
operability (HAZOP) analysis. Finally, all the alarms defined
in the design phase are reviewed and verified for implementation
in the design.
During the alarm review phase, the inputs provided by the
operators are of immense importance. The operator is expected
to make an assessment and to verify all alarms to ensure that
the plant is operating within safe limits at all possible operating
conditions. This requires the operators to participate in alarm
management studies, and the outcome of these studies should
be documented. The final step in the design phase is to test
the alarms during the pre-commissioning stage of the project.
The following aspects are critical from an operator's standpoint
during the discussion of process alarms in an alarm management
review meeting.
Ownership of the process alarm. Since plant operations are
run by different teams in a refinery, it is essential to define the
scope of ownership for a particular process alarm. For routine
flow, pressure, level and temperature alarms, ownership is usually
assigned to the refinery process team, which is responsible
for addressing the same. For the alarms associated with rotating
equipment, along with their auxiliary systems and machine
monitoring systems, ownership is assigned to the mechanical
team. Interface alarms are usually the responsibility of the shift
supervisor, who should consult with the unit operators and
make an informed decision with the refinery leader to overcome
the challenges arising out of that alarm situation.
The following example is a unique case of an alarm on a pressure
transmitter. The pressure transmitter is located on the battery
limit interface, and it measures the pressure of the incoming
acid gas feed to the sulfur recovery units (SRUs) from the upstream
amine regeneration units (ARUs). The pressure transmitter
is a common instrument used for all trains of an SRU. It is
equipped with high and low alarms to notify of any abnormalities
in the overall system. Since the necessary and immediate
modifications in operation must be done at the SRU, this alarm
is owned by the SRU's operating team, so that the plant load
may be varied accordingly to compensate for the fluctuations in
the upstream ARU (FIG. 1).
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