A fire incident in an oil
refinery or petrochemical plant can be a very frightening event—the vast flames, the
noises, the smells, and the feeling that at any moment, everything might
explode. Operators, by their job definition, are required to suppress their
natural reaction to run for their lives and remain at their posts and make
every effort to take control of the event to the best of their abilities. This
article presents a toolbox to help operators manage emergency incidents
professionally and effectively.
Managing an emergency
event in a petrochemical facility differs from a fire in a residential building
due to the presence of large quantities of hazardous and flammable materials. In
addition to basic firefighting and rescue operations, it is also essential to
carry out actions to isolate the fire incident area from fuel and energy
sources, reduce the fire intensity and prevent secondary events (i.e., the domino
effect). These operations are outside the scope of the firefighting and rescue
teams' skills.
Only those responsible for
day-to-day operations and those familiar with the location and function of
every piece of equipment and valve would know how to perform a "process
extinguishing" of the fire, which is the most effective type of extinguishing.
Only experienced operators
familiar with the facility will be aware of the risks close to the fire area,
such as liquefied petroleum gas (LPG)-containing vessels that might fail [creating
a boiling liquid expanding vapor explosion (BLEVE) hazard], fin-fan coolers
that may increase the height of the flames, pipes that might undergo heating
without enough room for thermal expansion, etc.
The main responsibilities
of the operations teams in handling emergency incidents include:
Sounding the alarm and initial reporting. When sounding the alarm by dialing the plant's emergency
number, it is essential to give a brief report that includes critical
information such as:
Examples of such a report
might include:
After receiving an
accurate report, firefighters, paramedics and security personnel can know where
to go, on what route, what tools to bring with them, which equipment they would
need to operate (high-pressure pumps, foam dosing tanks, SCBA, etc.), whether
road closures and restriction of access are required, and reporting to external
parties.
For plants with a central
control room, rather than assigning the job of alarming and reporting to the
board operator of the unit where the incident occurs, it is more helpful to
give that task to an operator in their vicinity whose units are unaffected.
After alerting the
emergency services, informing other parties about the incident is crucial. This
begins with reporting up the command chain—to a Shift Supervisor or Operations Manager—and alerting other
process units' teams, especially those units feeding the unit where the
incident occurred and units that are dependent on the proper operation of the
damaged facility.
Locating personnel. In the heat of an emergency event, people tend to forget that the most
important goal is saving human lives. In numerous emergency events, locating
employees was not the first priority of the responding operators—sometimes, this ended in
disaster.
During regular unit
operation, the shift manager (or foreperson) must always be aware of the people
who are present on the facility's premises and their general location. For this
purpose, the shift team and other employees or visitors who come to the
facility at routine times must be accustomed to some basic rules:
When an emergency incident
occurs, after sounding the alarm, the shift manager must locate all employees
in the facility and report missing persons and their approximate locations to
firefighting forces.
The natural tendency of
operators is to immediately perform actions to mitigate the incident, open
firewater monitors, etc. Training is required to get the staff accustomed to
remembering, first of all, to ensure that all personnel on the premises of the
process unit are accounted for.
Initial activation of firefighting equipment. Oil refineries and petrochemical plants have many means
of extinguishing fires, both fixed and portables. Rapid activation of
extinguishing devices may lead to quickly overcoming a fire event before it
develops into a significant one.
The decision of what means
to use and whether to do so before or in parallel with other emergency
operations is at the discretion of the senior person in the field—usually the shift
manager (foreperson)
In the event of a fire
caused by an uncontrollable gas burst, it is inadvisable to extinguish it
before the leak can be stopped for fear of an explosion. Efforts must be made
not to splash a large amount of water on very hot pipes and equipment to avoid
thermal shock and quenching of the steel that could cause it to become brittle.
The shift manager and
field operators must be skilled in choosing the correct fire extinguishing
devices for the event and operating them [e.g., monitors, carbon dioxide (CO2)
fire extinguishers, flood systems]. Acquiring and maintaining these skills
requires fire extinguishing refresher training that the facility manager must
initiate.
Care must be taken not to
"get stuck" with firefighting operations and to transfer
responsibility for them to the firefighters as soon as possible. Field
operators have many other functions and responsibilities during an emergency
incident, and standing in one place for a long time holding a fire hose is not
the best use of their time and skills.
Shutting down the plant and isolating the affected area
from fuel and energy sources. During
a significant event that cannot be "surgically" isolated, the operations
team must not hesitate to perform an emergency shutdown of the facility,
including closing all pumps and compressors and shutting down all fired and
electrical heaters. As simple and logical as this notion sounds, operators are
often reluctant to initiate a plant shutdown even if it is obvious that there
is no way to overcome the incident without shutting down the unit. It is often
a weak point that must be discussed with operators during their refresher
training.
The most efficient and
effective way to control fire or release of process fluid in a process facility
is by reducing the rate at which the material breaks out until it stops
completely. As long as we "add oil to the fire," the fire will only
intensify and the event might spread to other areas.
It is essential to try to
pinpoint the bursting point as accurately as possible, although this is not
always an easy task. If the location of the burst has been identified, it is
crucial to stop the operation of the pressure source of fluid that is flowing
to the point and close valves as close as possible to the bursting location.
Such sources might be pumps, compressors and pressurized liquid or gas supply
lines. Utilizing the control room as much as possible to perform the
disconnection tasks using remotely operated valves and switches is preferable.
At the plant's central electrical substation—or the local motor control center (MCC) of the
process area, an onsite building where electrical equipment such as
transformers, switchboards and motor control boards are located—there should be the
possibility of cutting off power to selected motors or entire process areas, if
necessary.
Adding heat from an
external source into the damaged sector is similar in effect to adding fuel
material. Therefore, it is also essential to omit heat sources, such as tower
reboilers, steam-heated heat exchangers, electric heaters, etc. Again, it is
worth using the control room to remotely shut down heat sources.
Even after an emergency
shutdown of the process unit has been performed, it is important to isolate the
affected area in a volume as small as possible to diminish the magnitude of the
burst in a shorter time frame.
Emptying process vessels of
flammable liquids (excluding LPG and its components) should be considered by
pumping out liquids from the affected system after ensuring the closure of all
pathways returning to the affected area (e.g., an overhead receiver pump that
sends the overhead product to the top reflux line as well as to the product
line).
Care must also be taken to
avoid pumping liquids through pipes that pass through the area under direct
fire or heat radiation. When it is impossible to get close to the epicenter of
the incident, the disconnection can be carried out at the facility's battery
limits valve stations or by using offsite isolation valves.
FIG. 1 shows a simplified flow
diagram of a reaction section in a vacuum gasoil (VGO) hydrotreating unit.
Heavy vacuum gasoil (HVGO)
is pumped through heat exchangers to a charge heater, which is also used to
heat the recycle gas, which consists mainly of hydrogen. The hot HVGO and
hydrogen (H2) enter a fixed-bed reactor where sulfur is removed from
the HVGO and combined with H2 to produce H2S. Next, the
reactor effluent stream flows to heat exchangers to preheat the HVGO and the
recycle gas and then flashes into gas/liquid separators. Finally, the treated
HVGO flows to a fractionation section, and the gas is recycled after passing
through an amine scrubber to remove H2S.
FIG. 2 shows a release of process fluids from one of the feed/effluent
exchangers, which operate at 48 barg and 330°C on the shell side, and 40 barg and 410°C on the tube side.
Recommended isolation points are shown as red valves that should be closed to
isolate the smallest possible volume around the burst-out point. The relevant
battery limit valves should also be closed. Pressure sources (i.e., the charge
pump and H2 compressors) must be shut down, as well as the external
heat source (i.e., the fuel to the charge heater).
Releasing pressure from a leaking or breached system. The most efficient and effective way to assume control of
a fire or breakout of fluid in a process facility is by reducing the rate at which
the material breaks out until it stops completely. The breakout rate, of
course, depends on the pressure difference between the inside of the system and
the atmosphere.
In a large system or a
high-pressure section, even after it is disconnected, it is inadvisable to wait
for the pressure inside the system to be released through the breakout point.
Therefore, simultaneously or immediately after isolating the system from its
surroundings, pressure should be quickly released from the affected sector to a
safe destination.
The most straightforward
pressure release destination is towards the plant's flare. In most refineries
and petrochemical plants, pressure may be released to the flare through control
valves or manual valves—such
as a relief valve’s by-pass line—from various sectors. Of course, the capability of the flare
lines to deliver the gas being released must be considered, and care must be
taken not to send a significant amount of liquids along with the gas. Additionally,
the operators responsible for operating the flare must take care of efficient
and smokeless combustion.
Pressure release towards
the plant's fuel gas header, if such a possibility exists, is a limited and
problematic solution and must be done gradually so that the pressure control
system of the fuel gas header prevents critical shocks in the supply pressure
to consumers.
In process units with
high-pressure vessels with thick walls, sudden decompression should be avoided
as much as possible. Therefore, it is worth studying in advance the
instructions of equipment manufacturers to avoid causing long-term damage.
In systems containing LPG
components, the release of pressure should be done only after applying judgment,
since the decreased pressure will cause increased evaporation of LPG while
cooling the equipment to extremely low temperatures and creating a risk of
brittleness. More importantly, one must consider the loss of liquid levels in
LPG receivers exposed to heat radiation must be considered—this can lead to a BLEVE.
If there is no heat
radiation risk, it is advisable to empty the liquid LPG by pumping it to a safe
destination after ensuring the closure of all pathways to the affected area.
The example shown in FIG. 2 shows that the
pressure can be released to the flare header through a manual valve. In
addition, after disconnecting the inlet to the amine scrubber, the pressure of
the section from this column to the compressor can be released to the fuel gas
header through a control valve.
Disconnecting fuel sources and releasing pressure by
remote operation. In
the control room and throughout the plant area, numerous means and devices
allow operators to remotely perform critical disconnections of fuel and energy
sources, and release pressure from the damaged sector.
Due to stress or
confusion, an operations team may forget to use some of these measures, inadvertently
extending the handling time of the event and potentially increasing the damage.
Some remotely operated
devices are listed below:
It is advisable to prepare in advance dedicated screen
displays in the control system for incidents of a fire or process materials
release to make it easier for the board operators to perform what is required
and (primarily) to ensure that no means at their disposal are overlooked.
Addressing and
neutralizing nearby risks. Care
must be taken during a fire incident in a process facility to deal with risks
that might occur due to the fire and the heat radiation. Some common risk
factors are listed below:
As
part of the emergency response, it is essential to address the neighboring
risks and alert the firefighting forces about them. In particular, it is
crucial to apply cooling by firewater monitors for steel beams at risk of
overheating, to operate deluge systems for LPG receivers, and to shut off the
motors of air coolers.
Teaming up with firefighting and
rescue forces. When
firefighting and rescue forces arrive at the facility's premises in an emergency,
crucial information must be transmitted quickly, including:
After their arrival, these
firefighting and rescue forces should assume command of the firefighting and
rescue activities. The operations team should focus on the operational
activities for process shutdown (i.e., disconnecting the affected area from
fuel and energy sources, releasing pressure, emptying liquids, and bringing the
facility to a state as safe as possible).
Training and practice. In most cases, the providers of the initial response to an emergency at the
facility will not be engineers or operations managers, but the field and
control room operators on duty. These operators may spend most of their
professional careers with only a few encounters with a severe emergency like a
major fire incident. Therefore, without proper training and practice, the
response of the operations team might be slow and incomprehensive, resulting in
a longer-than-necessary response time and incident duration, increased damage
and sometimes even harm to personnel.
Operations teams must
practice the principles presented here to ensure that these principles are
applied, even in moments of stress and excitement.
Plantwide exercises of
emergency events usually concentrate on the functioning of the plant's systems
and interfaces with external parties. Often, they do not deal specifically with
the required practice of operational response. A suggested solution is to carry
out orderly and structured emergency event exercises for the shift staff at
least once a year per shift, in a manner that will be explained here. In
addition, it is important to generate a constant dialogue on the subject and to
carry out a "tactical practice" of various emergency scenarios during
a conversation in an operators' room or control room. For example, a plant engineer
would present a question to the operators, "The vacuum tower's bottom pump
seal has failed, and a big fire started around the pump and under the pipe
rack. How do you respond?"
It is important to end
this discussion by presenting a formal solution consistent with the principles discussed
here. Discussions on the handling of emergencies should be an integral part of an
operations team’s everyday life so that in the decisive moment, the necessary
actions are taken quickly and efficiently.
Exercises for dealing with an emergency scenario in
refinery process units. The
exercises proposed below aim to train the operations team in handling the
hazardous material release or fire event by putting together exercise files
based on a credible event of a release of process material accompanied by a
fire or explosion. The files would hold all the materials required to provide
an appropriate response following the principles presented in this article.
The proposed contents of
an exercise file are:
Takeaways. The consequences of emergency incidents in oil refineries and petrochemical
plants may be mitigated significantly if operations teams onsite act diligently
to reduce the intensity of the fire or release of process fluids by using
process tools, dealing with nearby risks, and interfacing effectively with
firefighting and rescue forces.
Practicing fire scenario
exercises on a regular basis will increase the chances of achieving the correct
and efficient operational response from the operations team in the event of
actual emergency incidents.
To obtain a timely
response to emergency incidents, prepare dedicated screen displays on the
plant's DCS that include all the available tools that can be used during
emergencies and a convenient, straightforward means to activate them. HP
YARON NIMROD is a chemical engineer with more than 40 yr of experience in the oil refining and petrochemical industries. He has worked for the BAZAN Group of Haifa, Israel, as an Operations Manager, Projects Manager and VP for Technology and Projects. Nimrod is now teaching as part of the faculty of chemical engineering at the Technion in Haifa. He earned a BSc degree in chemical engineering from the Technion, Israel Institute of Technology, and an MBA from the University of Haifa.