Process Hazard Analysis | PHA concept, methodology, assessment and decision making
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| Process Hazard Analysis - PHA |
Process Hazard Analysis | PHA concept, methodology, assessment and decision making
Process Hazard Analysis (PHA) is a systematic approach to identify, evaluate,
and control the hazards of processes involving highly hazardous chemicals. The
primary objective of PHA is to minimize the probability of
occurrence and consequences of the release of hazardous substances by
identifying, evaluating, and controlling the events that could lead to the
release.
PHA Concept
It provides data to help you make decisions
to improve safety and reduce the effects of unwanted or unplanned release of
hazardous substances. Therefore, PHA begins with the simple
question "Is the risk acceptable?"
PHA must be performed by a highly knowledgeable, trained, experienced and
competent team of experts, including process engineers; otherwise, at the end
of the day, there would be no output commitments to actions and people will
think this was a waste of time. If team members are not confident due to lack
of knowledge and experience, the result of a PHA will be useless
and can be very bad.
When no one confident the design, the
process, the techniques, etc., people cannot apply the correct decision tools
to carry out an effective PHA. Most organizations understand the
severity of the consequences of accidents and of course it is more costly,
therefore accidents are an unnecessary cost of business. It is very important
to understand the correct cause of accidents in order to decide on the
appropriate controls and to take effective measures and other relevant
corrective actions to avoid losses or their recurrences.
The PHA is basically a
consequence and a loss causation model that helps companies to decide adequate
and effective controls on the identified risk. You must understand the exact
objective of any loss control program; you must not over-protect the facility
through a large amount of investment where the asset stops operating, but also
not insufficiently protect the facility; otherwise it will not help minimize
the risk to an acceptable level and installation will remains with excessive
exposure to risk.
Process Hazard Analysis (PHA) Principles
A Process Hazard Analysis is a
systematic, comprehensive review of a process to identify hazards, analyse the
significance of hazards, assess the adequacy of safeguards, and mitigate them
when warranted.
A PHA is not a method of
reviewing the quality or operation of the design, this step should be carried
out before your PHA meeting so that everyone has already accepted
the functionality of the design.
These are the building blocks of Process Safety Management (PSM) for
emergency shutdown, safety and alarm systems, process controls, and logic and procedures.
History says that most process accidents occurred due to equipment
failure or breakdown, improper operating procedures, unforeseen operating
conditions, and failure of hazard controls. Some events propagate accidents in
catastrophic situations such as design errors, incorrect situation, diagnosis
of operation or maintenance errors, alarm failures, shutdown system failures,
sources of ignition, management system failures, and site-specific conditions.
We can design engineering systems that can
mitigate accidents such as alarm, safety shutdown systems, control system,
response operator, response relief valves / liner systems, secondary
containment, emergency response contingency planning with emergency drills,
fire protection systems and site-specific conditions.
When to perform PHA
1. A new plant or project
2. For changes to an existing process
3. At existing facilities every five years to
assess process risks and changes in facility operations.
A proper PHA assessment will
collectively focus design and safety, operational teams to review risks,
incorporate input and perspectives, and develop stronger safeguards and
procedures to prevent accidents. Most of the time organizations prefer
techniques like What if or HAZOP.
PHA Methodologies
For a successful Process Hazard
Analysis, the most important thing is that people must have a common
understanding of risk acceptance, otherwise this creates endless discussions
that do not result in clear action. There are numerous methodologies, but
generally the PHA uses one or more appropriate to the complexity
of the process based on the PSM rule, 29 CFR 1910.119.
1. What-If
2. Checklist
3. Hazard and Operability Study (HAZOP)
4. Failure Mode and Effect Analysis (FEMA)
5. Fault Tree Analysis (FTA)
There are also other techniques, and some are
also combined.
Common elements in PHA techniques
Whatever the methodology or techniques of Process
Hazard Analysis, there are certain common elements that help to make an
effective and appropriate decision to minimize the process risk.
Process hazard Identification: In any PHA technique, the
first stage is to identify the inherent chemical or physical characteristics of
hazardous substances and processes that have potential harm to people or damage
to property and the environment.
Review
previous incident: Always review
past data addressing previous similar incidents or any previous incidents that
have had the potential for catastrophic failure or facility consequences.
Analyse controls and failures: This is a very important element in ensuring
that all existing engineering and administrative controls are adequate and effective.
All controls must be in place to keep process parameters within safe operating
limits. This will also help prevent challenges to system integrity.
Consider
facility siting: This is related
to facility design and best engineering practices. Analyse the layout and
spacing of facilities between process units, including the severity of the
consequences of possible accidents involving workers in the same location and
adjacent facilities.
Address
human factors: Since the
facility is operated mand monitored by operators, they always be available
within the operating facility, it is important to address the circumstances
where the operator response could negatively influence the level of protection.
Assess the effects of the incident: It can be done qualitatively to assess the
range of possible safety and health effects of employees.
Decide
the required actions: Evaluate each
scenario to determine whether design and/ or operating changes are needed to
further protect workers on site.
PHA Key Components
1. Formation of PHA Team
A team of people with experience in different
disciplines like engineering, process, design and operations should be there to
carry out the Process Hazard Analysis. The team should include
critical designers, operations, maintenance, processes, controls engineering,
and sometimes licensors representatives. Critical designers may include equipment
vendors, inspectors, fire protection and metallurgy specialists.
A qualified Process Hazard Analysis
facilitator should have experience in Process Safety Management (PSM), facility operations, and have the
analytical skills necessary to help the team identify hazards, understand risks, prioritize or rank the
hazards, and must be able to capture the team information.
The team should include personnel with
experience and specific knowledge for the process being evaluated. They must
have knowledge and experience in the Process Hazard Analysis
methodology used.
The PHA team leader must be
well informed in the implementation of the PHA method. Team
members must be competent, compatible, and the team leader must be able to
manage the team.
2. Process Safety Information
a) Highly hazardous process chemicals with
toxicity information including permissible exposure limit, physical,
flammability, reactivity, corrosivity data, etc. It should also include
identified incompatibilities and dangerous contaminants, and thermal data.
b) Process technology information should be
available, such as block flow diagrams or simplified PFDs, P&ID, material
and energy balance, process chemistry, criteria for maximum inventory levels
for process chemicals, process set points, qualitative estimates of
consequences of deviations, etc.
c) Information on process equipment such as
construction materials, electrical classification, design of relief systems and
design bases, design of ventilation systems, codes and standards of design and
safety systems.
3. Prioritization
Process Hazard Analysis must be performed on each process covered by
the Process Safety Management (PSM) rule. If multiple processes require PHA,
then PHA should be prioritized. For prioritization, the following
considerations are considered:
a. Potential severity of a chemical release.
b. Number of potentially affected employees
c. Operational history of the process,
including the frequency of past chemical releases and the age of the process.
4. Schedule
The Process Hazard Analysis must be in place
before the process begins. The PHA report should be updated and
revalidated at least every 5 years to ensure it is consistent with the current
process.
5. Finding, decisions, and recommendations
a. There must be a robust system to promptly
address the team's findings and recommendations.
b. The system should be in place to assure
that all recommendations are timely resolved and documented.
c. The system should be in place to document
all actions to be taken
d. The system should be in place to develop a
documented completion schedule for each action steps
e. Must have robust system to complete
actions as soon as possible and on schedule.
f. There must be a system to communicate the
actions to all concern personnel.
PHA philosophy of control
A control philosophy explains the P&ID to
describe how each piece of equipment is controlled and operated. The programmer
uses the control philosophy to program the PLC, a control philosophy describes the project
process and the interactive control of the system. It also describes the safety
system alarms and shutdown systems.
The first section of the control philosophy
describes the general process in words. The control philosophy also includes
shutdown and alarm set points, function and type of PLC. It includes control
loop tables that describe each loop function, loop variable, and parameters. A Safety Integrity Level (SIL) describes
the various layers of safety protection to prevent accidents.
How to reduce the likelihood of an accident?
Safe designs, preventive maintenance,
testing, inspections, procedures, and training will reduce the occurrence of
the initial event. The goal of a PHA is to prevent incidents by
identifying the process hazards, risk analysis, the significance of that
hazard, improving operations, and meeting company and legal requirements.
Effective Decision making
During the Process Hazard Analysis,
you must first identify the exposure to loss and then assess the level of risk
associated with each exposure before deciding on the appropriate controls.
For an effective PHA and its
decisions, a shared understanding of the objectives is very important when
designing a complex facility to operate safely, however, productively, there
must be a decision framework that everyone understands, that facilitates
discussion and encourage high-quality decisions.
The PHA
framework must be simple, understandable to all, and can be applied
consistently. It offers the approach that enables a team of participants to
systematically think about the design, comprehensively identify and clearly
assess risk. A well-executed PHA is like a shared language that allows a team
to make decisions based on shared knowledge.
To better understand, let's take an example,
suppose there is a liquid gas separator vessel and consider "no flow"
situation as abnormal process condition in the separator, now what could be the
cause, suppose there is pressure control valve at the container outlet that
could be inadvertently closed. If it closed, whether something catastrophic
would happen, maybe not, there is PSV on the separator vessel. But it is
possible that PSV may fail.
Here we can take some credit for it, but this
does not eliminate the risk. Now, since it doesn't completely eliminate risk,
then what would be the worst credible consequence? There could be some high
inlet pressures observed in the past so that the separator can overpressure.
There is another protection, a high-pressure automatic shutdown which means
that we have two protections, one is PSV and the other is an automatic
shutdown. Both safeguards can reduce risk.
Here, at this point, we have to make a
decision about risk acceptance using a standard risk matrix. Due to these two
safeguards, the risk matrix supports that the risk is acceptable. The PHA
team will document all of these logical decisions.
This is the correct and systematic approach
to performing PHAs where the risk is to clearly understand, make logical
decisions, and manage them by identifying, evaluating, and monitoring abnormal
process conditions.
Importance of risk-based decision
The risk cannot be zero, but it can be
minimized to an acceptable level. A risk-based decision is to choose the best
alternative to maximize the chances of meeting business objectives and minimize
the risk of loss.
Although a good risk-based decision does not
guarantee the result, it can make a good decision and still have a bad result,
but it helps to diversify the risk. If you always make good decisions based on
risk, the chances of getting a positive result will always be greater than bad
decisions.
In the Process Hazard Analysis,
the project team assesses the risk and operates the facilities by understanding
the consequences, if something goes wrong, and accounting for the chances of
these consequences occurring. If the risk is too high to accept, effective
steps must be taken to reduce it. A process risk analysis incorporates the
risk-based decision framework with a participatory decision-making process and
the objective is to apply the basic rule of risk-based decision-making which is
to keep the decision process as simple as possible. possible but not too
simple.
In the highly dangerous industry, risk is
inherited in all processes, but top performing organizations continually
develop, implement, and improve a risk management system as a key component of
their business management system.
There are four principles of operational risk management, i.e. accept the risk which compensate the
cost, unnecessary risk should be accepted, anticipate and manage the risk
through proper planning and full-proof controls, make risk decisions at the
right level. These risk management principles help organizations identify and
address risk consistently across the organization. It also improves stakeholder
confidence and trust during design and operation, establishing a reliable basis
for decision making.
Good risk management helps to allocate
resources effectively for improved risk reduction, operational effectiveness,
and efficiency. Finally, applying risk management principles will improve
organizational learning.
Example of Good risk-based decision
Organizations that have a positive safety culture show that they
have competent and knowledgeable decision makers who help them keep their
businesses accident free. In addition, they ensure adequate resource allocation
to minimize risk to an acceptable level. To understand, let's look at the
example of one of the control rooms of highly hazardous facilities, the panel
operator received the high level alarm in the separator vessel, and immediately
informs his supervisor and engineer in charge of making the decision shutdown
the process. They jointly examine the availability of process safeguards. They
also reviewed the availability of other safeguards on that vessel and want to
confirm the high-level shutdown system.
The engineer in charge suggests continuous
monitoring and sends a person to check it with this high alarm. They discuss
with other process experts and observe the situation for longer hours to decide
if shutdown is actually required or not.
They arrange for standby mechanical equipment
to reduce pressure under normal conditions without disturbing the shutdown
system. In addition, they organize a tank truck to transport the liquid. They
organize the standby fire services as a precautionary measure. In this way, the
team of competent people in an organization practices good risk-based decision
making to build the company culture.
Threat to risk-based decision
In most of the organization, the Process
Hazard Analysis is not carried out correctly, it may be due to the lack
of knowledge or incompetence of the team members. It may be due to cultural
deficiency because when it comes to making risk-based decisions, people risk
something to manipulate or relate to their past experience. Peoples are making
decisions without any technical or analytical basis and then are not sure if it
was a good decision or not. Company culture is also important because
when people make that decision, there may not be an effective standard to
measure the quality of a decision. In a time of uncertainty, how your company
rewards or punishes decisions that also matters and is therefore responsible
for the decision-making process.
For example, suppose there is a high-level
alarm on the DCS panel of some facility, say a separator vessel, then the panel
operator informs his supervisor or process engineer in charge and asks about
the need to turn off the equipment or the installation. Then, the process
supervisor discussed with the panel operator that it is normal, and the process
does not require any special attention since this alarm is not reliable, it is
being received every few days.
Then the DCS operator asked his supervisor
about the decision, what to do, if he just had to acknowledge it and do
nothing. Then the supervisor and engineer-in-charge start arguing with the
thinking considering it's time for the annual performance review, the plant is
working fine, downtime is below target and our safety record looks very good.
To achieve key performance metrics and get an annual increment more, it is best
to acknowledge the alarm without taking appropriate action. This is the threat
in the risk-based decision-making process.
People are repeatedly rewarded for making bad
decisions. This happens when results are the only measure of performance.
Unintentionally, organizations lead people to take excessive risks. Some
organizations may not clearly understand the usefulness of sound risk
management principles.
Conclusion
Process Hazard Analysis (PHA) is a systematic method of identifying,
evaluating, and controlling the risks associated with the hazardous chemical
handling process and helps to minimize the likelihood of consequences and
occurrences. PHA begins with the simple question "Is the
risk acceptable?" and therefore provides a systematic approach to
decision-making to improve safety and reduce the effects of unwanted or
unplanned release of hazardous substances.
There are different types of methodology or
techniques available for PHA, but there are certain common
elements such as team building, process safety information, prioritization,
schedule, findings and recommendation that help make an appropriate effective
decision for minimize the process risk.
Organizations that have a positive safety culture
help keep their business accident-free through a good risk-based
decision-making process, and therefore assist in allocating adequate resources
to minimize risk to an acceptable level by adopting the best Process
Hazard Analysis technique.
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