Latest post

Process Hazard Analysis | PHA concept, methodology, assessment and decision making


Process Hazard Analysis | PHA concept, methodology, assessment and decision making
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

Process Safety Information (PSI) must include complete and accurate documented information on:
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.



Related Articles

No comments

Please don't add links in the comments, they will be treated as spam comments