Process Hazard Analysis Team Research Articles

An overview of PHA templates and checklists developed for a refining system and lessons learned

AbstractThe Chevron Refining organization has completed a multi‐year effort to create process hazard analysis (PHA) templates and checklists to improve the consistency and quality of PHAs. The goal of this study is to provide an overview of the content, development process, and lessons learned. The lessons learned included the following. Members of PHA teams and SMEs have differing experiences and perspectives on the risk of loss of containment, necessitating a standardized method for developing consequences and modifiers. Typical PHA teams (e.g., facilitator, process and/or design engineer, and operator) will have differing levels of engineering and operating experience, making a thorough understanding of the various types of equipment and processes in a typical refining unit impractical. PHA teams cannot realistically bring in SMEs on an as needed basis to aid with the analysis. Concerns that templated solutions might cause PHA teams to lose their creativity and focus only on the templates, and that templates might omit or incorrectly assess a hazard, have been outweighed by the benefits of the templates.

PHA guidance for correlating H2S concentrations in process streams to severity of adverse health outcomes in the event of a leak

Process hazard analysis (PHA) teams are responsible for determining and categorizing the potential impact of a loss of containment. For streams containing hydrogen sulfide (H₂S), the health and safety consequences of a worker being exposed to H₂S are a function of airborne concentration in the breathing zone and duration of exposure. PHA teams often do not have the technical knowledge to link the known concentration of H₂S in the process stream to an adverse health outcome. This paper describes the methodology and the assumptions made in developing such guidance. H2S concentration in the process stream was correlated to concentration of H2S in the breathing zone. Dispersion modeling was used to assess vapor releases, while additional multi-phase release modeling was required to estimate the amount of H2S liberated from the released liquid. Modeling was completed for different H2S concentrations in process streams under a variety of conditions. Breathing zone concentrations were assessed against published occupational exposure levels associated with probable health outcomes. This study demonstrated that H2S stream concentrations can be associated directly with a consequence categorization that can be used in a PHA. Results were summarized, providing simplified guidance that is valid over a wide range of process conditions and release scenarios.

On the completeness of scenario identification in process hazard analysis (PHA)

Process hazard analysis is used to identify hazard scenarios so that the adequacy of process safeguards in protecting against incidents can be addressed. Of course, it is unlikely that this objective can be achieved with an incomplete set of scenarios. Also, scenarios from PHA are used as the basis for risk analysis studies such as LOPA and QRA which depend on having a complete set of scenarios to avoid underestimation of risk. Consequently, PHA studies should strive to identify hazard scenarios as completely as possible. The completeness of scenario identification is the most important issue for PHA. Missed scenarios can equate to the occurrence of incidents.The ability to achieve the identification of a complete set of hazard scenarios is limited by a number of factors. They include technical constraints posed by PHA methods and practices, human behaviors during PHA study sessions, and poor quality assurance and control in conducting studies. The latter arises from both external factors that adversely impact PHA team performance and internal factors that detract from the effectiveness of studies. This article identifies and discusses these factors and makes recommendations on how they can best be managed.

Selection of representative accident scenarios for major industrial accidents

Abstract This paper analyzes the problems with selecting representative accident scenarios, which are understood as the maximum credible accidents for major industrial accidents. The selection process is based on the risk ranking scheme, which is applicable to all potential accident scenarios identified during the process hazard analysis (PHA) for a major hazard plant. Unfortunately, the process implies a substantial level of uncertainty due to incomplete and vague information concerning the assessment of the frequency and severity of the categories required for the risk ranking matrix as well as the lack of data reflecting the impact of the layer of protection on those categories. In most cases, the uncertainty is caused by insufficient knowledge and experience of the PHA team. This uncertainty usually affects the credibility of the accident scenario identification process and, by the same token, results in underestimation or overestimation of the process risk level. To address all knowledge-based uncertainties, a new approach for the identification of representative accident scenarios is proposed. This approach consists of the inclusion of a semi-quantitative assessment of the safety performance of protection layers combined with a fuzzy logic approach to risk ranking assessment. The proposed methodology may be successfully used for any major hazard industry; a case study for the fictional model of LNG storage facilities is presented here. Preliminary tests confirmed that the final results of the risk index were determined in a more precise and realistic manner.

Benefits of simple consequence modeling for Burner Management Systems

The current approach used to analyze fired heaters during a Process Hazard Analysis (PHA) is inefficient and outdated. Fired heaters can be one of the more complex systems evaluated in a PHA, however they certainly aren't anything new. In fact, they are one of the most common pieces of process equipment throughout industry, and have been for quite some time. Why then is such a large amount of PHA team time still needed to analyze them? Why, when using the same Process Safety Information (PSI), methodology, and risk criteria, can the results still be inconsistent? The obvious answer is the PHA team; different teams yield different results. Since the results of a PHA can impact several facets of a facility and its operation, including driving the Safety Integrity Level (SIL) for the heater's Burner Management System (BMS), inconsistencies between analyses can have significant safety and financial impacts. If the consequence estimation is over conservative the selected SIL may be too high, which will result in an over designed and a very costly Safety Instrumented System (SIS). Conversely, if the consequence estimation is too low, the facility's risks may not be adequately reduced by the selected SIS. Therefore a means to efficiently and consistently determine the consequence is critical. This paper will describe how simple consequence modeling can solve this problem, its inherent benefits, and the cost savings it provides.

Identify SIF and specify necessary SIL, and other IPLs, as part of PHA/HAZOP - or - why it is not necessary to “boldly go beyond HAZOP and LOPA”

This article shows how to apply the qualitative definition of IPLs within the setting of a process hazard analysis (PHA) to get most of the gain from Layer of Protection Analysis (LOPA) without doing a LOPA (without using numerical values). The article includes an implementation path to develop PHA leader competencies to guide the qualitative approach. We also show the way we use a PHA team to identify when a SIF is needed and to select the proper target safety integrity level (SIL). This portion of the SIL evaluation and the identification and labeling of the IPLs during the PHA/hazard and operability analysis (HAZOP) does not take any longer than a normal PHA/HAZOP, once the right habits are established. Note that this approach eliminates the need for a separate SIL Evaluation Study to identify the SIFs and select the target SIL. Finally, the article ties together these two specific topics, along with the topic of making risk judgments, to show there is less than 5% need to go beyond HAZOP, and less than 0.01% need to go beyond LOPA. © 2016 American Institute of Chemical Engineers Process Saf Prog 35: 349–359, 2016

Cognitive biases in process hazard analysis

Many decisions are made by process hazard analysis (PHA) teams in identifying hazard scenarios and determining if there is a need to reduce the risk of catastrophic accidents. Observations of PHA teams conducting studies indicated that such decisions are not always made rationally.Cognitive psychologists have studied how people make decisions and the conditions under which those decisions may be unreliable. It has been shown that various cognitive biases influence decisions by people and can hinder rationality. This body of knowledge was researched and correlated with observations of decision making by PHA teams during the performance of studies to explain and understand why PHA teams may make erroneous decisions. The application of cognitive psychology to decision making in PHA has not been addressed previously.PHA facilitators must understand the impact of cognitive biases on PHA studies because they can seriously impact the quality of study results. Hazard scenarios may be missed, risks estimated incorrectly, and important recommendations for risk reduction omitted. This paper discusses cognitive biases that have been observed during the performance of PHA studies, gives examples of their effects, and provides guidelines to minimize their adverse impacts.

Competency requirements for process hazard analysis (PHA) teams

Process hazard analysis (PHA) is a cornerstone of process safety management programs. The quality of the PHA performed directly affects the level of risk tolerated for a process. The lower the quality of a PHA, the more likely higher risk will be tolerated. There are few requirements for PHA team members in the U.S. Occupational Safety and Health Administration's process safety management regulations. More detailed requirements for participation in a PHA are desirable.A competency management program should be used to ensure PHA practitioners and teams are appropriately qualified. Criteria for selecting PHA team leaders, or facilitators, and other team members are key to such a program and are described in this paper. The criteria cover both technical and personal attributes. Application of the criteria is described and team performance metrics, which can be used to correlate performance with the assessment of competency to validate the criteria and methods used, are discussed.Owing to the importance of the role played by team leaders, certification of their competency is desirable. Criteria for certification are described and their application is discussed.

Requirements for improved process hazard analysis (PHA) methods

In order to develop better process hazard analysis (PHA) approaches, weaknesses in current approaches first must be identified and understood. Criteria can then be developed that new and improved approaches must meet. Current PHA methods share common weaknesses such as their inability specifically to address multiple failures, their identification of worst-consequence rather than worst-risk scenarios, and their focus on individual parts of a process. There has been no comprehensive analysis of these systemic weaknesses in the literature. Weaknesses are identified and described in this paper to assist in the development of improved approaches. Knowledge of the weaknesses also allows PHA teams to compensate for them to the extent possible when performing studies.Key criteria to guide the development of improved methods are proposed and discussed. These criteria include a structure that facilitates meaningful brainstorming of scenarios, ease of understanding and application of the method by participants, ability to identify scenarios efficiently, completeness of scenario identification, exclusion of extraneous scenarios, ease of updating and revalidating studies, and ease of meeting regulatory requirements. Some proposals are made for moving forward with the development of improved methods including the semi-automation of studies and improvements in the training of team members.

Initiating events, levels of causality, and process hazard analysis

Process hazard analysis (PHA) is used to identify hazard scenarios for a process and determine if the risk from the scenarios is tolerable. Each scenario begins with an initiating event that is made up of one or more causes. These causes must be recorded in sufficient detail to allow the PHA team to determine the particulars of the scenarios and develop any needed risk reduction measures. There is a hierarchy of causality wherein there are immediate, basic, underlying, and root causes of events. A suitable level of causality must be used in PHA. This article describes the hierarchy, recommends the level that should be used in PHA, and provides guidelines for the information that should be recorded in a PHA worksheet for different types of causes. © 2013 American Institute of Chemical Engineers Process Saf Prog 33: 217–220, 2014

On the validation of safeguards for process hazards analysis

An article presented at the 8th Global Congress on process safety addressed the need to validate the adequacy of safeguards in order for them to be credited in process hazard analysis (PHA). Validation of safeguards is critical for process safety but its inclusion within PHA would cause a serious distraction from identifying hazard scenarios, which is the key objective of PHA. Furthermore, safeguard validation needs to be performed by qualified personnel with a different skill set than PHA team members using validation methods that are much different than PHA. Consequently, validation of safeguards, and other aspects of process safety that support PHA, should be performed before commencing PHA. The PHA team can then focus on the qualification ofsafeguards for specific hazard scenarios during the PHA. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Integrating job safety analysis into process hazard analysis

AbstractIn this article, the author will present and explain in some detail how the job safety analysis (JSA) technique can be integrated into and used in conjunction with any of the six process hazard analysis (PHA) techniques required by the Occupational Safety and Health Administration process safety management Standard for highly hazardous chemicals. The goal of this effort is to produce a rigorous and unified approach to performing a PHA for either a batch chemical process or a continuous chemical process with significant batch elements (i.e., startup and shutdown). This approach combines the typical approach to performing a PHA with representative operating, emergency, and maintenance procedures to allow PHA teams to evaluate process risks within the environment of specific modes of operation for the process equipment and PHA nodes. When this approach is used, the PHA team is less likely to miss something important. As a result, the PHA produces a set of preventive actions that, when implemented, will produce the best and safest way to operate the system reviewed. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2010

Process hazard analysis quality

In this article, the author will discuss the elements that go into a high quality process hazard analysis (PHA). Specific suggestions for performing a high quality PHA will be presented and discussed. The author will show that it is possible to adhere faithfully to the legal requirements in performing a PHA and still produce a poor quality PHA. It is only through continued focus on the basic principle underlying the performance of a PHA (i.e., the prevention of potential future incidents) in every aspect of the PHA's performance that a high quality PHA will result. When management realizes that they can expend valuable resources in the effort to perform either a poor quality PHA (i.e., just what the law requires) or a high quality PHA, the author is confident that focus will shift to a demand for high quality performance. In this article, we will discuss the elements that go into the performance of a PHA. It is through a better understanding of the application of these elements that PHA team leaders can infer the existence of a high quality PHA. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2010

Layers of protection analysis for human factors (LOPA‐HF)

AbstractProcess hazard analysis (PHA) performed to meet the requirements of OSHA and EPA regulations must address human factors. Both the human failures that can cause accidents and the human factors that can influence them must be addressed. This is important because it is generally believed that 50% to 90% of process accidents can be attributed to human failures. Human failures are usually identified in a PHA by simple brainstorming. However, PHA teams have a tendency to focus on equipment failures. A better approach is needed. Common approaches for identifying the human factors that influence human failures involve the use of checklists during the PHA. Unfortunately, these approaches have proven problematic. There is a need for an improved method that is both efficient and effective in helping to control process risk.This paper describes improved approaches for identifying human failures in PHA and human factors issues that impact on the hazard scenarios identified by PHA. The former is accomplished using an approach that conceptually identifies human failures in a manner analogous to generating deviations in a hazard and operability study. The latter is achieved by the application of the framework and methods of Layers of Protection Analysis (LOPA), a simplified risk assessment method. These approaches are described and illustrative examples are provided.

Managing the PHA team

AbstractLock 8 people in a room for 10 days with the charge to do a PHA (Process Hazard Analysis), to develop missing Process Safety Information, to make recommendations to reduce risk and to document all their work—What will result? Frustration and fatigue, or comradeship and accomplishment? The PHA effort must be managed to meet the objectives of the OSHA rule for Process Safety Management of Highly Hazardous Chemicals, and, equally important, to meet the needs of the individuals serving on the team. This paper presents learnings from over 14 years of leading and serving on HazOp teams. Here's how to get the best from the PHA experience.