Introduction to Hazard Identification and Risk Analysis | AIChE

Introduction to Hazard Identification and Risk Analysis


A thorough Hazard Identification and Risk Analysis, or risk, system is the core element in the RBPS pillar of understanding hazards and risk. This chapter describes the meaning of risk for RBPS purposes, the attributes of a risk system, and the steps an organization might take to implement a robust program for identifying hazards and analyzing risk. Section 9.2 describes the key principles and essential features of a management system for this element. Section 9.3 lists work activities that support these essential features, and presents a range of approaches that might be appropriate for each work activity, depending on perceived risk, resources, and organizational culture. Sections 9.4 through 9.6 include (1) ideas for improving the effectiveness of management systems and specific programs that support this element, (2) metrics that could be used to monitor this element, and (3) issues that may be appropriate for management review.

What Is It?

Hazard Identification and Risk Analysis (HIRA) is a collective term that encompasses all activities involved in identifying hazards and evaluating risk at facilities, throughout their life cycle, to make certain that risks to employees, the public, or the environment are consistently controlled within the organization’s risk tolerance. These studies typically address three main risk questions to a level of detail commensurate with analysis objectives, life cycle stage, available information, and resources.

The three main risk questions are:

  • Hazard – What can go wrong?
  • Consequences – How bad could it be?
  • Likelihood – How often might it happen?

When answering these questions, the objective is to perform only the level of analysis necessary to reach a decision, because insufficient analysis may lead to poor decisions and excessive analysis wastes resources. A suite of tools is available to accommodate varying analysis needs: (1) tools for simple hazard identification or qualitative risk analysis include hazard and operability analysis (HAZOP), what-if/checklist analysis, and failure modes and effects analysis (FMEA), (2) tools for simple risk analysis include failure modes, effects, and criticality analysis (FMECA) and layer of protection analysis (LOPA), and (3) tools for detailed quantitative risk analysis include fault trees and event trees (Refs. 9.2, 9.3, 9.4). For example, some companies may judge the mere existence of an explosion hazard to be an unacceptable risk, regardless of its likelihood. Others may be willing to tolerate an explosion risk if proper codes and standards are followed. Still others may be unwilling to accept an explosion risk unless it can be shown that the expected frequency of explosions is less than 10-6/y. HIRA encompasses the entire spectrum of risk analyses, from qualitative to quantitative. A process hazard analysis (PHA) is a HIRA that meets specific regulatory requirements in the U.S. Figure 9.1 illustrates the increasing rigor of risk analyses possible as the scope of the study becomes more focused on specific accident scenarios. Note that as risk studies become more focused and detailed, the cost per scenario analyzed increases, but the overall cost may decrease if only a few representative or bounding scenarios are analyzed.


Why Is It Important?

To manage risk, hazards must first be identified, and then the risks should be evaluated and determined to be tolerable or not. The earlier in the life cycle that effective risk analysis is performed, the more cost effective the future safe operation of the process or activity is likely to be. The risk understanding developed from these studies forms the basis for establishing most of the other process safety management activities undertaken by the facility. An incorrect perception of risk at any point could lead to either inefficient use of limited resources or unknowing acceptance of risks exceeding the true tolerance of the company or the community.

Where/When Is It Done?

HIRA reviews may be performed at any stage in a project’s life cycle – conceptual design, preliminary design, detailed design, construction, ongoing operation, decommissioning, or demolition. In general, the earlier that a hazard is identified (e.g., during conceptual design), the more cost-effectively it can be eliminated or managed. Studies performed during the early design stages are typically done at corporate or engineering offices. Studies performed once a process is near startup, during operation, or before decommissioning are typically done in a plant environment.

Who Does It?

A HIRA study is typically performed by a team of qualified experts on the process, the materials, and the work activities. Personnel who have formal training on risk analysis methods usually lead these teams, applying the selected analysis technique(s) with subject matter experts from engineering, operations, maintenance, and other disciplines as needed. A simple early-in-life hazard identification study may be performed by a single expert; however, a multidisciplined team typically conducts more hazardous or complex process risk studies, especially during later life cycle stages. Involving operating and maintenance personnel early in the review process will help identify hazards when they can be eliminated or controlled most cost effectively. When the study is complete, management must then decide whether to implement any recommended risk reduction measures to achieve its risk goals.

What Is the Anticipated Work Product?

The main process safety products of a risk system are: (1) guidelines for planning and conducting studies, (2) documented understanding of the risks of the process or activity, (3) documented risk tolerance criteria, (4) possible risk control measures, resolutions, and implemented actions, (5) documented understanding of the residual risks after control measures are taken, and (6) completed risk analysis reports. Other work products may include recommendations for improving asset integrity, procedures, and training as well as up-to-date action item tracking lists and risk communication materials. The scope of HIRAs is sometimes broadened to include operability issues, so the work products may also include recommendations to (1) improve quality and yield, (2) reduce equipment damage, and/or (3) reduce unplanned downtime. The results of risk studies are normally kept for the life of the process and are communicated to those who may be affected. Outputs of the risk element can also be used to facilitate the performance of other elements. For example, identifying potential accidents will help define scenarios the emergency element must address, and understanding the existing risks may enable the management of change element to identify the risks of a change.

How Is It Done?

At each stage in the project life cycle, a review team questions process experts about possible hazards and judges the risk of any hazards that are identified. Several common methods exist for questioning a design, ranging from simple qualitative checklists to complex quantitative fault tree analyses (Refs. 9.2, 9.3, 9.4). The results of the review process are typically documented in a worksheet form, illustrated in Figure 9.2, which varies in detail, depending on the stage of the project and the evaluation method used. Risk studies on operating processes are typically updated or revalidated on a regular basis.