Chapter 7. What-If Analysis
7.1. What-If Analysis
7.2. What-If Analysis(contd.)
7.3. What-If Analysis (contd.)
7.4. Five Basic Steps
7.5. Supporting Documentation
7.6. Analysis Must Include:
7.7. What-If Analysis
7.8. What-If Analysis(contd.)
7.9. What-If Team
7.10. Question Formulation
7.11. Analysis Results
7.12. Advantages
7.13. Disadvantages
7.1. What-If Analysis
What-If analysis one of the three simplest and easiest ways of conducting a hazard analysis. The others are checklists and preliminary hazard analysis which were discussed previously.
7.2. What-If Analysis (contd.)
What-If analysis is used during the conceptual design phase of a project. However, it can be used during the operating lifetime of a facility when improvements or changes are to be made.
It is considered one of the simplest forms of hazard analysis because it does not require special quantitative methods or extensive preplanning.
The what-if analysis uses input information to generate checklist-type questions.
7.3. What-If Analysis (contd.)
Addresses
A What –If analysis should address the items shown on this slide. It describes the process chemistry by evaluating potential chemical problems such as runaway reactions or processing of toxic chemicals.
First, the process hazards are defined that limit the scope of the study such as explosions, gaseous toxic releases, among others. The next step is to define the physical boundaries of the source of the potential hazard and the impact area.
The consequences for this impact area are in three groups. One is the consequences that affect workers at the site. The second is economic loss and production downtime and the third is the affected off-site population.
7.4. Five Basic Steps
There are five basic steps involved in conducting a What-If analysis. The first step is to define the scope of the analysis. In defining the scope, the hazards that impede the scope like fire, explosion, or gas release must be identified. Next, the source and boundaries of the potential hazards must be identified. The source and boundaries may include a piece of equipment, a process unit with several pieces of equipment, an entire facility or collection of process units, or a community (rail cars and pipelines). Then a team must be selected and documents applicable to the analysis must then be assembled. Next, questions are formulated and evaluated.
7.5. Supporting Documentation
This slide provides a list of some of the supporting documentation often used in a What-If analysis. Other information includes site plans, emergency response plans and electrical area classification drawings.
7.6. Analysis Must Include:
Questions prepared by team members are collected and consolidated by the team leader. These are the column headings for a What-If hazard analysis table. An example of this table is shown on the next slide.
7.7. What-If Analysis
What-If Question Answer/Hazard Critically Possible Recommendation
This table is incomplete before the team review begins. Each row is a What-If question. The consequences for criticality and recommended action are determined by the team. The team leader orchestrates the review, and the results are documented by the team clerk.
7.8. What-If Analysis(contd.)
A What–If analysis should be conducted by a multidisciplinary team. Within this team, a team leader and recorder must be assigned for the duration of the analysis. Before the team meets, questions for the analysis should be prepared. These questions may be prepared individually or in conference.
7.9. What-If Team
A What-If analysis team is multidisciplinary and consists of persons who can contribute in areas such as operations, design, maintenance, and safety. Typically, the team consists of a process operator who should be familiar with startup, shutdown, normal and abnormal operating situations. The team also includes a process engineer, a maintenance engineer, and a safety or plant manager who is familiar with overall on-site and off-site issues.
7.10. Question Formulation
All questions must be in “what-if” format, and they may address many areas. Only some of the areas are listed here. They include equipment failure which may include instrumentation failures as well as interfacing utility failures. Others are process condition upsets, operator improvisation, poor performance, or inattentiveness, departures from operating procedures and external events which includes storms, airplane accidents, or vandalism.
7.11. Analysis Results
Summary Tabulated
Critical Ranking Assigned
- Commonly used Criteria
The What-If hazard analysis table contains the results of the evaluation. At the end of the analysis, a separate form for the summary of the results is prepared to rank-order and establish a priority for the findings of the analysis. These results form the basis of a risk reduction plan.
7.12. Advantages
There are several advantages to using a What-If analysis. First, it is simple to use. Also, it is useful at all stages of plant life from conceptual design to the operation plant. It is relatively inexpensive to conduct this analysis as well. In addition, it provides a convenient tabular summary of the hazard and its consequence.
7.13. Disadvantages
The disadvantages associated with a What-If analysis are that it relies heavily on team experience. The analysis results, are, therefore, only as good as the experience of the team members. Also, the analysis is not very systematic because it is subjective. The last disadvantage is that the results lack numerical prioritization.