What If Analysis

The main purpose of the What If qualitati e method is to identify the hazards associated with a process by asking questions that sttut with What if. This method can be extremely useful if the design team conducting tlie c. aniination is experienced and knowledgeable about the operation if not, tlie results are usuall) incomplete. The e. amination usually starts at tlie point of input and continues in a railroad inamier according to tlie flow of the process.  

The first step of a Wliat If anal) sis is to define the study boundaries. There arc two types of study boundaries to be considered the consequence category boundary, which includes public risk, emplojee risk, and economic risk, and the ph)Sical boundary which addresses the section of the plant tlurt should be considered for analysis. 

The second stop is to obtain all the infomration about the process that will be needed for a thorough evaluation including but not limited to. the process materials used and their physical properties, the dicmistry and tlicnnodynamics of the process, a pkuit layout, and a description of all the equipment used including controls and instruincntation. The last part of the infomration gathering step nr iy be viewed as the preliminary foniiation of the What ir questions. 

The final step in the Wliat If aiuilysis is reporting the results in a systematic and easily understood fornuit. An o. anrple of a common fornrat is provided in Table 1.5.5.1, which includes tire question, Uieir consequences, and recoirrmendittions. An ethylene polyirrerization process is used to demonstrate the format for a What If analysis. 

Although the What If procedirre is not as stmetured as soirte other c citt/lrtr/nrd aird identification studies, it is a powerful procedure if the staff menrbers arc experienced. Otlrcrwisc ( md as indicated above), the results from the procedure may neither complete nor accurate. 

The purpose of a what-if analysis is to identify hazards, hazardous situations, or specific accident events that could produce an undesirable consequence. The what-if analysis is described in detail in Guidelines for Hazard Evaluation Procedures (CCPS, 1992). 

What-if analysis involves the examination of possible deviations from the design, construction, modification, or operating intent of a process. It can be used to examine virtually any aspect of facility design or operation. Because it is so flexible, it can be performed at any stage in the life of a process using whatever process information and knowledge is available. 

The what-if analysis is a creative, brainstorming examination of a process or operation conducted by a group of experienced individuals able to ask questions or voice concerns about undesired events. It is not as inherently structured as some other methods, such as the hazard and operability (HAZOP) study or a failure mode and effects analysis (FMEA). 

Rather, it requires the analysts to adapt the basic concept to the specific application. 

The what-if analysis method may simply generate a list of questions and answers about the process. However, it usually results in a tabular listing of hazardous situations, their consequences, safety levels, and possible options for risk reduction. 

There are several advantages and disadvantages of using the What-If technique. The advantages include  

Team of relevant experts extends knowledge and creativity pool. 

Ability to focus on specific element (i.e. human error or environmental issues). 

Quality is dependent on knowledge, thoroughness and experience of team. 

Loose structure that can let hazards slip through. 

The what-if analysis stimulates a PrHA team to ask What-if Through questions, the team generates a table of possible accidents, their consequences, safety margins, and mitigation. The accidents are not ranked or evaluated. 

What-if produces a table of narrative questions and answers suggesting accident scenano.s. consequences, and mitigation. Table 3.3.2-1 shows a typical What-If analysis for the Dock 8. in the left in the line above the table is indicated the line/vessel that is being analyzed. To the right is the date and page numbers. The first row in the table contains the column headings beginning with i ie what-if question followed by the consequences, safety levels, scenario number and comments. 11C comments column may contain additional descriptive information or actions/ recommendations. 

Wliat If Consequences Safety Level Scenario Comments 

The PSM Rule requires that a What-If analysis be performed by a team with expertise in the process and analysis method. For a simple process, two or three people may perfonn the analysis, but for a complex process, a large group subdivided according to process logic into small teams is needed. 

Once the individual nodes have been identified, the HAZOP study and What-If analysis can be initiated. As stated earlier, the information developed through the What-If analysis can then be used as input data for the more complete and detailed HAZOP smdy of the vapor degreasing system. 

While both the HAZOP study and What-If analysis are generally organized and conducted in a similar fashion, the HAZOP study is more comprehensive and structured, while the What-If approach is generally broader and less formal. For these reasons, each method will be presented and discussed separately. 

Process material characteristics (c.g.. To.xicity and reactivity information) 15.5 WHAT IF ANALYSIS  

The third step is to select a rc icw team. The team is usiuilly composed of two or three members that ha c combined experience in the process to be studied, knowledge in the consequenee field, and experience in general haziird e aluation. If the team is inexperienced, results may be incomplete or incorrect. 

Once the leant has been established, the review is conducted. Typically, the rc icw begins with the process inputs and proceeds through the syslcin to the outputs. Each of the What IF questions is addressed by identifying the hazard and it s consequence, and then recommending solutions or alternatives to alle ialc the risk.  

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Methods for performing hazard analysis and risk assessment include safety review, checkhsts, Dow Fire and Explosion Index, what-if analysis, hazard and operabihty analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis. Other methods are also available, but those given are used most often. 

What-If Analysis. The what-if analysis is simply a brainstorming technique that asks a variety of questions related to situations that can occur. For instance, in regards to a pump, the question What if the pump stops mnning might be asked. An analysis of this situation then follows. The answer should provide a description of the resulting consequence. Recommendations then foUow, if required, on the measures taken to prevent an accident. 

The what-if analysis approach is useful throughout the entire lifetime of a process and is frequendy used in conjunction with the checklist approach. However, the approach is very unstmctured and depends heavily on the experience of the analysts to ask the correct questions. 

Frequency Phase 1 Perform Qualitative Study, Typically Using HAZOP, FMEA, or What-if Analysis. To perform a qualitative study you should first (1) define the consequences of interest, (2) identify the initiating events and accident scenarios that could lead to the consequences of interest, and (3) identify the equipment failure modes and human errors that could contribute to the accident... 

What-if analysis This program should allow the user to do various studies of plant operating scenarios to ascertain the expected performance level of the plant due to environmental and other operational conditions. 

Working with a Process Hazards Analysis (PHA) team was particularly rewarding. The plant operators on the team pointed out items that they had considered safety problems for years, but that hadn t been fully addressed until the PHA team was formed. We used the What if analysis method. Many methods are available for PHA. 

The time and cost of a What-If analysis are proportional to team size and complexity. Table 3.3 2-3 presents estimates of the time needed to perform a PrHA using the what-if analysis method. 

The What-If analysis is a powerful PrHA method if the analysis team is experienced and well organized, but because it is a relatively unstructured approach, the results may be incomplete... 

Answer See Table 15.5.1-1 for the What-If analysis and Table 15.5.1-2 for the initiator list. 

What-If Analysis of the Cooling Tower Chlorination System. . <3... 

TABLE 15.5,1 What If Analysis on the Ethylene Polymerization Reactor... 

Table 4.7. Typical Format for a What-if Analysis Worksheet...

The what-if/checklist analysis method combines the creative, brainstorming features of the what-if analysis with the systematic features of the checklist analysis. The PrHA team uses the what-if analysis method to brainstorm the types of accidents that can occur within a process. Then the team uses one or more checklists to help fill in any gaps. Finally, the team members suggest ways for reducing the risk of operating the process. The what-if analysis encourages the PrHA team to consider potential accident events and consequences that are beyond the experience of the authors of a good checklist and, thus, are not covered on the checklist. Conversely, the checklist lends a systematic nature to the what-if analysis. 

Table 4.9. What-If Analysis of Dock 8 HF Supply System...

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