What-if approach

What if Approaches Hazind and Operability (HAZOP) Studies Preliminary Hazard Analysis (PLHA) Process Hazard Analysis (PHA)... 

Both HAZOP or What-If reviews are generally organized and conducted in a similar fashion. The HAZOP review is more detailed and structured, while the What-If approach is typically broader and free flowing. 

It has been found that the What-If style of process hazard analysis is a convenient method to use for a "simple" facility. For simple facilities, the detailed HAZOP approach has been found to be tedious and just as productive as a What-If method. The What-If approach stimulates generation of new ideas and discussion to cover issues associated with the items under review, as well as addressing generic issues. The specific HAZOP review is not necessary when the process is simple and well understood by the reviewing team. The team can readily review the major items of concern by asking What-If questions such as what happens when a pump fails, without relying on itemized and detailed variations of a process condition by the HAZOP method, such as high level, low pressure, etc. 

If doubt exist as to what method to apply, the HAZOP method should be chosen over the What-If method. The What-If approach relies on the team leader to ferret out the real hazards associated with the process. The systematic HAZOP approach will examine each portion of the system to determine hazardous conditions. 

These particular facilities may in fact be more suited to a checklist approach due to their usually identical features alternatively a one-time generic What-If approach may be employed that is representative of all the subject facilities (i.e. wellheads with similar GOR, H2S content, pressures etc.). 

Typically it takes an experienced team about two hours to thoroughly complete a single node for a HAZOP review and one hour for a What-If review. A P ID sheet with two nodes is estimated to require four hours to review for a HAZOP and two hours for a What-If approach. It can readily be seen that a What-If review typically requires one half the time to accomplish that of a HAZOP. A formula to estimate the manhours to accomplish a review has been formulated based on historical observations. Manhours expended to accomplish a review can be easily estimated by multiplying the estimate for... 

Pari 1, Making a Plan examining documentation, line identification and contents, isolation, hazards, and what if approach. Pari 2, Shutdown and Isolation steps to isolate work area, replace control valve, and reopen line. 

The Structured What-If Approach is considered to be a combination of the What-If and the HAZOP approaches to PHA. It is considered to be applicable to well understood processes and it adds some structure to a What-If without approaching the detail of a HAZOP. 

One way of conducting an IHA is with the What-If approach. A hazards analysis team can use a flowchart of the overall process to ask What-If questions such as the following ... 

A hazards analysis can be used to systematically review the operating instructions using a What-If approach. The team works through the procedures asking What-If questions regarding each instruction. The questions include the following ... 

PhiUey, J., 2011. Structured What-if Approach to Process Hazards Analysis. 24th Annual TCC/ACIT EHS Seminar. 

A what-if analysis is less stmctured than most of the other techniques. The lead analyst may open the session with a few generic questions. However, other questions will be developed and new scenarios explored as the brainstorming progresses. The what-if approach works well for evaluating procedures. 

On the other hand, specific scenarios corresponding to events of unpredictable probabilities can be developed to check the robusmess of the repository system to such events ("what if approach). Such specific scenarios may be introduced to represent extreme realizations of situations that generally fall into the "normal scenario. For example the ageing and progressive loss of effectiveness of shaft and access tuimel seals is assumed, due to lack of qualification, to prematurely allow for a short-circuit pathway in these seals this case is dealt with as an hypothetical scenario. Another example of a hypothetical scenario comes from the difficulty in very heterogeneous rock formations to correctly characterize the medium from a limited set of measurements this leads to introducing a hypothetical scenario corresponding to an undetected defect in the host formation. 

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. 

Most hazard identification procedures have the capabiUty of providing information related to the scenario. This includes the safety review, what-if analysis, hazard and operabiUty studies (HAZOP), failure modes and effects analysis (FMEA), and fault tree analysis. Using these procedures is the best approach to identifying these scenarios. 

The cost of performing the hazard identification step depends on the size of the problem and the specific techniques used. Techniques such as brainstorming, what-if analyses, or checklists tend to be less expensive than other more structured methods. Hazard and operability (HAZOP) analyses and failure modes and effects analyses (FMEAs) involve many people and tend to be more expensive. But, you can have greater confidence in the exhaustiveness of HAZOP and FMEA techniques—their rigorous approach helps ensure completeness. However, no technique can guarantee that all hazards or potential accidents have been identified. Figure 8 is an example of the hazards identified in a HAZOP study. Hazard identification can require from 10% to 25% of the total effort in a QRA study. 

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... 

Here again, no precise instructions can be given because each situation will demand a tailored approach. Note Numerical simulation in many ways resembles the what-if scenario technique available in spreadsheets programs. Several programs supplied with this book allow the reader to play with functions and noise levels.)... 

We take a Bayesian approach to research process modeling, which encourages explicit statements about the prior degree of uncertainty, expressed as a probability distribution over possible outcomes. Simulation that builds in such uncertainty will be of a what-if nature, helping managers to explore different scenarios, to understand problem structure, and to see where the future is likely to be most sensitive to current choices, or indeed where outcomes are relatively indifferent to such choices. This determines where better information could best help improve decisions and how much to invest in internal research (research about process performance, and in particular, prediction reliability) that yields such information. 

For example, a traditional checklist is, by definition, based on the process experience the author accumulates from various sources. The checklist is likely to provide incomplete insights into the design, procedural, and operating features necessary for a safe process. The what-if part of the analysis uses a team s creativity and experience to brainstorm potential accident scenarios. However, because the what-if analysis method is usually not as detailed, systematic, or thorough as some of the more regimented approaches (e.g., HAZOP study, FMEA), use of a checklist permits the PrHA team to fill in any gaps in their thought process. 

A What-if analysis is used to assess consequences of deviations from normal operating conditions by asking "what if... " questions. This approach is often used for reviewing plant or process modifications. Because the procedure is less structured than some other methods, e.g, HAZOP, care should be taken to identify also the less obvious hazards [2,3,255]. 

These reviews can be either in addition to or combined with periodic process hazard analyses (PHAs) by using methods such as what-if analysis and HAZOP studies. The latter should consciously focus on identifying scenarios in which intended reactions could get out of control and unintended reactions could be initiated. One means of accomplishing this as part of a HAZOP study has been to include chemical reaction as one of the parameters to be investigated for each study node. Johnson and Unwin (2003) describe other PHA-related approaches for studying chemical reactivity hazards. 

What-If Reviews - A safety study which by which "What-If investigative questions (brainstorming approach) are asked by an experienced team of a hydrocarbon system or components under examination. Risks are normally expressed in a qualitative numerical series (e.g., 1 to 5). 

The usual textbook approach is to take a piece of equipment, say something like This is a typical model, and go on from there, trying to illustrate some very common principles. Only what if your equipment is different Well, that s where you ll have to rely on your instructor to get you out of the woods. I m going to pick out specific instruments as well. But at least now you won t panic if the knobs and settings on yours are not quite the same. 

Needless to say, a simplified model leads to corresponding thermodynamic quantities, i.e. not all correlations are included. However, the thermodynamic framework itself is fully internally consistent. This is an important observation, because such a model can for this reason be of use to establish the thermodynamic feasibility of what-if questions. Full control over the absolute deviations from the true thermodynamic behaviour is unfortunately not possible. The approach ignores important (cooperative) fluctuations, and it is expected that especially near phase transitions the approach may give only qualitative results. In particular, comparison of SCF results with experiments or with simulation data can lead to insights into how rigorous the method is. 

How might you have approached this problem differently (Experience led to initial suspicion of metal shavings from worn machine parts. What if you do not have the experience to develop this initial hypothesis Would you have thought of using of a magnet, as opposed to a more sophisticated method like atomic absorption spectroscopy )... 

Several qualitative approaches can be used to identify hazardous reaction scenarios, including process hazard analysis, checklists, chemical interaction matrices, and an experience-based review. CCPS (1995a p. 176) describes nine hazard evaluation procedures that can be used to identify hazardous reaction scenarios-checklists, Dow fire and explosion indices, preliminary hazard analysis, what-if analysis, failure modes and effects analysis (FMEA), HAZOP study, fault tree analysis, human error analysis, and quantitative risk analysis. 

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