Process Hazards Analyses

Process Hazard Analysis (PHA) can be defined as the application of a systematic method to a process design in order to identify potential hazards and operating problems. It determines the causes and consequences of abnormal process conditions that arise from equipment failure, human error or other events. The goal is to determine whether opportunities exist to reduce the risks of the toll s hazards and then to implement warranted action items. The AJChE CCPS guideline Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples is a good resource for fully detailed approaches to process hazard analysis. It provides an introduction to hazard evaluation as well as guidance on  

PHAs are performed primarily to reduce losses resulting from incidents that can injure plant personnel or the public, or damage or destroy buildings, equipment, and material. There are other less measurable losses that occur after incidents. Companies reputations, the industry s reputation and the effect on customers and the public are all at stake. 

For every new tolling situation a process hazard analysis should be conducted using one of several acceptable methodologies in common use. The goal is to select a methodology appropriate to evaluate the hazards of the toll process in question. 

When the analysis is complete, the PHA team leader will issue a report with action items. Items required to be done before start-up 

Process hazard analysis is the cornerstone of the OSHA standard. The standard goes on to say that the employer may choose from one or more of the following safety analysis methodologies as a process hazard analysis  

The PSM Rule specifies that a PrHA be performed on every process covered under the rule. 

If several processes require PrHAs, the PrHAs must be prioritized. A preliminary hazard analysis (PHA) may be used to determine and document the priority order for conducting PrHAs. At a minimum, the PSM Rule requires the prioritization to consider the potential severity of a chemical release, the number of potentially affected employees, and the operating history of the process, including the frequency of past chemical releases and the age of the process. 

The schedule imposed by the PSM Rule allows for gradual completion of the required PrHAs. However, the PrHAs must be conducted as soon as possible, and according to the following schedule. 

PrHAs completed after May 26, 1987, which meet the PSM Rule were acceptable as initial PrHAs. 

Each PrHA must be updated and revalidated at least every 5 years after its initial completion to assure that it is consistent with the current process. 

The OSHA Process Safety Management standard requires completion of a process hazard analysis for any activity involving the use of highly hazardous chemicals. The OSHA standard applies to 

Included in OSH As JHA Booklet, 3071, is a good description of a process hazard analysis (PHA) [1]. This is being used in the Process Safety Management (PSM) program (29 CER 1910.119) to understand how hazards exist. There are some good methods listed in the manual that can be used to conduct a JHA. As you review each method you can determine which one may be useful for your operation. The typical method chosen is the checklist. 

PSM was created to help the management of hazards associated with processes using highly hazardous chemicals. In an appendix to the rule, OSHA discussed several methods of process hazard analysis. That 

For a relatively uncomplicated process, review the process from raw materials to finished product. At each handling or processing step, you formulate and answer what-if questions to evaluate the effects of component failures or procedural errors on the process. 

The what if/checklist is a broadly based hazard assessment technique that combines the creative thinking of a selected team of specialists with the methodical focus of a prepared checklist. The result is a comprehensive hazard analysis that is useful in training operating personnel on the hazards of the particular operation. 

Subsequently, the review team develops answers for eaeh question. 

A PHA analyzes potential causes and consequences of fires, explosions, releases of toxic or flammable chemicals, and major spills of hazardous chemicals. The PHA focuses on equipment, instrumentation, utilities, human actions (routine and nonroutine), and external factors that might affect the process. 

Finally, when a company has a large continuous process with several control rooms for different portions of the process, such as for a distillation tower and a blending operation, the organization may wish to do each segment separately and then integrate the final results. 

Small businesses covered by this rule will often have processes that have less storage voliune and less capacity and may be less complicated than processes at a large facility. 

Accordingly, it would not be a surprise to see the application of less complex methodologies being used to meet the PHA criteria in the standard. These PHAs can be done in less time and with fewer people being involved. A less complex process generally means that less data, P IDs, and process information are needed to perform a PHA. 

Many small businesses have processes that are not unique, such as refrigerated warehouses, cold storage lockers, or water treatment facilities. Where associations have a number of members with such facilities, a generic PHA, evolved from a checklist or what-if questions, could be developed and effectively used by companies to reflect their particular process this would simplify compliance for them. 

Selection of a PrHA methodology requires consideration of many factors including the availability of process information such as experience with the process, changes that have taken place, reliability, aging, maintenance, etc. If it is a new process, less reliance can be placed on experience and greater reliance must be placed on the analysis of possible accidents and accidents in similar or related processes. Size, complexity and hazard severity influences the dunce ot ihe most appropriate PrHA methodology. 

Simplifying assumptions used by the PrHA team and reviewers must be understood and recorded to indicate the completeness of the PrHA, and for use in future improvements of the analysis. The PrHA team and especially the team leader must thoroughly undcrsiantl ilic methodology that is selected 

A team consists of two or more people that know the process technology, design, operating procedures, practices, alarms, emergency procedures, test and maintenance procedures, routine and non-routine tasks. They must consider authorization and procurement of parts and supplies, safety and health standards, codes, specifications and regulations. The team leader provides m.iriagcment and goals to the process the team and consultants construct and interpret the analyses. 

Small operations, although covered by the PSM rule, may use simplified methodologies and still meet the criteria. Businesses with similar processes and equipment may pool resources and prepare a generic checklist analysis used by all members to meet the PSM rule. 

Operating procedures specify the way tasks are to be performed, data to be recorded, op iitions to be maintained, samples to be collected, and actions to enhar and 

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Process Hazards Analysis. Analysis of processes for unrecogni2ed or inadequately controUed ha2ards (see Hazard analysis and risk assessment) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects ha2ard and operabiHty (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify ha2ards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

Of these, the failure logic can easily be the most demanding. The simplest approach is to stop or hold on any abnormal condition, and let the process operator sort things out. However, this is not always acceptable. Some failures lead to hazardous conditions that require immediate action waiting for the operator to decide what to do is not acceptable. The appropriate response to such situations is best determined in conjunc tion with the process hazards analysis. 

A process hazards analysis is intended to identify the safety interlocks required for a process and to provide the following for each ... 

The process hazards analysis is conducted by an experienced, multidisciplinary team that examines the process design, the plant equipment, operating procedures, and so on, using techniques such as... 

Diversity is recognized as a useful approach to reduce the number of defects. The team that conducts the process hazards analysis does not implement the safety interlocks but provides the specifications for the safety interlocks to another organization for implementation. This organization reviews the specifications for each safety interlock, seeking clarifications as necessary from the process hazards analysis team and bringing any perceived deficiencies to the attention of the process hazards analysis team. 

Assure that the initial implementation comphes with the requirements defined by the process hazards analysis team. 

Process Hazard Analysis (PHA) (Dowell, 1994, pp. 30-34.) The OSHA rule for Process Safety Management (PSM) of Highly Toxic Hazardous Chemicals, 29 CFR 1910.119, part (e), reqmres an initial PHA and an update every five years for processes that handle listed chemicals or contain over 10,000 lb (4356 kg) of flammable material. The PHA must be done by a team, must include employees such as operators and mechanics, and must have at least one person skilled in the methodology employed. Suggested methodologies from Process Safety Management are listed in Table 26-1. 

TABLE 26-1 Process Hazard Analysis Methods Listed in the OSHA Process Safety Management Rule... 

Chemical Exposure Index (CEI) Chemical Exposure Index, 1994). The CEI provides a method of rating the relative potential of acute health hazard to people from possible chemical release incidents. It may be used for conducting the initial process hazard analysis and it establishes the degree of mrther analysis needed. The CEI also may be used as part of the site review process. 

The book does not focus on occupational safety and health issues, although improved process safety can benefit these areas. Detailed engineering designs are outside the scope of this work. This book intends to identify issues and concerns in batch reaction systems and provide potential solutions to address these concerns. This should be of value to process design engineers, operators, maintenance personnel, as well as members of process hazards analysis teams. While this book offers potential solutions to specific issues/concerns, ultimately the user needs to make the case for the solutions that provide a balance between risk... 

Perform process hazards analysis Perform management of change review... 

Process Hazard Analysis (PHA) A structured procedure whereby hazards associated with a process are identified and evaluated. 

Examining the lists above makes it clear that a good toller-client relationship with open and honest communication of process safety information, process hazard analysis input and early recognition of issues can help avoid potential problems. 

Any pre-existing process hazards analysis from the pilot development or other tolling efforts... 

In order to understand the chemical and process hazards, a Process Hazard Analysis (PHA) should be conducted. For tolls involving... 

While material safety data sheets (MSDS) provide important information they may not provide information on all hazards that may be encountered during processing. A review of the MSDS is not a substitute for conducting a process hazards analysis. Additional information to consider should include ... 

Process specifications will typically be set forth in the process technology package. However, a process hazard analysis (PHA) in preparation for startup may reveal additional useful measurements or sample points. These may be analyses or measurements for the startup period or for the life of the toll. 

The experts are the members providing the technical expertise for completing the study. Depending upon the process, a process hazard analysis could include any or all of the following types of experts. Some can be brought in on an as needed basis ... 

The toller and their client can work together to identify the appropriate method and detail required for the process hazard analysis. Consider adding a brief statement in the final PHA report documenting why the method was selected. 

A PHA has heen performed for new facilities. The management of change documentation packages and referenced documents should indicate when a process hazard analysis was performed for the modification or new facility. The PSSR Team should verify all of the PHA recommendations have been implemented or otherwise resolved before the toll process can be judged ready to operate. 

For new facilities, the initial process hazard analysis (PHA) has been performed and recommendations have been resolved. ... 

The effort and time that is required for a process hazard analysis for these examples should not be an issue. A thorough management of change system will call for the change coordinator to make a decision as to what type of review is appropriate for the change. 

Process Hazard Analysis (PHA) An organized effort to identify and evaluate hazards associated with chemical processes and operations to enable their control. This review normally involves the use of qualitative techniques to identify and assess the significance of hazards. Conclusions and appropriate rec-... 

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