Process Hazards Checklists

Process hazards checklists This is a list of items and possible problems in the process that must be checked. 

A process hazards checklist is simply a list of possible problems and areas to be checked. The list reminds the reviewer or operator of the potential problem areas. A checklist can be used during the design of a process to identify design hazards, or it can be used before process operation. 

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. 

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. 

Table 3.3.1-3 Simplified Process Hazards Analysis Checklist ...

Move set point to measured value Action Action Omitted Set point left at original value System may operate at wrong set point. Process hazard may occur (Moderate) Noticeable change of value of variable may occur at step 1.2 Introduce check in checklist... 

When derived from handbooks or similar sources, many entries in a checklist may not be applicable to the process being studied. In other cases, process hazards may be so unusual they are not in standard checklists. Thus, it may be difficult to assure that all hazards have been analyzed. Also, checklists may indicate that hazards exist, but not what accident scenarios are associated with them. 

V Process hazard analysis (PHA) must be performed by a team of experts, including engineers, chemists, operators, industrial hygienists, and other appropriate and experienced specialists. The PHA needs to include a method that fits the complexity of the process, a hazards and operability (HAZOP) study for a complex process, and for less complex processes a less rigorous process, such as what-if scenarios, checklists, failure mode and effects analysis, or fault trees. 

The first step in the procedure is to conceptually divide the process into separate process units. A process unit is a single pump, a reactor, or a storage tank. A large process results in hundreds of individual units. It is not practical to apply the fire and explosion index to all these units. The usual approach is to select only the units that experience shows to have the highest likelihood of a hazard. A process safety checklist or hazards survey is frequently used to select the most hazardous units for further analysis. 

The What-if, the checklists and Hazop are well publicized hazard identification tools. But as Bollinger et al. (1996) have pointed out the use of any of these techniques demands knowledge, experience and flexibility. No prescriptive set of questions or key words or list is sufficient to cover all processes, hazards and all impacted populations. Bollinger et al. find that refinement of the quantitative measurement techniques such as safety indices and convergence to a single set of accepted indices would be beneficial. 

Process hazard analysis (PHA) Any of a number of techniques for understanding and managing the risk of a chemical process or plant. Examples of PHA techniques include HAZOP, checklists, what-if methods, fault tree analysis, event tree analysis, and others. 

Loss-of-Containment Causes The list in Table 23-30 indicates four basic ways in which containment can be lost. These cause cate-ories can be used both as a checklist of considerations during the esign process and as a starting point for evaluating the adequacy of safeguards as part of a process hazard and risk analysis. 

The facility is subjected to a process hazard analysis commensurate to the level of hazard the facility represents (i.e., Checklist, PHA, HAZOP, What-If review, Event Tree, FMEA, etc.). The results of these analyses are fully understood and acknowledged by facility management. Where high risk events are identified, quantifiable risk estimation and effects of mitigation measures should be evaluated and applied if productive. 

This checklist may be used to stimulate the thinking of inherent safety review and process hazard analysis teams, and any other individuals or groups working on process improvements. It is intended to promote "blue-sky" or "out-of the-box" thinking, and to generate ideas that might be usable in an existing facility or a "plant of the future" concept. 

The topics for this checklist have been taken from CCPS (1993b) and Bollinger et al. (1996). Every effort was made to ensure that this checklist is comprehensive therefore, there may be some redundancy or overlap in questions among the different sections. It should be noted that some of the items in this checklist employ a very broad concept of inherent safety, as presented by Bollinger et al. (1996). As such, they may address inherent aspects of passive, engineered or even administrative controls, rather than the narrower inherent safety conception of reducing the underlying process hazards that must be contained and controlled to safely operate a facility. 

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. 

Flowcharts are used for process overview analysis of causes and consequences, lines of defense, and testing data requirements and review of hazard checklist, schedule, and followup on recommendations. 

Earlier method of identifying hazards involved a procedure consisting of asking questions such as what if This approach consists of questioning the proper function at every stage of the process, along with consequences or the remedial features. A checklist for the simplified process hazard analysis by the what if method is shown in Table 3.3. Although this method is an old method of hazard analysis compared with other methods such as hazop or fault tree analysis it has proven to be quite useful. 

Table 3.3 What if method checklist for simplified process hazard analysis6 (Courtesy of the American Institute of Chemical Engineers)...

What If/Checklist. The most frequently used method of process hazard review, the what if/checklist, is effective in reviews of relatively uncomplicated processes from raw materials to final product. The team formulates and answers What if questions at each handling or processing step to evaluate the effects of component failures or procedural errors. They use a checklist to ensure that all important subjects are addressed. This method should be used as the first step in all process hazard reviews. 

Identification can be as simple as asking what-iP questions at design reviews. It can also involve the use of a checklist outlining the normal process hazards associated with a specific piece of equipment. The major weakness of the latter approach is that items not on the checklist can easily be overlooked. The more formalized hazard-assessment techniques include, but are not limited to, hazard and operability study (HAZOP), fault-tree analysis (FTA), failure mode-and-effect analysis (FMEA), safety indexes, and safety audits. 

General safety checklist for identifying process hazards... 

HAZOP and What-If reviews are two of the most common petrochemical industry qualitative methods used to conduct process hazard analyses. Up to 80% of a company s process hazard analyses may consist of HAZOP and What-If reviews with the remainder 20% from Checklist, Fault Tree Analysis, Event Tree, Failure Mode and Effects Analysis, etc. An experienced review team can use the analysis to generate possible deviations from design, construction, modification, and operating intent that define potential consequences. These consequences can then be prevented or mitigated by the application of the appropriate safeguards. 

Burk, A. F., "What-If/Checklist - A Powerful Process Hazards Review Technique", AIChE Summer National Meeting, Pittsburgh, PA., August 18-21, 1991. 

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