Process hazards human error

A hazard is defined as the potential source of harm (3.5). Hazards include both the characteristics of things and the actions or inactions of people. Identifying hazardous human error potential, as well as the physical aspects of hazards, is an important part of the hazard identification process. All risks with which safety practitioners deal derive from hazards. There are no exceptions. For any particular hazard, the first and best approach is to eliminate the hazard. If there are no potentials for harm, there are no hazards. If there are no hazards, there are no risks. Hazards eliminated result in zero risk from those hazards. But, it is not possible to eliminate all hazards. 

Operations and support hazard analysis is a safety method that also has strong potential in manufacturing. The safety tool is applicable to any situation where human operators are an integral part of the process. For example, any plant that moves large amounts of material during the manufacturing process could benefit from using this tool. The analysis identifies the hazards at the critical points in the process where human error could have disastrous effects. 

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. 

As microprocessor-based controls displaced hardwired electronic and pneumatic controls, the impac t on plant safety has definitely been positive. When automated procedures replace manual procedures for routine operations, the probability of human errors leading to hazardous situations is lowered. The enhanced capability for presenting information to the process operators in a timely manner and in the most meaningful form increases the operator s awareness of the current conditions in the process. Process operators are expected to exercise due diligence in the supervision of the process, and timely recognition of an abnormal situation reduces the likelihood that the situation will progress to the hazardous state. Figure 8-88 depicts the layers of safety protection in a typical chemical jdant. 

A critical assembly is a split bed on which fissionable material used to mock up up a separated reactor core that is stacked half on each half. One half is on roller guides so that the two halves may be quickly pulled apart if the neutron multiplication gets too high. Use the Preliminary Hazards Analysis method described in section 3,2.1 to identify the possible accidents that may occur and the qualitative probabilities and consequences. List the initiators in a matrix to systematically investigate the whole process. Don t forget human error. 

Checks of critical process parameters and warnings about hazardous conditions that can cause injury or equipment damage are important factors which determine the occurrence and recovery of human error. The purpose of these checks is to emphasize critical process information. Because of the critical nature of this information, checks and warning should be highlighted in a way that distinguishes them from other notes, and should be located where process workers will not overlook them. 

Assume that the system described below exists in a process unit recently purchased by your company. As the manager, the safety of this unit is now your responsibility. You are concerned because your process hazard analysis team identified the potential for an operator error to result in a rupture of the propane condenser. You have commissioned a human reliability analysis (HRA) to estimate the likelihood of the condenser rupturing as the result of such an error and to identify ways to reduce the expected frequency of such ruptures... 

This is a situation where a plant appears to be operating successfully, without a major human error problem. However, management are interested in assessing the systems in the plant from the point of view of minimizing the error potential. This type of exercise is particularly relevant for plants dealing with substances or processes with high hazard potential, for example, in terms of... 

Bridges, W. G., Kirkman, J. Q., Lorenzo, D. K. (1994). Include Human Errors in Process Hazard Analyses. Chemical Engineering Progress, May. 

A part of the test plan must include testing for the consequences of equipment malfunction, deviations in process conditions, and human error. Bench-scale equipment, for example, the RC1, is quite suitable for such experiments. By analysis of the process, critical conditions can be defined, which then need to be tested in order to be able to proceed safely from the laboratory to pilot plant studies. In testing abnormal conditions or process deviations, caution is required to assure that no uncontrollable hazard is created in the laboratory. Typical deviations, including impact on the process, are discussed in the following paragraph. 

Lees (Loss Prevention in the Process Industries, 2d ed., Butter-worths, London, 1996), BP (Hazards of Trapped Pressure and Vacuum, 2003), and Kletz (What Went Wrong —Case Histories of Process Plant Disaster, Gulf Publishing Company, 1989) include additional case histories providing valuable lessons about how equipment failures and human errors can combine to inflict vacuum damage. 

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. 

Process hazard analysis considers equipment failure, human factors-including errors of omission and commission, and previous incidents. 

Fault tree analysis is based on a graphical, logical description of the failure mechanisms of a system. Before construction of a fault tree can begin, a specific definition of the top event is required for example the release of propylene from a refrigeration system. A detailed understanding of the operation of the system, its component parts, and the role of operators and possible human errors is required. Refer to Guidelines for Hazard Evaluation (CCPS, 1992) and Guidelines for Chemical Process Quantitative Risk Assessment (CCPS, 2000). 

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 ... 

The full range of process maloperations, including system failures that might lead to process runaway will first have to be considered by a systematic evaluation of the plant and process concerned141. These may, for examplel be due to human error, hardware failure, or due to failure of a computerised sequence controller. To assess the likely/ credible maloperations accurately, it is recommended that personnel who will be operating the plant are involved in the hazard assessment. 

Simplify—Design processes and facilities that eliminate unnecessary complexity and that are tolerant of human error. Example Design piping to permit gravity flow of hazardous materials in a plant, eliminating the need for pumps, which can leak. 

This one costly human error had a considerable effect on the Congress, just then in the process of hammering out certain provisions of TSCA—The Toxic Substances Control Act of 1976. In particular those sections dealing with the premarket testing of hazardous chemicals, their labeling and distribution were affected (ref. 154). 

Chung, P. and Broomfield, E. (1995), Hazard and Operability (HAZOP) Studies Applied to Computer-Controlled Process Plants, in Computer Control and Human Error (Ed. T. Kletz), Institution of... 

There are various types of analyses that are used for a process hazard analysis (PHA) of the equipment design and test procedures, including the effects of human error. Qualitative methods include checklists, What-If, and Hazard and Operability (HAZOP) studies. Quantitative methods include Event Trees, Fault Trees, and Failure Modes and Effect Analysis (FMEA). All of these methods require rigorous documentation and implementation to ensure that all potential safety problems are identified and the associated recommendations are addressed. The review should also consider what personal protective equipment (PPE) is needed to protect workers from injuries. 

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