Hazard process

Substitution of the processing route with one using less hazardous material or substitution of toxic process materials with nontoxic or less toxic materials. 

Containment sound design of equipment and piping, to avoid leaks. For example, specifying welded joints in preference to gasketed flanged joints that are liable to leak or suffer materials incompatibility problems. 

Prevention of releases by process and equipment design, operating procedures and design of disposal systems. 

Ventilation use open structures or provide adequate ventilation systems. 

Disposal provision of effective vent stacks to disperse material vented from pressure relief devices or use of vent scrubbers. Collection and treatment of sewer and runoff waters and liquids collected from relief systems. 

The major hazards associated with the AIMS were feed and product flammability, chemical exposure, and elevated process temperatures. The risk of hre in the system was reduced by the use of diluted feed streams that did not allow the formation of flammable mixtures in the system. In addition, system interlocks prevented the uncontrolled release of process gases in the event of an incident. These interlocks also minimized the risk of exposure of the system operators to process gases. In addition, the process was entirely contained in a fume hood, so following the system Standard Operating Procedures (SOPs) helped prevent such exposure. The risk of injury due to high temperatures in and around the system was also be minimized by closely following the system SOPs during operation and system maintenance. A detailed description of all process hazards is omitted here for brevity. 

Any notable accumulation of gas was unlikely since the two fans inside the chassis create a flow rate of approximately 180 CFM of air through the system. This corresponded to more than 95 complete air changes or turnovers every minute (Heck and Manning, 2000). The most likely zone of gas escape would be above the microreactor due to a membrane failure. If this occurs, the control system should have interlocked and shutoff the flow of combustible gas to that reaction channel. The flammable gas that does escape would have been immediately diluted by air flowing over the microreactor at an estimated rate of 120 ft min (Heck and Manning, 2000). To provide a more detailed analysis of gas mixing in the immediate vicinity of a microreactor die, a computational fluid dynamics (CFD) model was constructed to simulate the gas flow hydrodynamics. This simulation quantifies that there is a recirculation zone above the reactor with an airflow rate 

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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. 

Fire and uncontroUed polymerization are a concern in the handling of chloroprene monomer. The refined monomer is ordinarily stored refrigerated under nitrogen and inhibited. This is supported by routine monitoring for polymer formation and vessel temperature. Tanks and polymerization vessels are equipped for emergency inhibitor addition. Formalized process hazard studies, which look beyond the plant fence to potential for community involvement, are routine for most chemical processes. 

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. 

An interlock is a protec tive response initiated on the detection of a process hazard. The interlock system consists of the measurement devices, logic solvers, and final control elements that recognize the hazard and initiate an appropriate response. Most interlocks consist of one or more logic conditions that detect out-of-hmit process conditions and respond by driving the final control elements to the safe states. For example, one must specify that a valve fails open or fails closed. 

Safety interlocks. These are designed to protect the pubhc, the plant personnel, and possibly the plant equipment from process hazards. 

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. 

Hazards from combustion and runaway reactions play a leading role in many chemical process accidents. Knowledge of these reactions is essential for control of process hazards. It is important that loss of containment be avoided. For example ... 

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... 

Perform process hazard analyses Perform Management of Change review... 

Drake, E. M. and C. W. Thurston. 1992. A Safety Evaluation Eramework for Process Hazards Management in Chemical Eacilities with PES-Based Controls. Process Safety Management Paper 73d. AlChL 1992 Summer National Meeting, August 1992, Minneapolis, MN. 

Hazard and Operability Study (HAZOP) A systematic qualitative technique to identify process hazards and potential operating problems using a series of guide words to study process deviations. 

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. 

Safety issues due to unknown or insufficient information on processing hazards by the client Safety issues due to unforeseen operating and maintenance practices by the toller... 

Any prior process hazard analyses on this process ... 

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

New Learning about Processing Hazards and Production Efficiency... 

While these responsibilities seem straightforward, there are numerous responsibilities that are intertwined and discrete. Both parties need to understand their individual responsibilities especially regarding process hazards, environmental concerns, communication, and technology/knowledge transfer. 

Health, Safety and Environmental Information MSDS for Raw Materials and Product Previous Process Hazard Analyses... 

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 ... 

Both parties need to identify responsibilities for choosing the right equipment for the process, preparing equipment for the process, and decontaminating equipment. Consider whether chemical and process hazards have been addressed in the selection, preparation, and decontamination of equipment. Examine the need to contractually address containment and disposal of residual process fluids and decontamination materials. If food products or pharmaceuticals are involved, cleaning methods may also be an issue to address in the contract. 

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. 

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