Hazardous Chemicals and Processes

The hottest fires may be associated with those cases where the fire is big enough to give flames to fill at least half the structure volume, cases where it is stoichiometric or just under ventilated, and cases where the hot gas layer is 10 ft (3 m) or more deep. Heavier fuels would be less likely to give the hottest fires, asthey may not receive enough heat feedback to vaporize the liquid and therefore they may be self limiting in terms of the burn rate. Where these conditions may be encountered, heat fluxes of 1320-1584 BTU/ft (250 to 300 kW/m ) may be experienced. In certain circumstances, (which are not yet fully understood) highly efficient combustion can occur with fluxes of 1848-2112 BTU/ft (350-400 kW/m2) and temperatures of 2,500°F (1,400°C). 

Confined fires will spread the flames across the ceiling and, in general, this will be the hottest part of the fire. If the flame volume is more than 20% of the structure volume, then all of the ceiling beams and high level piping will be engulfed. It is possible that this could lead to simultaneous failure of all of the ceiling beams and upper module structure. This could lead to the release of any inventories supported on the level above or of total structure collapse. 

There are innumerable situations where gases, liquids, and hazardous chemicals are produced, stored, or used in a process that, if released, could potentially result in a hazardous fire condition. It is important to analyze all materials and reactions associated with a particular process, including production, manufacturing, storage, or treatment facilities. Each process requires analysis of the potential for fire. 

Hydrocarbon fires are the principal concern in many processing facilities. There are many different types of hydrocarbon fires. The mode of burning depends on characteristics of the material released, temperature and pressure of the released material, ambient conditions, and time to ignition. Types of hydrocarbon fires include  

Other fires that can occur in specific areas within a process plant include  

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Throughout their history, chemists have discovered some revolutionary molecules and synthetic pathways that bring new products and technologies to society. Production techniques have often neglected the impact of these materials and processes on the environ-maiL Today, with the increased environmental awareness, it is crucial to discover new ways of producing the same or similar molecules with desirable properties but with zero waste and zero pollution. New materials that are inherently nontoxic and have functionality that replaces hazardous chemicals, and processes to make these materials without the use of toxic intermediates or release to the environment, need to be developed. 

Reactive System Screening Tool (RSST) The RSST is a calorimeter that quickly and safely determines reactive chemical hazards. It approaches the ease of use of the DSC with the accuracy of the VSP. The apparatus measures sample temperature and pressure within a sample containment vessel. Tne RSST determines the potential for runaway reactions and measures the rate of temperature and pressure rise (for gassy reactions) to allow determinations of the energy and gas release rates. This information can be combined with simplified methods to assess reac tor safety system relief vent reqiiire-ments. It is especially useful when there is a need to screen a large number of different chemicals and processes. 

Understanding the chemistry of the process also provides the greatest opportunity in applying the principles of inherent safety at the chemical synthesis stage. Process chemistry greatly determines the potential impact of the processing facility on people and the environment. It also determines such important safety variables as inventory, ancillary unit operations, by-product disposal, etc. Creative design and selection of process chemistry can result in the use of inherently safer chemicals, a reduction in the inventories of hazardous chemicals and/or a minimization of waste treatment requirements. 

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

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. 

With the PHA methodology selected, the team assembled and the process safety information gathered, the analysis of chemical and process hazards, and the consequences and deviations associated with those hazards are identified. 

The safe design and operation of chemical processing equipment requires detailed attention to the hazards inherent in certain chemicals and processes. Chemical plant hazards can occur from many sources. Principal hazards arise from ... 

Review background information obtained from the facility to develop a general understanding of process safety hazards, areas of process safety concern, chemicals and processes used, etc. Typical background information includes ... 

Loss Prevention and Safety Promotion in the Process Ind.iLStries, 4th International S)Tnposium, Vol. 1 Safety in Operations and Processes Vol. 2 Hazardous Chemicals and. Liquefied Gases-Safe Transport, Vol. 3 Chemical Process Hazards, The Institution of Chemical Engineers, Symposium Series No. 82, 1983. 

Gibson, N., "Hazard Evaluation and Process Design," in Proceedings of Runaway Chemical Reaction Hazards Symposium, IBC, London, England (1987). 

Introduction The inherent nature of most chemicals handled in the chemical process industries is that they each have physical, chemical, and toxicological hazards to a greater or lesser degree. This requires that these hazards be contained and controlled throughout the entire life cycle of the facility, to avoid loss, injury and environmental damage. The provisions that will be necessary to contain and control the hazards will vary significantly depending on the chemicals and process conditions required. 

Using lists of chemicals is an inadequate approach for regulatory coverage of reactive hazards. Improving reactive hazard management requires that both regulators and industry address the hazards from combinations of chemicals and process-specific conditions rather than focus exclusively on the inherent properties of individual chemicals. (CSB 2002b)1... 

Revise the Accidental Release Prevention Requirements, 40 CFR 68 (RMP), to explicitly cover catastrophic reactive hazards that have the potential to seriously impact the public, including those resulting from self-reactive chemicals and combinations of chemicals and process-specific conditions. Take into account the recommendations of this report to OSHA on reactive hazard coverage. Seek congressional authority if necessary to amend the regulation. 

In many of the chemical catastrophes of the past, compliance with PSM and RMP would have ensured that the affected processes/plants had been thoroughly surveyed for processes using or producing highly hazardous chemicals and extremely hazardous substances. This survey would have determined, of course, that the sites used covered chemicals in their process. Moreover, the survey would have noted the normal quantity of listed chemicals stored on the plant site at any given time. This survey would also have made note if any quantities of listed chemicals stored on the plant site exceeded the PSM and RMP threshold quantities (TQ). 

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