Hazardous/flammable materials

Pneumatic conveyors may operate under pressure or suction, even within tiie same system (e.g., push/pull conveying). Both types are subject to similar hazards. Flammable materials are of particular concern and should therefore be transported by an inert gas. Inert gases should contain no caibon monoxide and have dew points low enough so that free moisture cannot condense or accumulate in the system. 

Low pressure. Low pressures are not in general as hazardous as the other extreme operating conditions. However, one particular hazard that does exist in low-pressure plants handling flammable materials is the possible ingress of air with the consequent formation of a flammable mixture. 

Substitution If intensification is not possible, then an alternative is to consider using a safer material in place of a hazardous one. Thus it may be possible to replace flammaole solvents, refrigerants, and heat-transfer media by nonflammable or less flammable (high-boiling) ones, hazardous products by safer ones, and processes which use hazardous raw materials or intermediates by processes which do not. As an example of the latter, the product manufactured at Bhopal (carbatyl) was made from three raw materials. Methyl isocyanate is formed as an intermediate. It is possible to react the same raw materials in a different order so that a different and less hazardous intermediate is formed. 

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. 

The results of the Flixborough investigation made it clear that the large inventory of flammable material in the process plant contributed to the scale of the disaster. It was concluded that limitations of inventory should be taken as specific design objectives in major hazard installations. It should be noted, however, that reduction of inventoiy may require more frequent and smaller shipments and improved management. 

Conclusions The use of an inert atmosphere can virtually eliminate the possibility of explosions and fire with flammable materials. However, inerting systems can be quite expensive and difficult to operate successfully and can be hazardous to personnel. Before using inert systems, alternatives should be explored, such as using nonflammable materials or operating below the flammable range. 

Oxidation Feedstocks generally hydrocarbons Hazard of fire/explosion arises from contact of flammable material with oxygen Reactions highly exothermic equilibrium favours complete reaction... 

Designation of restricted areas, e.g. containing flammable materials, eye protection zones, hearing protection zones, radiological hazards, microbiological hazards Ensuring freedom from obstruction of roads, stairs, gangways, escape routes Control of vehicles... 

Flashpoint — the lowest temperature of a liquid at whieh it gives off enough vapor to form an ignitable mixture with air near the surfaee of the liquid within the vessel used. Two tests are used—Open Cup and Closed Cup. Generally, the Open Cup method results in flashpoints 5° to 10° higher than the Closed Cup method. Flashpoint < 140°F (Closed Cup) is the eriterion used by EPA to deeide whether a ehemieal is hazardous by ignitability. DOT defines materials with flashpoints of < 100°F as flammable materials, and between 100° and 200°F as eombustible. 

Unfortunately, many times it is not clear which of several process alternatives is inherently safer. Because nearly all chemical processes have a number of hazards associated with them, an alternative which reduces one hazard may increase a different hazard. For example, process A uses flammable materials of low toxicity process B uses noncombustible materials, which are volatile and moderately toxic, and process C uses noncombustible and nontoxic materials but operates at high pressure. Which process is inherently safer The answer to this question will depend on the specific details of the... 

Does the SAHP provide for advising all subeontraetors about all flammable materials or hazardous eonditions of whieh they may not be aware [OSHA Referenee, 252(a)(2)(xiii)(D)]... 

The long list of vapor cloud explosion incidents indicates that the presence of a quantity of fuel constitutes a potential explosion hazard. If a quantity of flammable material is released, it will mix with air, and a flammable vapor cloud may result. If... 

A flash fire is the nonexplosive combustion of a vapor cloud resulting from a release of flammable material into the open air, which, after mixing with air, ignites. In Section 4.1, experiments on vapor cloud explosions were reviewed. They showed that combustion in a vapor cloud develops an explosive intensity and attendant blast effects only in areas where intensely turbulent combustion develops and only if certain conditions are met. Where these conditions are not present, no blast should occur. The cloud then bums as a flash fire, and its major hazard is from the effect of heat from thermal radiation. 

The main hazard posed by a BLEVE of a container filled with a flammable liquid, and which fails from engulfment in a fire, is its fireball and resulting radiation. Consequently, Lewis (1985) suggested that a BLEVE be defined as a rapid failure of a container of flammable material under pressure during fire engulfment. Failure is followed by a fireball or major fire which produces a powerful radiant-heat flux. 

In many plant sections a mixture of materials will be present. Since very few hazard models can handle mixtures, you will need to select a single representative material. For flammable materials it is generally most appropriate to choose the material whose boiling point is closest to the average nonnal boiling point of the mixture. For toxic materials you can select the most toxic material, but the initial concentration must be reduced to reflect the concentration in the released material. 

Carbon dioxide systems-Tliis system can be used where there is a handling and storage of gaseous and flammable materials, electrical equipment, and hazardous solids by introducing an inert gas (such as carbon dioxide) into the area in order to reduce the concentration of oxygen to the point where the fire will be extinguished. 

Acrylic resin systems developed in Germany are similar to polyester resins but, by careful formulation, the problems due to shrinkage have been largely overcome. The acrylic resin-based systems are currently based on highly flammable materials (flash point 10°C), which can present hazards during laying. However, there are systems available that can take foot traffic 2-3 hours after application and full service conditions within 24 hours, even at very low temperatures. 

Normal laboratory glassware must first be washed and cleaned. It has to be rinsed with deionised water. The clean glassware is sterilised in an oven set at 200 °C for 1 1 hours. It is suitable to cover glassware with aluminum foil to maintain aseptic conditions after removing the glassware from the oven. If aluminum foil is not available, special heat-resistant wrap paper can be used. The sterile glassware must be protected from the air, which has micro-flora, or any contaminants. Avoid the use of any plastic caps and papers. Detach any labelling tape or other flammable materials, as they are fire hazards. 

Fire and Explosion Hazard. Dangerous, as K nitrate is both a fire and expln hazard. As a strong oxidizer it can give up its oxygen to other materials to produce a vigorous reaction which may result in detonation. Toxic fumes are emitted on decompn. It is sensitive to shock, can be very easily detonated, and when mixed with flammable materials becomes very sensitive (Refs 6 10)... 

It is important to keep the amount of potentially hazardous waste in the laboratory to a minimum at all times. Periodically, contents of the laboratory waste containers will be transferred to appropriate containers for final disposal. These must be stored in a safe location, often outdoors, while awaiting pick-up by a disposal service. There will be local restrictions for such storage. A locked storage area may be needed, for example, to prevent unauthorized access to hazardous materials. The fire department niiay set strict limits as to how much flammable material may be present. All containers must be marked with contents, and the storage area will no doubt require warning signs. 

Lighted candles are only dangerous if they can ignite nearby flammable materials. They should never be left unattended or placed on or near anything that could ignite. All naked flames present a possible fire hazard. 

The term flammable is now more commonly used in the technical literature than inflammable to describe materials that will burn, and will be used in this book. The hazard caused by a flammable material depends on a number of factors ... 

G. Quantity of flammable material the potential loss will be greater the greater the quantity of hazardous material in the process or in storage. The factor to apply depends on the physical state and hazardous nature of the process material, and the quantity of material. It varies from 0.1 to 3.0, and is determined from Figures 3, 4 and 5 in the Dow Guide. 

The index works out at 21 classified as Fight . Ammonia would not normally be considered a dangerously flammable material the danger of an internal explosion in the reactor is the main process hazard. The toxicity of ammonia and the corrosiveness of nitric acid would also need to be considered in a full hazard evaluation. 

The accumulated energy (9.55 mJ) greatly exceeds the quantity required for ignition of flammable materials. This system is operating under hazardous conditions, b. This vessel will gradually level off to steady-state equilibrium conditions when the operating time significantly exceeds the relaxation time therefore the exponential term of Equation 7-36 is 0. Equation 7-36 for this case reduces to... 

Division 2 Hazardous only under abnormal conditions. Flammable materials are normally contained in closed containers or systems. 

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