Explosion upper

Explosive Upper Block Lower Block Total Mean... 

The Branching Chain Explosion Upper and Lower Limits... 

National Fire Protection Association. System gives a qualitative rating for health, flammability, and spontaneity. These values range from 0 to 4, with 4 being the most hazardous. These can be used for an initial screen to sensitize engineers to the potential hazard. Quantitative values are published elsewhere for each separate issue health (TLV, STEL, IDLFl) flammability explosivity (upper and lower explosive limits). 

Flash points and autoignition temperatures are given in Table 11. The vapor can travel along the ground to an ignition source. In the event of fire, foam, carbon dioxide, and dry chemical are preferred extinguishers. The lower and upper explosion limits are 1% and 7%. 

Flammability Acrolein is very flammable its flash point is <0° C, but a toxic vapor cloud will develop before a flammable one. The flammable limits in air are 2.8% and 31.0% lower and upper explosive limits, respectively by volume. Acrolein is only partly soluble in water and will cause a floating fire, so alcohol type foam should be used in firefighting. The vapors are heavier than air and can travel along the ground and flash back from an ignition source. 

The relatively low flash points of some acrylates create a fire hazard. Also, the ease of polymerization must be home in mind in ah. operations. The lower and upper explosive limits for methyl acrylate are 2.8 and 25 vol %, respectively. Corresponding limits for ethyl acrylate are 1.8 vol % and saturation, respectively. All possible sources of ignition of monomers must be eliininated. 

The explosive limits of hydrazine in air are 4.7—100 vol %, the upper limit (100 vol %) indicating that hydrazine vapor is self-explosive. Decomposition can be touched off by catalytic surfaces. The presence of inert gases significantly raises the lower explosive limit (10) (Table 2). 

Health and Safety Factors, Toxicology. Because low molecular weight phosphines generally are spontaneously flammable, they must be stored and handled in an inert atmosphere. The upper explosion limit is 1.6% and the upper limit is near 100% (93). The higher and less volatile homologues are more slowly oxidized by air and present less of a problem. 

Succinic acid is Generally Recogni2ed As Safe (GRAS) by the U.S. PDA (184) and is approved as a flavor enhancer, as a pH control agent in condiments, and for use in meat products. It causes irritation to the eyes (185), skin, mucous membranes, and upper respiratory tract. LD q in rat is 2260 mg/kg. Succinic acid, like most materials in powder form, can cause dust explosion. 

Because biphenyl is often transported in the molten state, a moderate fire ha2ard does exist under these circumstances. Biphenyl, with a flash point of 113°C, has a lower flammability limit of about 0.6% (by volume) at the flash point to an upper limit of 5.8% at 166°C (42). Dust explosions are a ha2ard when vapors from a hot Hquid surface condense in air in a confined space. 

The catalyst temperature is about 1100°C. Precious metal catalysts (90% Pt/10% Rh in gauze form) are normally used in the commercial processes. The converters are similar to the ammonia oxidation converters used in the production of nitric acid (qv) although the latter operate at somewhat lower temperatures. The feed gases to the converter are thoroughly premixed. The optimum operating mixture of feed gas is above the upper flammabiUty limit and caution must be exercised to keep the mixture from entering the explosive range. 

For apphcation of Eq. (26-48), x should not exceed 300 m (984 ft). The reason for selec ting 100 percent, instead of the upper flammable limit (UFL), in the equation for Vj is that in an incipient explosion vapor above the UFL may be mixed with additional air and, thereby, contribute to explosion pressure. 

Figure 2.1 The lower and upper limits of an explosive chain reaction as a function of temperature and pressure.

UEL, UPPER EXPLOSIVE (oR FLAMMABLE) LIMIT The maximum concentration of gas, vapour, mist or dust in air at a given pressure and temperature in which a flame can be propagated. 

Flammable or Explosive Limits — the upper and lower vapor eoneentrations at whieh a mixture will bum or explode. The lower explosive limit of p-xylene is 1.1 pereent by volume in air, whereas the upper explosive limit is 7.0 percent in air. A mixture of p-xylene vapor and air having a coneentration of <1.1 pereent in air is too lean in p-xylene vapor to bum. Conversely, a mixture containing more than 7.0 percent is too rieh in p-xylene to bum. By subtraetion (7.0 - 1.1), p-.xylene is said to have a flammable range of 5.9. Materials having low explosive limits and wide flammable ranges are extremely dangerous. 

Oxygen, the second requirement for combustion, is generally not limiting. Oxygen in the air is sufficient to support combustion of most materials within certain limits. These limitations are compound specific and are called the explosive limits in air. The upper and lower explosive limits (UEL and LEL) of several common materials... 

Let s take the example of benzene, which at 12,000 ppm, is 100% LEL. The National Fire Protection Association (NFPA) states that equipment can operate, without LEL monitors or controls, if the LEL is less than 25% LEL. For benzene then, 25% LEL is equal to 3,000 ppm. This upper boundary becomes a dictating factor in the selection and design of the oxidation equipment. If the concentration is higher than 25% LEL, the NFPA requirements state that an LEL monitor is required. Using an LEL monitor, NFPA guidelines allow operation up to 50% LEL (a 2 1 safety factor). Thus, 100% LEL is explosive if the stream is at 25%, a factor safety of four exists. 

The volatile solvents recoverable by the activated carbon system or any other system are nearly all organic, and many of them form flammable or explosive mixtures with air. Such mixtures may lie between upper and lower explosive limits. The activated carbon system can avoid the explosive range by staying well below the lowest percentage of vapor which is still explosive it functions well at very low concentrations. The system also recovers solvents efficiently even in the presence of water the recovery efficiency is high (98 percent and 99 percent are not unusual) it may be fully automatic. The annual maintenance charge rarely exceeds 5 percent of the cost of equipment. The recovery expense may be as low as 0.2 cent per pound in some installations it rarely exceeds 1 cent per pound. 

Flammable Limits in Air - This is a concentration expressed as percent by volume of the chemical in air, whereby spontaneous combustion will be supported. The lowest concentration where combustion will be supported is known as the lower flammability limit (LFL) or lower explosion limit (LEL). LEL and LFL are considered interchangeable. The upper concentration limit is the UFL (Upper Flammability Limit) or UEL (Upper Explosion Limit). 

Upper Explosive Limit (UEL) or Upper Flammable Limit (UFL) ... 

UEL/UEL Upper Explosive Limit/Upper Elammable Limit... 

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