Flammable hazards

Stanley M. Englund/ M S / Ch E / Fellow American Institute of Chemical Engineers Process Consultant, The Dow Chemical Company (retired). (Section Editor, Section 16 Introduction Hazard Analysis Storage and Handling of Hazardous Materials Reactive Chemicals Combustion and Flammability Hazards Hazards of Vacuum Hazards oflnei t Gases)... 

While it is rarely possible to add solids first, in certain cases it might be possible to reduce flammability hazards by planned sequential additions of solids and liquids, the objective being to avoid additions of easily ignitable powders where the solvent vapor exceeds about 50% LFL. Hybrid mixtures are discussed in 6-1.3. 

Flashing of vapour eontaining entrained mist may oeeur on venting equipment or vessels eontaining volatile liquids. This may ereate a toxie or flammable hazard depending on the ehemieal with steam the risk is of sealding. Rupture of equipment ean produee a similar effeet. 

Warning signs to indicate flammable hazard, no smoking etc. 

Provisions for primary and emergeney eommunieations (internal, e.g. with staff, emergeney personnel, and external, e.g. with die press, emergeney serviees, hospital, employees relatives, telephone links and radios) require eareful assessment. If diere is a flammable hazard on site, radios may need to be intrinsieally safe or flameproof. 

Landfill disposal of certain categories of solid waste may result in gas generation, mainly methane, and a highly polluted leachate. The methane may be drawn off, to avoid a flammable hazard on- or off-site. The leachate is pumped off for treatment. 

Figure 12-2T. Medium- or high-pressure, double-acting cylinder with flanged liner. The liner is locked in place by a flange between head and cylinder barrel. A step on the liner O.D. permits easy insertion. The cylinder may be made of cast-iron, nodular iron, or cast steel, depending on operating pressure. Note Optional two-compartment distance piece (type D) designed to contain flammable, hazardous, or toxic gases is illustrated. (Used by permission Bui. 33640, June 1985. Dresser-Rand Company.)...

Avoid contact with air at elevated temperatures because of its low (unstated) ignition temperature. Bums moderately in the open, but may explode in a nearly closed vessel. Presence of mono- and di-chloroacetylenes as impurities increases the flammability hazard, which may be reduced by addition of 1% of ethyl ether. 

Daniel A. Crowl, Ph.D. Professor of Chemical Engineering, Michigan Technological University Fellow, American Institute of Chemical Engineers (Section Editor, Process Safety Introduction, Combustion and Flammability Hazards, Gas Explosions, Vapor Cloud Explosions, Boiling-Liquid Expanding-Vapor Explosions)... 

Pyrophoric and other spontaneously combustible substances will generally be identified as such on their product literature, material safety data sheets (MSDSs), or International Chemical Safety Cards (ICSCs). If transported, these substances should be identified as DOT/UN Hazard Class 4.2 materials for shipping purposes and labeled as spontaneously combustible. For pyrophoric substances, the NFPA 704 diamond for container or vessel labeling has a red (top) quadrant with a rating of 4, indicating the highest severity of flammability hazard (NFPA 704, 2001). Note that pyrophoric materials often exhibit one or more other reactivity hazards as well, such as water reactivity. 

Injuries and fatalities from asphyxiation are often associated with personnel entry into inerted equipment or enclosures. Guidance on safe procedures for confined space access are provided by OSHA (OSHA, 29 CFR 1910.146, Confined Space Entry Standard, 2000), the American National Standards Institute (ANSI, Z117.1, Safety Requirements for Confined Spaces, 2003), Hodson (Hodson, Safe Entry into Confined Spaces, Handbook of Chemical Health and Safety, American Chemical Society, 2001), and BP (BP, Hazards of Nitrogen and Catalyst Handling, 2003). OSHA has established 19.5 vol % as the minimum safe oxygen concentration for confined space entry without supplemental oxygen supply (see Table 23-18). Note that OSHA imposes a safe upper limit on 02 concentration of 23.5 vol % to protect against the enhanced flammability hazards associated with 02-enriched atmospheres. 

Degree hazard Health hazard color code blue Flammability hazard color code red Instability hazard color code yellow... 

Release momentum. For jet releases, the amount of air entrained in an unobstructed jet is proportional to the jet velocity. Depending on the orientation of the jet relative to nearby obstructions, the momentum of a jet can be dissipated without significant air entrainment. The degree of initial air entrainment can be an important determinant of the hazard extent, particularly for flammable hazards. It would be (possibly overly) conservative to assume the source momentum is dissipated without air dilution. Explosive releases are high-momentum, instantaneous releases. For explosive releases, a rough first approximation is to assume that the mass of contaminant in the explosion is mixed with 10 times that mass of air. 

The hazard endpoint time scale th describes the length of time required for the contaminant to pose a hazard. There are many different time scales associated with various toxicity levels (e.g., TLV-C ceiling limit values are never to be exceeded, TLV-STEL values are not to be exceeded in a 15-min period, etc.). Time scales associated with flammability hazards reflect the maximum local concentration (and also typically including peak-to-mean concentration ratios) and for reasons discussed above are considered representative of dispersion model averaging times of around 20 s. 

Schaeffer, M. J., "The Use of Combustible Detectors in Protecting Facilities from Flammable Hazards", ISA Transactions, Vol. 20, No. 2, Instrument Society of America, Research Triangle Park, NJ, 1981... 

H M (Hennes Mauritz) uses no flame retardants in any product line, using instead natural materials that are inherently flame resistant. In a few cases, the company has cancelled clothing line items that proved a potential flammable hazard and could not be materially replaced. ... 

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