Steam, hazards

Many individuals do not realize the tremendous increase in volume that occurs when water vaporizes into steam. Hazard Workshop Module 1, developed by the Institution of Chemical Engineers, contains a slide that very simply illustrates this huge increase in volume. (See Figure 5-2.) Several problems with water and steam were discussed at length in Chapter 3. 

Toxicology LD50 (oral, rat) 810 mg/kg, (subcut., mouse) 680 mg/kg, (IV, mouse) 80 mg/kg LDLo (skin, rabbit) 2700 mg/kg poison by ing. and subcut. route mod. toxic by skin contact severe skin irritant TSCA listed Precaution Combustible liq. volatile with steam Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and fumes Uses Perfumes cosmetic ingred. synthetic flavoring agent in foods and pharmaceuticals fungicides disinfectant antiseptic organic synthesis... 

Process hazards Hazards of utilities Hazards of water Hazards of steam Hazards of ice Hazards of compressed gas Hazards of air Hazards of external events Hazards of equipment and instruments Hazards of piping, valves, and hoses... 

It must be borne in mind that in spite of the fact that the solvents have normal boiling points below 90-95°, they cannot always be completely removed by heating on a steam or water bath when they form part of mixtures with less-volatile liquids. Simple distillation may lead to mixtures with higher boiling points than the individual solvents, so that separation of the latter may not be quite complete. In such cases the distillation should be completed with the aid of an air bath (Fig. 77,5,3) or an oil bath the Are hazard is considerably reduced since most of the solvent will have been removed. 

Aqueous Eva.pora.tlon. Aqueous evaporation for hazardous waste treatment can be accompHshed in a closed process vessel that uses steam to evaporate the Hquid into a water vapor, which is ultimately condensed and may be reused, as shown in Figure 5. The concentrated Hquid is coUected for further treatment or disposal. 

The total emissions of hazardous air pollutants from a CGCC plant having wet cleanup are expected to be at least an order of magnitude lower than those achievable from a modem coal-fired steam plant (41). Metals removal in hot-gas cleanup systems is still under development. 

Hard rubber presents a fire hazard when reduced on steam-heated rolls (see subsection Organic Polymers ). Its dust is explosive [Twiss and McGowan, India Rtwber]., 107, 292 (1944)]. 

A normal enclosure is meant for a reasonably clean atmosphere and a relative humidity not more than 50% for LT and 95% for FIT indoor enclosures. Where the atmosphere is laden with fumes or steam, saline or oil vapours, heat and humidity, excessive dust and water or contaminated with explosive and fire hazardous gases, vapours or volatile liquids (Section 7.11) a special enclosure with a higher degree of protection is required as in lEC 60529 or lEC 60079-14. For non-hazardous areas, the enclosure can be generally one of those discussed in Tables 1. 10 and 1. 11, and when required can be provided with special treatment to the metallic surfaces. For hazardous areas, however, special enclosures will be essential as discussed in Section 7.11. 

NEMA SM23 Steam Turbines for Meehanieal Drive Serviee NFPA 70 National Eleetrieal Code, Artieles 500 and 501 Hazardous Loeations... 

Ejection of liquid can occur from open pipelines when solid blockages are released by external heating, e.g. by steam. (This hazard is increased if pressure is applied upstream of the constricton.)... 

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. 

Hazard and risk explained. Control of Substances hazardous to Health Regulations 1988 (COSHH) Do you use a steam/water pressure cleaner You could be m for a shock ... 

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