Ignition sources equipment

Acetone can be handled safely if common sense precautions are taken. It should be used in a weU-ventilated area, and because of its low flash point, ignition sources should be absent. Flame will travel from an ignition source along vapor flows on floors or bench tops to the point of use. Sinks should be rinsed with water while acetone is being used to clean glassware, to prevent the accumulation of vapors. If prolonged or repeated skin contact with acetone could occur, impermeable protective equipment such as gloves and aprons should be worn. 

Identify the at-risk equipment and the potential ignition sources in the piping system to determine where arresters should be placed and what general type (deflagration or detonation, unidirectional or bidirectional) are needed. 

Despite the use of explosion-pressure-resistant equipment for the full explosion pressure or other design measures outlined later, everything possible must be done to prevent effective ignition sources, because loss of product and interruption of production are equally undesirable. 

Vibration during Check plow and linkage for loose compo-plowing out—can nents/wear lead to premature. sharpen plow or use serrated blade for hardened equipment failure heels and a potential ignition source— Manually remove heel more frequently see above. Plow at lower bowl speed Advance plow more slowly Make sure plow system is well damped Avoid air actuated plows Avoid use of full depth plows with hard cakes Use nitrogen knife to scrape centrifuge ... 

Correct selection of heating equipment and zoning of electrical equipment to reduce the chance of an ignition source arising. 

As a general rule, vacuum relief devices are permitted on offsite storage vessels handling clean finished products, since there is essentially no possibility of an internal ignition source. However, vacuum relief devices which permit breaking of a vacuum with inerts or flammable vapors are not permitted on process equipment, since they are not judged to be sufficiently rehable to provide adequate protection under all circumstances. Vacuum devices which permit air to enter may be considered, however, in cases where the equipment does not or cannot contain flammables e.g., some steam systems. 

PR valve risers in flammable service should also be sized such that exit velocities are at least 30 m/s under all foreseable contingencies (except fire) which would cause the valve to release. On the basis of experimental work and plant experience, this minimum velocity, in conjunction with the riser elevation requirements, has been shown to ensure effective dispersion. Entrainment of air and dilution result in a limited flammable zone, with a negligible probability of this zone reaching any equipment which could constimte an ignition source. 

Flare systems are subject to potential flashback and internal explosion since flammable vapor/air mixtures may be formed in the stack or inlet piping by the entry of air, and the pilot constitutes a continuous ignition source. Flares are therefore always provided with flashback protection, which prevents a flame front from travelling back to the upstream piping and equipment. Design details are described later. 

Equipment Failures Safety system Ignition Sources Furnaces, Flares, Incinerators, Vehicles, Electrical switches. Static electricity, Hot surfaces. Cigarettes Human Failures Omission, Commission, Fault diagnosis. Decisions Domino Effects Other containment failures. Other material release External Conditions Meteorology, Visibility... 

Fire hazards are minimized by minimum inventories of chemicals. Control or miniini/e ignition sources, provide a confining area, reduce the temperature of the material as much iis possible, blanket the material to eliminate air contact. Have available fire protection equipment breathing apparatus, and protective clothing for the fire fighters. Use several hour fire walls to prevent the spread of fire to other process areas. 

Proper applicadon of a flame arrester can help avoid catastrophic fire and explosion losses by providing a flame barrier between at-risk equipment and anticipated ignition sources. 

The ignition sources described above cannot be eliminated, but tliey can be controlled by careful layout of tlie plant, proper design and maintenance of equipment, and tlie use of trip systems. 

If safe to do so, isolate equipment and ignition sources, and absorb or dike the spill. 

Directionality To select an arrester for any service, the potential sources of ignition must be established in relation to the pipe system and the equipment to be protected. The pipe connecting an arrester with an identified ignition source is the unprotected side oithe arrester. 

Autoignition temperatures are vitally important for process designs as it is the temperature at which to prevent or eliminate readily available ignition sources, (e.g., operating temperatures of electrical equipment, light fixtures, etc.). 

The overall intent of electrical area classification is to provide for safety of personnel and equipment. This is achieved by the elimination of electrical ignition sources near combustible gases or vapors that could explode or bum. The specific reasons for classifying facilities into electrical hazardous areas typically are ... 

---