Fire and electrical hazard & their prevention


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Fire & electrical hazards & their prevention:

Fire & electrical hazards & their prevention By: Sai Kishan Dept: Industrial pharmacy

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Fire hazards: Organic Dust Fire and Explosion: Fire initiated in a shell molding machine from an unknown source and then extended into the ventilation system ducts by feeding on heavy deposits of phenol formaldehyde resin dust. A small primary deflagration occurred within the ductwork, dislodging dust that had settled on the exterior of the ducts. The ensuing dust cloud provided fuel for a secondary explosion which was powerful enough to lift the roof and cause wall failures. Causal factors listed in the joint investigation report included inadequacies in the following areas : Housekeeping to control dust accumulations;

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Ventilation system design; Maintenance of ovens; and, Equipment safety devices . Metal Dust Fire and Explosion : Finely dispersed airborne metallic dust can also be explosive when confined in a vessel or building . Aluminium dust was involved in a primary explosion near a chip melting furnace, followed by a secondary blast in dust collection equipment . Elements of a Dust Explosion Elements Needed for a Fire (the familiar "Fire Triangle "): combustible dust (fuel ); Ignition source (heat); and Oxygen in air (oxidizer).

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An initial (primary) explosion in processing equipment or in an area were fugitive dust has accumulated may shake loose more accumulated dust, or damage a containment system (such as a duct, vessel, or collector).

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As a result, if ignited, the additional dust dispersed into the air may cause one or more secondary explosions. These can be far more destructive than a primary explosion due to the increased quantity and concentration of dispersed combustible dust.

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Facility Analysis Components: Facilities should carefully identify the following in order to assess their potential for dust explosions: Materials that can be combustible when finely divided; Processes which use, consume, or produce combustible dusts; Open areas where combustible dusts may build up; Hidden areas where combustible dusts may accumulate; Means by which dust may be dispersed in the air; and Potential ignition sources. Dust Control: NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, contains comprehensive guidance on the control of dusts to prevent explosions. The following are some of its recommendations:

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Minimize the escape of dust from process equipment or ventilation systems; Use dust collection systems and filters; Utilize surfaces that minimize dust accumulation and facilitate cleaning; Provide access to all hidden areas to permit inspection; Inspect for dust residues in open and hidden areas, at regular intervals; Clean dust residues at regular intervals; Use cleaning methods that do not generate dust clouds, if ignition sources are present; Only use vacuum cleaners approved for dust collection;

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Locate relief valves away from dust hazard areas; and Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods). Ignition Control: NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, also contains comprehensive guidance on the control of ignition sources to prevent explosions. The following are some of its recommendations: Use appropriate electrical equipment and wiring methods; Control static electricity, including bonding of equipment to ground; Control smoking, open flames, and sparks;

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Control mechanical sparks and friction; Use separator devices to remove foreign materials capable of igniting combustibles from process materials; Separate heated surfaces from dusts; Separate heating systems from dusts; Proper use and type of industrial trucks; Proper use of cartridge activated tools; and Adequately maintain all the above equipment. The use of proper electrical equipment in hazardous locations is crucial to eliminating a common ignition source. The classification of areas requiring special electrical equipment is discussed in the Facility Dust Hazard Assessment section above.

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Once these areas have been identified, special Class II wiring methods and equipment (such as "dust ignition-proof" and "dust-tight") must be used as required by 29 CFR 1910.307 and as detailed in NFPA 70 Article 500. It is important not to confuse Class II equipment with Class I explosion-proof equipment, as Class II addresses dust hazards, while Class I addresses gas, vapour and liquid hazards . Standard conformance and performance evaluation (SCOPE) SCOPE would evaluate the existing measures/ system based on applicable national/ international standards. SCOPE FP (Fire protection): Indian standards: IS 2189- standard for automatic fire detection and alarm system.

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IS 2190 – code of practice for selection, installation and maintenance of first aid fire extinguisher. IS 3844 - code of practice for installation and maintenance of internal fire hydrants and hose reels IS 6382 – carbon dioxide fir extinguisher system- fixed, desgin and installation. TAC Standards: Fire protection manual Water spray system Sprinkler rules Rules for fire alarm systems

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NFPA Standards: NFPA 12 Carbon dioxide fire extinguisher systems. NFPA 654 Prevention of fire & dust in pharmaceutical industry. NFPA 1600 Disaster management. NFPA 921 Fire & Explosion investigations. NFPA 45 Fire protection for laboratories using chemicals.

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Electrical hazards: Electricity has long been recognized as a serious workplace hazard, exposing employees to electric shock, electrocution, burns, fires, and explosions. In 1999, for example, 278 workers died from electrocutions at work, accounting for almost 5 percent of all on-the-job fatalities that year, according to the Bureau of Labor Statistics. What causes shocks? Electricity travels in closed circuits, normally through a conductor. But sometimes a person’s body — an efficient conductor of electricity — mistakenly becomes part of the electric circuit. This can cause an electrical shock. Shocks occur when a person’s body completes the current path with :

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both wires of an electric circuit; one wire of an energized circuit and the ground; a metal part that accidentally becomes energized due, for example, to a break in its insulation; or another “conductor” that is carrying a current. This table shows the general relationship between the amount of current received and the reaction when current flows from the hand to the foot for just 1 second. Current Reaction Below 1 milliampere 1 milliampere 5 milliamperes Generally not perceptible Faint tingle Slight shock felt; not painful but disturbing. Average individual can let go.

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6–25 milliamperes (women) 9–30 milliamperes (men) 50–150 milliamperes 1,000–4,300 milliamperes 10,000 milliamperes Painful shock, loss of muscular Control The freezing current or “let-go” range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated. Extreme pain, respiratory arrest, severe muscular contractions. Death is possible. Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely. Cardiac arrest, severe burns; death probable

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An electrical accident can result in an electrical burn, arc burn, thermal contact burn, or a combination of burns. Electrical burns are among the most serious burns and require immediate medical attention. They occur when electric current flows through tissues or bone, generating heat that causes tissue damage . Arc or flash burns result from high temperatures caused by an electric arc or explosion near the body. These burns should be treated promptly. A severe shock can cause considerably more damage than meets the eye. A victim may suffer internal hemorrhages and destruction of tissues, nerves, and muscles that aren’t readily visible. Renal damage also can occur. Static electricity also can cause a shock, though in a different way and generally not as potentially severe as the type of shock described previously.

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Static electricity can build up on the surface of an object and, under the right conditions, can discharge to a person, causing a shock. Static electricity can potentially discharge when sufficient amounts of flammable or combustible substances are located nearby and cause an explosion. Grounding or other measures may be necessary to prevent this static electricity build up and the results. Protection Against Electrical Hazards: Insulators: Insulators such as glass, mica, rubber, or plastic used to coat metals and other conductors help stop or reduce the flow of electrical current. This helps prevent shock, fires, and short circuits.

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To be effective, the insulation must be suitable for the voltage used and conditions such as temperature and other environmental factors like moisture, oil, gasoline, corrosive fumes, or other substances that could cause the insulator to fail. The insulation that covers conductors in non-construction applications is regulated by Subpart S of 29 CFR 1910.302 through 1910.308, Wiring Design and Protection. Subpart S generally requires insulation on circuit conductors. It also specifies that the insulation used should be suitable for the voltage and conditions. Conductors used in construction applications are regulated by Subpart K of 29 CFR 1926.402 through 1926.408 Guarding: Guarding involves locating or enclosing electric equipment to make sure people don’t accidentally come into contact with its live parts.

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Effective guarding requires equipment with exposed parts operating at 50 volts or more to be placed where it is accessible only to authorized people qualified to work with it. Conspicuous signs must be posted at the entrances to electrical rooms and similarly guarded locations to alert people to the electrical hazard and to forbid entry to unauthorized people. Grounding: “Grounding” a tool or electrical system means intentionally creating a low-resistance path that connects to the earth. This prevents the build-up of voltages that could cause an electrical accident. Grounding is normally a secondary protective measure to protect against electric shock. It does not guarantee that you won’t get a shock or be injured or killed by an electrical current.

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A service or system ground is designed primarily to protect machines, tools, and insulation against damage. One wire, called the “neutral” or “grounded” conductor, is grounded. In an ordinary low-voltage circuit, the white or gray wire is grounded at the generator or transformer and at the building’s service entrance. circuit protection devices: Circuit protection devices limit or stop the flow of current automatically in the event of a ground fault, overload, or short circuit in the wiring system. Well-known examples of these devices are fuses, circuit breakers, ground-fault circuit interrupters, and arc-fault circuit interrupters. Fuses and circuit breakers are designed to protect conductors and equipment. They prevent wires and other components from overheating and open the circuit when there is a risk of a ground fault.

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Ground-fault circuit interrupters, or GFCIs, are used in wet locations, construction sites, and other high-risk areas. These devices interrupt the flow of electricity within as little as 1/40 of a second to prevent electrocution. Arc-fault devices provide protection from the effects of arc-faults by recognizing characteristics unique to arcing and by functioning to deenergize the circuit when an arc-fault is detected. What work practices help protect you against electrical hazards? Electrical accidents are largely preventable through safe work practices. Examples of these practices include the following: • deenergizing electric equipment before inspection or repair, • keeping electric tools properly maintained,

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• exercising caution when working near energized lines, and • using appropriate protective equipment. What protection does personal equipment offer? Employees who work directly with electricity should use the personal protective equipment required for the jobs they perform. This equipment may include rubber insulating gloves, hoods, sleeves, matting, blankets, line hose, and industrial protective helmets designed to reduce electric shock hazard. All help reduce the risk of electrical accidents.

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OSHA standards: OSHA standards cover many electrical hazards in many different industries. OSHA’s general industry electrical safety standards are published in Title 29 Code of Federal Regulations (CFR), Part 1910.302 through 1910.308 — Design Safety Standards for Electrical Systems, and 1910.331 through 1910.335 — Electrical Safety-Related Work Practices Standards. OSHA also has electrical safety standards for the construction industry, in 29 CFR 1926, Subpart K. OSHA’s standards for marine terminals, in 29 CFR 1917, and for long shoring, in 29 CFR 1918, reference the general industry electrical standards in Subpart S of Part 1910.

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