Fires, accidental installations

Electricity is an ignition source ttiat can cause fires and explosions if equipment is installed or wired inadequately or if a static discharge occurs. Table 2-2 showed that electrical systems are the leading cause of fires. Improperly installed electrical systems may also cause accidental electrocution. Stray ciurents may result in corrosion of piping and equipment. 

Moist potassium peroxodisulphate was accidentally exposed to traces of potassium hydroxide. It combusted spontaneously, causing the installations to catch fire. It is impossible to put out a fire involving this peroxydic compound with carbon dioxide or extinguishing powders although these agents are suitable for fires of chemical substances. Only water, which is usually not recommended in this case, can put out this type of fire. 

The father of this system was the so-called fault tree that was developed for the U.S. missile program. The developers ran into the problem of testing the electric circuits of the Minute Man missiles. No one wants a nuclear warhead accidentally fired into space. Yet all the electric circuits had to be tested so that in case of an attack the missiles could be relied on. The fault tree was a method of predicting the probability of an unplanned launch as a result of testing. If the probability were high then either another way would have to be found to test the circuits or more safety devices would have to be installed. 

The security and economic stability of many nations and multinational oil companies are highly dependent on the safe and uninterrupted operation of their oil, gas and chemical facilities. One of the most critical impacts that can occur to these operations are fire and explosions from accidental or political incidents. The recent Gulf War amply demonstrates the impact these events can have on oil installations. 

Unattended operations must be planned with automatic safety switches that prevent serious damage (fire, flooding, explosion) in case of accidental equipment failure or interruption of utility services such as electricity, water, or gas supplies. Of special concern are the constant flow of cooling water and the operation of high-temperature baths. In the case of water flow, a device should be installed in the water line to (1) automatically regulate the water pressure (so as to avoid surges that might disconnect or rupture a water hose), and (2) automatically turn off electrical connections and water-supply valves in case of a total loss of water supply. In the case of hot thermostat baths or ovens, a sensor/control device should be installed that automatically turns off the electrical power to all heaters if the temperature exceeds some preset upper limit. 

Other Ignition Sources Hazardous classification of locations for electrical installations is covered in Articles 500-504 of the National Electrical Code (NEC) (NFPA 70). Proper hazardous classification is essential for safety and for prevention of explosion and fire losses. Class 1 in the NEC is for vapors and gases in the United States, in brief. Division 1 of Class 1 includes those locations where flammable concentrations exist continuously or frequently. Division 2 includes locations where flammable concentrations may exist only in case of accidental escape of vapors or gases, or in case of abnormal operation of equipment. Static electricity, which causes fires and explosions with flammable vapors and gases, is covered later in Sec. 26. Cither ignition sources include friction and impact plus rubbing with rubbing... 

Radioactive particles have been identified in connection with accidental releases from nuclear installations under high- and low-temperature conditions, in particular in releases from the accident in Unit 4 at Chernobyl (Loshchilov et al., 1992 Devell et al., 1986 Raunemaa et al., 1988) in 1986 and releases from the Windscale piles both during the fire in 1957 (Arnold, 1992) and earlier during the normal operation of the plant (Jakeman, 1986). 

In the last twenty years, PCDD and PCDF were identified as by-products in many industrial processes which involve chlorine or chlorinated compounds. Additionally both groups of compounds were found to be formed in a broad range of combustion processes, including accidental fires. Municipal waste incineration is particularly considered to be a very important, if not the most important, of the identified source of environmental dibenzo-p-dioxin and dibenzofuran contamination. As a consequence, the evaluation and close control of new and existing installations for their dioxin releases has become a major concern. Based on this relative importance of municipal waste incinerators, and taking into account the relative toxicity data actually available for PCDD and PCDF, it was decided to prepare and certify a crude fly ash extract (CRM 429) for the twelve more toxic PCDD and PCDF [18,19]. 

Areas that could be flooded with nitrogen, carbon dioxide, or halon-like materials should have oxygen detectors installed. Their use is particularly important in electrical switch gear rooms because inert gases are used to suppress fires. It is vital to know if the inert gas is accidentally leaking into the confined space. 

Safety improvements emanate from the re-evaluation of installation safety in light of the current standards, primarily in the areas of earthquake resistance, spray sodium fires and water and steam pipe rupture. In order to guarantee the main safety functions with respect to reactor shutdown, to the decay heat removal and to the confinement of radioactive materials, in all the aforementioned accidental operating conditions, the following safety improvements were required ... 

Several studies were devoted to the assessment of passive fire protection performances in the framework of fixed installations. Technical standards and data of bonfire tests are thus available in the literature concerning the use and the optimal specifications for both coating and PRVs in fixed tanks (Droste Schoen 1988). However, less attention was dedicated to the analysis of the performances of such devices in the specific accidental scenarios that may take place during the road and rail transportation of LPG. It is well known that in road and rail accidents severe fire engulfrnent or impingement may take place, while external cooling due to rescue teams or fire brigades may be widely delayed... 

Accidental fires interact with their environment, should this be pipework, equipment and structures in process plants in petrochemical industry, or facilities on offshore oil and gas installations. For plant design and risk assessment, cautious best estimates and uncertainty ranges are required for a number of combustion parameters. These include release rates, flame size and shape, heat output, thermal radiation to its environment, and the heating-up of structures, pipework and items of equipment. The estimate can result in the assessment of time to loss of functionality of these structures and pressurized equipment. 

The employer is required to regularly and properly maintain, according to established procedures, equipment and systems installed on heat-producing equipment to prevent accidental ignition of combustible materials. The maintenance procedure must be included in the written fire prevention plan. 

Lead-bismuth coolant reacts very slightly with water and air. Progression of accidental processes caused by failures of primary circuit tightness and steam generator (SG) inter-circuit leaks takes place without hydrogen release or exothermic reactions. In addition, there are no materials within the core and the reactor installation that release hydrogen as a result of thermal or radiation effects, or chemical reactions with the coolant. Therefore, the likelihood of chemical explosions and fires as internal events is virtually eliminated. 

The principal focus of this book is the mitigation of accidental releases of toxic or flammable materials throu release countermeasures, in particular, postrelease systems. Postrelease systems are designed for control of a hazardous material once it has been released into the environment. Control measures can include passive systems, such as dikes or berms around storage tanks, as well as active methods, such as water-spray or deluge systems installation around a process unit, or q>plication of foam on a chemical spill. However, fire fighting, blast protection and environmental control of response methodolo es are not covered in this guideline. 

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