It Is Needed to Control Combustible Dusts Hazard - Research Paper Example

Combustible Dusts Abstract Several catastrophic incidences stemming from combustible dust explosions have been reported in the recent past. Combustible dusts continue to pose potential hazards to the lives of those who handle them. The most disturbing fact concerns the unawareness of these potential hazards to some manufactures, importers and most importantly the end users. This paper examines the extent to which combustible dusts pose a threat to all the stakeholders. The paper will begin by defining combustible dusts and then give a summery of incidences that were caused by combustible dust explosions. It will then show how the explosions develop and then give safety measures to be taken in preventing such occurrences. The paper will also discuss some debatable issues regarding combustible dusts. The paper will then conclude with an overview of the recommendations needed to control combustible dusts hazard. Key word: combustible dust Introduction Combustible dusts comprise of fine particles that cause an explosion hazard when suspended in the air and certain conditions (OSHA, 2009). A hazardous product has the capability of being ignited (Willy, 1995). Dust explosions cause tragic loss of life, serious body harm and devastating destruction of property. The potential for dust explosions remains unknown to most workers. This calls for the evaluation of potential chemical hazards, and the communication of hazard information to workers. Background Information According to OSHA (2009), materials that have the capability of forming combustible dust include wood, paper, sugar, metals such us aluminum & magnesium, coal, dried blood, soap, biosolids, plastics and certain textiles. They are found in a variety of industries and work places. Combustible dust can build up within process equipment and/or escape from process equipment settling on surfaces in the general working environment (L & I, 2009). These accumulations are extremely explosive especially when dispersed in the air in the presence of ignition sources like standard electricity switches. The U.S Chemical Safety and Hazard Investigation Board (CBS) identified two hundred and eighty of combustible dust incidences between 1980 and 2005 that led to the death of one hundred and nineteen workers, injured seven hundred and eighteen, and extensively damaged numerous industrial facilities (OSHA, 2009). Massachusetts suffered a similar fate in February 1999, when deadly fire broke in a foundry… investigations in the incidence revealed that a fire stemmed from a shell molding machine and then extended in the ventilation of the system ducts by feeding on heavy deposits of phenol formaldehyde dusts (OSHA, 2009). A small primary deflagration occurred within the duct work, forcing dust that had settled on the ducts’ surface to come out. The dust cloud produced acted as the fuel for a series of powerful explosions, lifting roofs and seriously damaging the walls. In February 2003, Kentucky acoustics insulation was the site for another fatal dust explosion. Reports from the investigations in the incident suggested that a small fire started in an oven ignited a dust cloud formed by nearby line cleaning. This was then followed by a series of horrifying dust explosions in the plant. Seven people died and thirteen injured in the incidence (OSHA, 2009). In another incidence, that left one person dead and another seriously injured, involved an explosion that stemmed from metallic dust. Aluminum dust was involved in the explosion followed by secondary blast in dust collection equipment. This incident occurred in October 2003 in Indiana (OSHA, 2009). In late 1970s, deadly explosions of gain dust in grain elevators left fifty nine people dead and forty nine others seriously wounded. On February 7, 2008 in Port Wentworth, Georgia, a deadly explosion led to the death of fourteen people and left scores of other workers injured with severe burns. The explosion involved sugar dust (OSHA, 2009). It was later discovered that, in a majority of these incidences the potential for dust explosions was unknown to most managers and workers because they failed to identify the complex nature of dust risks. These incidences made CBS launch investigations regarding the safety protocols taken by companies manufacturing substances that produce combustible dust. A review of Material Safety Data Sheets (MSDS), by CBS, revealed that most of these sheets did not warn users on potential explosion hazards. However, some did not state information in a manner understandable to users or the information lacked notes on combustible dust hazards. The previous incidences showcased a red signal to the state agencies that something needs to be done. OSHA endeavors to provide safe and healthy working conditions for all workers and ensuring the enforcement of its set standards (OSHA, 2009). But from the turn around of these incidences a lot needs to be done to assure workers safety. Factors and Substances Implicated in Explosions Like any other fire, a dust fire occurs when fuel (in this case combustible dust) comes into contact with a source of ignition in the presence of oxygen. Therefore, it will be noted that the three components fuel (combustible dust), ignition and oxygen; must be present for an explosion to occur. But when to explosions involving dusts, two additional requirements are needed (Health Canada, 2010). Dust explosions also need confinement and dispersion of dust particles in sufficient quantity and concentration. Confinement allows for pressure to build up. Also, suspended dust burns more rapidly. Dust explosion could occur in primary or secondary form. Primary explosion makes dust that might have settled for years air bone resulting in the disastrous secondary explosion that propagates thought the plant often with catastrophic results (Health Canada, 2010). A primary dust explosion in processing equipment may shake loose accumulated dust or damage the containment systems which enable the release of dust in the air, and this additional airborne dust may be ignited causing one or several secondary fires (OSHA, 2009). The five (pentagon) elements that include oxygen, fuel, ignition, confinement and dispersion need to be present for a combustible dust explosion to occur. The figures 1 & 2 below give a pictorial illustration of how a primary explosion propagates into a secondary explosion. Figure 1 illustrates the role of the pentagon elements. Source: OSHA, 2009; http://www.osha.gov/dsg/combustibledust/index.htm Diagram showing how the pentagon elements contribute to an explosion. Source: OSHA, 2009; http://www.osha.gov/dsg/combustibledust/index.htm Diagram illustrating how primary dust explosion propagates to a secondary explosion. The pentagon elements must be present for the explosion to occur. It might be possible to contain the ignition source, fuel (dust) and dispersion. However, containment of oxygen and dust confinement (within processes and buildings) poses a great challenge. Parameters for classifying combustible dusts According to the U.S research council (NMAB, 1988); several parameters need to be considered during the determination of combustible dusts. Such parameters include the ignitability, dispersibility, spontaneous ignition tendency and ignition susceptibility by frictional sparks, static generation tendencies, reactivity with moisture (humidity) oxidizers other than oxygen, thermal stability and explosion development in closed or partially closed systems. Although considerable research data are available on measurement of other parameters, intensive and extensive studies are needed to provide information on the basic information yet to be revealed. This will then provide industry, government and the general public with tools to promote safe working and living environments (NMAB, 1988). There is a need for findings from research to receive universal acceptance and application so that international exchange of equipment and results can be promoted. In this regard, systems for classifying dusts are needed to promote safety key parameters for classification should in cooperate combustibility of dusts, including those of an electrical conductive nature, which in the United States are recognized as special hazardous category. The current technique for measuring combustibility is not satisfactory. The report suggests the development of a classification scheme that takes into account the combustibility of clouds and layers, including those having high electrical conductance (NMAB, 1988). A wide majority of industries handle combustible dusts. Such industries include Agriculture, Food Products, Chemicals, Textiles, Forest and furniture products, metal processing, Tyre and rubber manufacturing Plants, Paper products, Pharmaceuticals, Waste water treatment, Recycling Operations (metal, paper and plastic), Coal handling facilities (OSHA,2009). In this regard, combustible dusts likely to cause fires and/or explosions include metals (aluminum and magnesium), wood, coal and carbon dusts, plastic dusts and additives, Biosolids, organic dusts (sugar, flour, soap & dried blood) and certain textile materials. According to OSHA’s (2009) definition, the combustible dust particles have a diameter of 420 microns. Lager particles can cause a deflagration effect. Identifying and Controlling the Risk for Dust Explosions To determine the potential for gas combustible dust explosion, all physical and health hazards should undergo a serious assessment. OSHA’s reports from the investigations of earlier incidences revealed that importers and manufacturers (of combustible dusts) did not give proper communication of the risk hazards to the users. In October, 2007 OSHA instituted the Combustible Dust National Emphasis Program (NEP), so as to develop a counter checkup mechanism on importers and manufacturers or any other combustible dust handler. OSHA discovered the need for Combustible dust manufacturers and importers to inform users about potential hazards of their products that may occur under normal conditions of use or in foreseeable emergencies on the products MSDS or product labels. These includes operations that comprise of abrasive blasting, cutting, grinding, polishing or rushing of materials; conveying sifting, mixing or screening dry materials; and the build up of dried residues from processing wet materials (OSHA, 2009). In this case, the chemical and common name(s) of the hazardous chemicals should be stated (OSHA, 2009). This should include the physical and chemical properties of the chemical in question, (for example vapor pressure/flat point), including the potential for fire, explosion or reactivity. In addition, general applicable precautions for safe handling and use, known to the chemical manufacturer, importer, and employer preparing the MSDS should be communicated…this should include hygienic practices, safety guidelines essential in the repair and maintenance of equipment that could be contaminated and procedures for clean up of spills and leaks (Oregon Sec, 2011). Different states should develop and implement job safety and work plans. On the other hand, employers handling combustible dusts should also device safety policies in their work place. The policy should be understood by all employees and followed to the latter. Penalties should be exercised in employees who fail to observe the safety policy to encourage strict adherence to the set standards. Employees should be made to understand that simple avoidable errors could cause serious harm to everyone within or close to the facility. This should include proper training for its workers in relation to the safety policy. Widespread non compliance with engineering control set standards should be avoided. Coker (2007) argues that without properly sized and internally detailed hardware, a process may not obtain its unique objective. Initial preventative measures require the confinement of combustible dust to properly located and designed areas, with ignition sources either eliminated or controlled. Equipment should be designed in a manner to prevent leaks that might cause escape of dust to the work place (OSHA, 2009). Processing equipment and work surfaces should be cleaned routinely to get rid off settled dust. Other mitigation strategies may include providing an oxygen deficient environment in areas at a greater risk for explosion. Areas or equipment subject to explosion should including dust collection ducts, should be designed in a manner to relieve excess pressure, a common risk factor for explosions. The ignition protection relies on the limitation of the maximum surface temperature of an enclosure and the restriction of dust ingress into the enclosure by use of dust tight /protected enclosure (Rolf, 2000). At the national level, OSHA endeavors to work with other stakeholders to ensure the safety of all workers. The program helps encourage, assist and recognize the effort of partners to eliminate serious hazards in the work place and achieve high levels of worker safety and health. OSHA also offers training and consultation services to stake holders. Debate on Combustible Dust Standardization The aspect of combustible dust standardization continues to draw a big debate, with stake holders still contemplating on the parameters to be used in the standardization process. The initial grain handling facilities standard (29 CFR 1910.272) addressed industry specific issues, including combustible dust, but with limitations. OSHA put into consideration the possibility of developing a more conclusive general standard that would encompass all aspects of safety. The general standard should cover all businesses whether small or big across many industries with a wide range of processes and dust types (OSHA, 2009). OSHA is for the opinion that including all facilities with any amount of combustible dust site, especially those with low hazard magnitude appears inappropriate. However, the general standard should be in a position to identify all facilities with serious combustible dust hazards are covered in the general standard. This will allow employers owning facilities with minimal combustible hazards to avoid unnecessary cost. Controversy is still raging on whether to exclude certain materials based on their explosibility and whether the exclusion should go beyond the noncombustible dusts to some minimally combustible as well. Experts remain divided on the criteria that should be employed. This concerns the fact that, some dusts (like sugar dust) have low Kst values (explosibility defining threshold) range but usually produce striking effects on exploding. Some experts think that the standard should not attempt to exclude materials on the basis of explosibility potential. Some view combustible dust as any dust that supports flame propagation. The American Society for Testing Materials provides the criterion for testing explosibility of dusts. Therefore, some experts think that any dust that passes the explosibility test should be considered combustible. On the other hand, other experts view the idea of using thresholds to define explosibility as incorrect, because such criteria contain inherent limitations and thus should be avoided. Some experts even propose the use of equations for explosions severity and ignition sensitivity. Another standardization scope that continues to draw debate involves the cutoff point for the selection of facilities that subscribe to the general standard. Experts remain divided on the suggestion of excluding facilities with fewer incidences of injuries/fatalities. Those that oppose the exclusion of industries with fewer incidences of fatalities/injury claim that the available data seems to be an unreliable measure for potential hazards. Also, discrepancy prevails on whether to exclude smaller entities or whether a different level of controls would be appropriate. Conclusion The hazard caused by combustible dusts will always exist since most of the dusts are commonly used materials. The destruction and fatalities caused by such combustible dusts so far are outraging. Such incidences indicate that the current regulations and policies regarding combustible dusts need to be reviewed. The evidence revealed from various state agencies in the previous explosions caused by combustible dusts, denoted lack of proper communication and information on the safety issues regarding combustible dusts. Most manufactures and importers of these products fail to communicate adequately to their end users about potential hazards from combustible dusts. On the other hand, the current standardization procedures continue to draw debate from various stake holders because of the lack of a consensus on several criteria that are needed to streamline the industry. Findings from research need to receive universal acceptance and application so that international exchange of equipment and results can be promoted. This will equip industry experts, the government and the general public with in formation required to safeguard their working and living environments. Since the potential for dust explosions is unknown to most workers, there should be an evaluation of potential chemical hazards and the communication of hazard information to workers. References Coker, A.K. (2007). Ludwig’s applied process design for chemical and petrochemical plants. Burlington: Elsevier. Combustible Dusts (2009). - Labor & Industries (L&I), Washington State. (n.d.). Retrieved on Dec.5th,2011fromhttp://www.lni.wa.gov/Safety/Topics/AtoZ/CombustibleDusts/default. Health Canada, (2010). Dust Explosibility. Retrieved on Dec. 5th, 2011 from. http://www.hc- sc.gc.ca/ewh-semt/occup-travail/whmis-simdut/dust-poussiere-eng.php National Material and Advisory Board (NMAB), (1988). The explosion hazard classification of gases and dusts, relative to the use of electrical equipment. Springfield: National Academy Press. Occupational Safety and Health Administration (OSHA), (2008). United States Department of Labor.RetrievedonDec.6th,2011from.http://www.osha.gov/dsg/combustibledust/index.hm Oregon Secretary of State Archives Division. (2011) (n.d.). Retrieved on Dec. 5th, 2011 from http://arcweb.sos.state.or.us/pages/rules/oars_400/oar_437/437_004.html Rolf, K. E. (2002). Design of electrical equipments for area containing combustible dust: why standards cannot be extensively harmonized with gas standards. Journal of Loss Prevention in the Process Industries, 3 (3-5), 201-208. Willy, O. E. (1995). Classifying Explosions-prone areas for the petroleum, chemical and related industries. California: Noyes publication. Read More