Figure 238 Influence of fuel concentration in mixtures with air on MESG for the three lower alkanes Data from Alfert

Primary chamber was positioned at the chamber axis, and the distance Xj from the ignition point to the entrance of the transmission hole was varied. Figure 2-40 gives a set of results showing the critical distance Xj for explosion transmission as a function of the hole diameter D. As can be seen, the critical hole diameter for flame transmission with X 0 was about 3 mm. In this case the conditions were probably close to laminar, and what was measured was the critical laminar quenching tube...

242 Preventing and Limiting Size of Explosive Gas Vapor Clouds

2.4.2.1 Preventing Gas Leaks from Process Equipment The following is based on Statoil (2004) Piping, pipelines, tanks, heaters, mechanical equipment, vessels design integrity and related inspection, maintenance, and operation activities shall ensure that leaks of hydrocarbon fluids (and chemicals and toxic gases) do not occur. This is accomplished by the following measures the inspection system and execution shall verify that the chosen monitoring parameters are within specified limits a...

235 The Beek Explosion the Netherlands 1975 2351 Summary

Some central data of this event are given in Table 2-14. Congested process area of naphta cracker installation Entire plant and a nearby tank farm destroyed. Window breakage in surroundings up to 2.5 km from explosion centre. Reviews of this accident were given by Gugan (1979) and Lees (1994). A comprehensive two-part report of investigation in the Dutch language (Anonym, 1976) was issued by the Directorate of Labour of the Ministry of Social Affairs, in the Netherlands. This report contains...

245 Mitigating Gas Vapor Cloud Explosions that Occur Despite Preventive Measures

2.4.5.1 Control and Mitigation Two Different Concepts Tam (2002) suggested that the terms control and mitigation of accidental explosions should have different specific meanings. He defined mitigation as an action causing a reduction of the consequences of an explosion event, without there being any reduction in the explosion severity at the explosion source. Control, on the other hand, would be when a device or technique has a direct impact on the severity of an explosion at its source....

715 Explosives Pyrotechnics and Propellants

CENELEC (1997) defines explosive substances as solid, liquid, pasty or gelatinous substances and preparations which are liable to react exother-mally and under rapid gas generation even without the participation of atmospheric oxygen, and which, under specified test conditions under partial confinement will detonate or deflagrate rapidly during heating. It is important to note that this definition not only comprise the genuine explosives, but also pyrotechnics and propellants. 7.1.5.2...

712 Gases and Vapors

7.1.2.1 Definition of Area Classification The area classification approach has traditionally been used as a basis for specifying requirements for electrical equipment for use in potentially explosive atmospheres. According to The Institute of Petroleum (2002) area classification is the assessed division of a facility into hazardous areas and non-hazardous areas, and the subdivision of the hazardous areas into zones. A hazardous area is defined as a three-dimensional space in which a flammable...

651 General Safety Considerations for Facilities Producing Explosives According To Sejlitz 1987

The planning of a process and or a workplace should always be based on the following basic rule a minimum number of persons for handling the smallest possible quantity of explosive material in 6.5.1.2 Characteristics of the Explosive Material Before conducting any work with explosive materials, all their basic safety properties must be known. These data makes it possible to evaluate both the various risks of ignition initiation associated with handling and processing the material, and expected...

644 Pyrotechnics Disaster in Enschede Netherlands 2000

The following short summary is based on the accounts by Bruyn et al. (2002) and Weerheijm et al. (2002), which are in turn based on the results of the extensive forensic and technical investigations of this catastrophic accidental fire explosion undertaken by Netherlands Forensic Science Institute (NFI) and TNO Prins Maurits Laboratory (TNO-PML). 6.4.4.2 Overall Development and Consequences of the Disaster The disastrous explosion occurred on Saturday afternoon, 13 May 2000, on the premises of...

236 The Arendal Explosion Gothenburg Sweden 1981

Some central data of this event are given in Table 2-15 Details of this accident have been obtained from the Special Working Group (1981), Brandsjo (1988), and Nilsson (1991). The site of this explosion is not, strictly speaking, a process plant, but the event provides valuable information that is relevant even in the present context. Figure 2-56 gives a view of the explosion site and indications of the local damage caused by the explosion. The site was a large obstacle field in the open...

563 Preventing Ignition Sources 5631 Introduction

A question asked frequently is whether preventing ignition sources can be relied upon as the only means of protection against dust explosions. The general consensus is that this is not possible. Relying on preventing ignition sources only is definitely inadequate if the minimum electric spark ignition energy of the dust is in the region of vapors and gases, i.e. < 10 mJ. However, for dusts of very high MIEs it may be argued that several types of process plants could be satisfactorily...

544 Major Linen Dust Explosion in Harbin China 1987

In the middle of the night, at 0239 on 15 March, 1987, the spinning section of the large linen textile plant in Harbin, P.R. China, was afflicted with a catastrophic dust explosion. The losses were substantial. Out of the 327 women and men working night shift in the spinning section when the explosion occurred, fifty-eight lost their lives and 177 were injured. 13,000 m2 of factory area was demolished. The explosion accident has been discussed in detail by Xu Bowen (1988) and Zhu Hailin (1988)....

353 Spray Mist Explosions in Crank Cases in Large Diesel Engines

Crank case explosions, their origin and nature, and means of prevention and mitigation were discussed in detail by Minkhorst (1957) in a comprehensive literature survey. Engines fitted with cranks are normally equipped with a lubrication system by which oil is supplied to the bearings by pressurization. In order to protect the environment from oil spray and to prevent loss of oil, the crank system is usually fully enclosed by a case. Explosive spray clouds may be generated within the case by...

323 Coalescence of Drops in Sprays Mists

A comprehensive review of the state of the art more than forty years ago was given by Green and Lane (1964). Much of this information is still valid. The same applies to the comprehensive review by Zebel (1966), who considered three main categories of coalescence mechanisms. The first was thermal coalescence, driven by Brownian movement of the droplets, the second coalescence influenced by inter-droplet forces (van der Waals and electrical magnetic forces). The third category was coalescence...

225 Ignition by Burning Metal Particles Thermite Reactions and Transient Hot Spots

In the past, the initiation of accidental gas explosions was sometimes attributed to friction sparks without any further explanation. However, this imprecise term covers a multifarious category of potential ignition sources, comprising mechanical hot-work operations such as grinding and cutting, repeated impacts on one spot, and single impacts. However, in all these cases, the ignition source is generated by transformation of mechanical energy (impact and friction) into heat. Existing knowledge...

532 Smoldering or Burning Nests

As discussed in Chapter 4, experience has shown that combustible dusts, when deposited in heaps or layers, may under certain circumstances develop internal smoldering nests of high temperatures. This is due to the porous structure of dust deposits, which gives oxygen access to the particle surface throughout the deposit, and also makes the heat conductivity of the deposit low. The initial oxidation inside the deposit may sometimes be due to the deposited dust or powder having initially a higher...

622Experimental Methods for Measuring Detonation Properties 6221 Dautriche Method

The Dautriche method for determination of detonation velocities of explosives, as described by Meyer (1987), is illustrated in Figure 6-1. Table 6-2 Comparison of Deflagration and Detonation Properties of a Nitro-glycole Explosive of Density 1.5 g cm3 a Table 6-2 Comparison of Deflagration and Detonation Properties of a Nitro-glycole Explosive of Density 1.5 g cm3 a Flame front propagation velocity Thickness of reaction zone Liberated energy in reaction zone Mass conversion rate Energy...

222 What Is Ignition The Basic Theory of Thermal Runaway

Explosive gas mixtures can be ignited by a variety of ignition sources including open flames (matches, welding and soldering flames etc.) glowing or smoldering materials burning metal particles and thermite flashes from impacts, grinding etc. electrical and electrostatic sparks, arcs, and other discharge forms jets of hot combustion gases light radiation, e.g. light conveyed through optical fibers or cables The question then arises whether ignition by all these quite different sources can be...

522 Flame Propagation Processes in Dust Clouds

5.2.2.1 Basic Differences between Premixed Gas Flames and Flames in Dust Clouds Leuschke (1965) pointed out some characteristic differences between a laminar premixed gas flame and a laminar dust flame. One important difference is that the reaction zone in the dust cloud is considerably thicker than in the gas, irrespective of the type of dust, and of the order of at least 10-100 mm. When discussing this feature of dust flames, it is useful to distinguish between two flame types. The first, the...

244 Controlling Ignition Sources

This section is based on Statoil (2004). The concept of ignition source control, as opposed to ignition source prevention, implies that potential ignition sources may exist in an area as long as there is no significant concentration of combustible gas or vapor in the atmosphere. However, as soon as significant concentrations of combustible gas vapor are detected these potential ignition sources shall be removed from the area, de-energized, or in some other relevant way be brought in a state...

547 Major Polyethylene Dust Explosion Kinston North Carolina USA 2003

On 29 January 2003, a dust explosion occurred at the West Pharmaceutical Services, Inc. plant in Kinston, North Carolina, U.S.A. Six workers lost their lives and thirty-eight were injured, including two fire fighters. Because of the number of deaths and injuries, the U.S. Chemical Safety and Hazard Investigation Board (CSB) launched an investigation to determine the root and contributing causes of the explosion and to make recommendations to prevent similar occurrences The present account is...

Some central data of this catastrophic event are given in Table 213 Table 213 The Flixborough Explosion

Congested process area of cyclohexane oxidation section of caprolactam production plant (basic raw material for Nylon 6) Entire plant demolished. 1821 houses and 167 shops in nearby residential areas suffered various degrees of damage The Flixborough disaster is probably the most well documented major accidental industrial vapor cloud explosion world wide. The comprehensive public report by Parker et al. (1975) contains references to about sixty detailed reports on various aspects that were...

Figure 535 Influence of dust moisture content on minimum electric spark ignition energy MIE for three dusts From van

Strengths than the brush discharges, and the discharge energies will therefore also be much lower. Consequently, the possibility of igniting dust clouds by corona discharges can be ruled out. Brush discharges, illustrated in Figure 2-34 in Section 2.2, occur between a single curved, earthed metal electrode (radius of curvature 5-50 mm) and a charged non-conducting surface (plastic, rubber, dust). Brush discharges can ignite explosive gas mixtures. However, according to Glor (1988), no ignition...

643 Explosives Mix Explosion in Mustang Nevada USA 1998 6431 Introduction

On 7 January 1998, at 0754, two explosions in rapid succession destroyed the Sierra Chemical Company's Kean Canyon plant east of Reno near Mustang, Nevada, U.S.A. killing four workers and injuring six others. Because of the loss of life and extensive damage, the United States Chemical Safety and Hazard Investigation Board (CSB) sent a team to investigate the explosion in an attempt to understand the causes of this incident. The present account is a brief summary of the comprehensive CBS (1998)...

536 Electric Sparks and Arcs Electrostatic Discharges

It has been known for more than 100 years that electric sparks and arcs can initiate dust explosions. The minimum spark energy required for ignition varies with the type of dust, the effective particle size distribution in the dust cloud, the dust concentration and turbulence, and the spatial and temporal distribution of the energy in the electric discharge or arc. For many decades it was thought that the electric spark energies needed for igniting dust clouds in air were generally much higher,...

523 Closeto Laminar Flame Propagation in Dust Clouds

Close-to-laminar 20 mm diameter burner flames of clouds in air of lyco-podium and polyvinyl alcohol were studied by Kaesche-Krischer and Zehr (1958) and Kaesche-Krischer (1959). The burning velocity, defined as the ratio of air flow and flame cone area, was determined photographically from the height of the flame cone. Some results are given in Figure 5-7. Figure 5-7 Burning velocities of flames of lycopodium and polyvinyl alcohol dust (< 60 pm particle diameter) flames as functions of dust...

525 Turbulent Flame Propagation in Dust Clouds

5.2.5.1 Basic Features of Closed-Bomb Studies of Turbulent Dust Flames Much of the published experimental study of turbulent dust explosions has been conducted in closed vessels of the type illustrated in Figure 5-13. Figure 5-13 Schematic illustration of the type of apparatus commonly used in closed-vessel turbulent dust explosion experiments. From Eckhoff (2003). The explosion vessel of volume Vj and initial pressure Pj is equipped with a dust dispersion system, a pressure sensor and an...

354 Major Oil Spray Mist Explosion in a Transformer Room of a Hydroelectric Power Station

This accident, in which three men were killed and several others injured, was described by Johnsen and Holte (1973). Further details were given by Schjelderup (1990). The accident occurred in 1973 in the hydroelectric power station at Tonstad, Sirdal in Norway. The entire station is located underground. Figure 3-10 gives a top view of the entire underground installation. Figure 3-11 gives a cross-section of the oil-filled cable junction box, and Figure 3-12 a cross-section of the main...

214 Maximum Pressures Generated from Constant Volume Adiabatic Combustion of Premixed Gas Vapor and

If the combustion occurs at constant volume, a pressure rise will result. The adiabatic temperature rise at constant volume can be expressed as where AE is the liberated combustion heat per mole at constant volume, Cv is the mean specific heat of the gaseous system at constant volume, Tj is the initial gas mixture temperature (prior to combustion), and T2 is the final temperature of the combustion products and the nitrogen (from the air) after complete combustion. Ideal T2 values computed using...

34 Ignition of Clouds of Liquid Droplets in Air Spray Mist 341 Ignition by Hot Surfaces

The problem is of the same nature as discussed in Chapter 2 with hot-surface ignition of gases and vapors. However, it has not been possible to trace any standardized test methods for measuring minimum ignition temperatures of sprays mists. Figure 3-5 gives some results from hot-surface ignition of suspensions of JET-A fuel droplets flowing through a vertical furnace. Note that the vertical axis in Figure 3-5 covers only 120 C. This figure also gives corresponding data for premixed propane air,...

239 Catastrophic Gas Explosion in Taegu South Korea April 1995

This gas explosion catastrophe did not occur in the process industry, but in the middle of the busy city Taegu in South Korea (see Figure 2-58). However, the lessons to be learned are also indeed relevant for the process industries. The following provisional summary is taken from the brief report by Spaeth (1995) published shortly after the accident At 0750 hours on April 28, 1995, an immense fireball tore through the heart of Taegu, South Korea's third-largest city, of a population of 2.3...

238 The West Vanguard Explosion The North Sea 1985

Some central data of this event are given in Table 2-16. A detailed discussion of this accident is given in the report by the Public Commission of Investigation (1986). The explosion occurred on board Table 2-16 The West Vanguard Explosion Table 2-16 The West Vanguard Explosion Haltenbanken, Norwegian continental shelf the comparatively new, well equipped and well maintained mobile oil drilling platform West Vanguard, while performing test drilling on Haltenbanken on the Norwegian continental...

524 Maximum Pressures Generated from Constant Volume Adiabatic Combustion of Dust Clouds in

In Table 5-1 calcium, magnesium, and aluminum top the list with 1,100-1,300 kJ mole oxygen consumed. The lowest values are 300 kJ mole oxygen for copper and sulphur. It would be expected that this difference will to some extent be reflected in the maximum pressure of explosions, when performed adiabatically at constant volume. Zehr (1957) made some calculations of the maximum pressures to be expected under such conditions. In Figure 5-11, his results have been plotted against data from...

226 Ignition by Electric Sparks and Arcs and Electrostatic Discharges

2.2.6.1 Electric Sparks between Two Conducting Electrodes Electric sparks are produced when the strength of the electric field in the gap between two conducting electrodes exceeds what the dielectric medium in the gap can resist. For a given dielectric medium, e.g. air at atmospheric conditions, the relationship between the gap distance and the critical gap voltage for gap breakdown depends on the electrode shape and the electrode material. Figure 2-23 gives some results obtained in two...

542 Historical Perspective Wheat Flour Explosion in Turin 1785

The dust explosion hazard has probably been recognized in Europe for several centuries, but the flour explosion in Turin in 1785 seems to be the first accident of this kind that was investigated extensively. When the Academy of Science of Turin heard about Morozzo's investigations, they asked him to prepare a written account of his findings. Only very rarely are details of Count Morozzo's (1795) fascinating account mentioned in modern literature. It is considered appropriate, therefore, to...

546 Major Aluminum Dust Explosion at Gullhaug Norway 1973

The main source of information concerning the original investigation of the accident is Berg (1989). The explosion occurred during the working hours, just before lunch, while ten workers were in the same building. Five of these lost their lives, two were seriously injured, two suffered minor injuries, whereas only one escaped unhurt. A substantial part of the plant was totally demolished, as illustrated by Figure 5 48. The premix preparation plant building was completely destroyed. Debris was...

352Oil Mist Explosion in a Compressor Test Loop

This explosion, discussed by Schmitt (1973), occurred in 1959 in a compressor test facility at Ingersoll-Rand Co.'s plant in Phillipsburg, N.J., USA. The test of a centrifugal compressor was being conducted in accordance with standard procedure, which involved the use of a closed loop for containment and re-circulation of the gas used during the test. The test was nearly completed when, after approximately six hours of test opera tion, an explosion occurred. The inlet side of the loop pipe...

Figure 217 Minimum hot surface ignition temperatures for a propaneair mixture at atmospheric pressure determined by

2.2.4.2 Minimum Ignition Temperatures of Multi-Component Fuels in Air In offshore oil and gas production, minimum ignition temperatures of mixtures of multi-component fuels and air are often of interest. For example, natural gas is a multi-component fuel, containing higher hydrocarbons in addition to the methane. For mixtures of methane, propane and air Kong et al. (1995) investigated the dependence of the ratio of propane methane on Tmjn of the mixtures. Figure 2-18 shows a significant...

72 Basic Design Concepts for Electrical Apparatus 721 Gases and Vapors

A series of standardized basic design concepts for electrical apparatuses intended for use in explosive gas atmospheres have been available for a long time. The details are described in a corresponding series of international standards (IEC, CENELC etc.). The following summary is mainly based on BBC (1983). The figures are from Eckhoff (1996). This design concept can be used for apparatuses to be used in all three Zones (0, 1 and 2). An intrinsically safe circuit is a circuit in which no spark...

53 Ignition of Dust Clouds in Air 531 Introduction

A combustible dust cloud will not start to burn unless it becomes ignited by a source of heat of sufficient strength. The most common ignition sources are open flames welding, cutting, matches, etc. hot surfaces hot bearings, dryers, heaters, etc. heat from mechanical impacts electrical discharges and arcs In addition, there are some more sophisticated potential ignition sources including adiabatic compression and shock waves There is considerable variation in the ignition sensitivity of clouds...

342 Ignition by Electric Electrostatic Sparks Discharges

Explosive sprays mist can be ignited by electric spark discharges in the same way as premixed gaseous fuel air mixtures can. In principle, therefore, the concepts of Minimum Ignition Energy MIE and Quenching Distance QD are equally valid for sprays mists as for premixed gases. However, in the case of spray mists the experimental determination is considerably more difficult. Figure 3-7 gives a set of data showing the influence of spark gap length on minimum ignition energy of a suspension of...

543 Three Grain Dust Explosions in Norway 19701988

Diy Bucket Elevator Design

5.4.3.1 Wheat Grain Dust, Stavanger Port Silo, June 1970 The explosion occurred in Norway's largest and newly built import grain silo in Stavanger on a hot and dry summer day. Fortunately, no persons were killed, but some workers suffered first degree burns. Although the extent of flame propagation was considerable, the material damage was moderate due to the comparatively strong reinforced concrete structure of the buildings and the venting through existing openings. The entire event lasted...

212 Laminar Burning of Premixed Gas Vapor and

Figure 2-3 gives experimentally determined relationships between the so-called laminar burning velocity and the concentration of combustible gas in the mixture with air for four common combustible gases. The ideal laminar burning velocity is the lowest velocity at which a flame front can propagate through a given gas mixture given ratio of gas to air, 60 80 loo 120 140 160 Fuel conc. in of stoichiom. conc.