Showing papers by "Rolf K. Eckhoff published in 2016"

A catastrophic aluminium-alloy dust explosion in China

Abstract: On August 2, 2014 a catastrophic dust explosion occurred in a large industrial plant for polishing various aluminium-alloy parts in Kunshan, China. The explosion occurred during manual polishing of the surfaces of aluminium-alloy wheel hubs for the car industry. 75 people lost their lives immediately and another 185 were injured. Subsequently, 71 of the seriously injured also died, which increased the total loss of lives to 146. The direct economic loss of was 351 million yuan. This is probably one of the most serious dust explosion catastrophes known apart from some very major coal dust explosion disasters in coal mines. Based on measurements of explosion parameters of dust samples collected on the explosion site and on-site investigations and interviews, it was concluded that a series of consecutive explosions was initiated in one of the external dust filters. Then it propagated into the main building via the dust extraction ducting and further onto the second floor. At the same time the propagating in-house dust flame was sucked into the ducts leading to seven other external dust filters, which also exploded. On the basis of investigations on site after the explosion and subsequent laboratory experiments and data analyses it was concluded that the explosion was most probably initiated by self-ignition of contaminated aluminium-alloy dust in the dust collecting barrel below the external bag filter unit in which the initial primary explosion took place. General ignorance of the potential risk of dust explosions in industries producing fine metal dusts as a low-mass waste by-product is the most probable basic root cause of this catastrophic accident. Therefore, avoiding accumulation of deposits of such dusts indoors by good regular housekeeping and other means is regarded the most effective and practical way of loss prevention due to metal dust explosions in such plants. In addition, explosion isolation between dust collecting systems and workshops appears to be another important measure towards minimizing the consequences of such explosions.

Water vapour explosions – A brief review

Abstract: There are basically two kinds of water vapour explosions, viz. confined and unconfined. Confined explosions can occur in various situations in industry. Unconfined explosions typically occur when very hot molten metal accidentally makes contact with water. In order to explain the extremely rapid production of water vapour that can then occur, “fine fragmentation” of the molten metal must take place. The paper first presents some early suggestions for the nature of the fine fragmentation process. In more recent theories the Weber number, We, is used as a measure of expected extent of molten-metal fragmentation in a given situation. Film boiling plays a central role. Attempts at developing mathematical models of unconfined water vapour explosions have been made. The next section of the paper is devoted to case histories of unconfined water vapour explosions. Then various kinds of confined water vapour explosions are discussed, including water boiler explosions, water vapour BLEVEs, and water vapour explosions in the paper industry. Some case histories of confined water vapour explosions are also given. The final section of the paper is devoted to measures for preventing and mitigating water vapour explosions in industry.

Design of Electrical Apparatuses for Hazardous Areas

Abstract: The chapter starts with explaining the concept of “area classification.” What is the overall objective of area classification? Then, specific features of area-classification concepts for gases and vapors, dust clouds, and explosives, propellants, and pyrotechnics are described. In the following main part of the chapter, basic design concepts for electrical apparatuses for use in contact with substances that can cause explosions are described for gases and vapors, clouds of liquid droplets, dust clouds, and explosives, propellants, and pyrotechnics.

Gas and Dust Explosions Caused by Smoldering Combustion in Powder Layers and Deposits

Abstract: The chapter begins by discussing burning velocities/burning rates in powder layers/deposits.

Gas and Vapor Cloud Explosions

Abstract: The chapter first discusses combustion of gases/vapors. The distinction between “diffusion” combustion and “premixed” combustion is made. The concepts of laminar burning in premixed combustion and flammable fuel concentration ranges are presented. Then the concept of maximum pressures in constant-volume adiabatic combustion of premixed gas/vapor and air is discussed and that of “expansion ratio” presented. Then, turbulent combustion and detonation are discussed, followed by ignition of premixed gas/vapor and air. The question “what is ignition?” is posed and the basic idea of “thermal runaway” is presented. Then a review of ignition by hot surfaces, electric sparks/electrostatic discharges, and some other sources follows. The subsequent section is a review of a number of case histories of accidental gas/vapor cloud explosions, from 200 years ago until recently. The final section is a discussion of various means of preventing and mitigating gas/vapor explosions in the process industries.

Boiling Liquid Expanding Vapor Explosions (BLEVEs)

Abstract: BLEVE is defined as a Boiling Liquid Expanding Vapor Explosion. Chains of events leading to BLEVEs and their consequences are discussed. Typically, a vessel containing pressurized liquefied gas (PLG), eg, propane, is accidentally exposed to heat by an outside fire. This causes the temperature and pressure inside the vessel to increase. Eventually the vessel bursts, and there will be sudden depressurization and explosive evaporation of the hot liquid. This emits a blast wave into the surroundings. Missiles (fragments) from the shattering of the first vessel may cause perforation and shattering of nearby secondary vessels. If the liquids are flammable, large fireballs and extensive pool fires can result. If the liquid is toxic, emission of toxic gases/vapors into the surroundings is a main hazardous effect. The central role of superheat limit temperature (SLT) of the liquid in BLEVE development is discussed. Then, a section presenting BLEVE case histories, including BLEVEs in storage tank facilities and transportation facilities, follows. The final parts of the chapter discuss various means for preventing the occurrence of BLEVEs and mitigating harmful/destructive effects if BLEVEs do occur.

Review of Some Methods of Hazard and Risk Analysis

Abstract: In this chapter, a selection of methods for hazard and risk analyses in industrial plants producing, handling, and/or storing materials that can give rise to accidental explosions, are outlined. The intention with the chapter is not to provide comprehensive manuals for applying the various methods, but rather to provide a gateway to selection of more in-depth descriptions of suitable methods. The methods reviewed include preliminary hazard inventory; process/systems check-list; safety audit; relative risk ranking using Dow and Mond indices; “what-if” analysis; hazard and operability studies (HAZOP); failure mode, effect, and criticality analysis (FMECA); fault tree analysis; event tree analysis; cause–consequence analysis; and human-error analysis (HEA). Quantitative risk analysis (QRA) is also briefly discussed.

Explosions of Clouds of Combustible Liquid Droplets in Air

Abstract: The first section discusses mechanisms of generation of clouds of liquid droplets in air. A distinction between “mist” and “spray” is made, and the phenomenon of “coalescence” of drops in sprays/mists is presented. Then a discussion of combustion of clouds of liquid droplets in air, with laminar and turbulent flame propagation, follows. Experimental maximum constant-volume adiabatic explosion pressures in spray/mists explosions in air are presented and detonation-like phenomena are discussed. Then various ignition sources are discussed including hot surfaces and electric/electrostatic sparks/discharges. The following section is devoted to some case histories of accidental mist/spray explosions. Spays/mists may in fact have been involved in some well-known reported major “vapor cloud” explosions. The final part of the chapter is devoted to means of preventing and mitigating spray/mist explosions in the process industries.