(80h) The 20-L Chamber and the Provision of Dust Explosion Data for Industrial Use

The 20-L chamber has a 40-year history of widespread use for dust explosibility testing and research. Skjold (2018) describes its origin in the late 1970s when Richard Siwek demonstrated good agreement between his 20-L design and Wolfgang Bartknecht’s 1-m³ vessel in terms of comparable K_St (size-normalized maximum rate of pressure rise) values. There are now over a hundred 20-L chambers in operation globally.

The current presentation draws on the experience of the authors in providing test data to industry and conducting fundamental and applied research using the 20-L chamber. The objective is to elucidate key features that should be kept in mind both when operating this device and when analyzing the explosibility data it yields. Each of the items in the following list will be explained in detail with supporting examples and references to the technical and standards literature. The 20-L chamber:

• is a workhorse that has served the dust explosion community well for many years.
• has been used to produce an enormous amount of explosibility data.
• is more plentiful worldwide than the 1-m³ chamber.
• has more than one design.
• must be operated following standardized protocols if test results are to be used for explosion prevention and protection.
• typically uses multi-point ignition sources.
• is capable of producing repeatable and reproducible results.
• can be used to test for a variety of explosibility parameters (e.g., maximum explosion pressure, size-normalized maximum rate of pressure rise, minimum explosible concentration, and limiting oxygen concentration).
• can be used to test a variety of materials (e.g., spherical or near-spherical dusts, nano-size dusts, flocculent dusts, and hybrid mixtures).
• turbulence levels decay with time (Mercer et al., 2001).
• dust concentrations are nominal (Kalejaiye et al., 2010).
• process of dust dispersion can alter the dust particle size distribution.
• can be overdriven or underdriven with respect to the 1-m³ chamber.
• can be modelled.
• can yield results that might be surprising to the user (e.g., when testing nano-size dusts).
• is a significant improvement over the 1.2-L Hartmann bomb.
• is the best laboratory-scale alternative we have to the 1-m³ chamber.

Overall conclusions on present and future use of the 20-L chamber will also be given in the presentation. Emphasis will be placed on the quality of the explosibility data produced by the 20-L chamber (especially for marginally explosible dusts), relative to the usefulness of the data for design of industrial prevention and mitigation measures.

References

Kalejaiye, O., Amyotte, P.R., Pegg, M.J. & Cashdollar, K.L. (2010). Effectiveness of dust dispersion in the 20-L Siwek chamber. Journal of Loss Prevention in the Process Industries, 23(1): 46-59.

Mercer, D.B., Amyotte, P.R., Dupuis, D.J., Pegg, M.J., Dahoe, A., de Heij, W.B.C., Zevenbergen, J.F. & Scarlett, B. (2001). The influence of injector design on the decay of pre-ignition turbulence in a spherical explosion chamber. Journal of Loss Prevention in the Process Industries, 14(4): 269-282.

Skjold, T. (2018). Dust explosion modeling: Status and prospects. Particulate Science and Technology, 36(4): 489-500.