Abstract
Recently, the Committee responsible for NFPA 654 came up with two new consensus criteria for determining that a compartment is a dust explosion hazard: one aimed at mitigation of burn injuries, and the other for room/building collapse prevention. As described in Rodgers and Ural (2010), the criteria are based on maximum allowable airborne combustible dust mass. Both formulas rely on an empirical entrainment fraction, ηD, representing the fraction of dust accumulations that can become airborne during an accident. After much discussion, the Committee selected a value of ηD = 0.25 which offers the same level of protection NFPA 654-2006 does for typical occupancies, pending the outcome of this Research Foundation sponsored project.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
The rate of mass removal per unit area per unit time.
- 2.
The nominal dust loading assumes that all of the dust was dispersed uniformly throughout the cross-section.
- 3.
The particle densities for the coal dust and rock dust are 1330 and 2750 kg/m3, respectively. Since tested mixtures were mostly rock dust (64 to 80% rock dust by weight), rock dust particle density was used to estimate the threshold velocity.
- 4.
Dynamic pressure impulse is the integral of dynamic pressure over time.
- 5.
See, for example, CCPS (2010) for a calculation procedure.
- 6.
The threshold radius scales with the cube root of the bursting enclosure volume, and can conceivably be utilized to establish safe separation distances.
- 7.
Temporal evolution process of the vent discharge jet was not considered to keep the analysis simple for the end user.
References
ASHRAE (2005), “Space Air Diffusion,” 2005 ASHRAE Handbook Fundamentals, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Chapter 33.
Cashdollar K L, Sapko M J, Weiss E S, Harris M L, Man C, Harteis S P, and Green G M (2010). Recommendations for a new rock dusting standard to prevent coal dust explosions in intake airways, NIOSH, RI 9679, 49 pp.
CCPS (2010) Guidelines for Vapor Cloud Explosion, Pressure Vessel Burst, BLEVE and Flash Fire Hazards, Wiley, section 7.4.
Harris, M. L. (2010), Private Communication, Pittsburgh Research Center, NIOSH.
Harris, M L, Cashdollar, K L, Man, C, and Thimons E (2009). Mitigating coal dust explosions in modern underground coal mines, in Proceedings of the 9th International Mine Ventilation Congress, 8 pp (New Delhi, India, November 10–13, 2009).
Kalman, Haim, Andrei Satran, Dikla Meir, Evgeny Rabinovich (2005), “Pickup (Critical) Velocity Of Particles,” Powder Technology, 160, pp. 103–113.
Rodgers, S.A. and Ural, E.A. (2010), “Practical Issues with Marginally Explosible Dusts - Evaluating the Real Hazard,” Accepted for publication in the Process Safety Progress.
Tamanini, F. (1983), “Dust Explosion Propagation in Simulated Grain Conveyor Galleries,” FMRC Technical Report, J.I. OF1R2.RK, July 1983.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2011 Fire Protection Research Foundation
About this chapter
Cite this chapter
Ural, E.A. (2011). Proposed Strawman Method. In: Towards Estimating Entrainment Fraction for Dust Layers. SpringerBriefs in Fire. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-3372-9_3
Download citation
DOI: https://doi.org/10.1007/978-1-4614-3372-9_3
Published:
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4614-3371-2
Online ISBN: 978-1-4614-3372-9
eBook Packages: EngineeringEngineering (R0)