Ignition of Dust Layers by Mechanical Sparks

Global Congress on Process Safety
2011 Global Congress on Process Safety
Global Congress on Process Safety
March 14, 2011 - 8:00pm

Dust explosions represent a considerable safety risk in process industry. Statistical records of dust explosions show that 32.7 % of these explosions are initiated by mechanical sparks or hot surfaces due to mechanical friction [1]. Laboratory investigations however show that direct ignition of dust clouds by mechanical sparks and hot surfaces caused by friction processes is not that straightforward [2]. A possible explanation of this anomaly may be that the mechanical sparks and hot surfaces cause an indirect ignition of a dust cloud through ignition of a dust layer. This paper addresses the ignition of dust layers by mechanical sparks.

An experimental study has been performed investigating ignition of dust layers by sparks generated from metal rods pushed against a grinding wheel. A large number of parameters were varied including: ? Contact pressure and contact time between metal rod and grinding wheel ? Distance between grinding wheel and dust layer ? Type of metal used

? Ventilation flow rate across dust layer

? Dust type (in total 17 different organic and inorganic dusts were involved in the investigation), ? Moisture content of dust ? Particle size distribution of the dust ? Density of dust layer ? Dust layer thickness

Of the dusts investigated standard dust combustion properties (minimum ignition temperature of dust layer and burning velocity of dust layer) and particle size distribution and moisture content were determined.

The main experimental findings are: The experiments showed that a relatively high spark density is needed to establish smoldering combustion in dust layers for the dusts investigated. Ignition of a dust layer by a single impact spark therefore seems to have a very low probability. A relatively large median particle size dust is easier ignited by mechanical sparks than fine dust. Dust layers with a median particle size diameter of The paper will give more detailed conclusions. [1] Beck, H. and Jeske, A. Berichte über Staubexplosionen ? Einzelereignisse und Dokumentation, VDI- Berichte, 1272, 365-387, 1996 [2] Bartknecht, W., Explosionsschutz. Grundlagen und Anwendung, Springer-Verlag, 1993

Professional Development Hours
0.5 PDHs
You will be able to download and print a certificate for these PDH credits once the content has been viewed. If you have already viewed this content, please click here to login.

Would you like to access this content?

No problem. You just have to complete the following steps.

You have completed 0 of 2 steps.

  1. Log in

    You must be logged in to view this content. Log in now.

  2. Purchase Technical Presentation

    You must purchase this technical presentation using one of the options below.
    If you already purchased this content recently, please click here to refresh the system's record of ownerships.


Credits 0.5 Use credits
List Price $25.00 Buy now
AIChE Members $15.00 Buy now
AIChE Undergraduate Student Members Free Free access
AIChE Graduate Student Members $15.00 Buy now