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Thread: Dust Explosion Characteristics

  1. #1
    Ben Guest

    Question dust explosion characteristics

    I can`t find the correct dust explosion characteristics(like MIE in proportion to sieve analysis, LEL, MIT,...) of the products (plastics) we grind for third parties.
    The received MSDS`s are inadequate en when i ask for more info, they don`t have it (even large companies don`t have the correct info).
    We grind over hundred different plastics so it is impossible to have the characteristics determined by a lab.
    We need this info to work safely and i don`t know how obtain.
    Who does?

  2. Dust Explosions

    Try Childworth Technology, Beta House, Chilworth Research Centre, Southampton. SO16 7NS

    Tel.44 (0)23 8076 0722 Fax 44 (0)23 9076 7866 www.chilworth.com.

  3. #3
    boursr Guest

    explosion characteristics

    Dear Ben


    you might want to contact also

    Fike Europe
    Toekomstlaan 52
    B2200 Herentals, Belgium


    Tel.: ++32 14 210031
    Fax.: ++32 14 210743

  4. dust ex characteristix

    ben,

    please go in touch with mr. roland bunse @ rembe, brilon.
    email: bu@rembe.de
    phone: 0049 2961 74 05 - 40
    postal: REMBE GmbH SAFETY + CONTROL,
    Gallbergweg 21, 59929 Brilon - Germany.

    stefan

    PS:
    do also visit: http://biaonline.hvbg.de/EXPLO.htm and an
    english version under http://www.hvbg.de/d/bia/fac/expl/exple.htm
    - push "OPEN DATABASE" - there you will find the search engine.
    for further queries you can also contact me directly!

  5. Unfortunately there is not a universal dust law similar to that for gases. Dusts behave in more random ways and there are several factors that influence the explosive behavior of any given dust. Particle size distribution, chemical structure, moisture content, suspended dust cloud concentration, strength and duration of the ignition source, and homogeneity of dispersed dust cloud to name some. Since these variables are constantly different, the only safe thing to do is to have your dust tested.

    You say you have over 100 different dusts so it is obvious that having separate data for every one would be a very expensive proposition. Can you separate them into broad groups based on chemical composition for example? If so, then take the finest particle size distribution sample from each group and test only it. In this way you would have a set of data for the group that should represent a near worst case. Other dust in the group that are chemically similar but are comprised of overall larger particle sizes can be considered to be similar, but slightly less reactive than the test reference for the group. By using the data for the reference dust for each group it can be presumed that you would be conservative and safe.

    The basic data you need in all cases is Kst and Pmax. These values are derived from either a 20-liter sphere test, or a 1-cubic meter sphere test. This data is used to size explosion-vents and other protection schemes.

    MIE would only be important for dusts that are very sensitive to ignition. Dusts that are mixed with flammable gases or vapors would be an example. A skilled test person can develop a sense of when a dust might be very ignition sensitive from the 20-liter sphere test. Not every dust needs this data point. Let your chosen lab provide guidance on when MIE testing would be prudent.

    MAIT would normally only be important if the dust is being exposed to elevated temperatures such as in a heated dryer for example. MAIT is further complicated because there is a test for dust layers and another for dust clouds. If you are unsure which is appropriate, the layer test provides the lower, safer value. Not every dust is routinely exposed to elevated temperatures and as such, this test is not always useful.

    Regards,

    Bill

  6. #6
    srowe Guest
    Most dust explosion tests have a particle size requirement to provide data that can be compared from sample to sample (and is also conservative ie. worst case). The particle size requirement is generally < 75 or 63 micron. Therefore, if you submitted a sample to a test lab (like Chilworth Technology), the sample would be prepared according to the standard method. Basically, the tests should be performed on the smallest particle size processed (or < the test stipulation, whichever is lowest).

    Most companies MSDS's are notoriously ignorant of dust explosion hazard data.

    If you have a large number of samples to be assessed, a tailored program of test work can be designed to minimise the number of tests required to generate worst case data - it may not, therefore, be necessary to perform a full analysis of every parameter for every powder. A good test house would guide you through this screening procedure to minimise the extent (and hence cost) of this.

  7. #7
    boursr Guest

    Lightbulb

    Please go to following webpages where you could find interesting information on explosion characteristics:


    www.bia.de, then select "Technical Information" followed by "GESTIS-DUST EX". The products you may be working with could be there.

    A word of caution: physical characteristics (particle size, humidity, etc) may influence the explosion parameters dramatically; testing your product sample may still be the option to choice.

    Roger

  8. #8
    tominer Guest

    A question regarding dust suppression

    Please Note:

    Pure Hyperbole and theory - only experiential - no engineering background to make comment on this topic but (that said):

    Using an experience I had when working with bulk solids processing sludge for Industrial Incinerator Corp:

    We used a polymer to develop flocks in hydrated sludge - using both the chemical and disposition to bonding (as related to the charge characteristics of the sludge - IE. positive/negative) we used polymers that bound the sludge by interposing a charged substance having a dissimilar charge.

    Why is air treated as different from water in one context (bulk handling) whereas treated as if a liquid medium in such industries as HAVC?

    Point: Can a medium be introduced into a gaseous space that, like the polymers that we used to create flocks create flocks of airborne dust for the purpose of supplementation as well as recycling of the materials back into the product of which they are sourced?

    Can the medium introduced to the gaseous medium be constantly re utilized - if for example - the medium actually be neutrally charged - passed through an ionizer - create the flock and after saturation be recovered once again as a neutral medium only to be recharged once again - the ionization being positive or negative - depending upon the material currently in the enclosed environment?

    Is this possible?

    tominer

  9. #9
    The lower explosion limits (LEL) for many substances do not take into account particle size distribution. They are often only stated as so many milligrams per litre or grams per cubic meter of "fines or dust". Dust particle size is crucially important in determining explosivity.

    What is often stated is that the particle size being refered to is "less than so many microns". This is an improvement but it is not the particle size distribution. A dust sample containing 50% particulate less than 10 microns is much more sensitive to igniton than one with 90% between 10 and 50 microns and only 10% less than 10 microns. Yet both would fall under the same classification if "less than 50 microns" was used to define the LEL.

    In addition, modern investigation has shown that the SHAPE of fine particles can significantly affect the explosivity. This is related to charge concentration at sharp points and edges. Modern measurement techniques are now getting to the point where BOTH particle size distribution and particle SHAPE can be defined and this should lead to a finer definition of LEL's.

    But we are not there yet.

  10. dust control techniques

    Your idea is quite interesting, Tominer. The closest thing to what you suggest that I can recall is some work that was done by FM Research several years ago on ways and means to control dust cloud formation inside large silos. This was done for the grain industry.

    The technique involves the use of oil to attract and agglomerate dust particles so that they would fall out of suspension. I do not recall if anything was done with static charge in those experiments. But I do know that the technique is viable within certain parameters and I believe is widely used in the grain industry.

    Regards,

    Bill

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