Minimum Dust Quantities for an explosion

Posted in: , on 6. Dec. 2007 - 15:55

As part of our powder handling operations we handle 3 kg lots of powders in an isolator. These 3 kg lots are subdivided into bags attached to the isolator into maximum sizes of 2.5 kg.

I do not belive that Hazardous Area Classification is required insofar as the requirements are for powder to be present in sufficient quantities. I have found a HSE document (though for the food industries) that mentions a 10 kg size 9with no reference).

Does anybody use a standard cut-off quantity for powders where they employ hazardous area classification.

For the particularly technical minded personnel the isolator is 1m3 and the discharge chamber is 0.5m3

Re: Minimum Dust Quantities For An Explosion

Posted on 12. Dec. 2007 - 12:00

Happy to help.

What dust is being handled - do you have an LEL for the powder?

What is an isolator - what function does it preform.

Tony Vierboom Nova Protection Systems

Re: Minimum Dust Quantities For An Explosion

Posted on 12. Dec. 2007 - 10:54

Hi Tony,

The materials vary, however the worst case material has an MIE of less than 3mJ. The Minimum Explosive Concentration is not known however we are currently using a value of 25g/m.

An Isolator is essentially a Glove-Box. The materials are generally scooped from one container onto another container on a set of scales and then discharged via a split butterfly valve into a discharge containers (polybottle).

If you need any further information let me know.


Posted on 8. Jun. 2008 - 03:17

Hazardous locations are based on possibilities. So, if your process has the possibility to reach the LEL, it is necessary to consider the location classified, despite the amount of powder present. Remember that some explosion experiences can be made using a small spoon of powder.

The critical point in your message I think is: "The Minimum Explosive Concentration is not known ". This is dangerous, because this value for different samples of the same material varies a lot, depending on moisture content, grain size and process characteristcs. I recommend to perform tests to know the characteristcs of the powder you handle in your plant.