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Spark Ignition Hazard

Dust Explosion
When dispersed as a dust, adipic acid is subject to normal dust explosion hazards. The minimum ignition energy (MIE), a measure of dust explositivity, is 5 mJ. Tests show that unloading 1000 Kg big bags of adipic acid can generate voltage levels necessary to constitute a spark hazard. The spark hazard is of concern, as it can potentially be an ignition source for solvent/air mixtures typical for some ester reaction applications.
Adipic acid dust explosion properties
(Tested on a range of samples of differing particle sizes)

Minimum exlplosible
concentration (MEC)
39 to 60 g m -3
Minimum ignition
energy (MIE)
5 - 50 mJ
Minimum ignition
temperature (MIT)
375 to 490 ºC
Minimum ignition
temperature (MIT)
375 to 490 ºC
Limiting oxygen
concentration (LOC)
10.5% by volume
Explosion severity
159 to 184 bar m s -1
Explosion severity
7.5 to 8.0 bar

These values are known to be correct at the time of writing. However the particle size distribution can have a significant effect on the actual values for the product.
Spark Reducing Packaging
INVISTA Adipic acid is available in two types of big bag:

Type B:
The bag has been tested to have a breakdown voltage of less than 4kv across the wall of the bag. This means that the energy of any spark created will be insufficient to ignite any flammable powder. Therefore this bag is compatible for use in areas where there are no flammable vapours present.

Type C:
The bag fabric contains conducting threads. These bags must be earthed to avoid the spark discharge hazard. Can be used with flammable dusts in hazardous areas where flammable liquids are handled.
However, if they are not earthed during use, the hazard is increased and sparks are possible.
Safety Precautions:
•     Handlers should avoid generating dust
•     Use in a well ventilated area
•     Use appropriate safe handling procedures when handling big bags, examples are:
•     Use of properly grounded loading chutes
•     Use of rotary valves to regulate flow
•     Provision of exhaust for dust and flammable vapours
•     Use of an inert control system
•     Use of personal protective equipment
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