Soap Based Combustible Dust?
Does anyone have experience with Stearate containing soap dust, test results show combustible but it seems to have large amount and very high ignition source temp.
Do you have a msds link for it
You might want to get the sample tested according to ASTM E1226 (Explosive Severity Test ) to determine Pmax, dp/dt and Kst which are needed to assess the hazard - try Fauske & Associates Burr Ridge Illinois (email@example.com) for analytical
Thanks I have this data currently from Fauske for the dust in question.
Did they also provide the Minimum Explosive Concentration (MEC)? When you say "high ignition source temp", do you mean Minimum Ignition Energy or the Minimum Auto-Ignition Temperature?
MEC was 211g/m3, 570degrees c and greater than 10000mj ignition energy.
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While that type of spark is possible, the more typical type of spark is 10-50 mJ. See information below from FM Global. Also some classifications say ignition sensitivity of MIE more than 10mJ is "normal ignition sensitivity range" and only becomes extremely sensitive when it is under 3mJ. Also CCPS states that dusts with MIEs below 30mJ, the spark from a person can ignite a dust cloud. Depending on your process the 10,000 mJ might be OK, it's a pretty high MIE. If you send me your contact information I can reach out to you with more details.
Static electricity is a source of ignition when a spark discharge has sufficient energy to ignite nearby combustible
materials. The minimum ignition energy varies for different combustible mixtures. Energy in a spark
discharge is equal to 1⁄2 CV2×10-9, where the energy is in millijoules (mj), C is the capacitance in micro-microfarads
(picofarads), and V is the potential in volts
Although the capacitance of an object depends on its physical dimensions and its nearness to other objects,
most pieces of machinery have a capacitance from one hundred to a few thousand picofarads. Capacitance
of the human body is estimated to be about 200 picofarads. Assuming an insulated object is charged
to 10,000 volts, the energy in the spark discharge would be about 50 mj from a machine or about 10 mj
from a person. These energies are sufficient to ignite many combustibles.
In general, hydrocarbon gases and vapors require about 0.25 mj of energy for ignition with air. Acetylene is
a notable exception; in air it needs about 0.02 mj. The minimum energies for bituminous coal and cornstarch
dust clouds are about 60 and 30 mj, respectively.
Per NFPA 13 - 2019 Edition, Figure 5.5.1, a spark can have an energy of discharge significantly above 10,000 mJ. So, it appears that the stearate containing soap dust can be ignited by a 'simple' spark.
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