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Temperature for atmospheres with combustible dusts

The flash point of the dust must be taken into account when providing protection against flammable dust, where it is found in both cloud form and in layers.

The surface temperature of the enclosure indicated on the motor nameplate must be less than the reference ignition temperature.

The reference temperature is the lowest between the two values thus calculated:

TS1 = 2/3 Tcl
(Tcl = ignition temperature of the cloud of dust)

TS2 = T5mm – 75K
(T5mm = ignition temperature of a 5mm layer of dust).

Tamm = lowest between TS1 and TS2.

CALCULATION OF THE FLASH POINTS FOR COMBUSTIBLE DUSTS
Dust ignition
temperature
Cloud
Tcl
Layer
T5mm
Safety temperature Ts1 = 2/3 Tcl Ts2 = T5mm - 75K
Maximum surface
temperature
Tamm = lowest between Ts1 and Ts2
Surface temperature of the motor ≤ Tamm


EXAMPLES OF FLASH POINTS FOR COMBUSTIBLE DUSTS
  Cloud
[°C]
Layer
[°C]
Aluminium 590 >450
Carbon dust 380 225
Flour 490 340
Wheat dust 510 300
Methylcellulose 420 320
Phenolic resin 530 >450
Polyethylene 420 melting
PVC 700 >450
Soot 810 570
Starch 460 435
Sugar 490 460

source SIRIA Ltd