Page 529 - Dust Explosions in the Process Industries

496 Dust Explosions in the Process Industries

7.7.2.4
The Grewer-Furnace Test

Grewer (1971) developed a more refined version of the original U.S. Bureau of Mines
test. A cross section of the Grewer furnace is shown in Figure 7.19.
The furnace has six vertical cylindrical cavities in which small metal gauze baskets
are placed. One of the baskets contains an inert reference sample, the other five hold test
samples. The furnace can be programmed to give a specificrate of temperature rise, such
as 1"C/min. The temperature at which a test sampletemperature starts to rise faster than
that of the inert reference sample is taken as the minimum ignition temperature of that
sample. Figure 7.20 shows an example of a set of results.

TO TEMPERATURE
DIFFERENCE RECORDER

THERMOCOUPLES

8 cm3 METAL GAUZE BASKETS
FOR TEST SAMPLE AND
INERT REFERENCE SAMPLE

COPPER FILLER

HEATED TEMPERATURE-
CONTROLLED JACKET

Figure 7.19 Crewer furnace for determination of
minimum ignition temperatures of dust deposits
(From Crewer, 1971).

K-SORBATE

LYCOPODIUM
NA-ISOPROPYLXANTHATE

AIR AND REFERENCE SAMPLE

Figure 7.20 Example of temperature record-
0 ings during a 4-hour test of five combustiblepow-
100 200 300 400 500
FURNACEITEST SAMPLE TEMPERATURE ['CJ ders in the Crewer furnace (From Crewer, 1971).