Page 136 - Advanced Mine Ventilation

Characteristics of Respirable Coal Dust Particles 117

Figure 8.3 Andreasen sedimentation pipette.

8.5.1 Experimental Procedure for Mass Distribution
Measurement

The following procedure was followed and is recommended for such work [12]:
1. The density of the coal dust ( 37 mm) was determined with a pycnometer and distilled
water.
2. Sufficient dust was weighed out so that on dilution with 550 cc of water in the cylinder (to
reach the 20 cm mark on the cylinder), the concentration of solids would be 0.5% by
volume.
3. A suspension of the weighed coal sample was made in 100 cc of distilled water using 5e 6
drops of Aerosol O-T, a wetting agent.
4. The suspension was next transferred to the cylinder and fluid volume was made up to the
20 cm mark.
5. The stopper, L, was inserted, and the apparatus was insulated with glass wool. About
20 min were allowed for the fluid temperature to stabilize.
6. The small vent in the stopper was closed with a finger, and the apparatus was shaken for
2 min.
7. A clock was started as soon as the shaking was stopped, and the apparatus was put on a firm
stand.