Experimental Studies on Charging of Static Electricity and it's Predicting Method in Use of the Pipes of Synthetic Moterials in the Underground Coal Mining

Abstract

The miners sometimes meet some electric shocks of the static electricity charged by friction of rock dust flowed in the pipe against it's wall, and such shocks were experienced very often in use of the pipe of synthetic materials
This work was done as for declare the phenomena of charging of static electricity on the synthetic pipes undergoing the concrete conditions of coal mining, and then, to find out some appropriate measures to predict it easily,
In the experimental stands of laboratory the following materials were tested:
-small pipes of vinyl chloride used for rock dusting, -blasting wire rested nearby the small pipes abovementioned;-air pipes of vinyl used for local ventilation.
As a result of these studies the authors declared some general characteristics of static electricity charged in use of the pipes of synshetic materials as follows:
1) As the rock dusts flow in the pipe at velocity of 5m/s and the more this pipe is charged by static electricity, and we can sometimes see the sporks of electric discharge when the velocity of flowing dust surpasses 20m/s;
2) Blasting wiles rested nearby the pipes of vinyl chloride being used for rock dusting are probably induced to charge the static electricity in them, attaining the static voltage 4kV and the more. The short spark by this voltage can ignite the air-mixture of methane;
3) Air pipes of 250mm diameter are charged by static electricity when the rock dust of 41g/min. and the more at the velocity exceeding 5.3m/s, and this static charge growsup with the flowing speed of rock dusts.
The authors found out some appropriate countermeasures against such static electric charges and successfully experimented some ones of them in a laboratory