Editor’s Note: The complete MSHA Program Information Bulletin on Rock Dust is attached below.
From: WTRF.com
By Taylor Kuykendall, Reporter
A bulletin sent to underground miners from a federal regulatory body warns operators of rock dust which does not meet federal standards.
According to a Program Information Bulletin (PIB) from the Mine, Safety and Health Administration, samples of various rock dusts samples taken from underground coal mines found that 47 percent of samples collected did not particle size standards. Noncompliant dust was found at 51 percent of the mines sampled.
Rock dust is used by underground coal mines to dilute the atmospheric content of highly combustible coal particles with inert rock such as pulverized limestone, shale, adobe, dolomite, anhydrite or some other inert material.
Investigators of the Upper Big Branch mine disaster have largely pointed to inadequate rock dusting as one of the causes of the explosion that resulted in the death of 29 men.
In addition to improper particle size, MSHA found that when wetted and dried, the fine particle size of the material had a tendency to cake. When this occurred, the requirement to subject the material to a light blast of air was not sufficient to disperse the materials throughout the mine.
“These two issues indicate a possible lack of product quality control during the manufacturing process of rock dust that is intended for use by mine operators,” the bulletin states. “It should be noted that the Low Temperature Ashing procedure used by MSHA to determine the incombustible content of coal dust samples is insensitive to both oversized and caked particles.”
This means that even though a mine operator may achieve the necessary 80 percent or greater incombustible content, the “mixture may not prevent a coal dust explosion from propagating.”
MSHA is recommending coal mine operators test their supplies of rock dust upon receipt and ask for documentation of quality testing from the manufacturer.
The bulletin was sent Oct. 27.
