Q18 What effects, if any, is there on an inactive storage pile of PRB coal in terms of weight, btu etc over
 a period of time. The pile has been compacted and chemically treated for erosion.
 
A18 The catch there is the word inactive. The stockpile inventory folks do borings and quality samples,
 but shouldn’t be able to provide the data w/o the client’s permission.  If the clients would like to participate 
then the data could be reviewed.  An inactive pile that has been assessed for quality more than once 
would be a rarity. Espcially on PRB, which disappears quickly in todays market. Still, PRB coal is extremely
friable and will break down into smaller particles, virtually independent of how the coal is transported or 
handled. 
 
PRB represents the extremes of handling problems: dust is an issue when the coal is fine and dry. 
Bunker and chute plugging is an issue when the same fine coal is wet.  Once the coal is exposed by mining,
 the degradation process begins – the majority of the damage can occur in a very short time, even as short 
as a few days.  The extent of the degradation that occurs depends in large part on the distance to the plant 
from the mine, i.e., how long the coal is exposed to the atmosphere during transportation. Additional factors
 such as crushed run of mine (CROM) size, and specific handling procedures also impact the degradation 
process. Additional decomposition occurs during handling and storage in a pile and bunker, bin or silo.
 
The following citation summarizes it well. "We believe that the root cause of the degradation is loss of moisture that impacts the coal both 
mechanically  and through the generation of additional surface reaction area, chemically.  The combination 
of the two is what makes PRB coal so difficult to handle."　 Hossfeld and Hatt, "PRB Coal Degradation – 
Causes and Cures", www.coalcombustion.com/.../PRB%20Coal%20Degradation.doc 
 
This is a good citation because it shows the fragile nature of the Sub bituminous C coal,  and should be 
enough to satisfy the question without going into the specifics of individual stockpiles. 
 
Here is a second citation that is often quoted. "There is a loss of heating value for coal stored for long 
periods as they tend to react with oxygen in the air, a process called weathering. The rate is normally 
around 1% in the first year of storage, but may be as high as 3% for low rank coals (Skorupska, 1993).
　

Q17:  Where in HB44 does it state that you must material test a belt-conveyor scale annually?

Q16:  During a discussion with a client,  the question came up as to why are sampling manufacturers changing from the standard three roll idlers under the sweep sampler to multiple rolls, when all the manufacturers have said bias tests have proved no bias with the three roll idlers.  I understand one of the reasons was they are trying to get all the material in the corners, but again the three rolls didn't show bias in the past, so why change?