Re: Skirtboard Friction Factors, Cs
When faced with a new product I ask for a representative sample. I can then use this to compare against products I already know and select factors accordingly. There's also the consideration that one companies "Material X" may be totally different to another companies "Material X" yet sharing the same name 
Another consideration is the effect of one part of a power calculation on the overall power. If it's just a small part then errors in a factor may not be worth worrying about too much.
I do have experience with one belt conveyor where an underestimate in skirt friction resulted in overloading the drive. A factor had been selected from CEMA and applied to a conveyor with continuous skirts. Unfortunately, when the conveyor was made and the skirts fixed in position, they were jammed hard down on the belt resulting in burning of the belt top cover. A little common sense also needs applying along with published factors 
As an aside, how is this factor measured? ■
Skirtboard Friction Factors, CS
As CEMA implies, the skirtboard friction factor is an imperical value that is tabulated in Section 6 of the book. Very often I refer to this table, and about half the time, the material my client needs to convey is not listed. I can, of course, make a guess at what material is most similar and estimate the value to use. I imagine that many experts on this forum have a similar experience and would like to see a more comprehensive table. Thankfully, we can use this forum as a means to share the values that we have determined are appropriate for various materials, and hopefully CEMA members can incorporate the values into future editions.
I'll start the thread out with the values we know from Table 6-7 of CEMA. Please add the values that you use for other materials not listed.
Alumina, pulv. dry - 0.1210
Ashes, coal, dry - 0.0571
Bauxite, ground - 0.1881
Beans, navy, dry - 0.0798
Borax - 0.0734
Bran, granular - 0.0238
Cement, Portland, dry - 0.2120
Cement clinker - 0.1228
Clay, ceramic, dry fines - 0.0924
Coal, anthracite, sized - 0.0538
Coal, bituminous, mined - 0.0754
Coke, ground fine - 0.0452
Coke, lumps and fines - 0.0186
Copra, lumpy - 0.0203
Cullet - 0.0836
Flour, wheat - 0.0265
Grains, wheat, corn or rye - 0.0433
Gravel, bank run - 0.1145
Gypsum, 1/2" screenings - 0.0900
Iron ore, 200 lbs/cu ft - 0.2760
Lime, burned, 1/8" - 0.1166
Lime, hydrated - 0.0490
Limestone, pulv, dry - 0.1280
Magnesium chloride, dry - 0.276
Oats - 0.0219
Phosphate rock, dry, broken - 0.1086
Salt, common, dry, fine - 0.0814
Sand, dry, bank - 0.1378
Sawdust, dry - 0.0086
Soda ash, heavy - 0.0705
Starch, small lumps - 0.0623
Sugar, granulated dry - 0.0349
Wood chips, hogged fuel - 0.0095
And one new entry to get it started
Municipal sludge - 0.200 ■