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Thread: Friction Coefficient

  1. #1

    Post Friction coefficient

    Lyn,

    I went through your other articles and hence I am posting my question.

    I am Enginneer working in India and I am in the process of design of Apron feeder with a belt.

    I want to know
    1. what value to be given for internal friction coefficient for various materials. (what does it depend on?)

    2. what value should be given for friction coefficient between skirt plates and material. (what does it depend on?)

    3. what value of coefficient to be given between steel and steel under full lubrication(e.g chain roller on steel)

    4. does these values changes with respect to liner materials?


    I hope u could help me in this regard.

    Thanking you,
    Pranesh

  2. Friction co-efficient

    Dear Sir,
    I have not seen any apron feeder with rubber belt. For friction, please refer any handbook. However the following may please be consider as referance.
    1.Internal frictional angle for most of the material will vary between 40 t0 60 deg.
    2.Skirt friction can be consider as 8 Kg/M.( Data collected from skirt manufacturer)
    Regards.
    A.Banerjee
    Last edited by A.Banerjee; 8th May 2008 at 12:33.

  3. #3
    Join Date
    Mar 03
    Posts
    1,641
    Different bulk materials are not like dirfferent grades of steel where you just look up a specification book/chart and read off the answer. Internal friction needs to be MEASURED using a sample of bulk material to be handled.

    Some figures for skirt friction are contained in publications like the CEMA belt conveyor guide. (Does anyone know how to measure these figures or are they just empirical??)

  4. I am very surprised at the comment that internal friction is 55 in most cases. Internal friction is considered to be one of the most difficult parameter to measure in powder handling and it also the most important in determining various silo design parameters.
    Mantoo

  5. Friction coefficient

    Dear Mr. Mantoo,

    Please open page no. 131 of book ( Bins & Bunker by W. Reisner& M Rothe) wherein it is written that angle of internal friction would be 40 to 60 deg.
    Also I like to refer another book ( Weighing & proportioning by H. Colijn ) at page no. 257 it is written DELTA would be 30 to 60 deg. May be it is difficult to measure but form the book I indicated the figure.

    Regards.
    A.Banerjee
    Last edited by A.Banerjee; 8th May 2008 at 12:45.

  6. Indeed both books have given the normal range nothing wrong with that.
    What I cannot understand is why give a range when 55 degrees will work for everything? it will make life of lot of people very easy.
    Regards
    Mantoo

  7. Friction coefficient

    Dear Mr. Mantoo,
    You are very much correct that 55 deg. is may not applicable to every materials specially powder materials.
    Regards.
    A.Banerjee

  8. #8
    Join Date
    Mar 03
    Posts
    1,641
    I tend to be sceptical of data written in books without a full description of the material and methods used.

    If I measure something myself I know what I'm talking about.

    I get the impression these days that too many people are treating materials handling as "here's a formula, here's some numbers, there's the result". Fourty years of materials handling experience has illustrated that is the road to ruin, and frequently seems to lead to forums like this and the question "I designed a machine/system/bunker but it doesn't work, please help me fix it".

  9. Thumbs up

    Couldnt agree more with Designer.
    Mantoo

  10. Friction coefficient

    Barring few,almost all designer take data either from handbook or from reputated book & there is no much faliure.
    Regards.
    A.Banerjee

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