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Thread: HammerMill Vibration loading on steel frame

  1. #1
    jeffbob
    Guest

    HammerMill Vibration loading on steel frame

    I am working a steel frame supporting a hammer mill. I have used Staad to find the natural frequency of the frame without imposiing the hammer mill loads.

    I am not sure how to convert the vendors load info to loads I need to impose on the frame. This would be dynamic loading. Here is the info given me.

    U=normal rotating vector = 3033 pound feet
    P=abnormal rotating vector = 11,176 poud feet
    W=static weight = 12,750 pounds
    Rotor Assembly moment of inertia = WR, where R is squared = 2,500 pound feet-feet squared

    they say to multiply P by 1.5 and apply resulting vector independently in horizontal and vertical direction.

    next they instruct the primary forcing frequencys are
    (1) speed of the rotor @ 720 RPM and
    (2) rotor speed multiplied by the number of hamme rows (3)

    Next they say that the above loading should include rotationg vector "U", as a dynamic steady state harmonic load.

    Finally, after all that:

    "The worst load condition is the sum of "U" and "P"--as modified by the above.

    I hope someone can help me figure out what the loads to the frame will be and help me with the dynamic loads imposed.

    thanks
    Jeff

  2. #2
    Principle Engineer
    Join Date
    Mar 2011
    Posts
    175
    Very poor instructions.

    What does the prime mover look like?

    Go back to the vendor and find out:

    1) what is the meaning of
    U=normal rotating vector = 3033 pound feet
    P=abnormal rotating vector = 11,176 pound feet

    2) is U the normal uniform torque load on the unit with or without loading?
    is P an oscillatory torque (dynamic at frequency)developed under loading?

    Come to think about it, maybe the vendor should do the calculations for you since you are buying or bought a very expensive piece of equipment and you ( and I) don't have a clue.

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