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Thread: Impact Idlers vs. Impact Bars

  1. Our company has installed a 60 inch Metalcord belt underground in an extremely high impact situation.
    Ore of over 14 inches is dropping over 10 ft onto the belt
    and a special impact bed.
    After 2 years the impact bed is beaten up to the point that is not giving any shock absorption but merely pinching the belt.
    Sharp material has punctured the belt causing about 2 inch slits in various places, some of which have pendtrated through the belt.
    The transverse cords in the belt are 4mm apart so the impact absorption and ripping has been excellelnt.
    The customer has been told to consider garland type impact idlers but is a bit skeptical.
    Has anyone had experience with these kinds of situations and whether the idler is superior.
    Impact is about 5000 ft-lbs.
    Belt is rated for 4500 ft-lbs.
    R. Butterworth
    AFM Industries
    345 Marwood Drive
    Oshawa, Ontario
    Canada L1H 7P8

    PHO: 905-443-0150
    FAX: 905-443-0155

  2. #2
    David Beckley Guest

    Inpact Idlers

    To R Butterworth

    In 1994 we had a client with a similar problem ie up to 600mm (24 inch) lumps falling 3m onto a belt supported by slide bed impact bars. The belt and impact bars were destroyed in a couple of years by the severity of the impact forces. We designed and installed an impact idler and skirt system that overcame these impact problems and after four years in operation the belt was still in good condition. The system uses 200mm diameter heavy duty rollers that were fitted with spherical roller bearings. The rollers incorporated 50mm thick rubber disks. Three rows of these iders were supported on a common frame that was mounted on a rubber suspension system. The roller assembly was narrower than the belt so that the belt edges could be supported by UHMWPE bars, therby providing good support at the skirt line.

    If you would like me to send you more information please contact me directly.

    David Beckley.
    Conveyor Design Consultants of WA.
    Perth, Western Australia.
    61 8 9383 4303

  3. Mr. Butterworth:

    There are a number of possible solutions to the impact problem. The one proposed by David Beckly should work for your client, as it provides greater belt impact support than slider beds or garland type impact rollers.

    If possible, it would be better to reduce the impact by changing the chute arrangement, by using a grizzly, or by using a sacrificial collector belt or impact slide that would feed the production belt at a reasonable rate.

    I cannot advise on the best solution without seeing the operation and discussing what the client will (or will not) accept. If you would like to explore options, please contact me.

    Dave Miller
    Dave Miller
    ADM Consulting
    10668 Newbury Ave., N.W.,
    Uniontown, Ohio 44685 USA
    Tel: 001 330 265 5881
    FAX: 001 330 494 1704

  4. #4
    Rick Backeberg Guest
    Mr Butterworth,

    This could be an application for an apron feeder.

    An alternative to an apron feeder could be dropping the ore through a sloping grizzly so that the fines would go directly onto the belt. The impact energy of the coarse ore would be absorbed by the grizzly bars. Large pieces would slide down and be laid on a bed of material downstream from the fines.

    If all ore consists mainly of large pieces say 8 inches plus and there is enough headroom, an impact plate could be installed above the belt. Very thick cast manganese steel liners would be ideal for this kind of application.

  5. #5

    Garland type Impact Idlers vs. Impact Bars


    All comments in the replies so far are valid but I don't believe these answer your question as I understand it. Are garland idlers, at the impact area, superior to impact bars?

    I believe that they are far superior and will improve the impact absorption.

    There is not a concensus on the merrit of impact bars for the purpose of impact absorption. In fact they are more commonly called slider beds. Everyone agrees that they are good for affecting skirtsealing because they elliminate the belt sag that is common between impact idlers.

    Energy (or work) is the product of force and displacement. The five roll garland idler is an ideal impact absorber because of its ability to change shape and undergo large local displacement when impacted by large lumps. We have designed garland idler impact areas with special seal skirts that work well with large deflections because they ride the belt and flex to follow its deflections.

    The writer has studied the mechanics of impact at large rock belt feeders for run-of-mine (as blasted) material. Impact must be absorbed by components of relatively low mass (low inertia), at the belt and at the rolls. Grouping multiple rigid idlers onto a heavy frame which is then mounted on springs or shock absorbers is largely inaffective because the large inertia will not allow the immediate deflection and a large impact force results.

    Rigid impact idlers absorb impact energy in the deflection (compaction) of the rubber discs. Rubber discs are not required at the rolls of the five-roll garland idler.

  6. #6
    Author Guest

    High Impact Situation

    Dear Mr Butterworth:

    What you experienced is probably the toughest belt that can be produced
    for a heavy impact situation.

    The 4 mm pitch btw transverse steelcord is very tight given the 2 mm
    diameter of those cords. Also the stretch at 3,25 % under reference load
    and 15% to break allow the cords to cumulate their strengths, bending
    over each other in such a way that you have to cut a dozen cords at the
    same time to start the rip.

    Note that the belt you mention has 500 transverse steelcords per meter
    long...and longitudinal cords are only 3 mm apart one from each other...
    no wonder if it is difficult to rip.

    We know a number of heavy impact situations with simmilar successes.
    The Taiba ICS flintstones-waste conveyor system in Senegal is also an
    impressive showpiece of that technology: 18 feet drop with beautiful
    sparks at night !

    Best regards.

    Jean-Paul Pelissou
    Export Manager
    10, Rue des Charretiers
    95104 Argenteuil Cedex


  7. #7
    Author Guest

    Use of Slider Bed

    I have some experience in situations like this during my Dravo days.

    I have had many customers solve high impact belt damage problems through the use of a properly designed and installed slider bed. Back in the mid 80s very few brands were available. Now many brands are available. My favorite is an UHMW slider bed with rubber shock absorbers beneath the plastic strips. Your friend can go on the Internet and search for Ultra High Molecular Weight (UHMW) slider bed. Make sure that the rubber shock absorbers are 60 durometer or softer.

    Best regards,

    Mike Gawinski
    Sales Manager
    Interroll Corporation
    3000 Corporate Drive
    Wilmington, NC 28405


  8. #8
    Author Guest

    High Impact Situation

    In this kind of situation, the attention should be focused on the chute feeding the belt. The kinetic energy can by easily absorbed by a rock box or a suitably placed impact plate. It does not make sense to try to absorb the impact energy in the belt. Even in the worst spacial layouts some sort of energy absorption arrangement can be designed.

    Mr. Conrad Kelly
    Application Engineer
    RAHCO International
    P.O. Box 7400
    Spokane, WA 99207-0400


  9. impact bars

    Dear Sir,
    Many of the comments are applicable. Obviously reduction of lump size (by grizzly), introduction of rock boxes and modified chute geometry will result in reduced impact loads. As regards the question of impact bars vs garland idlers I believe that Joe Dos Santos has responded most effectively. The 5 roll garland impact idler is perfectly suited to this application. Obviously the bearings need to be carefully considered and the use of spherical roller bearings (high rating and capable of operating under high shaft deflection levels) as suggested elsewhere may be required. The tricky part comes in ensuring that even in the deflected condition an adequate seal between skirts and belt is achieved. The garland string can obviously be made even more flexible by the introduction of special mountings onto the steelwork - springs, rubbers and 'Rosta' type end fixings have been used effectively.

  10. #10
    JOHN L. BRINK Guest


    Please check out website where you will find our Hi-Impact systems, many of which are in use in similar conditions as described.
    Regards John

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