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Thread: Five Piece Garlands

  1. #1

    Five Piece Garlands

    Please enumerate the merits and demerits of using Five Piece Idler Garlands in an impact zone instead of Three Piece Idler Garlands.

  2. #2
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

    Professional Experience 58 Years / 8 Month Lawrence K. Nordell has 58 Years and 8 Month professional experience

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    5 ROLL GARLAND NOTES

    Some Reasoning:

    1. 5 rolls would signify a wider belt, generally speaking, and the need to have more bearings to support the wider belt and its load.

    2. 5 rolls will produce more degrees of freedom when trying to control belt tracking and transfer station ore spillage sealing under the skirtboards

    3. 5 rolls will decrease the cross sectional capacity due to the first set of banked rolls are at a smaller trough angle

    4. 5 rolls allow for a superior U-shape trough and control spillage better than 3 -roll

    5. Although I do not recommend using garland for horizontal curve design, 5 roll would provide better horizontal tracking control due to the shape benefit, but, poorer control due the added degrees of freedom.

    6. 5 rolls are more likely to cause spillage on steep inclined conveyors due to the flatter region of the center that allows a higher degree of roll back.

    7. 5 rolls may create more noise due to higher degrees of freedom.

    8. 5 rolls will reduce the impact force of large rock due to the degree of freedom allowed.

    9. 5 rolls should not be used on downhill sections due to their nature of promoting belt mal tracking.

    10. 5 rolls allow for a reduced belt binding force between idlers on different end rolls of the stringer groups due to their added degree of freedom.

    Lawrence Nordell
    Conveyor Dynamics, Inc.
    www.conveyor-dynamics.com

  3. #3
    Thanks very much for your posting.

    The main reason for this posting was that the top rollers of a five piece garland are failing nearly immediately upon their installation. The main reason so far analyzed is due to the position of the top rollers in a near vertical condition and that theya re in a dust collecting position. However, the other questions rasied are whether deep groove ball bearings can be used in view of the axial load that is being exerted on the bearings. The second question is that because of the position of these rollers whether lubrication deprivation will occur leading to early failures.

  4. #4
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

    Professional Experience 58 Years / 8 Month Lawrence K. Nordell has 58 Years and 8 Month professional experience

    Discussions 2608 Lawrence K. Nordell acceded to 2608 discussions, Articles 0 Lawrence K. Nordell wrote 0 articles, Publications 0 Lawrence K. Nordell Nordell released 0 publications

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    Know-How Design (1521) Lawrence K. Nordell used this tag 1521 times, Pipe Conveyor (238) Lawrence K. Nordell used this tag 238 times, Chutes (119) Lawrence K. Nordell used this tag 119 times

    Giridharan,

    Good point. Yes, the end roll is notorious in failing bearings due to bad seal design and not having a proper weather shield. Failing in a few months, is more indicitive of a bad idler design and not so much the idler trough angle configuration.

    Rolls that have greater than 45 deg orientation, often are equipped with a rain and dust shield that is mounted on the support frame. The shield does not rotate. It prevents direct impingement of refuse and rain. Idler spin keeps the contaminants from accessing the bearing seal.

    Lubrication is an issue, if you do not fit the bearing with internal factory grease seal/shields. The high orientation angle does, in time, cause lubricant leakage. It would not fail for many years.

    Poor roll TIR, material buildup, mal-tracking, off-center material loading, hydroscopic drying of the lubricant, yada, yada, as well as many other factors may play on the design.

    Look to Rhinebraun and other like large 5 roll shiftable systems that are not plagued with faliures. Look to the Precismeca design.

    Your success is near.

    Lawrence Nordell
    Conveyor Dynamics, Inc.
    web: www.conveyor-dynamics.com

  5. #5
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

    Professional Experience 58 Years / 8 Month Lawrence K. Nordell has 58 Years and 8 Month professional experience

    Discussions 2608 Lawrence K. Nordell acceded to 2608 discussions, Articles 0 Lawrence K. Nordell wrote 0 articles, Publications 0 Lawrence K. Nordell Nordell released 0 publications

    Searching nothing specified

    Know-How Design (1521) Lawrence K. Nordell used this tag 1521 times, Pipe Conveyor (238) Lawrence K. Nordell used this tag 238 times, Chutes (119) Lawrence K. Nordell used this tag 119 times

    Another Point,

    On ocassion, less than reputable bearing manufacturers sell reject bearings for great prices. The race and ball metallurgy is not to industrial standard, and the bore tolerance is not to industrial standard. The end disk concentricity to shell may not be to industrial standard. The end disk to end disk run-out, the roll run-out, and weldment warpage may not be to IS ..........

    The proper analysis of the L10 or B-U life is not the simple published formula. The list of pitfalls that may make up your excessive failure rate exceeds my patients to list.

    I do wish you sucess.

    Lawrence Nordell
    Conveyor Dynamics, Inc.
    web: www.coneyor-dynamics.com

  6. Dear Mr. Giridharan,

    In general for the impact zone, all the 5 rollers of garland idlers have same size of bearings. The bearing size is governed by worst impact and other load on central roller. Therefore, although end rollers have unfavorable orientation resulting into axial load on to bearings, but the magnitude of this axial load is comparatively less, because impact and material momentum pressure load are negligible on end rollers. Therefore, bearings should not fail so easily.
    The best way is to calculate load on each roller and work out the bearing life, instead of guess-work.

    The primary advantage of 5 roller garland idlers at impact zone is that the idler configuration can yield by large magnitude in the direction of load. Now impact energy = Force x Yield distance.
    Therefore, impact force will be less compared to three roll garland idlers. You already have my book, please refer serial number 6 of page 89, which mentions this aspect.

    Others have already mentioned many points, which I am not referring.

    Please analyze the failure reasons of concerned item, and one needs to rectify the size or specification.

    Regards,
    Ishwar G Mulani.
    Author of Book : Engineering Science and Application Design for Belt Conveyor
    Email : parimul@pn2.vsnl.net.in

  7. #7
    bronalds Guest

    5 Part Garlands

    We in the brown coal operation have used five part impact garlands for many years. It is interesting your problems of short life with the upper rolls. I am not aware of this problem with our idlers, however it is worth us looking at the statistics. I would think you might have an idler manufacture quality problem. The top idler should last as long as the others, as it was suggested by one contributor, they see little load. There may be a tendency for water ingress if sprays are prevalent around the impact area.

    Our problems relate to elongation of the connecting links and resultant varying lengths of garlands within the impact zone. This causes the idlers to swing and clang together. This is a problem with large lumps which do occur especially on overburden. The garlands can be adjusted by shimming the rubber supports at the top however this is another maintenance task. In the main they are high maintenance items.

    I personnally do not like 5 part garlands. They are heavy and generally high maintenacnce. If one fails, all have to be removed. Fixed three part impacts can be changed individually and can be more easily handled especially these days with retractable frames etc.

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