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Thread: Spillage From Inclined Coal Conveyor

  1. #1

    Spillage From Inclined Coal Conveyor

    Spillage occurs when fines and water accumulate on the inclined section of the conveyor and gain sufficient volume to form a stationary "teardrop" shape which can not be transported by the belt up the incline. Installation of skirting did not fix the problem as the volume increased until it spilled over the skirts. Removing the water is the first solution to investigate, but are there other options? How have members solved this problem by other means?

  2. Mr. Cloake:

    I was involved with a system that had a similar problem (where the source of water was from rain). After going through the skirting stage with unsatisfactory results, we determined that the best approach was to stop the water from getting on the belt in the first place. This was accomplished with covers.

    Depending on where the excessive water is coming from with your system (elements or process), this may work for you. If the water is from a processing step, you may have to remove excess water before putting the coal on the belt - this can be done by installing a filter belt system as a feder to your incline belt.

    Another option would be to turn your incline belt into a quasi-filter belt . However, if you do this you will need to install a means of handling the water run-off.

    Regards,
    Dave Miller
    ADM Consulting
    10668 Newbury Ave., N.W.,
    Uniontown, Ohio 44685 USA
    Tel: 001 330 265 5881
    FAX: 001 330 494 1704
    E-mail: admconsulting@cs.com

  3. Hi Steve,

    It would be helpful to know where the water is coming from. If it is coming from hosing out chutes or another intermittent source, then one option is to fit a plough to the carry side of the belt to remove the water. The plough can be lowered as required, and has an adjustable idler system to level the belt.

    The water/slurry is directed into a chute on the side of the conveyor and can be collected in a sump or bin. There are many of these installed in WA. I can send you details if you are interested.

    Best regards,

    Peter

  4. #4
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

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    Have you thought of chevron cleating the belt carry side surface? This will break through the hydroplane effect if the water is not more than a film.

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

  5. #5
    Brian Moore Guest
    With regard to your "standing water wave" on the incline section of a belt, I am quite familar with this occurrence, and the spillage cleanups! Although this experience relates to coal handling at 1000 - 1500 tph, I am sure it can be applied to other bulk solids.

    The frequency of "flow backs" was significantly reduced by introducing a "dewatering" chute at the transfer feeding onto the inclined belt. The chute operated on the different trajectories between water/slurry and the burden, and allowed the water to be "stripped" from the conveyed material.

    Email me if you wish further discussion on bcmoore@mpx.com.au

  6. #6
    George Baker

    George Baker

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    BELT SPILLAGE

    double check belt incline, may be too steep. check motor sizing, may be too small, causing gang up, slow down, build up, etc which would eventually overflow belt. What is the actual troughing idler angle......20, 35, 45 degrees? may be too shallow.

    Consider going to different style of conveyor belt:
    FOLD OVER CONVEYOR BELT = ZERO SPILLAGE
    COMPARTMENTIZED BELT = NO SPILLAGE
    CABLE BELT VS CONVEYOR BELT
    HERRINGBONE DESIGN BELTING VS STANDARD BELTING


    bael@golden.net CANADA

  7. #7
    Lawrence K. Nordell

    Lawrence K. Nordell

    President and CEO

    Conveyor Dynamics Inc. [eDir]

    Conveyor Dynamics Inc.

    Professional Experience 57 Years / 11 Month Lawrence K. Nordell has 57 Years and 11 Month professional experience

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    Steve

    Thanks for the feedback.

    Another thought to add to your list is the use of cleats in lieu of chevrons. The cleats can be raised to a higher level than the chevrons and allow for better troughing, allow water to snake through the maze and below the granular medium, and do a better job of grabbing the granular medium.

    The trough bending point needs to be addressed and how you arrange the cleats or chevrons. The chevrons need to be spaced to control ratching of rib impacts in cadence with the idler spacing. The cleat pattern likewise needs some simple thought to keep out of trouble.

    Larry

  8. Dear Mr. Steve,

    Somehow, the issue is not very clear to me. However, you may also think about following aspects:

    1) Feed chute incorporating water drainage provision i.e. feed chute bottom is perforated and water dripping is taken out by pipe. This kind of arrangement has been used for very wet coal at mines or at storage place subjected to heavy rains. This will be feasible only if the coal size is sufficiently large and it is not containing large proportion of fine dust. Or the coal dust will be wasted.

    2) Possibility of water removal from coal, when being in storage hopper (by similar method)

    3) If the excessive water is due to dust separation system, the same shall be adjusted.

    4) Material build-up at skirt plates can be reduced by providing UHMW liners.

    5) As some people have said, how the water is getting into the coal? This has to be analysed and to be prevented, unless it is part of fundamental process like mining etc.

    Regards,
    Ishwar G Mulani.
    Author of Book : Engineering Science and Application Design for Belt Conveyor.
    Email : parimul@pn2.vsnl.net.in
    Tel.: 0091 (0)20 5882916

  9. #9
    Dear Sir,

    We have experience conveying wet materials such as coal refuse, bottom ash, FGD and others during inclement weather. We also have experience conveying sticky and light materials during rain downpours.

    Conveyor belting is somewhat porous. When excess water from rain or wash-down gets on a belt, the water molecules fill the pours on the belt and can freeze which reduces the coefficient of friction between the belt and the material being conveyed.

    If the material being conveyed will convey up the incline on the conveyor when its dry, maintaining a dry belt when it rains should solve the problem. This can be accomplished by a squeegee/belt cleaner. If your material is wet, squeegee the belt dry prior to loading to remove as much water as possible. If material characteristics change, the materials inherent angle of inclination may decrease.

    Weve had a similar experience conveying fine coal refuse. When processed effectively the material has less than 18% surface moisture. However, during start-up and plant shutdown the 28 mesh x 0 refuse exceeded 50% moisture! This material with this amount of moisture is typically pumped. It was not only wet, but also slimed the belts. To resolve the problem, we employed additional belt wipers at the head discharge and at the tail end to wipe the belts effectively.

    Second, we worked to control/reduce the feed rate during start-up and shut down. This provided a column/uniform flow rate of material onto the belt at the given belt speed (reducing the material bed depth or head pressure of wet material).

    If weather is the source of excess moisture, protection is the best remedy.

    Weather protective conveyor covers are used to protect the material, conveyor belting and idlers from the elements. Covers also help to keep wind blown rains and snow off of belts and protect the belting from sunlight. Ultra Violet light attacks conveyor belting and makes it brittle, causes belt cracking, reduced friction and premature belt life.

    To help prevent material sliding on wet or frost laden belts, squeegee the belt on the return run to remove excess moisture to increase the coefficient of friction between the belt and material.
    In cold weather climates, belt wipers and belt heaters that are activated during inclement weather on the return belt run, (just prior to material loading area) are beneficial. Belt heaters help to release the ice crystals from belts and the wipers wipe off the icing. Heaters can be interlocked with the belt speed indicators for safe operation. Anti-freeze agents/surfactants (glycol, grapefruit extract or other citric product are also known as quick remedies used as de-icers).

    If the belt is cleaned properly and is dry, wet material will STICK to it. If the belt is wet (pours are filled with water, wet and/or dry material or ice crystals), both wet and dry material may well slide over it.

    I recommend that you run your belts empty and let your wipers dry and clean your belts effectively before introducing material onto the belts. Once dry; continue to wipe them during normal operation.

    Inspections should be made of your conveyor belting to ensure the top cover of the belt is not made slick by belt wipers and/or from the material being caked-onto the belting. Some belt wiper compounds fill the pours of the belt as they wear, making them "slicker". The same goes for some materials being conveyed. A change in wiper compound or a more aggressive wiper may be required.

    A uniform and consistent feed to prevent material from surge loading will prevent periodic material voids on the belts and minimize the possibility of material sliding. Avoid stopping and starting belts under load.

    Feed your material onto the belt using an effective chute design to continually spoon feed the material at a velocity, near to that of the belt speed in the direction of the belt travel.

    Material may also migrate and try to nest on the conveyor belt as the belt shifts over idlers. If the belt is wet and the material won't convey up the incline, the belt may slide underneath the material until dryer material pushes (head pressure) the sliding material back the incline. Consequently, a dry section of the belt may grip the wet material and work to bring the sliding material up to the belt speed. Until all the material is brought up to the belt speed, material spillage, sloughing, and sliding may occur. Belt lift-off of idlers, due to excessive belt tension in concave curves may also occur. If this is the case, the result is material rolling and varying PIW requirements within the belt.

    "Increasing the coefficient of friction" between the belt surface and the material being conveyed is paramount. Effective belt wipers at the head discharge and a wiper near the tail that can be activated in foul weather are my immediate suggestions.

    Effective wipers will increase conveyor performance/up-time by reducing additional material carry-back, belt tracking from idler build-up, and potential belt damage and idler failure.

    However, as a word of caution, please note that some of the more agressive belt wipers have been known to cause premature belt damage from improper installation, maintenance and miss-use.

    On applications where the conveying incline or decline angle exceeds the materials natural angle of repose, alternate belting technology and system designs have proven effective.

    Imperial Technologies offers alternate belt designs (i.e. our Multi-Fold and Flexi-Cleat) had proven effective for steep angle conveying. Please visit our website: www.imperial-technologies.com

    We wish you the best of luck with your endeavor and let us know how you resolve your situation.

    Respectfully,

    Ron Tschantz
    Imperial Technologies, Inc.
    rontschantz@imperial-technologies.com
    (330) 305-2100

  10. #10
    There is no easy solution to removing ponds from inclined belts.

    A plough must be raised before the coal rips it away. Also, the plough must be located far enough ahead of the pond to accomodate the run down travel; you have to interlock the plough to the drive so that if the plough falls the conveyor stops. You will find that the run down & start up times involve locating the plough so far ahead of the pond that the water will run into the transfer tower anyway.

    Cleated belts will be notoriously hard to clean from wet coal accretions. The best cleaner for wet coal is a multi blade assembly e.g. Hosch or similar copies.

    A de-watering chute is quite big box to retrofit. Further you will have to treat the collected suspension, if you are in a develped country. This can be quite expensive compared to the material recovered.

    I have corrected r-o-m coal transfer points where there was free water/slurry exiting through the chute side doors. If you need any design assistance ask johngateley@hotmail.com.

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