Proper RAP system maintenance promotes longevity

Mike Devine, Asphalt Drum Mixers
February 05, 2019
By Mike Devine, Asphalt Drum Mixers
Scalping screens, lump breakers and impact crushers — key RAP system components — take the brunt of system wear.
Scalping screens, lump breakers and impact crushers — key RAP system components — take the brunt of system wear.
With 74.2 million tons of reclaimed asphalt pavement being used each year, it’s not surprising that asphalt is America’s most recycled product — and has been for almost 25 years.
Suppliers need to ensure their recycled asphalt pavement feed system is up to par for meeting growing demand as well as keeping costs low. Neglecting equipment can cause unplanned downtime or lost profits as a result of needing to use more expensive virgin aggregate.

Scalping screens, lump breakers and impact crushers — key RAP system components — take the brunt of system wear. Stay on top of potential problems by regularly checking for damage in those and other components. Also create a regular maintenance and inspection schedule to ensure the most uptime.



A few vital components to monitor for RAP system longevity include:
  1. Bin grizzly: A clean bin hopper grizzly helps ensure proper material flow. The grizzly keeps oversized lumps out and helps break up clumped material that may otherwise get stuck in the feed gate. Keep the grizzly clean throughout the day to reduce material flow problems.
  2. Bin: Abrasive recycled asphalt pavement may wear out and thin bin walls over time. Keep an eye on the bin wall thickness to help avoid material leaks and a possible wall blowout, which would require an expensive bin replacement. A bin wall less than 3/16 inches thick should be lined, but there must be material left to weld onto. An optional wear liner can help prolong a bin wall’s life.
  3. Air cannon/vibrator: Air cannons and vibrators help maintain material flow in the RAP system. Regularly check air cannon air lines, valves and bin inlet pipes for wear and tear. That includes watching for cracks and leaks in air lines and material buildup around the air inlet pipe. Check vibrators’ mounting bolts to prevent them from vibrating off the bin wall. Also monitor bin wall thickness as vibrators can tear a hole in a wall that’s become too thin.  
  4. Bin feeder: Check rollers for wear and make sure they are all rotating properly. Rollers that don’t turn correctly can develop flat spots, which become worse over time. These flat spots can turn into holes that can become sharp and damage the belting. Also check the belt and splice for wear and proper tracking. If present, check bin skirting for wear to prevent material leaks.
  5. Processing equipment: Watch screen cloth for damaged or large openings that could result in oversized material getting into the mix and — as a result — financial penalties. Also look for clogged openings that would prevent proper-sized material from getting through the screen. In addition, regularly inspect and replace any dull or worn down wear bars and teeth as needed on lump breakers and impact crushers. This helps ensure material is broken down evenly and larger pieces don’t make it through to potentially cause damage in the paver drum or the road.
  6. Weighing devices: Regularly check weighing device calibration and performance. Use testing weights and perform regular calibrations as recommended by the manufacturer. The wrong calibration can mean an out-of-spec completed product that may result in penalties as well as unhappy customers.
  7. Conveyors: Belting experiences more wear than any other RAP system component as a result of friction from the material on one side and friction with the rollers on the other. Check all conveyor belting and repair or replace any that has tears, stretching, cuts, missing pieces, damage to splice, thin spots on the belt or visible inner mesh. A tear on belting can cause severe problems, including getting caught in other conveyor parts and making the tear larger or jamming the conveyor and causing damage. A tear can also allow material to spill on the equipment and on the ground, something that is both hazardous and wasteful.
  8. Bearings and drives: Complete proper lubrication cycles on all bearings and drives either weekly or by hours of operation, depending on lubrication charts. Visually inspect the entire RAP system while moving through the lubrication process. Watch for any visual oddities as well as cracked air lines and wear on rollers, belts and iron. Also check sensors and limits and look for loose bolts or parts and visible oil leaks.

Creating and following a regular maintenance and inspection schedule goes a long way toward reducing downtime and preventing premature wear. Talk to Asphalt Drum Mixers for more advice about specific recycled asphalt systems.

For more tips from ADM on vital components to monitor for RAP system longevity, check out the full-length version of this article at www.rocktoroad.com.

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