THE IMPORTANCE OF ANNUAL MAINTENANCE SHUTDOWNS

Why we perform annual maintenance shutdowns

1. Optimizing production efficiency

Our plants operate under significant strain during peak production periods. Over time, this wear and tear can reduce operational efficiency, leading to slower production rates and higher energy consumption. A dedicated maintenance shutdown allows for comprehensive inspections and repairs, ensuring that equipment runs at optimal performance levels.

2. Preventing costly breakdowns

Unplanned equipment failures during production can disrupt supply chains, delay projects, and incur high repair costs. A planned maintenance shutdown reduces the risk of such unexpected failures, as issues can be identified and resolved proactively.

3. Extending equipment lifespan

Asphalt plants in general represent a substantial capital investment. Regular maintenance during a shutdown helps protect this investment by preventing excessive wear, mitigating damage, and extending the lifespan of the plants and equipment.

4. Ensuring high Standard quality asphalt production

Consistent quality is essential in asphalt production to meet client specifications and industry standards, which we hold at utmost importance. Properly maintained equipment minimizes inconsistencies in the final product, reducing rework and maintaining customer satisfaction.

5. Compliance with health, safety, and environmental standards

Our plants must adhere to strict health, safety, and environmental regulations. Maintenance shutdowns provide an opportunity to address any potential compliance issues, such as emissions control systems, ensuring that operations meet or exceed required standards.

6. Preparing for the upcoming construction season

The year-end shutdown allows us to prepare for the heavy demands of the new construction season. By entering the new year with well-maintained and fully operational equipment, we can deliver reliable and uninterrupted supply to our clients.

Key maintenance activities during shutdown

• Inspections: Conduct thorough inspections of critical systems, including burners, heating systems, mixing drums, conveyors, storage silos, gearboxes, bearings, rollers, and control systems.
• Repairs and Replacements: Address wear and tear, replace worn-out components, drain and replace oils and lubricants, and perform necessary upgrades to ensure reliability.
• Cleaning: Remove buildup of materials, such as asphalt residue, that can impair equipment performance and contaminate the final product.
• Calibration: Ensure all systems are accurately calibrated to maintain product quality and consistency.
• Testing: Conduct post-maintenance testing to verify that equipment is fully operational before production resumes.

Strategic planning for the maintenance shutdown

To maximize the benefits of the annual maintenance shutdown, we do the following:

• Schedule in advance: Plan the shutdown to coincide with the construction industry’s year-end downtime, minimizing disruptions to clients.
• Allocate resources: Ensure that the necessary parts, tools, and skilled personnel are available to complete maintenance tasks efficiently.
• Implement a checklist: Use a detailed checklist to ensure all critical maintenance activities are completed.
• Review and document: Keep records of maintenance activities and identify any areas for improvement in future shutdowns.

Conclusion

For National Asphalt, an annual maintenance shutdown during the year-end construction break is not just a recommended practice; it is a strategic necessity. By investing in regular maintenance, we can enhance operational efficiency, reduce downtime, maintain product quality, and ensure regulatory compliance. This proactive approach positions National Asphalt for success in the competitive asphalt supply industry, enabling us to meet client demands with reliability and consistency.

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CLIFFDALE ASPHALT PLANT

The following plant-specific plan was prepared for the Cliffdale Asphalt Plant.

Cold feed & RA bins

• Condition of bin checked.
• Aggregate flow door in good condition and secure. (Worn door can result in bad mix quality.)
• Belt tension correct. (Belt that slips can result in grading fluctuations.)
• Skirting rubbers to be checked to ensure proper feeding of aggregate.
• Rollers and bearings to be checked to avoid damage to belt and reduce drag on belt.
• Condition of overall belt, not perished, no cracks.
• Bin vibrators, function check and vibrators plates for wear.
• Belt tracking, ensure belt is running true and feeding directly onto collector for no aggregate loss.
• If bin has a scale, check condition of the unit that the loadcell is clear of dust that could give a false reading, calibrate to insure validity of unit.
• Electrical drive motors, clean of any access dust to avoid overheating, check fan condition and make sure cowling is secure. Check breather is clear of obstruction.
• Drain oil through a cloth and check for steel filings, if present replace gear box. (This will avoid failure in the new year.)

Inclines & collectors

• Belt tension and belt free of cracks, check splices are still secure.
• Rollers and bearings to be checked to avoid damage to belt and reduced drag on belt.
• Belt tracking, ensure belt is running true and feeding directly onto collector for no aggregate loss.
• If belt has a scale, check condition of the unit that the loadcell is clear of dust that could give a false reading, calibrate to ensure validity of unit.
• Electrical drive motors, clean of any access dust to avoid overheating, check fan condition and cowling secure. Check breather is clear of obstruction.
• Drain oil through a cloth and check for steel filings, if present replace gearbox. (This will eliminate failure in the new year.)
• Some drive pulleys have rubber lagging, and if the lagging is worn will need to be changed.
• Belt scrapers, assess condition and replace.

Scalping screen

• Replace screen if needed.
• Check vibrator function.
• Ensure all skirting rubber is working optimally.
• Check springs and rubber dampers.

Dryer drum

• Drum air seals to be checked. Scavenged cold air can reduce burner performance.
• Drum condition monitored every 6 months, if at this stage we require new lifters, this will be installed, worn dryer lifters will reduce plant performance and worn combustion lifters can damage the drum shell. This can also lead to aggregate being directly exposed to the flame.
• Drum alignment to be checked, plus drive sprocket and chain.
• Trunnions overall condition checked/ thrust rollers inspected.
• Oil sample will dictate replacement of main gearbox, if not, only oil will be changed. The drive pulleys and belts will be checked for wear, and belts will be checked for cracks, if so, belts will be changed to avoid slippage during production.
• Transfer shute, possibly liners should be replaced depending on condition.
• RA ring, ensure all chambers are clean, not to contaminate on startup with lumps.

Mixing drum

• Drum condition monitored every 6 months, if at this point we require new lifters, this will be installed, worn lifters will promote segregation of final product.
• Drum alignment to be checked plus drive sprocket and chain.
• Trunnions overall condition checked/ thrust rollers inspected.
• Oil sample will dictate replacement of main gearbox, if not, only oil will be changed. The drive pulleys and belts this will be checked for wear, and belts for cracks, if so, belts will be changed to avoid slippage during production.
• Inspect condition of injection system and support rods, if not inspected could cause binder content fluctuations and breakdowns.

Discharge hopper

• Clean out any excess asphalt.
• Check door condition and function.
• Air cylinder clevis condition, inspect for excessive wear.
• Check liner condition.

Skip and rail

• Skip is clean and free from asphalt buildup.
• Skip wheel condition and bearings, ensure door moves freely.
• Check draw bar main link and cables, check cable adjustment.
• All rollers free of asphalt buildup and moving freely.
• Oil sample will dictate replacement of main gearbox, if not, only oil will be changed.
• Check brake condition, adjust if necessary.
• Skip rail, free from asphalt build up and check structural condition.

Asphalt silo

• Silo cone to be cleaned of any buildup.
• If cone is worn, replace as per maintenance schedule.
• Clam door operation and free of leaks. (Leaking door can injure staff.)
• Actuators clevis, check for abnormal wear.

Baghouse system

• Maintenance checks should dictate ducting replacement. Holes in ducting will result in loss of airflow, this will influence fines in the asphalt.
• All seals to be checked to avoid moisture from entering the baghouse.
• Bag condition will be dictated by differential pressure gauge, replacement will be done accordingly.

Exhaust fan

• Check overall condition.
• Drive pully and belt check, check tension, a slipping fan can reduce dust extraction and burner performance.
• Check damper function, ensure damper is moving freely and operational as this can influence mix quality.

Rotary valve screws

• Check all couplings and overall condition of components for excessive wear. (Worn rotary valve can give inconsistent fillers.)
• Drain oil through a cloth and check for steel filings, if present, replace gearbox.
• Electrical drive motors, clean of any access dust to avoid overheating, check fan condition and cowling is secure. Check breather is clear of obstruction.
• On screws, check gland packing and screws for signs of wear.
• Check screws are clear for start-up.

Bitumen system

• Inspect mixing tanks for carbon buildup. (Poor performance and carbon can cause pump to break.
• Inspect pumps for leaks; Excessive leaks normally indicate worn bushes, which should be replaced to avoid breakdown.
• Electrical drive motors to be cleaned of any access dust to avoid overheating, check fan condition and cowling secure. Check breather is clear of obstruction.
• Drain oil through a cloth and check for steel filings, if present replace gearbox.
• Check couplings on pumps for wear.
• Pipes are clear of bitumen for startup in the new year.

Safety checks

• Ensure pull rope switches function correctly. (Malfunction will result in injury.)
• Check all emergency stops. (Malfunction will result in injury.)
• Plant siren check.
• Skip slack rope limits check. (If skip jams, drive motor will stop.)
• Air temp safety check, ensure safety door opens at set temp. (If malfunction, baghouse can catch fire.)

Electrical

• Cables should be visually inspected for hot connections.
• Panel fans should be working to avoid overheating of components.
• Dust should be vacuumed out of panels.
• Thermal camera can be used to identify problem areas.

Burner

• Check blower pressure, if not correct can result in unburnt fuel contaminating stone with oil.
• Check blower pipe, free from holes and make sure clamps are secure.
• Clean burner nozzle and air cavities from dust, blocked air passages can result in poor atomization, and unburnt fuel can enter the process.
• Clear any carbon build up on combustion cone.
• Ensure all linkages are secure.