Most asphalt plant faults have simple causes. This table lists the common symptoms, what usually causes them and what to check first. It is a general guide — your plant manual and supplier have the final word, and safety procedures always come first.

Output and temperature

Symptom Likely causes Check first
Output well below rated Wet aggregate; burner not at full heat; uneven cold feed; trucks or silo full Stockpile moisture; burner flame and fuel; bin levels; truck queue
Mix too cold High moisture; burner under-firing; feed rate too high Moisture; burner settings; feed rate vs drum capacity
Mix too hot Feed too low for burner setting; temperature control fault Feed rate; control settings; sensor reading
Temperature swings Varying moisture; feed interruptions; burner control loop Stockpile face; bin flow; control tuning
Blue smoke Overheated binder or mix Mix and aggregate temperatures

See mix temperature control and rated vs real output.

Burner and combustion

Symptom Likely causes Check first
Burner will not light No fuel; blocked filter; ignition electrode; flame sensor; interlock Fuel supply; filters; electrode gap; interlock status
Burner trips during run Flame sensor dirty; fuel pressure drop; airflow interlock Sensor; fuel pressure; damper and fan
Black smoke Too much fuel, too little air; poor atomization Air-fuel ratio; nozzle; heavy oil temperature
High fuel use Wet aggregate; poor tuning; air leaks into drum Moisture; combustion check; drum seals

See burner tuning.

Dust and emissions

Symptom Likely causes Check first
Visible dust at stack Torn or loose bag; tube sheet leak Clean-air side for dust trails
High baghouse pressure drop Blinded bags; pulse cleaning failure; condensation Pulse valves; compressed air; temperatures
Dust escaping at drum ends Worn seals; low exhaust draft Seals; fan and damper

See baghouse care.

Weighing and mix quality

Symptom Likely causes Check first
Wrong batch weights Scale out of calibration; material hanging up; load cell fault Zero and span; hopper build-up; cables
Binder content off Bitumen scale or meter error; temperature/viscosity Calibration; bitumen temperature
Gradation off Worn or blinded screen; bin overflow; cold feed proportions Screen meshes; hot bin levels; feeder calibration
Segregation in trucks Dropping mix from height; loading in one heap Loading method; silo practice
Uncoated particles Short wet mix time; cold aggregate; low binder Mix time; temperatures; binder content

See calibration and batch cycle time.

Mechanical

Symptom Likely causes Check first
Drum noise or wobble Tyre-roller misalignment; worn rollers; build-up Alignment; roller surfaces; cleanliness
Belt slipping or wandering Tension; misaligned idlers; spillage Tension; tracking; clean-up
Elevator noise Worn chain or sprockets; loose bucket Chain elongation; buckets
Mixer knocking Loose or broken paddle; foreign object Lock out and inspect
Screen vibration abnormal Broken spring; bearing; loose mesh Springs; bearing temperature; mesh fixing

When to call the supplier

Call when a safety device keeps tripping without a clear cause, when the control system shows faults you cannot clear, after any structural damage, or when parts covered by warranty fail. Send the plant serial number, screen readings and a short video — it speeds up diagnosis.

Return to the maintenance checklist, or contact our engineers.