The Service Life Of Heat Transfer Oil In Asphalt Stations

• Posted by Mavis Chai April 21, 2025 Filed in Technology #asphaltplant  #asphaltbatchingplant  80 views
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  The heat transfer oil system of an asphalt mixing plant is a key equipment for heating asphalt, and its service life directly affects production efficiency and operating costs. Under normal circumstances, high-quality heat transfer oil can last for 3 to 5 years when used properly. However, if not managed properly, it may age and fail prematurely. The following are the influencing factors of the service life of heat transfer oil and practical methods to extend it.

  Main Influencing Factors of The Service Life of Heat Transfer Oil

  1. High-temperature oxidation and cracking

  If the working temperature exceeds the maximum allowable temperature of the heat transfer oil for a long time ( such as over 300℃), it will cause the oil to crack, generating carbon deposits and resins, and reducing the heat transfer efficiency.

  2. Local overheating

  When the circulation of heat transfer oil is not smooth (such as when pipelines are blocked or pumps malfunction), local high temperatures will accelerate the deterioration of the oil.

  3. Pollutant Mixture

  Moisture, air, metal debris or asphalt impurities entering the system can trigger oxidation reactions or corrode equipment.

  4. Improper operation

  Frequent starts and stops of the system, sudden temperature changes, and failure to exhaust regularly will shorten the lifespan of the oil.

  Key Measures For Extending The Service Life Of Heat Transfer Oil

  1. Choose the right heat transfer oil

  - Matching Model: Select the type of heat transfer oil (mineral oil or synthetic oil) based on the system design temperature, for example:

  Mineral-based heat transfer oil:

  Applicable temperature ≤ 300℃

  Hydrogenated triphenyl (synthetic oil)

  Applicable temperature ≤ 350℃

  - Priority Antioxidant: Choose brands with good thermal stability and strong antioxidant capacity (such as THERMINOL from Shounuo and L-Q series from Zhongneng).

  See more details on asphalt batching plant on lutonmachinery.com.

  2. Strictly Control The Operating Temperature

  - Upper temperature limit: The actual operating temperature should be at least 10-20℃ lower that the maximum allowable temperature of the heat transfer oil.

  - Avoid Local Overheating

  Regularly check the flow rate of the heat transfer oil in the hearing furnace to ensure that the circulating pump has sufficient flow (flow rate ≥1.5m/s).

  - Heating/Cooling Gradient: Adjust the temperature slowly during startup and shutdown (recommended ≤50℃/hour) to prevent thermal shock.

  3. Prevent Contamination And Oxidation

  - System sealing performance

  Regularly check the sealing performance of flanges and valves to prevent air and moisture from entering.

  - Dehydration Treatment

  Dehydration is required before new oil or oil replenishment (heat to 100-120℃ and open the exhaust valve)

  - Filtration and Purification: Install magnetic filters or online filtration devices to remove metal particles and impurities.

  4. Regular Inspection and Maintenance

  Oil Product Testing: Take samples and test the following indicators every 3 to 6 months.

  Test Items	Control Standards	Abnormal Consequences
  Acid value (mgKOH/g)	≤0.5 (New oil ≤0.1)	Intensified oxidation, corroding equipment
  Viscosity change rate	≤15% (compared with new oil)	Cracking or polymerization
  Flash point (℃)	Decrease by ≤20% (compared with new oil)	Reduced safety
  Residual carbon (%)	≤1.5 (New oil ≤0.1)	Carbon deposits clogging pipelines

  System Cleaning: Clean the carbon deposits on the pipes and the inner walls of the heating furnace during the annual shutdown (using a dedicated cleaning agent).

  5. Optimize Operation Management

  - Avoid dry burning: When the machine stops, the heater should be turned off to prevent the heat transfer oil form remaining at high temperatures without circulation.

  - Thorough exhaust: The system is fully vented before strartup to prevent local high temperatures caused by air bubbles.

  - Oil replenishment specification: Replenish the same type of heat transfer oil. Before mixing new and old oils, compatibility tests should be conducted.

  6. Equipment Maintenance and Upgrade

  - Expansion Tank Management

  The expansion tank is filled with nitrogen for protection to isolate oxygen.

  - Standby Circulating Pump

  Configure a standby circulating pump to prevent system stagnation due to pump failure.

  - Temperature Monitoring

  Install multiple temperature sensors to monitor the oil temperature sensors to monitor the oil temperature distribution in real time.

  Warning Signals Of Heat Transfer Oil Failure

  If any of the following situations occur, the machine should be stopped immediately for inspection and replacement of the heat transfer oil:

  1. The heating efficiency drops significantly (a higher temperature is required to reach the set value);

  2. Obvious carbon deposits or coking appear on the pipes or valves;

  3. The color of the oil becomes darker and its viscosity increases abnormally;

  4. Detect that the acid value or residual carbon exceeds the standard.

  Disposal Of Waste Heat Transfer Oil

  - Environmental Protection Recycling

  Entrust professional companies to recycle waste oil (direct discharge is prohibited)

  - Recycling

  Some deteriorated oil can be regenerated through techniques such as distillation and filtration.

  Summary

  Through comprehensive management in four aspects: scientific selection, temperature control, pollution prevention and control, and regular inspection, the service life of heat transfer oil can be significantly extended to more than five years, while energy consumption and maintenance costs can be reduced. It is recommended to formulate a targeted maintenance plan by combining the equipment operation logs and detection data.