Detailed Structure of a Thermal Oil Heating System

1. Detailed Structure of the System

A thermal oil heating system consists of the following main components:

1. Thermal Oil Heater / Boiler:
   • Fire-tube or water-tube type, burning fuels such as DO, FO, gas, biomass, or electric heating elements.
   • Includes combustion chamber, heating coils/tubes, insulation shell, flue gas chamber, and chimney. 

1. • 
2. Burner:
   • Creates the flame and supplies heat to the combustion chamber.
   • Equipped with ignition system and air–fuel ratio control.
   • 
3. Thermal Oil Circulation Pump:
   • Ensures continuous flow of hot oil to heat consumers and returns cooled oil back to the heater.
   • Requires ≥ 2 bar pressure and flow rate according to design.
   • 
4. Expansion Tank:
   • Compensates for oil volume expansion during heating.
   • Typically installed ≥ 6 m above the highest point of the system.
   • 
5. Deaerator / Vent Tank:
   • Removes air, moisture, and dissolved gases from the oil.
6. Heat Exchanger:
   • Transfers heat from the thermal oil to bitumen, chemicals, air, steam, or other process materials.
7. Piping and Accessories:
   • Heat-resistant steel pipes (ASTM A106 Gr.B or equivalent).
   • Includes flanges, valves, expansion joints, and insulation (FOAMGLAS or mineral wool).
   • 
8. Safety and Measuring Devices:
   • Temperature, pressure, and flow sensors.
   • Safety valves, relief valves, low-flow switches.
   • Automatic control system (PLC/SCADA).

2. Working Principle of a Thermal Oil Heater

1. Fuel (gas, oil, coal, biomass) is burned in the combustion chamber → generates heat.
2. Heat is transferred through tube walls/heat transfer surfaces → heating the circulating thermal oil.
3. The circulation pump delivers hot oil through piping to heat exchangers or consumers.
4. After transferring heat, cooled oil returns to the heater for reheating.
5. The expansion tank maintains a stable oil level and absorbs volume changes due to temperature variations.

This is a closed-loop system: the oil only transfers heat and is not consumed (minor losses may occur due to leakage or oxidation).

3. Functions

• Provides high temperature (150 – 320 °C) for industrial processes without the need for high pressure like steam boilers.
• Long-term temperature stability: ensures even heat distribution and accurate temperature control.
• Energy efficiency: high heat transfer efficiency.
• Safer than steam: thermal oil achieves high temperature at low operating pressure.

4. Technical Inspection & Safety in Operation

1. Before start-up:

• Check oil level in the expansion tank (1/3 – 1/2 full).
• Ensure no leakage, all valves in good condition.
• Verify oil quality meets standards (viscosity, Acid Number AN, flash point).

2. During operation:

• Monitor line pressure (2 – 4 bar at <300 °C, >4 bar at >300 °C).
• Maintain oil flow velocity ≥ 1.5 – 3 m/s.
• Control oil temperature within design limits (≤ 320 – 340 °C depending on grade).
• Ensure circulation pump runs continuously, avoid stopping while burner is on.
• Maintain proper ventilation in heater room, keep oil catch trays clean.

3. Regular maintenance:

• Take oil samples every 6 months for analysis (AN, viscosity, flash point, carbon residue).
• Replace oil periodically or when AN exceeds recommended limits.
• Clean piping, heat exchangers, and remove oil deposits.

4. Safety measures:

• Provide fire-fighting equipment (CO₂, dry powder extinguishers, sprinklers).
• Install temperature, pressure, and flow sensors linked to emergency shutdown systems.
• Avoid mineral wool/silicate insulation at leak-prone points → use FOAMGLAS instead.
• Install backup generator to keep pumps running during power outages.

5. Industrial Applications

• Asphalt Plants: heating bitumen, drying aggregates, maintaining asphalt mix temperature.
• Chemical & Polymer Industry: reactor heating, composite and plastic production.
• Building Materials: cement, bricks, raw material drying.
• Food Industry: edible oil refining, drying agricultural products.
• Metallurgy & Mechanical Engineering: closed-loop heating systems, metal processing.
• Textile Industry: fabric dryers, stenter frames for heat-setting.