Thermal Oil Heaters
High-Temperature Heat Transfer for Industrial Processes
Thermal oil heaters circulate an organic heat-transfer fluid to provide controlled process heat at elevated temperatures in industrial facilities.
They can achieve high process temperatures without the saturation pressures associated with steam at the same temperature. However, the complete system still requires pressure, fire, flow, expansion and thermal-fluid safety engineering.
Process Heat up to 300°C
Temperatures around 300°C may be possible when permitted by the selected fluid and complete system design.
Lower Pressure Than Steam
High temperatures can generally be reached at lower pressure than an equivalent saturated-steam system.
Automated Safety Control
PLC control can monitor temperature, flow, pumps, burner status, expansion-vessel level and safety trips.
What Is a Thermal Oil Heater?
A thermal oil heater transfers combustion heat to a selected organic heat-transfer fluid. Circulation pumps move the fluid through the heater and process users before returning it through a closed or appropriately engineered expansion system.
Safe design depends on fluid bulk and film-temperature limits, minimum circulation, coil heat flux, combustion geometry, expansion volume, fuel, pressure, oxidation control, emergency shutdowns and operating scenarios.
Key Technical Features
Defined by process demand, heater design and the fluid manufacturer’s maximum bulk and film temperatures.
Often lower than steam at the same temperature, but design pressure and applicable pressure rules still apply.
Horizontal or vertical arrangements can be evaluated according to duty, footprint, circulation and maintenance access.
Gas, liquid or suitable solid-fuel firing can be evaluated with the required combustion and emission controls.
The applicable code is selected for destination, heater construction, fluid system, pressure category and fuel train.
PLC, PID control, independent trips, HMI, alarms and controlled remote monitoring can be integrated.
Thermal Oil Heater Design Considerations
Heater Coil
Coil geometry, velocity, pressure loss and heat flux are calculated to maintain adequate circulation and limit film temperature.
Combustion Chamber
Burner compatibility, flame geometry, furnace volume, heat release and flue-gas path are evaluated together.
Safety Functions
Low-flow, high-temperature, flame-failure, pressure, level and pump-status trips are defined by risk assessment.
Automation Control
Burner, pumps, fluid temperatures, flue-gas temperature, flow and expansion-vessel conditions can be monitored.
Types of Thermal Oil Heaters
Solid-Fuel Thermal Oil Heaters
Furnace geometry, fuel feeding, combustion air, ash handling, emissions and stack connection must be matched to the specified solid fuel.
Gas- or Liquid-Fired Heaters
Burner, fuel train, purge sequence, flame safeguard, controls, chimney and possible heat recovery are engineered as one system.
Horizontal Thermal Oil Heaters
A horizontal arrangement can be considered according to capacity, installation space, coil support and maintenance access.
Vertical Thermal Oil Heaters
A vertical arrangement may reduce footprint where height, maintenance clearances and structural conditions permit.
Materials and Construction Basis
Pressure-equipment grades such as EN 10028-2 P355GH may be used when suitable for the selected code and calculations.
Suitable seamless tubes, such as an appropriate EN 10216-2 grade, are selected from pressure, temperature and fluid data.
Materials, pressure ratings and facing types are selected according to the piping code, temperature and joint design.
Insulation material, thickness, cladding and surface-temperature targets are calculated for the operating environment.
Film Temperature in Thermal Oil Heaters
Film temperature is the local temperature of the thin fluid layer next to the heated tube wall. It is normally higher than the measured bulk-fluid temperature. Exceeding the fluid manufacturer’s film-temperature limit can accelerate cracking, oxidation, sludge and coke formation.
Therefore, minimum flow, coil velocity, surface heat flux, burner turndown, fouling and start-up or shutdown circulation must be verified through thermal and hydraulic calculations.
Thermal Oil System Safety Functions
HMI and Automation Control
The automation system can monitor burner sequence, circulation pumps, filling equipment, supply and return temperatures, flue-gas temperature, fluid flow and expansion-vessel conditions. Safety shutdowns should remain effective independently of ordinary operator commands where required.
Safety Standards and Regulatory Scope
The applicable rules are defined according to the destination, fuel, pressure, heater construction and scope of supply. DIN 4754-1 addresses safety requirements and testing for installations using organic heat-transfer fluids.
For EU projects, stationary equipment with maximum allowable pressure above 0.5 bar may fall within the Pressure Equipment Directive. Hazardous-area classification and suitable equipment must also be evaluated where flammable gas, vapour, mist or dust can form an explosive atmosphere.
Advantages of Thermal Oil Heating
Thermal Oil Heater Applications
System Components and Project Options
Request Information About Thermal Oil Heaters
Selection should be based on process temperature, duty, fuel, fluid properties, circulation, expansion volume, safety functions, automation, environmental requirements and site layout.
Contact Airtes Industrial for an application review and project-specific thermal oil heater information.
