Valves and flow equipment for thermal oil systems

Thermal oil systems are used in industrial processes where heat transfer is required at high temperatures with lower operating pressure compared with equivalent steam systems. Thermal oil circulates in a closed loop and supplies heat exchangers, reactors, presses, dryers, tanks, moulds and thermal process units.

Valves in thermal oil networks are selected according to operating temperature, pressure, fluid viscosity, circulation rate, differential pressure and sealing requirements. Particular attention is required for stem sealing, gasket and sealing material compatibility, and the behaviour of materials under continuous thermal stress.

Typical applications

• Heating circuits on reactors, tanks and heat exchangers.
• Thermal oil systems on dryers, ovens, presses and moulds.
• Thermal oil supply and return lines in industrial networks.
• Temperature control circuits in chemical, petrochemical, food, paper and tyre production.
• Heating systems for bitumen, asphalt materials, resins and viscous fluids.
• Solar thermal and energy applications using heat transfer fluids.
• Auxiliary filling, draining, venting and bypass lines.

Equipment selection criteria

• Maximum and minimum operating temperature of the thermal oil.
• Operating pressure, differential pressure and start-up conditions.
• Fluid viscosity during cold start and normal operation.
• Compatibility of body, seat, stem, gasket and packing materials.
• Required flow rate and allowable pressure drop in the circuit.
• Need for isolation, control, non-return, relief or draining function.
• External leakage risk and stem sealing requirements.
• Access for periodic inspection, tightening, cleaning and replacement of components.

Indicative equipment

• Isolation valves for thermal oil supply and return lines.
• Globe valves for controlled flow variation and isolation.
• Bellows-sealed valves for applications requiring reduced stem leakage.
• Control valves for temperature, flow or differential pressure regulation.
• Check valves for pump protection and backflow prevention.
• Safety and thermal relief valves for protection of circuit sections.
• Line strainers for protection of pumps, control valves and heat exchangers.
• Electric and pneumatic actuators for connection to an automation system.

For each application, the design temperature, pressure, thermal oil type, installation point, start-up and shutdown conditions and required valve function should be reviewed. These parameters define the valve type, nominal size, pressure class, construction materials, sealing arrangement and suitable actuation method.