Thermal Fluid Systems

Thermal fluid heating is a type of indirect heating in which a liquid phase heat transfer medium is heated and circulated to one or more heat energy users within a closed loop system. Thermal oil, glycol, and water are common heat transfer mediums for these systems.


There are two types of standard thermal fluid heating systems that Sigma Thermal offers, the HC-1 and HC-2.  For electric process thermal fluid systems, we provide circulation heaters.

Standard and custom thermal fluid heaters, complete comprehensive systems and a full range of parts and support services are available to meet your process needs.

For help selecting the right solution for your project, submit an RFQ to our application engineers today.

Typical Applications

  • Tank heating
  • Suction heating
  • Reactor vessel heating
  • Process reboilers
  • Platen/Press heating
  • Ovens and fryers
  • Natural gas heating
  • Jacketed vessel heating
  • Indirect steam generators
  • In line liquid heating
  • In line gas heating
  • Heated molds or dies
  • Crude oil heating
  • Calendar roll heating
  • Building heaters
  • Autoclaves

Thermal Oil Heating Systems

Thermal oil offers the user the capability of high-temperature operation (up to 600F with organic thermal oils and 800F with certain synthetics) at very low pressures. Due to the low operating pressure and properties of thermal fluids, most heaters are built to ASME Section VIII, and a licensed boiler operator is not typically required.

Many people around the world refer to these systems by different names. The phrases thermal oil heater, thermal oil system, thermal oil boiler, thermal fluid heater, thermal fluid system, thermal oil boiler, hot oil heater, hot oil system, and hot oil boiler generally all refer to the same type of closed loop liquid phase heat transfer system. Note that many people use the terms thermal oil boiler or thermal fluid boiler even though most systems do not involve any type of vaporization.

Water-Glycol Heating Systems

Due to its superior thermophysical properties, water is an ideal heat transfer medium. Closed loop liquid phase hot water or glycol solution systems are an excellent choice for indirect process heating up to approximately 300F. Because the water is used in a closed loop with no direct feed water source, heaters are typically built to ASME Section VIII and do not require a licensed boiler operator. Heaters can be built to ASME Section I when required.

Complete Thermal Fluid Systems and Custom Engineering

For customized needs, Sigma Thermal offers engineered thermal fluid heaters and complete thermal fluid systems. With a broad range of design capabilities, Sigma Thermal can create a complete system to support any application.

  • Dow A/Therminol VP-1 Vaporizer
  • Pump Skid Packaging
  • Temp Control Skid Packages
  • Tanks & Vessels
  • Exhaust Stacks
  • Ladders & Access Platforms
  • Fuel Train & Valve Manifolds


With the typical elevated operating temperatures associated with thermal oil systems, it can be difficult to obtain high efficiencies in the heater alone. Sigma Thermal offers a wide variety of economizers to fit your process requirements, increase your thermal efficiencies, and lower your operating costs.

Common Waste Heat Consumers
  • Combustion Air Pre-heat
  • Boiler Feedwater
  • Steam Ejectors
  • ORC Generators
  • Building Comfort Heat
  • Wash Water Pre-heat
  • General Process Heat

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