Thermal Fluid Systems

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Sigma Thermal offers various types of thermal fluid heaters as well as complete thermal fluid systems.

Thermal Fluid System - Sigma Thermal

A thermal fluid system is more than just a heater, and all the components of the system must work together in harmony for proper performance.

Purchasing a complete thermal fluid system from Sigma Thermal will ensure that your system operation functions reliably.

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.

Standard and custom heaters are available in gas-fired, oil-fired, electric and biomass-fired configurations. While the basic components of a complete thermal fluid system are the same, the heater designs vary considerably based on the fuel source. For detailed information on specific heater designs please select from one of the heater options below.

If you would like to speak with a thermal fluid systems expert or if you already understand your needs, contact us or, submit an RFQ  to our application engineers today.


Pre-Engineered HC2 Gas Fired Heaters

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Pre-Engineered Thermal Fluid Heater

Thermal Fluid Heating Systems

The pre-engineered HC2 thermal fluid heater is available in standard sizes from 500,000 to 100 MM BTU/hr. Configuration options include vertical up-fired, vertical down-fired, and horizontal. This system is skid mounted with a burner and integrated control panels.

To view all heater models, technical specifications, and standard dimensions download our pre-engineered HC2 brochure.

Sigma Thermal also offers custom thermal fluid heater designs for a wide variety of project-specific design challenges.

Pre-Engineered Design Features

  • Dual helical coil design with 3 flue gas passes along the coil
  • Liquid or vapor phase service up to 675°F
  • Flue gasses are significantly cooled, eliminating the need for most internal shell insulation
  • Vertical and horizontal configurations
  • The heater shell is externally insulated with mineral wool insulation and covered with aluminum cladding
  • High turndown gas or oil-fired burners for use with traditional or alternative fuel sources
  • Advanced control systems with standard configurations for simple and cost-effective control and for PLC-based control with HMI
  • Available option for economizers to increase thermal efficiency to 93% or higher LHV Basis
  • Option for ultra-low emissions burners meet the most stringent requirements
  • Option for alternative area classifications and code compliance such as CSA, ATEX/CE, etc

If you already understand your needs, you can submit an RFQ here. If you have questions, contact an application engineer today.

Waste to Power

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NextGen Emissions Reduction System + Power

Waste to Energy Conversion System by Sigma Thermal & ElectraTherm

To convert waste heat energy into usable electricity, Sigma Thermal has partnered with ElectraTherm, to offer an integrated package containing an Organic Rankine Cycle (ORC) generator, helical coil heater, condenser, and evaporator. The waste fuel is captured by an existing industrial process and used for power conversion. When the NextGen Emissions Reduction System + Power is utilized, gas and oil production, wastewater treatment plants, landfills, farms, and other waste fuel-producing facilities can greatly reduce emissions while minimizing or eliminating flaring.

This total waste to power packaged solution converts waste gas to heat energy for the on-site generation of power that can be used to offset expensive on-site energy costs or provide a backup energy source. The system only requires gas and electrical interface to the skid edge, with multiple burner options available to meet strict emissions requirements.Waste to Energy Conversion System by Sigma Thermal & ElectraTherm

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Dewpoint Heating

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Natural Gas Dew Point Heaters

The temperature at which air becomes saturated with moisture is referred to as dew point. This means that in a saturated state the air is holding the maximum amount of moisture possible at its current temperature. Dewpoint heating increases the established temperature above the dew point to remove excess moisture content.

Dewpoint heating is a crucial component of fuel gas heating for gas turbines and power generation. Fuel gas often contains moisture and contaminants; therefore, dewpoint heating must be utilized as part of the fuel gas conditioning system to deliver clean gas (fuel) to turbines. Typical fuel gas conditioning systems include a fuel gas heater (also known as a dew point heater, or natural gas heater), pressure regulators, and coalescing filters.

Gas Turbines

Dewpoint heating ensures that water or fuel gas condensates do not enter the gas turbine, as they can damage the equipment. Moreover, dewpoint heating guarantees the gas is heated to the most efficient temperature before entering the turbine. During natural gas processing, fuel gases are pushed through a sophisticated network of pipelines from the location at which they originate to other locations where they are needed (i.e. turbines).

The gas must be highly pressurized to move efficiently through the pipelines. This means that the high pressure of incoming fuel must be reduced before it can be used at its destination. When the pressure of the gas is reduced, its corresponding temperature is also reduced; this is known as isenthalpic expansion or the Joule-Thomson effect. Depending on how much the pressure is reduced, water can condense, or in the case of a hydrocarbon, hydrate formation can occur. This occurrence can cause damage to equipment or devices downstream of the pressure reduction. One way to mitigate this is to heat the gas before the pressure is reduced. Therefore when the pressure is reduced, the temperature of the gas stays above the dewpoint or hydrate formation threshold.

Power Generation Demand

With rising power demands, anticipate that EPCs and OEMs will take longer to complete their project cycles. This makes it vital to coordinate the procurement of fuel gas heaters well in advance to avoid delays. Also, take note of some of the dewpoint heating challenges that arise when power demands increase:

• Lower efficiency fuel gas heater due to poor shell side heat transfer.
• Large fuel gas heaters that are existing, become even larger as power demand increases.
• Flow rates might vary, based on the number of turbines or auxiliary systems firing off the fuel gas.


Jacketed Vessels

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Fluid management can be a sensitive business; whether dealing with chemical, food and beverage, or simply water for industrial processing, efficient and accurate liquid maintenance is crucial to an operation’s success.

At Sigma Thermal, we craft custom thermal fluid heating systems to outfit tanks, vessels, heated molds, building heaters, autoclaves, reactors, and much more. Using thermal oil, glycol, and water as heat transfer mediums, these systems can be combined with a jacketed vessel for exceptional fluid management solutions.

What Are Jacketed Vessels?

Jacketed vessels and pressure vessels can be crafted in a wide assortment of styles to meet an operation’s particular processing needs. Put simply, a standard jacketed vessel introduces a secondary enclosure over a structural shell. The jacket creates a cavity to be utilized for heating and cooling management, usually by filling the space with a circulating fluid.

These systems create excellent heat transfer: they’re efficient, easy to control, and maintain excellent product quality. By introducing agitation in the jacketed vessels, it’s also possible to improve the homogeneity of the fluid properties, allowing for more consistent temperature or concentration levels.

Types of Jacketed Vessels

There are three main styles of vessel jackets available:

  • Conventional vessel jackets offer a complete extra covering for all or part of the vessel. These are ideal for high-pressure applications and offer unique insulation benefits, creating both an inner and outer vessel wall. These jackets come in baffled and unbaffled styles, with agitating nozzles helping to improve turbulence and overall efficiency in the absence of baffles.
  • Dimple vessel jackets utilize a light-gauge metal jacket affixed to the original vessel via spot or plug welds. This type of system offers strength and durability with minimal additional weight or expense, plus the advantage of natural turbulence as media flows past the dimple points.
  • Half-pipe coil vessel jackets are preferred for high-temperature industrial processing applications. These jackets are also excellent for heat transfer and thermal fluid heating systems, particularly when the utility fluid is a liquid. These jackets can be divided into multi-pass zones for maximum flexibility.

Heat transfer efficiency can vary dramatically from one design to another and from one processing application to another. Generally speaking, a conventional jacket will demand greater shell thicknesses and engineered expansion joints to compensate for the stresses of thermal expansion, especially if the jacket and shell have been manufactured from different materials. For a thermal fluid heating system, dimpled jackets and half-pipe coil vessel jackets are typically the most efficient options.

Industries and Applications

The closed-loop heating system of a jacketed vessel allows for great convenience in batching processes. Many industries require that a vessel be both heated and cooled as part of a single process; a well-designed jacket with a thermal fluid system is a seamless way to achieve the necessary temperatures.

Glass-clad vessels and setups that require frequent cleaning also benefit from jacketed systems, as it’s difficult to equip such vessels with internal coils for heating or cooling. Below are just a few of the many industries benefitting from the convenience and reliability of thermal fluid heating in jacketed vessels.

Thermal Fluid Systems for Jacketed Vessels From Sigma Thermal

The team at Sigma Thermal is proud to offer a full range of thermal fluid heating systems for jacketed vessels and jacketed reactor heating and cooling applications. Our engineers can develop custom designs to fit any set of operating parameters, working closely with clients throughout every step of the process.

To learn more about our thermal fluid systems, or to discuss how Sigma Thermal can help with your next project, request a quote today.

Molten Salts

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Molten salts, sometimes referred to as salt melts, are a family of products used for a wide range of applications like high-temperature process heating, heat treating and annealing of steel, and thermal storage in solar thermal power plants.  These salts are composed of fluoride, chloride, and nitrate salts.

Molten salts have the advantage of very high liquid phase operating temperatures (1,000°F or higher) with little or no vapor pressure.  Molten salts can replace organic or synthetic oils in heat transfer applications. While molten salts do offer a substantial benefit with their high operating temperatures, they can also have the undesirable characteristic of very high freezing points (ranging from 248°F to 428°F).

There are three primary types of molten salt heating systems: salt bath heaters, circulated molten salt, and direct heating for applications like heat treating metal assemblies. There can challenges with all of these system types: metallurgy, instruments, system component selection, heat tracing, melting and draining, just to name a few.

Circulated Molten Salt Systems

Circulated molten salt systems are used to distribute hot liquid salt as a heat medium to heat exchangers or other process heat consumers.

Function & Design

Once the energy is needed, the molten salt circulation process begins. Most systems maintain the salt above its freezing point to avoid the process of remelting, but during commissioning or a cold restart situation the salt is melted in a hot salt tank. The molten salt is then circulated through a closed loop system using a circulation pump specifically designed for pumping hot salt.  Fluid circulates from the hot salt tank to a fired heater or electric heater, out to the user, and then back again to the hot salt tank.

The system is generally designed in such a way that hot salt will return to the hot salt tank if and when the circulation pumps are turned off. It is unique from other closed loop heating systems because of the freezing point of the salt.  The system has to be designed using a hot salt tank, to which the fluid always returns when the system is down.

These systems should be heated and designed to prevent freezing or thermal shock in the circulation piping. Molten salt is stored in these systems at temperatures of 1050°F at normal atmospheric pressure. In these systems, sensors are applied to measure and monitor liquid levels, pressures, temperatures, and flow rates.

Circulated molten salt systems can provide plants with an integrated energy storage option designed to meet specific application needs. This energy storage concept is commonly used in solar power plants to store heat energy for power production at night time or overcast periods.

Hot Salt Tanks

The hot salt tank is a critical part of a circulated molten salt system, helping to move molten salt through the generator, and then providing electric power to the application.

Molten salt systems typically function with two storage tanks at different fill levels and temperatures, hot and cold salt tanks. The molten salt in the cold storage tank moves back through the cycle, while the salt contained in the hot salt tank moves on to generate energy for the system.

The system circulation pumps are typically installed in this tank, along with either electric elements or a fire tube that is used as a heat source for melting solid salt. These tanks are also frequently heat traced and can be insulated with ceramic material and a protective liner. By insulating the tank, you insure the best possible performance.

Salt Bath Heaters

Salt bath heater systems rely on natural convection processes without the use of circulation pumps. These systems are designed to perform at high temperatures to provide energy for a variety of applications.

Function & Design

Salt bath heaters work by heating a vessel of salt with a fire tube style burner or electric elements submerged at the bottom of the vessel. The hot salt then heats a submerged process coil, in which the flowing process medium is then heated.  Heat energy is transferred from that tube to the bath fluid. The heat transfer salts operate in temperatures up to 800°F.

Design considerations must be made for loading and melting of solidified salt.  A poor design could result in damage to the heater vessel or fire tube during start-up from a cold condition.

Salt bath heaters are commonly used for regeneration gas heating in molecular sieve applications, although they are suitable for other applications requiring a simple indirect heating system design with elevated operating temperature capabilities.

At Sigma Thermal, we design and manufacture circulated molten salt systems, hot salt tanks, salt bath heaters and electric heaters. We can custom design a fully automated system for your process needs, contact us today to learn more about our capabilities.

HC2 Thermal Fluid Heaters

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The HC2 Gas fired thermal fluid heater is available in standard sizes from 1 to 100 MM Btu/hr. Configuration options include vertical up-fired, vertical down-fired, and horizontal. Custom heater designs are also available to meet a wide variety of project-specific design challenges. Sigma Thermal also offers HC1 gas fired thermal fluid heaters, biomass-fired thermal fluid heaters as well as options for electric process SHOTS electric heaters.

If you already understand your needs, you can submit an RFQ here. If you have questions, contact an application engineer today.


Design Features

  • Designed to meet all area classifications and to endure harsh environments, including offshore, arctic, and deserts
  • Capacities from 1MM to 100MM Btu/hr – custom sizes also available
  • Advanced control system options – Sigma Automation
  • Double helical coil design for three passes of flue gas along conservatively designed coil surface area
  • Base efficiencies can exceed 88% (LHV Basis) depending on process inlet temperatures, and with an optional economizer can exceed 93% (LHV basis)
  • Flue gasses are significantly cooled, eliminating the need for most internal shell insulation
  • Heater shell is externally insulated with mineral wool insulation and covered with aluminum cladding
  • Standard or engineered burner configurations for use with both traditional and alternative fuel sources
  • Low emissions burners available to meet all emission requirements


High-Pressure Steam Generators

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The high-pressure steam generator produces non-toxic process heat.

NUK® High-Pressure Steam Generator

The NUK® High-Pressure Steam Generator is a closed-looped (hermetically sealed) system that produces steam for high-temperature applications. Therefore, this steam generator is able to produce non-toxic process heat while offering the same advantages of a conventional hot oil system.

Oil Deodorization

Sigma Thermal developed the NUK ® specifically for the application of oil deodorization, typically used within the food industry. During deodorization, the NUK is used as a heat source in the process to safely remove undesirable flavors and odors from edible oils; leaving the oil free from toxins.

Submit an RFQ – To specify your high-pressure steam generator.

Indirect Bath Heater

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Indirect bath heaters are excellent choices for applications in the oil and gas industries. They are suitable for many types of work, including natural gas and crude oil heating.

How is the Sigma Thermal indirect bath heater designed?

Our standard indirect bath heater consists of one or multiple firetubes, a heavy duty housing and an ASME Section VIII coil. The Sigma firetube is designed to efficiently transfer the heat from the combusted fuel into the bath solution. The flow coil is designed to safely contain the process fluid and transfer the required heat from the water bath to the process streams. The coil is designed specifically for your process to allow for the most economical and compact arrangement.

Long-term service plans are available to guarantee your indirect bath heater’s performance year in and year out.

  • Regular system audits by a qualified technician
  • Scheduled service with a rate guarantee for the entire contract
  • Factory direct low pricing on all components
  • Priority response

Sigma Thermal teams stand by every piece of their equipment for the duration of its service. We go the extra steps to truly understand your business and pairing it with an indirect bath heater system that will consistently exceed your expectations. The heavy duty industrial design of our indirect bath heater systems can be optimized for indoor, outdoor or hazardous classifications. Our heaters are extremely efficient, especially when paired with waste heat capture systems.

The Sigma Thermal system packages are designed to meet all expectations for your indirect bath heater including:

  • Design
  • Manufacturing specifications
  • Automation controls
  • Management of the heating system installation process
  • Expertise in parts and equipment …and much more!

Our parts and engineering representatives are ready to serve you. Contact our home office team to find your nearest Sigma Thermal representative.   You may also call our main facility at 770-427-5770.

Calendar Rolls

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The calendering process of smoothing and compressing a sheet of material by passing it through a number of pairs of heated rolls is widely used in the manufacture of paper, textiles, and plastic sheeting to provide it with the desired surface finish and texture.

Pressures, temperatures, and dwell times play a significant role toward achieving a homogeneous surface with a superior finish. In order to guarantee consistent and uniform quality and properties, the correct roll temperature with the least amount of variance is vital.

Many calendar roll applications call for a high temperature, low pressure, hot oil system.  At Sigma Thermal, our application engineers can help you plan and design individual solutions that provide uniform heat distribution on the roll surface to guarantee a consistently high level of quality and uniform, even finish.

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