The Four Components of the Thermal Loop

Authored by Isabel McCord

The Four Components of the Thermal Loop

In the world of plastics manufacturing, the thermal loop stands as a critical process, directly influencing product quality, production efficiency, and overall process stability. With its four interconnected components, the thermal loop ensures precise temperature control throughout the entire production cycle. Let’s dive into the components of the thermal loop and meet the key players: sensors, controllers, switches, and electric heaters.

1. Sensors: The Temperature Detectives

Imagine tiny temperature detectives – thermocouples and RTDs (temperature-sensing resistors) – stationed throughout the process, constantly monitoring the material and machinery. These sensors are the eyes and ears of the thermal loop, providing real-time updates on temperature to the control center.

  • Thermocouples: Made of two different metals joined at one end, thermocouples generate a voltage proportional to the temperature difference when exposed to heat. Their responsiveness to rapid temperature changes makes them ideal for injection molding, where precise and quick temperature measurement is crucial for achieving the desired shape and surface finish of plastic part
  • RTDs: Made of a pure metal (typically platinum), exhibit a predictable change in electrical resistance with temperature. RTDs offer exceptional accuracy and stability over a wide temperature range, making them perfect for demanding applications where precision is paramount. For instance, in extrusion processes, RTDs help maintain consistent material flow and prevent defects like under- or over-extrusion.

Adjustable Depth ThermocoupleHose Clamp ThermocoupleMelt Bolt RTD


2. Controllers: The Masterminds

Meet the masterminds behind the scenes – temperature and pressure controllers. These high-tech brains process the data from the sensors and make split-second decisions to adjust the heating or cooling systems. Think of them as the conductors of a symphony orchestra, ensuring every instrument (or heating element) plays its part perfectly.

  • Temperature Controllers: These diligent overseers compare the actual temperature to the desired setpoint and adjust the heating or cooling elements accordingly. Using control algorithms like PID (Proportional-Integral-Derivative), they optimize temperature stability and response time. In thermoforming, precise temperature management controlled by temperature controllers is crucial for creating accurate and durable plastic products.
  • Pressure Controllers: Maintain the system within safe and efficient operating limits. They regulate the flow of materials or gases to ensure consistent pressure levels, preventing fluctuations that could impact product quality or equipment performance. Pressure controllers play a vital role in injection molding, ensuring even distribution of molten plastic within the mold cavity.

Eurotherm 3200 Series Temperature ControllerGefran 1350 Series Temperature ControllerGefran 40T Pressure Controller


3. Electric Heaters: The Muscle

Electric heaters are the muscle of the thermal loop, converting electrical energy into thermal energy to heat the plastic material. Let’s delve deeper into some of the most common types:

  • Cartridge Heaters: Cartridge heaters are cylindrical heating elements inserted into drilled holes in the equipment. They offer precise heat delivery and are available in various lengths, diameters, and wattages.
    • Advantages: Compact size, precise heat control, and easy installation.
    • Applications: Commonly used in molds, dies, and extrusion equipment for localized heating.
    • Types: Stainless steel, copper, and sheathed cartridges, with different wattage densities and temperature ratings.
  • Band Heaters: Band heaters are flexible heating elements that wrap around cylindrical surfaces, providing even heat distribution. They are available in various widths, lengths, and voltages.
    • Advantages: Versatility, easy installation, and even heat distribution.
    • Applications: Commonly used in extrusion barrels, pipes, and hoses for maintaining consistent temperatures.
    • Types: Mica band heaters, ceramic band heaters, and mineral insulated band heaters.
  • Cast-In Heaters: Cast-in heaters are embedded directly into the equipment, offering superior heat transfer and durability. They are typically made of aluminum, bronze, or iron and can be customized to fit various shapes and sizes.
    • Advantages: Excellent heat transfer, long lifespan, and resistance to harsh environments.
    • Applications: Commonly found in extrusion barrels, hot runner systems, and other applications requiring consistent and reliable heating.
    • Customization: Cast-in heaters can be tailored to specific heat output, shape, and mounting requirements.
  • Infrared Heaters: Infrared heaters use radiant energy to transfer heat to the target material. They offer precise heat control and rapid heating times.
    • Advantages: Non-contact heating, fast response times, and energy efficiency.
    • Applications: Widely used in preheating, drying, curing, and forming processes.
    • Types: Ceramic infrared heaters, quartz infrared heaters, and shortwave infrared heaters.
  • Tubular Heaters: Tubular heaters are cylindrical heating elements composed of a resistance wire encased in a metal sheath. They are versatile and find application in various heating processes.
    • Advantages: Even heat distribution, durability, resistance to corrosion, customizable shapes and sizes.
    • Applications: Heating liquids and gases, Mold heating, Plastic extrusion, Chemical processing.
    • Types: Straight tubular heaters, U-shaped tubular heaters, Immersion tubular heaters
  • Strip Heaters: Strip heaters are flexible heating elements that can be easily installed on various surfaces. They come in different widths, lengths, and wattages to accommodate diverse heating needs.
    • Advantages: Versatility, easy installation, and precise temperature control.
    • Applications: Used in molds, platens, and other equipment requiring localized or uniform heating.
    • Types: Silicone rubber strip heaters, finned strip heaters, and mica strip heaters.

Mica Band HeaterSplit Sheath Cartridge HeaterTubular Heaters

4. Switches: The Power Players

Switches are the power players in the thermal loop, controlling the flow of electricity to the heating elements.

  • Solid-State Relays (SSRs): These use semiconductor components to switch electrical loads on and off without any moving parts, resulting in lightning-fast response times, high reliability, and long lifespans, making them the preferred choice for demanding applications.
  • Mercury Relays: While gradually being phased out due to environmental concerns, mercury relays have been workhorses in the industry for decades. They offer exceptional durability and the ability to handle high current loads, making them suitable for heavy-duty applications.

Watlow DIN-A-MITE ACrydom Series 1 Solid State RelayMercury Relay


The beauty of the thermal loop lies in the seamless collaboration of these components. Sensors gather vital temperature data, controllers make informed decisions, switches deliver the power, and heaters provide the heat. It’s a well-orchestrated dance that results in consistent product quality, maximum efficiency, and reduced energy consumption. By understanding the role of each component and how they work together, plastics manufacturers can fine-tune their thermal processes for optimal performance.

Our experienced sales engineers would be happy to assist you in selecting the right components for your thermal loop.

Contact us today for more information!

History of Southern Heat Corporation

History of Southern Heat Corporation

Founded in 2005 by Tony Evans and Jason Reed, Southern Heat Corporation has grown from humble beginnings to become a leading manufacturer and distributor of high-quality process heating products. The journey of these two fraternity brothers and best friends, who met at Kennesaw State University while pursuing Engineering degrees, is a testament to their dedication and vision.

Tony Evans (left) and Jason Reed (right)

The Early Days

After graduating, Tony and Jason were both hired by a company providing maintenance, repair, and operations (MRO) supplies to the plastics industry. After eight years of experience in the industry, they were inspired to start their own business with a clear mission:

  • Treat customers according to the golden rule
  • Treat employees like family
  • Only sell products that allow us to sleep well at night
  • Make lots of sales calls

With the expertise of Tony’s wife, Dede Evans, a business accountant and consultant, Southern Heat Corporation was incorporated on August 8, 2005, in a basement in Cartersville, GA. Despite the chaos of running a business from a basement, the company experienced exponential growth, prompting a move to its current location in Cartersville, GA, in 2006.

Growth and Development

As Southern Heat Corporation expanded, more employees were hired, and the product line grew. The company prides itself on the family-like atmosphere it has built, attributing its success to a team effort. Today, Southern Heat Corporation continues to thrive, offering a wide range of products and services.

Products and Services

Today, Southern Heat Corporation is a leading distributor of:

  • Electrical Heaters
  • Thermocouples
  • Process Controllers
  • Power Controllers
  • Pressure Transducers
  • Rupture Disks
  • Insulation Blankets
  • Accessories and More

The company’s primary focus is on the plastics industry, but it also engages in process heating projects across various industries. Southern Heat Corporation is dedicated to improving customers’ bottom lines by supplying high-quality products at competitive prices.

Commitment to Innovation

As innovators in the field, Southern Heat Corporation stays at the forefront of technological advancements to meet the evolving demands of its customers. The company delivers cost-effective and efficient solutions for process heating requirements, pioneering new developments in heater technology.

Why Choose Southern Heat Corporation?

  • Expertise and Experience: Over 20 years of experience in the industry.
  • Customer-Centric Approach: Committed to treating customers and employees with the utmost respect and care.
  • High-Quality Products: Only sells products that meet stringent quality standards.
  • Comprehensive Solutions: A full-service provider of total heating solutions.
  • Innovative Technology: Leading the way in heater technology and process heating solutions.

Contact Southern Heat Corporation

For all your process heating needs, trust Southern Heat Corporation to deliver the best and most cost-effective solutions. Whether you are in the plastics industry or another vertical market, we are here to help.

Reach out to us today and experience the difference that comes with working with a company dedicated to excellence, innovation, and customer satisfaction.