Watlow Brand Logo
  • English
    • 中文
    • Deutsch
  • Products & Services

    Products & Services

    Products Services Configure a Product Part Lookup Help Me Choose Product Documentation
    Products
    View All

    Electric Heaters
    Cartridge Insertion Heaters Circulation Heaters Immersion Heaters Air Heaters Flexible Heaters Tubular Heaters Gas Delivery and Exhaust Heaters High-Temperature Heaters Specialty Heaters View All
    Temperature & Process Control
    Multi Loop Controllers Single Loop Controllers Indicators and Alarms Limits and Scanners Operator Interfaces
    Power Control
    Power Controllers Power Switches
    Data Management
    Data Recorders
    Panels & Systems
    WATCONNECT® Control Panels POWERSAFE™ Thermal System
    Sensors
    Thermocouples Resistance Temperature Detectors (RTDs) Fiber Optic Sensing
    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Services

    thermalwatch thumbnail image of laptop with modern analytics dashboard
    THERMALWATCH™ Intelligent Analytics Solution

    THERMALWATCH leverages our deep understanding of thermal systems to provide secure data integration and management, along with expert analysis, to transform data into valuable information.

    Learn More
    Configure a Product

    vd_
    Watlow SELECT® Visual Designer™

    Quickly configure a product to meet the unique requirements of your application. Instantly access lead times, dimensional drawings, and more - at your own pace. No login required.

    Get Started

    Prefer to talk to a human? Find a Distributor or Sales Office 

    Part Lookup

    Know Your Part Number?

    Enter your part number exactly as marked.

    #
    Tip

    Many parts have lead times, dimensional, drawings, and more available on-demand. Click "Request a Quote" on the search result to access.

    Help Me Choose

    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Still need help? Locate a Rep Contact Us
    Product Documentation

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals
    catalog-ebook
    Try Our Interactive Catalogs

    Click Here

    Products
    View All

    Electric Heaters
    Cartridge Insertion Heaters Circulation Heaters Immersion Heaters Air Heaters Flexible Heaters Tubular Heaters Gas Delivery and Exhaust Heaters High-Temperature Heaters Specialty Heaters View All
    Temperature & Process Control
    Multi Loop Controllers Single Loop Controllers Indicators and Alarms Limits and Scanners Operator Interfaces
    Power Control
    Power Controllers Power Switches
    Data Management
    Data Recorders
    Panels & Systems
    WATCONNECT® Control Panels POWERSAFE™ Thermal System
    Sensors
    Thermocouples Resistance Temperature Detectors (RTDs) Fiber Optic Sensing
    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant

    Services

    thermalwatch thumbnail image of laptop with modern analytics dashboard
    THERMALWATCH™ Intelligent Analytics Solution

    THERMALWATCH leverages our deep understanding of thermal systems to provide secure data integration and management, along with expert analysis, to transform data into valuable information.

    Learn More

    Configure a Product

    vd_
    Watlow SELECT® Visual Designer™

    Quickly configure a product to meet the unique requirements of your application. Instantly access lead times, dimensional drawings, and more - at your own pace. No login required.

    Get Started

    Prefer to talk to a human? Find a Distributor or Sales Office 

    Part Lookup

    Know Your Part Number?

    Enter your part number exactly as marked.

    #
    Tip

    Many parts have lead times, dimensional, drawings, and more available on-demand. Click "Request a Quote" on the search result to access.

    Help Me Choose

    man with dual monitors using product selection assistant
    Not Sure? Try Our Digital Product Assistant

    Take the complexity out of product selection with our innovative Digital Product Assistant. Answer a few application questions and our interactive tool will recommend a product from our catalog.

    Launch Assistant
    Still need help? Locate a Rep Contact Us

    Product Documentation

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals
    catalog-ebook
    Try Our Interactive Catalogs

    Click Here

  • What We Do

    What We Do

    The Thermal Loop Industry Solutions Electrification Industry 4.0
    The Thermal Loop
    Learn More

    icon representing a thermal loop system
    The Thermal Loop

    For Watlow, the underlying concept behind everything we do is that of the thermal loop. Every product we offer, and every project we work on, is ultimately about the creation and control of a thermal loop in an application. 

    Learn More
    Industries

    Heat Treatment Energy and Environmental Technologies Life Sciences
    Clinical Equipment Semiconductor Processing Foodservice Equipment
    Electrification

    thumbnails of white papers relating to electrification and decarbonization
    Electrification

    Over 100 years ago, Watlow began designing and manufacturing electric heating elements to replace steam in the shoe industry. We've been electrifying equipment and processes ever since. Wherever thermal is critical, no one is better equipped to help you reach your energy transition goals. Learn why leading companies partner with us.

    Learn More
    Industry 4.0

    thumbnail of industry 4.0 white paper on tablet and print
    The Thermal Loop & Industry 4.0

    Industry 4.0 technology enables the capture and processing of data in real time, both where its generated and where it is needed, to implement effective improvements to industrial processes. Capturing data, though, is not enough. The advantage Watlow® brings to an Industry 4.0 project are its thermal experts, who understand both the important role thermal loop systems play in key applications and industry 4.0 implementations.

    Learn More

    The Thermal Loop
    Learn More

    icon representing a thermal loop system
    The Thermal Loop

    For Watlow, the underlying concept behind everything we do is that of the thermal loop. Every product we offer, and every project we work on, is ultimately about the creation and control of a thermal loop in an application. 

    Learn More

    Industries

    Heat Treatment Energy and Environmental Technologies Life Sciences
    Clinical Equipment Semiconductor Processing Foodservice Equipment

    Electrification

    thumbnails of white papers relating to electrification and decarbonization
    Electrification

    Over 100 years ago, Watlow began designing and manufacturing electric heating elements to replace steam in the shoe industry. We've been electrifying equipment and processes ever since. Wherever thermal is critical, no one is better equipped to help you reach your energy transition goals. Learn why leading companies partner with us.

    Learn More

    Industry 4.0

    thumbnail of industry 4.0 white paper on tablet and print
    The Thermal Loop & Industry 4.0

    Industry 4.0 technology enables the capture and processing of data in real time, both where its generated and where it is needed, to implement effective improvements to industrial processes. Capturing data, though, is not enough. The advantage Watlow® brings to an Industry 4.0 project are its thermal experts, who understand both the important role thermal loop systems play in key applications and industry 4.0 implementations.

    Learn More
  • Who We Are

    Who We Are

    About Us Core Values Sustainability News Events & Webinars
    About Us

    We solve the world's toughest and most important thermal problems.


    About Us Leadership Team Company History Watlow Worldwide
    Core Values

    core values compass
    The Watlow Way

    At Watlow, our lean journey, as well as our core organizational beliefs are aligned with the Watlow Way, a set of core principles, behaviors and values which guides our company and is woven through every decision we make.

    Learn More
    Sustainability

    sustainability graphic - green earth
    Some of our best work is performed in areas intended to protect and preserve our environment

    We believe protecting the environment is everyone's responsibility and both our products and our own lean manufacturing processes are designed to address these challenges.

    Learn More
    News

    Find the latest news, press releases and annoucements.


    News
    Shiyi Zhou Joins Watlow® as Regional President for Asia Watlow® Welcomes Klaus Aarestrup as New Regional President of Europe Watlow’s New Large and Extra Large WATCONNECT® Control Panels Maximize Process Uptime with a Small Footprint Watlow’s New PM PLUS® 1/8 DIN PID Controller Watlow® Obtains KGS Certification on Flange and Circulation Heaters Watlow® Completes Acquisition of Eurotherm®
    View All News 
    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More

    About Us

    About Us Leadership Team Company History Watlow Worldwide

    Core Values

    core values compass
    The Watlow Way

    At Watlow, our lean journey, as well as our core organizational beliefs are aligned with the Watlow Way, a set of core principles, behaviors and values which guides our company and is woven through every decision we make.

    Learn More

    Sustainability

    sustainability graphic - green earth
    Some of our best work is performed in areas intended to protect and preserve our environment

    We believe protecting the environment is everyone's responsibility and both our products and our own lean manufacturing processes are designed to address these challenges.

    Learn More

    News

    News
    Shiyi Zhou Joins Watlow® as Regional President for Asia Watlow® Welcomes Klaus Aarestrup as New Regional President of Europe Watlow’s New Large and Extra Large WATCONNECT® Control Panels Maximize Process Uptime with a Small Footprint Watlow’s New PM PLUS® 1/8 DIN PID Controller Watlow® Obtains KGS Certification on Flange and Circulation Heaters Watlow® Completes Acquisition of Eurotherm®
    View All News 

    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More
  • Resources

    Resources

    Product Documentation Tools and Calculators Customer Service Knowledge and Insights CMRT/EMRT & Russian Material Disclosure Events & Webinars
    Product Documents

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals Retrofit Guides
    Tools and Calculators
     

    Wattage Calculator Ohm's Law Calculator 3-Phase Delta / Wye Calculator Glossary Equations Reference Data
    Customer Service Documents

    Invoice Payment Options Supplier Requirements Environmental Polices and Statements Copyright and Trademark Information Certifications & Approvals Policies Return Materials Authorization (RMA)
    Knowledge and Insights

    thumbnails of white papers relating to electrification and decarbonization
    White Papers
      Browse White Papers
    Tech Tips logo
    Tech Tips
      Browse Articles
    CMRT/EMRT & Russian Material Disclosure
     

    Conflict/Extended Mineral Russian Material Disclosure [.PDF]
    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More

    Product Documents

    Watlow Catalogs Specification Sheets User Manuals Software and Demos Brochures
    CAD Drawings Mobile Applications Watlow Patents Certifications & Approvals Retrofit Guides

    Tools and Calculators

    Wattage Calculator Ohm's Law Calculator 3-Phase Delta / Wye Calculator Glossary Equations Reference Data

    Customer Service Documents

    Invoice Payment Options Supplier Requirements Environmental Polices and Statements Copyright and Trademark Information Certifications & Approvals Policies Return Materials Authorization (RMA)

    Knowledge and Insights

    thumbnails of white papers relating to electrification and decarbonization
    White Papers
      Browse White Papers
    Tech Tips logo
    Tech Tips
      Browse Articles

    CMRT/EMRT & Russian Material Disclosure

    Conflict/Extended Mineral Russian Material Disclosure [.PDF]

    Events

    Watlow & Eurotherm tradeshow booth at SPS 2024
    Events & Webinars

    Stay connected with Watlow through a variety of events, including upcoming trade shows, webinars, corporate and community involvement activities.

    Learn More
  • Careers

    Careers

    Careers
    Career Opportunities

    Are you looking for an opportunity to make a great living and be part of a thriving cross functional community? Select an option below to view opportunities in your region.


    View Openings
    United States Europe Asia Mexico
    STM
    Student Programs
    At Watlow®, we recognize the importance of learning, experimenting, and building your career. Our student programs are a great way for you to gain hands-on experience and on-the-job learning from the start. Learn More

    Career Opportunities

    View Openings
    United States Europe Asia Mexico
    STM
    Student Programs
    At Watlow®, we recognize the importance of learning, experimenting, and building your career. Our student programs are a great way for you to gain hands-on experience and on-the-job learning from the start. Learn More
  • English
    • Español
    • Français
    • Italia
    • Dutch
    • 中文
    • Deutsch
  • Contact Us
    • Contact Watlow
    • Locate a Partner

Search

  1. Tech Tips
tech tips blog logo

The Coefficient of Thermal Expansion and your Heating System

Popular tags: F4T/D4T Part Numbers Process Controllers VISUAL DESIGNER™

By: Admin on May 06, 2021

Download Share

 

 

 

 We’ve all been there. The lid on pickle jar is impossibly tight, but when you run hot water over the jar you can easily unscrew the lid.  The metal lid expands more than the glass jar, which is a simple illustration of how materials, when heated, expand at different rates. The relationship of how materials expand or contract through temperature change is driven by the coefficient of thermal expansion or CTE of those materials and is a critical factor when designing a heater.

Determining the appropriate materials for the heater is not as simple as running warm water over a metal lid. The coefficient of thermal expansion is a critical factor when pairing dissimilar materials in a system. With the help of Watlow representatives, you can make sure your system is designed for success, efficiency and a long lifespan.

What is the coefficient of thermal expansion?

To understand the science behind the coefficient of thermal expansion (CTE), one must first understand the basics of thermal expansion. Physical property changes, such as shape, area, volume and density, occur during thermal expansion.  Every material or metal/metal alloy will have a slightly different expansion rate. CTE, then, is the relative expansion or contraction of materials driven by a change in temperature. 

Metals, ceramics and other materials have unique coefficients of thermal expansion and do not expand and contract at equal rates. For example, if the volume of a section of aluminum and a section of ceramic are equal and are heated from X to Y degrees, the aluminum could increase in dimension by a factor of four compared to the ceramic.  While that may not seem like much of a difference, such variations could cause a catastrophic failure within a thermal system.  

Metal sheathed heaters, such as cartridge or tubular heaters, are designed with a variety of metal alloys carefully chosen for each application. The CTE of these materials should always be considered in the design phase of a project.

The coefficient of thermal expansion calculation

The coefficient of thermal expansion is determined with this formula:

ΔL = αL(ΔT)

In this equation, ΔL is the change in length in the direction of interest; L is equal to the starting length of material in direction of interest; and ΔT is the temperature difference from start to end. α is the CTE and can be determined from various materials databases.

It is important to note: All units of the equation must be consistent in Celsius or Fahrenheit as there are two different sets of coefficients for each measurement system.

What happens when materials are heated?

When metals or ceramics are heated or cooled, the substance expands or contracts depending on the material and the temperature at which it is heated. If the material is restricted, this stress can be destructive, as a tremendous amount of force can be generated with thermal expansion.

Consider railroad tracks. Modern railroad tracks are made of hot-rolled iron. As the track is installed, railway workers leave space between each rail. This space allows the track to expand as it is exposed to the hot summer sun. Without adequate spacing, the railway could buckle, potentially causing a derailment.

Roadway bridges have a similar feature with bridge joints. Bridge temperatures change faster than road temperatures. The bridge joint allows the pieces of the bridge to expand and contract at their respective rates. Without a bridge joint, bridge could suffer damage or be destroyed from expansion or contraction.

When designing a thermal system where a heater is necessary, it is critically important to accommodate for the movement of the materials within the system. As the examples above illustrate, failure to account for the coefficient of thermal expansion can have devastating effects on a system. While a failure in your system may not make headlines in the local newspaper like a train derailment, downtime is costly and leaves your business scrambling to fix the issue.

The hazards of using materials with different CTE

Using materials with different CTE in the same application can be problematic. For example, if enough force is generated by thermal expansion, damage to the heater system can produce enough force to cause a catastrophic system failure and potentially injure workers.

Failure to match CTE can cause the heated system to damage itself. When materials with different CTE are used together in the same heated application, they may experience failures such as fretting, galling, bending, cracking or warping. Fretting occurs when two materials rub against each other causing a degradation of the materials surface qualities. Galling occurs when certain materials rub together and form a bond, like a cold weld causing permanent damage.

Many of Watlow’s customers have very complex, thermal systems. Heater damage can cause a system to be underproductive or shut down. In business, time is money, and losing a system for even a couple hours could cost a business hundreds of thousands of dollars.

Designing and accounting for the CTE of various materials involved in the thermal process is one of the many ways Watlow can help design engineers to overcome these challenges.

Other considerations when selecting metals

While CTE is a vital design factor to consider, there are many other considerations. By working with a Watlow specialist, we will walk through the unique variables of your system. We provide insight and options on all aspects of the thermal system and materials, including:    

Ramp rate: The rate of change in temperature over time, ramp rate involves the speed at which the material is heated. A heater that causes one part of the system to get hotter than another (aka “thermal nonuniformity”) can create problems, even if the material has a compatible CTE. If the thermal energy is not allowed to spread evenly to all components of the system, expansion can occur at an uneven rate.

Properties of the metal: Understanding other properties of the metal is also critical. For example, aluminum has one of the highest thermal conductivity rates. However, aluminum melts at a much lower temperature compared to other metals. A system that needs to be heated to, say, 1500º F would leave a puddle of aluminum in the system. Another example is titanium, which has a low thermal conductivity. Titanium may not expand as much as other materials, but it acts almost as insulation instead of a thermal conductor.

Cost versus life of the system: When designing your system, cost may be a consideration. Some materials are more expensive than others. However, the more expensive substance may last 10 times longer than the less expensive material, so an understanding of quality and lifespan is important.

The right materials and the best information

Watlow representatives are prepared to evaluate your system and provide valuable expertise and advice on the best type, size and shape of materials for your application. Our team will help you avoid any issues that might be caused by thermal expansion or contraction. Allow our knowledgeable specialists to ensure that your heating system is well designed to serve you for years to come.

Contact a Watlow® representative today to learn more about the coefficient of thermal expansion and how it applies to your system.

Related Topics

F4T/D4T
Part Numbers
Process Controllers
VISUAL DESIGNER™
Back to top
About Us
  • Core Values
  • Environmental Sustainability
  • Social Responsibility
  • Governance
  • Watlow Worldwide
  • Company History
  • News
Contact Us
  • Submit an Inquiry
  • Locate a Partner
  • Locate a Sales Office
  • Application Assistance
  • e-Solutions Login
Industries We Serve
  • Heat Treatment
  • Energy and Environmental Technologies
  • Semiconductor Processing
  • Clinical Equipment
  • Foodservice Equipment
  • Life Sciences
Resources & Support
  • Customer Service & Support
  • Engineering Tools
  • Technical Library
  • Know Your Rights: Workplace Discrimination is Illegal
  • OFCCP Pay Transparency Non-Discrimination Provision
  • Environmental Product Information Request Portal
    • Core Values
    • Environmental Sustainability
    • Social Responsibility
    • Governance
    • Watlow Worldwide
    • Company History
    • News
    • Submit an Inquiry
    • Locate a Partner
    • Locate a Sales Office
    • Application Assistance
    • e-Solutions Login
    • Heat Treatment
    • Energy and Environmental Technologies
    • Semiconductor Processing
    • Clinical Equipment
    • Foodservice Equipment
    • Life Sciences
    • Customer Service & Support
    • Engineering Tools
    • Technical Library
    • Know Your Rights: Workplace Discrimination is Illegal
    • OFCCP Pay Transparency Non-Discrimination Provision
    • Environmental Product Information Request Portal
Policies Privacy Policy Terms of Use Data Protection Policy - GDPR
© 2025 Watlow Electric Manufacturing Company. All Rights Reserved.