Heat shrink tubing is a versatile solution used across various industries for numerous applications. Initially, it starts as a larger tube and shrinks to fit snugly around wires and cable components when heat is applied. It’s user-friendly, straightforward to apply, and quick to install. However, the various sizes and performance requirements make selecting the right heat shrink tubing seem daunting.
To ensure successful use of heat shrink tubing, it’s essential to understand the specific application, take accurate measurements, distinguish between available materials, and follow proper installation techniques. This basic guide to heat shrink tubing will walk you through these crucial steps.
Common Uses for Heat Shrink Tubing
Heat shrink tubing is an incredibly versatile product for applications across various industries. Its ability to provide protection, insulation, and organization makes it an essential tool in numerous settings. Below are some of the most common and impactful uses for heat shrink tubing, highlighting its importance in maintaining the integrity and functionality of various systems and components:
Mechanical Protection
Heat shrink tubing offers a robust defense against external threats, such as abrasion, cut-through, denting, and other physical damage. By providing this layer of protection, the tubing helps ensure the longevity and reliability of wires and cables, even in harsh or demanding environments.
Environmental Protection
Heat shrink tubing shrinks when heated to form a tight, conforming seal around components. This seal effectively blocks moisture, chemicals, dust, and other environmental elements that could harm the wires or compromise performance. This protective barrier is particularly valuable in applications where the components are exposed to harsh or unpredictable conditions.
Electrical Insulation
Serving as an excellent insulator, heat shrink tubing is commonly used to cover terminals, splices, connectors, and wire repairs. Preventing electrical shorts and enhancing overall safety help maintain the integrity of electrical systems, making them an essential component in both industrial and residential applications.
Identification
Heat shrink tubing is available in various colors, making it ideal for color-coding and component identification. This feature is particularly useful in complex wiring systems where easy identification is critical. Additionally, some types of tubing, such as PVC, can be custom-printed with text or symbols, simplifying the process of labeling and identifying wires and components for maintenance or troubleshooting purposes.
Strain Relief
The tubing also plays a crucial role in strain relief by alleviating stress on wire and cable components. This helps to reduce the risk of damage caused by tension, bending, or movement, thereby extending the lifespan of the wiring and ensuring stable connections over time.
Wire Bundling
Heat shrink tubing is frequently used in wire harnesses to organize multiple wires into a single, manageable bundle. This simplifies handling and installation and contributes to a cleaner, more efficient wiring layout, reducing clutter and the potential for interference between wires.
Application Considerations for Heat Shrink Tubing
To ensure the tubing’s longevity in its application, it’s crucial to evaluate all necessary performance characteristics and industry specifications. Additionally, you should consider the environmental conditions the tubing will need to endure.
Electrical Requirements
Like most wire and cable products, heat shrink tubing is subject to various industry standards. When used to bundle or insulate electrical wires, it typically needs to comply with guidelines set by standards organizations such as UL, CSA, or ASTM. Depending on the specific application, the tubing may also need to meet rigorous automotive, aerospace, or military specifications. For more detailed information on wire and cable standards, click here.
Environmental Requirements
Environmental factors are crucial when selecting heat shrink tubing. Will the tubing be used indoors or outdoors? Will it be exposed to harsh elements like water, chemicals, or physical impacts such as crushing? Identifying all the environmental challenges the tubing will face ensures that you choose a sufficiently durable option to meet the demands of the application.
Measuring for Heat Shrink Tubing
While measuring for heat shrink tubing is straightforward, it can be intimidating for those new to the process. Spec sheets often include measurements that might seem unfamiliar, making it difficult to correlate them with the tubing and the parts you’re covering. This section will break down the key points to consider when determining the correct heat shrink tubing size.
Sizing Requirements for Application
Accurate measurement of both the largest and smallest parts the tubing must cover is essential. For non-circular parts, measure the perimeter and divide by pi (3.14) to approximate the diameter. Although not exact, this provides a useful reference when reviewing spec sheets for appropriate tubing diameters.
Expanded & Recovered Inside Diameters
The expanded inside diameter (expanded ID) refers to the diameter of the tubing before heat is applied. The recovered inside diameter (recovered ID) is the diameter after the tubing has shrunk. Ensure the expanded ID is larger than the largest part it needs to cover, and the recovered ID is smaller than the smallest part, to achieve a snug fit. Checking these measurements will help ensure the tubing is both large enough to cover wide or irregular parts and capable of shrinking tightly around smaller components.
Shrink Ratio
The shrink ratio provides insight into the difference between the expanded and recovered IDs of the tubing. For example, a tubing with a 3:1 shrink ratio means the expanded tubing is three times larger than its fully shrunken form. Conversely, the shrunken tubing will be one-third the size of the original expanded tubing. Understanding the shrink ratio is crucial for determining the appropriate size, especially if only one measurement (expanded or recovered ID) is provided on the spec sheet.
Wall Thickness
Wall thickness typically refers to the minimum thickness of the tubing once it has fully shrunk (in its fully recovered state). However, this measurement does not account for cases where an object prevents total shrinkage. If the object being covered is larger than the tubing’s recovered diameter, the actual wall thickness will be thinner than listed on the spec sheet.
Length & Longitudinal Shrinkage
When heat is applied, tubing may shrink in diameter and longitudinally. Although this longitudinal shrinkage is usually less than 15%, it’s important to account for potential length loss by ordering extra tubing. Consult your supplier for specific information on longitudinal shrinkage, which can vary depending on the tubing material.
Common Heat Shrink Tubing Materials
Despite the common misconception that all heat shrink tubing is the same, this versatile product is available in various materials, each specifically engineered to meet the unique demands of different applications and environmental conditions. The choice of material can significantly impact the tubing’s performance, including its durability, flexibility, temperature resistance, and protective qualities.
PVC vs. Polyolefin
Polyolefin and PVC are among the most commonly used materials for heat shrink tubing. PVC tubing is suitable for applications with operating temperatures below 105°C (221°F). It offers benefits like low cost, good tensile strength, abrasion resistance, and color quality. However, polyolefin is the most popular heat shrink material, known for its durability and higher temperature tolerance, typically ranging from 125°C to 135°C (257°F to 275°F). Polyolefin tubing also boasts an extended shelf life, making it reliable for long-term storage.
Adhesive-Lined Heat Shrink
Also known as ‘dual wall’ polyolefin tubing, adhesive-lined heat shrink tubing features an inner adhesive layer that melts when heat is applied. This adhesive molds around the object, creating a robust seal against environmental hazards, making it ideal for applications requiring additional protection.
Specialty Heat Shrink Products
For challenging applications, heat shrink tubing may be crafted from advanced materials like fluoropolymers (PTFE, FEP), PVDF, Neoprene, Kynar, Mylar, or Viton. Although more expensive than PVC or polyolefin, these materials offer exceptional resistance and are necessary for applications requiring extreme temperature performance or specialized chemical resistance.
Heat Shrink Tubing Handling & Installation Considerations
Storage
PVC heat shrink tubing, unlike polyolefin, is more sensitive to high temperatures. To prevent premature shrinkage, it should be stored away from direct sunlight and maintained at temperatures below 32°C (90°F). Proper storage is essential to ensure the tubing remains effective until it’s ready.
Heating
A hand-held heat gun is the most commonly used tool for heat shrinking, offering precision and control for various applications. For larger-scale or industrial projects, flow-through ovens are often employed, providing uniform heat distribution over extensive lengths of tubing. Another, though less common, method involves using focused light to achieve the required shrinkage.
For optimal results, PVC tubing should be exposed to 150°C (300°F) heat for approximately three minutes. While the same guidelines apply to polyolefin tubing, its higher temperature resistance allows for greater flexibility in both the heat application duration and temperature settings, offering more room for adjustment based on the project’s specific requirements.
Minimizing Longitudinal Shrinkage
To minimize longitudinal shrinkage during installation, apply heat to the ends of the tubing first, ensuring they securely grip the wire or component before moving on to the middle section. This technique helps maintain the tubing’s length and provides a more precise fit.
From understanding application considerations to mastering the measurements, materials, and handling techniques, you have a solid foundation in heat shrink tubing. To explore a wide range of heat shrink tubing options available from Allied Wire and Cable, visit our online catalog or contact a wiring expert today to discuss your next project.