Heat shrink tubing and cable sleeving are the first line of defence for wire harness protection. They insulate splice points, seal cable entries against moisture, protect wire bundles from abrasion, and organise routing for easier maintenance. Choosing the wrong material — or the wrong shrink ratio — leads to premature failures that cost far more than the tubing itself. This guide covers everything you need to select, size, and specify heat shrink and sleeving for Australian industrial, mining, medical, and automotive applications.
Standard polyolefin continuous rating
PTFE maximum operating temperature
Maximum common shrink ratio
Adhesive-lined seal rating
Why Wire Harness Protection Matters
A wire harness without proper protection is exposed to mechanical abrasion, moisture ingress, chemical attack, UV degradation, and thermal stress. In Australian conditions — where mine sites reach 50°C ambient, coastal installations face salt spray, and UV indices regularly exceed 11 — unprotected wire insulation degrades faster than in temperate climates.
Heat shrink tubing and cable sleeving serve different but complementary roles. Heat shrink provides a tight-fitting, sealed barrier at specific points — splices, terminations, and transitions. Cable sleeving provides continuous protection along the length of the wire bundle, guarding against abrasion and organising multiple conductors into manageable bundles.
Heat Shrink Tubing Protects Against
- •Moisture ingress at splices, terminations, and breakouts
- •Electrical short circuits from exposed conductors
- •Mechanical stress at cable-to-connector transitions
- •Chemical and solvent damage to wire insulation
Cable Sleeving Protects Against
- •Abrasion from vibration, rubbing, and cable routing
- •Heat and flame exposure in engine bays and panels
- •Rodent and pest damage in outdoor installations
- •UV degradation in exposed outdoor cable runs
"The most expensive heat shrink tubing is the one you have to replace in the field. I see engineers default to the cheapest polyolefin without checking the operating environment. In Australian mining and outdoor applications, adhesive-lined heat shrink with UV-stabilised material pays for itself within the first year — the cost difference is cents per termination, but the rework cost is hundreds of dollars per site visit."
Heat Shrink Tubing Types
Heat shrink tubing is manufactured from cross-linked polymers that are expanded during production and "remember" their original diameter. When heated above the material's activation temperature, the tubing recovers to its original size, conforming tightly around the cable or component underneath. The two primary construction types are single-wall and dual-wall (adhesive-lined).
Single-Wall (Standard)
- •One layer of cross-linked polymer
- •Provides insulation and light mechanical protection
- •Does not create a watertight seal
- •Lower cost, suitable for indoor/dry environments
Best for: Control cabinets, indoor wiring, colour coding, wire identification
Dual-Wall (Adhesive-Lined)
- •Outer cross-linked polymer + inner hot-melt adhesive
- •Adhesive flows when heated, filling gaps and sealing
- •Creates watertight seal rated to IP67
- •Higher cost, essential for outdoor/harsh environments
Recommended for: Australian outdoor, marine, mining, and automotive applications
Heat Shrink Material Comparison
The base polymer determines the tubing's temperature range, chemical resistance, flexibility, and cost. Polyolefin is the workhorse for 90% of applications, but specialty materials are essential for extreme temperatures, aggressive chemicals, or aerospace-grade requirements.
| Material | Temp Range | Shrink Ratio | Chemical Resistance | Relative Cost | Best For |
|---|---|---|---|---|---|
| Polyolefin | -55°C to +135°C | 2:1, 3:1 | Good | $ | General purpose, most applications |
| PVC | -30°C to +105°C | 2:1 | Moderate | $ | Low-cost colour coding, labelling |
| Elastomeric (Viton) | -75°C to +200°C | 2:1 | Excellent | $$$ | Fuel lines, chemical exposure, military |
| PTFE (Teflon) | -65°C to +260°C | 2:1, 4:1 | Exceptional | $$$$ | Aerospace, extreme heat, chemical immersion |
| FEP | -65°C to +200°C | 1.3:1, 1.6:1 | Exceptional | $$$$ | High-clarity, medical, aerospace |
| Silicone rubber | -60°C to +200°C | 1.7:1 | Good | $$$ | Medical, food-grade, high flexibility |
| Kynar (PVDF) | -55°C to +175°C | 2:1 | Very good | $$ | Thin-wall, military, high abrasion |
Australian Climate Consideration
Standard PVC heat shrink becomes brittle below -10°C and degrades rapidly under Australian UV conditions. For any outdoor application in Australia, specify UV-stabilised polyolefin as a minimum, or upgrade to PTFE or elastomeric for extreme heat zones like engine bays and mining equipment. Always request a UV ageing test report from your supplier if the tubing will be exposed to direct sunlight.
Shrink Ratios Explained
The shrink ratio is the ratio of the tubing's supplied (expanded) diameter to its fully recovered (shrunk) diameter. Getting this right is critical — too low a ratio and the tubing won't grip the cable; too high and you waste material and money.
| Shrink Ratio | Supplied → Recovered | Ideal Application | Example |
|---|---|---|---|
| 2:1 | 20 mm → 10 mm | Straight wire runs, uniform diameter cables | Insulating solder joints on same-gauge wire |
| 3:1 | 24 mm → 8 mm | Connectors, solder joints, irregular shapes | Covering a butt splice or ring terminal |
| 4:1 | 40 mm → 10 mm | Large connector-to-cable transitions | Sealing over a Deutsch or Amphenol connector body |
| 6:1 | 60 mm → 10 mm | Retrofit, mixed diameter cable bundles | Field repair where connector cannot be removed |
Sizing Rule of Thumb
Select tubing where the component sits at 50–80% of the supplied diameter. If the cable is 10 mm, choose tubing with a supplied diameter of 12–20 mm (depending on ratio). After shrinking, the recovered diameter should be smaller than the cable diameter to ensure a tight grip. Always verify both the supplied and recovered diameters on the datasheet — do not rely on the ratio alone.
Cable Sleeving Types for Wire Harnesses
While heat shrink protects individual points, cable sleeving protects the entire run of a wire bundle. Each sleeving type offers a different balance of abrasion resistance, flexibility, heat protection, and installation ease. The right choice depends on the operating environment, whether the harness needs to be serviced in the field, and cost constraints.
| Sleeving Type | Material | Temp Range | Abrasion Protection | Flexibility | Cost |
|---|---|---|---|---|---|
| Expandable braided | PET polyester | -50°C to +150°C | Very good | Excellent | $$ |
| Split loom (corrugated) | Nylon or polypropylene | -40°C to +120°C | Good | Good | $ |
| Spiral wrap | PE or nylon | -50°C to +100°C | Moderate | Good | $ |
| Fiberglass braid | E-glass fibre | -60°C to +650°C | Excellent | Moderate | $$$ |
| Silicone-coated fibreglass | Fibreglass + silicone | -60°C to +260°C | Excellent | Good | $$$ |
| Metal braided shield | Tinned copper or SS | -65°C to +200°C | Excellent | Moderate | $$$$ |
| Conduit (flexible) | Nylon, metal, or PE | Varies by material | Excellent | Limited | $$–$$$ |
Expandable Braided Sleeving
Expandable PET braided sleeving is the most popular choice for wire harness bundling. It expands to slide over connectors and then contracts to grip the cable bundle tightly. It provides excellent abrasion resistance, allows airflow for heat dissipation, and is available in a wide range of colours for wire identification. Companies like Techflex offer diameters from 3 mm to over 100 mm.
Split Loom (Corrugated Conduit)
Split loom is the automotive industry standard for aftermarket wire protection. The lengthwise split allows installation over existing harnesses without disconnecting. It provides good abrasion and crush protection but does not seal against moisture. Per SAE J1128, split loom is widely specified in automotive wire harness routing for protection against engine bay heat and road debris.
Fiberglass and Silicone Sleeving
For extreme heat applications — exhaust proximity, furnace wiring, smelting equipment — fibreglass sleeving handles continuous temperatures up to 650°C. Silicone-coated fibreglass adds flexibility and a smoother surface finish while maintaining ratings to 260°C. These are standard in high-temperature wire harness applications across Australian mining and heavy industry.
"Expandable braided sleeving with heat shrink at each end is our go-to specification for mining harnesses. The braid handles the abrasion from vibration and rubbing against chassis edges, while the adhesive-lined heat shrink seals the entry and exit points against red dust. This combination has cut our field failure rate by over 60% compared to split loom alone."
Sizing and Specification Guide
Correct sizing ensures a tight seal and reliable protection. An undersized tube will not slide over the component; an oversized tube will not grip tightly enough to provide protection or sealing. Follow this step-by-step process to select the right size.
Heat Shrink Sizing Steps
Measure the largest diameter
Measure the widest point the tubing must slide over (connector body, solder joint, etc.). This is your minimum supplied diameter.
Measure the smallest diameter
Measure the cable or component at the point where the tubing must grip tightly after shrinking. This is your maximum recovered diameter.
Select the right shrink ratio
Divide the largest diameter by the smallest. If the result is less than 2, use 2:1 tubing. If 2–3, use 3:1. If over 3, use 4:1 or 6:1.
Verify with the datasheet
Confirm that the supplied ID is larger than your largest diameter, and the recovered ID is smaller than your smallest diameter. Check wall thickness meets insulation needs.
Add 10–20 mm extra length
Heat shrink also shrinks longitudinally by 5–15%. Add extra length to ensure adequate coverage after full recovery.
| Application | Recommended Ratio | Adhesive-Lined? | Material |
|---|---|---|---|
| Wire-to-wire solder splice | 2:1 | Optional (indoor) / Yes (outdoor) | Polyolefin |
| Crimp terminal insulation | 2:1 or 3:1 | Yes | Polyolefin |
| Connector-to-cable transition | 3:1 or 4:1 | Yes | Polyolefin or elastomeric |
| Cable breakout (Y-split) | 3:1 (moulded boot) | Yes | Polyolefin |
| Engine bay / exhaust proximity | 2:1 | No (adhesive melts) | PTFE or silicone |
| Field repair over connector | 4:1 or 6:1 | Yes | Polyolefin |
Installation Best Practices
Proper installation technique is as important as material selection. Poor technique creates weak spots, air pockets, and uneven sealing — all of which compromise the protection that the heat shrink is designed to provide.
Do
- •Use a heat gun, not an open flame or lighter
- •Start heating from the centre and work outward to push air out
- •Rotate the cable to apply heat evenly around the circumference
- •Allow adhesive to flow visibly at both ends before stopping
- •Let the tubing cool completely before handling
- •Pre-clean cable surfaces to remove oils and dust
Don't
- •Use a cigarette lighter — creates hot spots and soot
- •Overheat until the tubing bubbles, chars, or discolours
- •Heat from one end only — traps air bubbles inside
- •Apply heat shrink over dirty or oily surfaces
- •Pull or flex the joint before the adhesive sets
- •Use undersized tubing that is stretched to fit — it will split
Heat Gun Temperature Guide
Polyolefin / PVC
Heat gun: 120–150°C
Full recovery: ~130°C
Elastomeric / Viton
Heat gun: 150–200°C
Full recovery: ~175°C
PTFE / FEP
Heat gun: 340–400°C
Full recovery: ~350°C
Industry-Specific Applications
⛏️ Mining & Resources
- •Adhesive-lined polyolefin (3:1) at all splice points
- •UV-stabilised sleeving for exposed cable trays
- •Heavy-wall tubing for IP69K washdown environments
- •Fibreglass sleeving near exhaust and furnace zones
🏥 Medical Devices
- •FEP clear tubing for visual inspection of connections
- •Silicone heat shrink for autoclave-sterilised devices
- •Biocompatible materials per ISO 10993 requirements
- •Colour-coded identification per IEC 60601-1
🚗 Automotive & EV
- •Split loom for underbody and engine bay routing
- •PTFE tubing near exhaust manifolds and turbochargers
- •Orange high-voltage sleeving per AS/NZS 3000 EV requirements
- •Adhesive-lined heat shrink at all underbody splice points
🛡️ Defence & Aerospace
- •Raychem-spec DR-25 and ATUM for MIL-DTL applications
- •PTFE over-sleeving for fuel and hydraulic line proximity
- •IPC/WHMA-A-620 Class 3 installation criteria
- •Identification marking per MIL-STD-130
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Not sure which heat shrink or sleeving is right for your application? Our engineering team provides free material selection guidance and DFM review on every cable assembly project.
Request Free Quote — 10% Off First Order8 Common Heat Shrink & Sleeving Mistakes
1. Using standard tubing in outdoor applications
Standard single-wall polyolefin provides no moisture seal. In Australian outdoor conditions, it wicks moisture along the cable jacket through capillary action, accelerating corrosion. Always use adhesive-lined tubing for any joint exposed to weather.
2. Incorrect shrink ratio for the application
Using 2:1 tubing over a connector-to-cable transition where the diameter difference is 3:1 leaves a loose, unsealed gap at the narrow end. Always calculate the ratio from the actual diameters, not from habit.
3. Applying heat unevenly
Directing the heat gun at one spot creates a charred section while the opposite side remains unshrunk. Rotate the cable or move the heat gun continuously around the circumference for even recovery.
4. Not accounting for longitudinal shrinkage
Heat shrink tubing shrinks in length by 5–15% during recovery. If you cut the piece to exact length, it will be too short after heating. Always add 10–20 mm extra length to compensate.
5. Using open flame instead of a heat gun
Lighters and torches create hot spots exceeding 1,000°C, far above the material's activation range. This burns through the tubing, deposits soot on the surface, and can damage underlying wire insulation. A temperature-controlled heat gun costs under AUD $50 and is the correct tool.
6. Ignoring UV resistance for outdoor use
Clear, white, and light-coloured heat shrink degrades rapidly in Australian UV conditions, becoming chalky and brittle within 6–12 months. Specify black or UV-stabilised formulations for any outdoor exposure. Check the UV resistance rating on the datasheet.
7. Mixing adhesive-lined tubing near high heat
The hot-melt adhesive in dual-wall tubing softens and flows at temperatures above 110°C. In engine bays or near exhaust systems, the adhesive can re-melt and leak out, destroying the seal. Use non-adhesive PTFE or silicone tubing for high-temperature zones.
8. Choosing split loom alone for harsh environments
Split loom provides abrasion protection but does not seal against dust or moisture. For mining and outdoor applications, combine braided sleeving with adhesive-lined heat shrink at each end, or use sealed corrugated conduit with IP-rated fittings.
"I always tell our production team: if you can see adhesive squeeze-out at both ends of the heat shrink, you know it's sealed properly. If one end is dry, hit it with the heat gun again. That visible adhesive ring is your quality check — no adhesive, no seal, no pass."
Frequently Asked Questions
What is the difference between 2:1 and 3:1 heat shrink tubing?
The ratio indicates how much the tubing shrinks. A 2:1 tube shrinks to half its original diameter; a 3:1 shrinks to one-third. Use 3:1 or 4:1 for covering connectors, solder joints, or transitions where there is a large difference between the widest and narrowest diameters. For uniform-diameter cable runs, 2:1 is sufficient and more cost-effective.
Should I use adhesive-lined heat shrink tubing?
Use adhesive-lined (dual-wall) heat shrink whenever the joint will be exposed to moisture, dust, chemicals, or vibration. The adhesive creates a watertight seal rated to IP67. For dry indoor environments like control cabinets, standard single-wall is adequate. For all Australian outdoor and mining applications, adhesive-lined is strongly recommended.
What temperature should I use to shrink heat shrink tubing?
Standard polyolefin begins shrinking at ~90°C and fully recovers at 120–130°C. Set your heat gun to 120–150°C. Apply heat evenly, starting from the centre and working outward to expel trapped air. Avoid open flames — they create hot spots exceeding 1,000°C that burn through the tubing.
Can heat shrink tubing be used for high-temperature applications?
Standard polyolefin is rated to 135°C continuous. For higher temperatures, use PTFE (260°C), FEP (200°C), or elastomeric Viton (200°C). These specialty materials cost more but are essential for engine bays, exhaust proximity, and high-temperature industrial wiring.
What is the difference between heat shrink tubing and braided sleeving?
Heat shrink conforms tightly to the cable and provides insulation and moisture sealing. Braided sleeving is loose-fitting, does not seal, but provides superior abrasion protection and allows cables to flex freely. Use heat shrink at termination points and splice joints; use braided sleeving for cable run protection and bundle management.
How do I size heat shrink tubing correctly?
Measure the largest diameter the tubing must slide over (supplied diameter must be larger). Measure the smallest diameter it must grip (recovered diameter must be smaller). Select tubing where the component sits at 50–80% of the supplied diameter. Add 10–20 mm extra length to account for longitudinal shrinkage of 5–15%.
Sources & References
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