Dual Wall Tubing
Heat shrinkable dual wall tubing with twin-layer construction designed to deliver reliable insulation performance, controlled electrical characteristics, and durable field protection in cable accessory applications.
Twin-Layer Construction for Layered Electrical Performance
Dual wall tubing combines two co-extruded functional layers in a single heat-shrinkable tube. The outer layer provides primary electrical insulation, mechanical protection, and weather resistance. The inner layer delivers a controlled semi-conductive or functionally differentiated performance — forming a composite tubing system that addresses both insulation and controlled electrical characteristic requirements in a single installed component.
Designed for medium-voltage cable accessory systems up to 15 kV, the product supports cable core reconstruction, joint and termination insulation, and protection applications where a single-layer tubing solution is insufficient for the electrical system requirements.
- Construction Twin layer — co-extruded
- Shrink ratio 3:1 minimum
- Voltage class Up to 15 kV
- Min. recovery temperature 130°C
- Standard colours Black, Red
- Halogen-free Yes
- Operating temperature –55°C to +110°C
Why Dual Wall Tubing Is Specified
A composite tubing system that delivers layered electrical and mechanical performance in a single heat-shrinkable installation step.
Twin-Layer Construction
Two discrete functional layers in a single tube eliminate the need for sequential application of separate tubing types — reducing installation steps, material handling, and the risk of layer misalignment or omission during accessory assembly.
Co-Extruded Material Design
The co-extrusion process bonds the two layers at the material interface, ensuring consistent layer thickness, stable inter-layer adhesion, and uniform electrical performance across the full recovered length — eliminating the variability of separately applied components.
Reliable Insulation Performance
The outer insulation layer maintains dielectric integrity across the service voltage range — providing consistent electrical isolation over cable cores, connectors, and accessory interfaces in both indoor and outdoor MV applications.
Controlled Electrical Performance
The semi-conductive or functional inner layer provides controlled electrical characteristics at the cable insulation interface — supporting stress grading, field control, and defined electrical behaviour within the cable accessory system design.
3:1 Shrink Ratio
The 3:1 shrink ratio accommodates a broad range of cable and accessory dimensions within a single tubing size — simplifying project procurement and reducing the number of stocked sizes required without compromising recovery performance.
Durable Field Performance
Resistant to moisture, UV exposure, and mechanical stress in recovered state — maintaining structural and electrical integrity across the operational life of the installation in outdoor, underground, and industrial environments.
Material & Performance Data
Reference data for engineering and procurement. Contact our technical team for full test reports or project-specific qualification data.
| Construction | Twin layer — co-extruded insulation and semi-conductive / functional inner layer |
|---|---|
| Outer layer | Crosslinked polyolefin — electrical insulation and mechanical protection |
| Inner layer | Semi-conductive / functional crosslinked compound — controlled electrical characteristics |
| Standard colours | Black, Red |
| Shrink ratio | 3:1 minimum |
| Voltage class | Up to 15 kV |
| Min. full recovery temperature | 130°C |
| Operating temperature | –55°C to +110°C (continuous service) |
| Halogen-free | Yes |
| UV / weather resistance | Yes — suitable for outdoor and exposed installations |
| Shelf life | 10 years from manufacture date when stored per IEC 60684 storage guidelines |
| Applicable standards | IEC 60684 (heat-shrinkable tubing) |
Where Dual Wall Tubing Is Used
Deployed in medium-voltage cable accessory systems and electrical insulation applications where a single-layer tubing is insufficient.
MV Cable Accessories
Used as a composite insulation component in medium-voltage cable joint and termination kits — providing both insulation and controlled inner-layer electrical performance in a single applied tubing.
Insulating Composite Tubing Applications
Suited to applications where a composite layered insulation system is required — replacing multi-component tape or sequential tubing build-ups with a single co-extruded tubing installation.
Cable Core Reconstruction
Applied over stripped MV cable cores during jointing to reconstruct the insulation and screen interface — restoring the cable's original layered electrical design at the joint zone.
Jointing and Termination Support
Integrated into MV jointing and termination kits as a structural insulation component — supporting consistent installation practice and reducing component count in the accessory assembly.
Utility and Infrastructure Applications
Supplied to utilities, EPC contractors, and infrastructure project teams for MV cable accessory installations in power distribution, substation, and underground cable network projects.
Electrical Insulation Systems
Used wherever a defined composite insulation system is required at the cable-accessory interface — providing layered dielectric performance in a repeatable, field-applicable format.
How to Select the Right Dual Wall Tubing
Six criteria determine the correct size and specification. Work through each before ordering to ensure the tubing is correctly matched to the cable accessory system and installation requirements.
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01
Voltage Class
Confirm the system voltage and the rated voltage class of the cable accessory being installed. Dual wall tubing is designed for MV applications up to 15 kV — ensure the product is compatible with the operating voltage before specifying.
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02
Cable Diameter
Measure the outer diameter of the cable insulation at the point of application. For jointing applications this is typically the stripped insulation diameter; for termination applications it may be the overall cable or insulation screen diameter depending on the accessory design.
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03
Recovered Size Requirement
Select a tubing size whose recovered inner diameter is equal to or slightly smaller than the cable insulation outer diameter. For a 3:1 product, the recovered diameter is the supplied diameter divided by three — confirm this matches the required coverage before ordering.
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04
Layer and Performance Requirement
Confirm whether the application requires the semi-conductive inner layer for electrical stress control, or whether a functional differentiated inner layer is specified by the accessory system design. Contact our technical team if the layer performance requirement is not clearly defined in the installation documentation.
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05
Installation Environment
Both indoor and outdoor installations are supported. Confirm whether the installation is underground, above-ground, or within enclosed switchgear — this affects requirements for UV resistance, moisture exposure, and mechanical protection in the applied state.
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06
Required Tubing Length
Determine the coverage length required from the cable accessory installation instruction or engineering drawing. Allow for axial shrinkage during heat application — typically 5–10% depending on tubing size. Cut lengths to requirement before installation where the accessory kit does not supply pre-cut pieces.
For MV cable accessory applications, always confirm the tubing specification against the accessory kit design documentation. Contact our technical team for assistance with product selection and cable compatibility.
Common Technical Questions
Standard single-layer heat shrink tubing provides one functional material property — typically insulation, mechanical protection, or environmental sealing — from a single compound. Dual wall tubing combines two co-extruded layers into a single product, with each layer performing a distinct and separate function. This allows a composite electrical or mechanical performance profile to be achieved in a single installation step, replacing what would otherwise require sequential application of two separate tubing components.
In medium-voltage cable accessory systems, the interface between the cable insulation and the applied accessory component is a critical electrical boundary. A semi-conductive inner layer at this interface provides controlled electrical characteristics — supporting field grading, eliminating voids at the insulation surface, and establishing a defined electrical condition at the cable-accessory boundary. This is particularly important in cable jointing and termination applications where the accessory must electrically continue the cable's own semi-conductive screen layer at the joint zone.
The minimum full recovery temperature for dual wall tubing is 130°C. This is higher than many standard thin-wall products due to the co-extruded twin-layer construction — both layers must reach sufficient temperature for complete and uniform recovery. Under-heating results in incomplete recovery, uneven wall thickness, residual shrinkage potential, and reduced adhesion at the inner layer interface. Use a calibrated hot air gun and confirm full recovery visually — the tubing surface should be smooth and wrinkle-free with the profile of the substrate clearly defined.
Yes. Dual wall tubing is designed for direct integration into MV cable jointing and termination kits as a structural insulation component. When specifying for this use, confirm the tubing dimensions against the kit design documentation — particularly the required recovered inner diameter relative to the cable insulation outer diameter, and the required coverage length at the joint or termination zone. Western Cablex can supply dual wall tubing to project-specific cut lengths for kit assembly if required.
Dual wall tubing is available in black and red. Black is the standard colour for general MV insulation and cable accessory applications. Red is typically specified where the accessory design or project documentation requires colour differentiation between tubing components — for example, to distinguish the dual wall insulation layer from other applied tubing in a multi-component kit, or to meet a project colour-coding requirement. Confirm colour requirements before ordering as availability may vary by size.
Dual wall tubing is specified by its supplied (pre-shrink) inner diameter. The recovered inner diameter is the supplied diameter divided by the shrink ratio — for a 3:1 product, a 45mm supplied size recovers to approximately 15mm. Select the size whose recovered diameter is equal to or slightly smaller than the cable insulation outer diameter at the point of application. Western Cablex dual wall tubing is available across a size range covering MV cable accessory dimensions. Contact our technical team for the current size schedule, cut-length availability, and project supply options.
Need Help Selecting the Right Dual Wall Tubing?
Speak with our technical team for sizing, application guidance, and product recommendations.