Medium wall and heavy wall heat shrink tubing both provide mechanical protection for cables. The difference is wall thickness — and that difference determines whether the tubing is suitable for underground burial, subsea exposure, or just general abrasion resistance.
Wall Thickness Definitions
Medium wall tubing has a recovered wall thickness of 1.0 to 2.0 mm. Our DWT series ranges from 1.7 mm (small sizes) to 2.5 mm (larger sizes). It provides good mechanical protection and, in adhesive-lined versions, a waterproof seal.
Heavy wall tubing has a recovered wall thickness of 2.0 mm or more. It's designed for direct burial, subsea exposure, and high-impact environments. Heavy wall is stiffer, harder to install, and requires more heat to shrink fully.
When Medium Wall Wins
Medium wall tubing is the right choice for:
Cable jacket repair. When the outer jacket of an LV or MV cable is damaged but the insulation is intact, medium wall tubing restores the mechanical and moisture barrier. DWT adhesive-lined tubing, with 1.7-2.5 mm recovered wall and a hot-melt inner seal, creates an IP68-equivalent repair.
Above-ground mechanical protection. In cable trays, on walls, or in areas where cables are subject to abrasion or impact, medium wall provides adequate protection without the bulk and cost of heavy wall.
Transitions and terminations. At the transition from a cable pit to a riser, or at a termination point where the cable exits the ground, medium wall seals the vulnerable transition.
When Heavy Wall Wins
Heavy wall tubing is necessary for:
Direct burial. Underground installations subject the tubing to soil pressure, root growth, and potential damage from digging. Heavy wall (2.0 mm+) resists deformation and penetration.
Subsea or splash zone. Marine installations with continuous water immersion or wave-zone exposure need the thickest wall available to resist water pressure and mechanical damage from debris.
High-impact areas. Industrial environments with forklift traffic, falling objects, or chemical exposure benefit from the additional mechanical margin of heavy wall.
DWT: Adhesive-Lined Medium Wall
Our DWT series combines a semi-rigid crosslinked polyolefin outer layer with a hot-melt adhesive lining. Key specifications:
- Recovered wall: 1.7-2.5 mm depending on size
- Shrink ratio: 2.5:1
- Operating temperature: -55°C to 105°C
- Available sizes: 22 sizes from Φ8/2 to Φ260/80
The adhesive lining flows during shrinking to fill cable surface irregularities, creating a seal rated for direct burial in most soil conditions.
Comparison Table
| Factor | Medium Wall (DWT) | Heavy Wall |
|---|---|---|
| Recovered wall | 1.0-2.0 mm | 2.0 mm+ |
| Direct burial | Yes (with adhesive) | Yes |
| Subsea immersion | Splash zone only | Yes |
| Flexibility after recovery | Semi-rigid | Rigid |
| Shrink time | 2-3 min | 4-6 min |
| Cost per meter | Moderate | Higher |
FAQ
Can I use medium wall for direct burial?
Yes, if it's adhesive-lined like DWT. The adhesive seal prevents moisture ingress in typical soil conditions. For continuously waterlogged soil or subsea applications, heavy wall with additional protective layers is recommended.
How much heat does medium wall need?
A propane torch or high-output heat gun (≥1500 W) is recommended. Full recovery typically takes 2-3 minutes per meter with continuous movement. The adhesive layer requires reaching 110°C to flow.
What sizes does DWT cover?
22 standard sizes from Φ8/2 (8 mm expanded, 2 mm recovered ID) to Φ260/80 (260 mm expanded, 80 mm recovered ID). This covers cable diameters from 6 mm (small control cable) to 75 mm (large MV power cable).
Written by Long, Sales Engineer at ZZ Heat Shrink. For DWT medium wall tubing specifications, see medium wall tubing. For a quotation, contact our engineers.