Zipper Heat Shrink Tube — Wrap-Around Repair
A repair sleeve shaped like a question other tubing never answers: how do you get a tube onto a cable whose ends you cannot reach? This one arrives as a flat sheet of irradiation cross-linked polyolefin with a zip rail along both edges and a hot-melt seal strip underneath. Wrap it around the installed line at the damaged or modified section, zip it closed into a tube, and recover it with a heat gun: the wall tightens onto the cable while the strip bonds the seam. No disassembly, no re-termination. Heat recovery, but everything else about this construction is different from ordinary tubing, and the page treats it that way.
Specification
| Material | Irradiation cross-linked polyolefin + hot-melt seal strip |
|---|---|
| Construction | Wrap-around sheet; zip closure along both edges; seal strip under the seam |
| Installation | Over an installed line, no disassembly; hot-air recovery |
| Colours | Black / standard |
Construction: three parts, one recovery
The wall. A cross-linked polyolefin sheet, pre-expanded and supplied flat. Heated past its recovery temperature it tightens down onto whatever it wraps. The same relax-onto-the-part behaviour as any cross-linked polyolefin sleeve, which is why the finished repair grips rather than merely covers.
The zip. A moulded rail system along both long edges that snaps the flat sheet into a tube around the cable. The zip's job ends when the sleeve is closed: it positions the edges for the seal strip and holds the geometry during the wrap, so a repair around a fixed line becomes a one-person job instead of a two-person taping exercise.
The seal strip. A hot-melt strip laid under the seam. During recovery it melts, wets both edges and the cable surface, and sets as the wall cools: closing the seam and anchoring the sleeve axially. It is the strip, not the zip, that determines whether the finished repair keeps water out.
The retrofit logic
Every installed line eventually needs jacket work in the middle: sheath abrasion where a cable crossed a sharp edge, a splice re-jacketed after rework, a section cut to add a tee and then restored. Continuous tubing cannot reach any of these without breaking the line. Tape builds thickness layer by layer and depends entirely on operator technique. The zipper sleeve exists between those options: tubing-grade recovery and a bonded seam, applied at the middle of a live route. The trade to accept: it is a permanent, one-shot repair, once recovered, it comes off only by cutting.
Selection inputs
- Largest wrapped OD. The cable jacket : or the built-up diameter at a splice if the repair bridges one. This sets the sleeve's flat width; the wrapped tube must close with recovery margin, not skin-tight before heating.
- Repair length. Damage plus overlap onto sound jacket at both ends. The overlap is what carries the seal at each sleeve end; the length tables are being verified per the data note, so we confirm the overlap figure per size on order.
- Environment. Burial, immersion, sunlight or indoor dry : the wall grade and seal system are confirmed against the duty before we quote.
- Access. Whether the section sits in open air or against tray and neighbours : this decides heat-gun technique more than anything else on the job.
Failure modes specific to wrap-around zipper sleeves
Four ways this construction fails that ordinary tubing never sees, plus the one it shares.
Cold seam: the zip closed but the strip never bonded
Root cause: heat went to the easy places (the flat wall), and only passed quickly over the rail. The zip geometry shadows the strip underneath, so the seam can look finished while the strip stayed solid. Weeks later the seam opens at that spot and the first wet spell finds it.
Fix: a dedicated, slower heat pass along the full seam after the wall has recovered, until the strip's melt line shows evenly along both edges. On long repairs, work the seam in sections so the strip is never warmed and cooled in patches.
Wrapped too tight: no recovery left before heating
Root cause: the sleeve was zipped around the OD with no slack. The cross-linked wall only recovers so far, if the wrapped diameter already sits at or below the recovered size, heating adds nothing and the wall sits loose over the damage.
Fix: size so the zipped sleeve is comfortably above the cable OD before heat. The flat-width tables (being published per the data note) exist exactly to prevent this; on a splice repair, measure the built-up diameter, not the jacket.
Ends landed on damaged jacket
Root cause: the sleeve was cut or ordered to the damage length. Both ends then seat on compromised sheath, and the axial seal of the whole repair is only as good as the cracked jacket it shrank onto.
Fix: lengthen the repair so each end overlaps sound, clean jacket by the specified margin. Clean and abrade the seating bands before wrapping: the seal strip bonds the ends, and it bonds surface, not dirt.
Trapped air bubble along the wrap
Root cause: heating ran from both ends toward the middle, pushing air under the wall until it pooled as a blister that will not conform.
Fix: recover from one end to the other, or from the centre outward in both directions: one consistent direction, so air escapes ahead of the recovery front instead of being sealed in.
Reopened after recovery
Root cause: someone expected the zip to be a service door. After recovery the strip has bonded the seam; peeling it open tears the wall and the cable jacket with it.
Fix: treat the finished repair as terminal. For positions with a maintenance schedule, specify a re-openable textile sleeve instead: different product family, different trade.
Frequently asked questions
When is zipper construction preferable to continuous tubing?
Whenever the line already exists and the ends are not free. Continuous tubing must slide over the cable from an end. That means cutting the line, pulling connectors, or re-terminating before the repair can even start. The zipper sleeve wraps around the middle of an installed run: open the zip, wrap the sheet around the damaged or modified section, close the zip, apply heat. That is the whole decision, if both cable ends are accessible, ordinary tubing is simpler and cheaper; if the run is fixed, buried, dressed into a tray or terminated at both ends, the wrap-around construction is the only tubing-family option that does not require disassembly.
Can it be reopened after final installation?
No, treat the finished repair as permanent. Once the sleeve has been heated, the seal strip has melted and bonded the zip seam and the cable surface, and the cross-linked wall has recovered onto the cable. Reopening after recovery means cutting the sleeve off, exactly as you would cut off ordinary recovered tubing. The zip exists to close the sleeve around an installed line before heating. It is a formation mechanism, not a service door. If a position must be repeatedly opened for maintenance, that is a job for hook-and-loop or self-winding textile sleeves, which trade sealing for re-openability.
What dimensions are required around an existing cable or joint?
Three numbers about the line and one about the repair. First, the largest OD the sleeve must wrap, that is, the cable jacket, or the built-up OD at a splice or connector if the repair covers one. Second, the length of the damaged or modified section. Third, the minimum bend and routing context, that is, whether the section sits straight in open air or in a tray with neighbours, which affects heat-gun access and the sleeve's recovered stiffness. Fourth, the environment: burial, water, sunlight or indoor air. The seal and wall grade are confirmed against the duty. From these we size the sleeve's flat width (it must wrap the largest OD with recovery margin) and its length (damage plus overlap onto sound jacket at both ends). The per-size tables with these figures are being verified per the data note on this page; until they are published, we size each repair from your three numbers.
Does the zip seam really seal against water?
The seam is sealed by the seal strip, not by the zip itself: the zip only pulls the sheet into a tube, and the strip underneath melts during recovery and bonds the overlap together. So the sealing quality depends on the strip receiving full recovery heat along its whole length; a cold spot in the seam is a leak path. What we do not yet publish is a measured sealing or ingress rating for the completed repair; that figure is being confirmed per the data note on this page. Until it is on the data sheet, state the water duty your repair must survive: splash, burial, continuous immersion. We then confirm the suitability of the seal system for that duty rather than quoting an unqualified "waterproof" claim.
How does heating a wrap-around sleeve differ from heating ordinary tubing?
Two extra rules. First, the seam is the sensitive zone: the heat must reach the zip rail and seal strip fully, so the pass along the seam is slower and more thorough than the pass over the plain wall. An underheated seam is the failure mode ordinary tubing does not have. Second, the cable is already installed and possibly energised-adjacent equipment: shield the surrounding surfaces from the hot-air stream, and work at a gun distance that warms the sleeve without cooking the cable's own insulation. The recovery direction is the same as any cross-linked polyolefin sleeve. Start at the centre or one end and sweep toward the other so air does not get trapped under the wall.
Request a quote for Zipper Heat Shrink Tube
Send the largest OD to wrap (jacket or built-up splice), the repair section length, the environment and quantity. We return the sleeve size, overlap allowance and lead time.