26 August 2026
We've seen a few cases recently where a cable joint looked fine from the outside, but the Heatshrink hadn't actually sealed.
The sleeve had shrunk down around the cable, but the adhesive inside hadn't properly flowed. In some cases, the Heatshrink could be cut and peeled away with very little effort. If it comes off that easily, chances are it never formed a proper moisture seal in the first place.
That's a problem because Heavy Wall Heatshrink isn't just there to protect the joint mechanically. It's a key part of keeping moisture out. If water gets in, the risk of failure increases, along with the cost and inconvenience of having to revisit the job later.
What's Causing It?
One of the most common causes appears to be insufficient heat during installation.
Heavy Wall Heatshrink relies on enough heat reaching the internal adhesive for it to melt, flow and bond to the cable sheath. In many applications, an LPG or propane torch is the most effective way of achieving this.
We've seen situations where alternative heat sources have successfully shrunk the outer sleeve, but haven't generated enough heat for the adhesive to activate properly. The finished joint looks acceptable, but the seal underneath hasn't been formed.
A good rule of thumb is simple:
Don't just look for shrinkage. Look for adhesive flow.
If you can't see evidence of adhesive emerging from the ends of the tubing, there's a good chance it hasn't fully sealed.
Don't Forget About Hot Works Permits
Many sites require a hot works permit before a torch can be used.
It's tempting to look for workarounds when permits take time, but a failed joint will usually create far more disruption than following the correct process from the start.
Plan ahead, obtain the permit if required, and use the installation method the product was designed for.
A Few Things Worth Checking
The cable surface has been cleaned and prepared correctly.
Any areas forming part of the seal have been lightly abraded where required.
Heat has been applied evenly around the circumference of the sleeve – you don’t want ‘frog-skinning’
The heating process starts from the centre and works outward
Adhesive flow is visible at the ends of the Heatshrink
Most importantly, don't assume the job is complete just because the sleeve has recovered.
Winter Can Make a Difference
As temperatures drop, Heatshrink installations often require more attention.
Cold cables and cold ambient temperatures can make it harder for the adhesive to fully activate and flow. During winter, it's worth taking extra time to confirm the seal has been achieved before moving on.
The Bottom Line
Heatshrink is often one of the final steps in the jointing process, but it can have a major influence on the long-term reliability of the joint.
We've always said that if a Heatshrink joint can be peeled off cold, it probably wasn't sealed properly to begin with.
Taking a few extra minutes during installation is far easier than dealing with moisture ingress, a return visit, or a failed joint down the track.
If you're unsure about the correct heatshrink product or installation method for your application, get in touch with the ECL team today.